Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > sci.physics.relativity > #411547 > unrolled thread
| Started by | someone <glenn.spigel@googlemail.com> |
|---|---|
| First post | 2017-03-03 07:04 -0800 |
| Last post | 2017-04-08 12:28 -0700 |
| Articles | 20 on this page of 253 — 35 participants |
Back to article view | Back to sci.physics.relativity
Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-03 07:04 -0800
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-03 09:09 -0600
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-03 08:12 -0800
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-03 10:32 -0600
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-04 07:08 -0800
Re: Twin paradox rotchm <rotchm@gmail.com> - 2017-03-04 07:47 -0800
Re: Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-03-04 09:15 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-04 10:23 -0800
Re: Twin paradox Sylvia Else <sylvia@not.at.this.address> - 2017-03-05 11:42 +1100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-05 08:55 -0800
Re: Twin paradox wugi <brol@brol.be> - 2017-03-14 22:31 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-15 03:22 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-17 18:39 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-17 13:56 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-17 22:54 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-17 17:32 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-18 18:16 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-19 08:28 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-19 23:09 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-20 08:14 -0700
Re: Twin paradox Sylvia Else <sylvia@not.at.this.address> - 2017-03-19 13:05 +1100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-19 09:44 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-19 22:38 +0100
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-19 19:30 -0500
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-19 22:41 -0700
Re: Twin paradox mlwozniak@wp.pl - 2017-03-20 00:29 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-20 08:59 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-21 10:53 -0500
Re: Twin paradox wugi <brol@brol.be> - 2017-03-21 18:59 +0100
Re: Twin paradox Sylvia Else <sylvia@not.at.this.address> - 2017-03-22 17:45 +1100
Re: Twin paradox wugi <brol@brol.be> - 2017-03-22 11:25 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-22 06:42 -0700
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-22 00:26 -0700
Re: Twin paradox Sylvia Else <sylvia@not.at.this.address> - 2017-03-22 19:30 +1100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-22 07:56 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-22 05:49 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-22 06:17 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-22 08:20 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-22 11:08 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-22 11:41 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-22 11:51 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-22 12:02 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-23 07:06 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-29 11:24 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-27 13:50 -0500
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-28 06:18 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-28 12:13 -0500
Re: Twin paradox dickorrich@gmail.com - 2017-03-29 10:45 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-29 11:22 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-30 00:17 -0500
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-30 06:02 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-04-03 12:31 -0500
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-04 02:14 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-03 17:21 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-04-04 10:37 -0500
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-04 08:52 -0700
Re: Twin paradox Poutnik <poutnik4nntp@gmail.com> - 2017-04-04 18:51 +0200
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-05 02:39 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-20 08:36 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-20 17:27 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-20 10:49 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-20 21:10 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-20 16:59 -0700
Re: Twin paradox wugi <brol@brol.be> - 2017-03-21 12:37 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-21 06:13 -0700
Re: Twin paradox Gary Harnagel <hitlong@yahoo.com> - 2017-03-21 08:03 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-21 11:03 -0700
Re: Twin paradox "Dono," <sa_ge@comcast.net> - 2017-03-04 06:20 -0800
Re: Twin paradox Ed Lake <detect@newsguy.com> - 2017-03-04 09:41 -0800
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-05 14:59 -0600
Re: Twin paradox alsor@interia.pl - 2017-03-05 13:23 -0800
Re: Twin paradox Mike Fontenot <mlfasf@comcast.net> - 2017-03-07 09:46 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-07 10:10 -0800
Re: Twin paradox Mike Fontenot <mlfasf@comcast.net> - 2017-03-07 12:13 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-07 13:32 -0800
Re: Twin paradox Poutnik <poutnik4nntp@gmail.com> - 2017-03-08 07:58 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-08 09:09 -0800
Re: Twin paradox Poutnik <poutnik4nntp@gmail.com> - 2017-03-08 23:04 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-08 16:19 -0800
Re: Twin paradox John Heath <heathjohn2@gmail.com> - 2017-03-04 11:23 -0800
Re: Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-03-04 14:02 -0800
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-06 12:05 -0800
Re: Twin paradox John Heath <heathjohn2@gmail.com> - 2017-03-06 16:34 -0800
Re: Twin paradox "Paul B. Andersen" <relativity@paulba.no> - 2017-03-07 12:57 +0100
Re: Twin paradox John Heath <heathjohn2@gmail.com> - 2017-03-07 20:29 -0800
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-04 22:13 -0600
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-09 12:58 -0800
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-10 07:25 -0600
Re: Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-03-10 13:21 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-05 08:44 -0800
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-06 12:03 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-06 18:02 -0800
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-07 14:15 -0800
Re: Twin paradox "Paul B. Andersen" <relativity@paulba.no> - 2017-03-05 21:31 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-05 15:09 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-05 15:18 -0800
Re: Twin paradox "Paul B. Andersen" <relativity@paulba.no> - 2017-03-06 23:10 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-10 11:39 -0800
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-13 09:53 -0500
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-13 08:33 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-14 10:50 -0500
Re: Twin paradox mlwozniak@wp.pl - 2017-03-15 00:43 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-15 04:08 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-16 16:48 -0500
Re: Twin paradox mlwozniak@wp.pl - 2017-03-17 01:01 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-17 07:40 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-18 14:16 -0500
Re: Twin paradox Idimi Higame <iumia@igmwwad.hh> - 2017-03-18 20:05 +0000
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-19 09:28 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-20 13:55 -0500
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-20 16:34 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-21 10:56 -0500
Re: Twin paradox Julio Di Egidio <julio@diegidio.name> - 2017-03-19 21:38 -0700
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-19 22:52 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-21 00:14 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-21 13:43 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-22 01:39 -0800
Re: Twin paradox mlwozniak@wp.pl - 2017-03-22 01:52 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-22 11:12 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-22 11:56 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-22 12:06 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-15 04:16 -0700
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-06 09:34 -0800
Re: Twin paradox "Paul B. Andersen" <relativity@paulba.no> - 2017-03-06 23:01 +0100
Re: Twin paradox alsor@interia.pl - 2017-03-06 15:09 -0800
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-07 09:49 -0800
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-07 14:04 -0800
Re: Twin paradox "Paul B. Andersen" <relativity@paulba.no> - 2017-03-08 10:40 +0100
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-08 07:11 -0800
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-08 15:04 -0600
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-08 14:30 -0800
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-09 10:39 -0600
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-09 13:20 -0800
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-10 07:27 -0600
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-10 06:05 -0800
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-10 08:45 -0600
Re: Twin paradox alsor@interia.pl - 2017-03-14 13:19 -0700
Re: Twin paradox "Paul B. Andersen" <relativity@paulba.no> - 2017-03-10 11:49 +0100
Re: Twin paradox wugi <brol@brol.be> - 2017-03-17 17:37 +0100
Re: Twin paradox Julio Di Egidio <julio@diegidio.name> - 2017-03-19 21:33 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-03-20 09:05 -0700
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-09 13:12 -0800
Re: Twin paradox Otplate Yuugaku <yu@yotwaglwt.pa> - 2017-03-09 22:50 +0000
Re: Twin paradox Dirk Van de moortel <dirkvandemoortel@hotspam.not> - 2017-03-10 11:01 +0100
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-10 11:14 -0800
Re: Twin paradox Priscilla Groll <lloi@wgnprlw.sl> - 2017-03-11 17:27 +0000
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-04 06:13 -0700
Re: Twin paradox Hermelinda Riess <hsr@ermeemw.ei> - 2017-04-04 15:10 +0000
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-04 08:36 -0700
Re: Twin paradox Hermelinda Riess <hsr@ermeemw.ei> - 2017-04-04 17:51 +0000
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-05 02:52 -0700
Re: Twin paradox Hermelinda Riess <hsr@ermeemw.ei> - 2017-04-05 17:17 +0000
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-05 13:31 -0800
Re: Twin paradox Julio Di Egidio <julio@diegidio.name> - 2017-03-08 14:17 -0800
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-08 14:34 -0800
Re: Twin paradox Julio Di Egidio <julio@diegidio.name> - 2017-03-08 15:32 -0800
Re: Twin paradox someone <glenn.spigel@googlemail.com> - 2017-03-09 13:20 -0800
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-09 13:35 -0800
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-12 00:07 -0800
Re: Twin paradox ronjresnick@gmail.com - 2017-03-13 13:58 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-14 10:28 -0500
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-14 12:31 -0700
Re: Twin paradox "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-14 22:11 +0000
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-14 22:34 -0500
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-15 00:46 -0700
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-15 00:53 -0700
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-15 09:19 -0500
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-16 23:50 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-16 23:54 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-17 08:15 -0800
Re: Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-03-17 09:03 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-18 18:37 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-03-19 00:20 -0800
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-15 09:15 -0500
Re: Twin paradox rotchm <rotchm@gmail.com> - 2017-03-15 07:54 -0700
Re: Twin paradox Julio Di Egidio <julio@diegidio.name> - 2017-03-15 02:53 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-15 15:18 -0500
Re: Twin paradox Koobee Wublee <koobee.wublee@gmail.com> - 2017-03-19 22:43 -0700
Re: Twin paradox mlwozniak@wp.pl - 2017-03-15 03:22 -0700
Re: Twin paradox "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-15 21:31 +0000
Re: Twin paradox alsor@interia.pl - 2017-03-16 16:56 -0700
Re: Twin paradox mlwozniak@wp.pl - 2017-03-15 00:41 -0700
Re: Twin paradox Ron Resnick <ronjresnick@gmail.com> - 2017-03-15 03:09 -0700
Re: Twin paradox rotchm <rotchm@gmail.com> - 2017-03-15 08:02 -0700
Re: Twin paradox "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-14 22:10 +0000
Re: Twin paradox rotchm <rotchm@gmail.com> - 2017-03-15 07:41 -0700
Re: Twin paradox Odd Bodkin <bodkinodd@gmail.com> - 2017-03-15 10:02 -0500
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-14 11:19 -0700
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-18 11:51 -0700
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-18 14:13 -0700
Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-03-19 09:26 -0700
Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-03-19 09:53 -0700
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-19 12:59 -0700
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-20 10:29 -0700
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-22 09:40 -0700
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-22 09:44 -0700
Re: Twin paradox numbernumber1964@gmail.com - 2017-03-22 14:32 -0700
Re: Twin paradox Deon Joubert <dhjoubert@gmail.com> - 2017-03-30 09:27 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-30 23:34 -0500
Re: Twin paradox Deon Joubert <dhjoubert@gmail.com> - 2017-03-31 00:33 -0700
Re: Twin paradox Deon Joubert <dhjoubert@gmail.com> - 2017-03-31 02:43 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-03-31 21:43 -0500
Re: Twin paradox mlwozniak@wp.pl - 2017-04-01 00:52 -0700
Re: Twin paradox Deon Joubert <dhjoubert@gmail.com> - 2017-04-01 01:41 -0700
Re: Twin paradox Domonique Corle <oreuni@wwerwo.co> - 2017-04-01 13:01 +0000
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-04-01 10:27 -0500
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-01 20:44 -0800
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-03 00:05 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-03 00:28 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-03 04:14 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-03 17:15 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-04 11:47 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-04 05:57 -0700
Re: Twin paradox Paparios <mrios@ing.puc.cl> - 2017-04-04 07:05 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-04 07:43 -0700
Re: Twin paradox Paparios <mrios@ing.puc.cl> - 2017-04-04 09:20 -0700
Re: Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-04-04 09:58 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-05 02:25 -0700
Re: Twin paradox Paparios <mrios@ing.puc.cl> - 2017-04-05 04:22 -0700
Re: Twin paradox mlwozniak@wp.pl - 2017-04-05 06:23 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-05 09:58 -0700
Re: Twin paradox Paparios <mrios@ing.puc.cl> - 2017-04-05 10:21 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-05 11:36 -0700
Re: Twin paradox Hermelinda Riess <hsr@ermeemw.ei> - 2017-04-04 15:01 +0000
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-05 00:32 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-05 02:55 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-07 21:32 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-08 07:38 -0700
Re: Twin paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-04-08 10:31 -0500
Re: Twin paradox mlwozniak@wp.pl - 2017-04-08 08:42 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-09 14:29 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-10 22:18 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-11 06:11 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-12 00:13 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-12 07:00 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-12 14:49 -0700
Re: Twin paradox Ned Latham <nedlatham@woden.valhalla.oz> - 2017-04-13 09:44 +0000
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-13 06:03 -0700
Re: Twin paradox Ned Latham <nedlatham@woden.valhalla.oz> - 2017-04-13 20:40 +0000
Re: Twin paradox "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-04-14 10:42 +0100
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-14 08:27 -0700
Re: Twin paradox Gary Harnagel <hitlong@yahoo.com> - 2017-04-16 05:49 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-17 08:05 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-17 08:22 -0700
Re: Twin paradox Nocasto Aboyar <oocaao@syeoby.ao> - 2017-04-17 15:36 +0000
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-17 09:08 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-17 10:45 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-17 10:56 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-19 10:14 -0700
Re: Twin paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-04-20 08:48 -0700
Re: Twin paradox mlwozniak@wp.pl - 2017-04-17 08:52 -0700
Re: Twin paradox The Starmaker <starmaker@ix.netcom.com> - 2017-04-08 09:51 -0700
Re: Twin paradox "David (Lord Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-04-08 12:28 -0700
Page 7 of 13 — ← Prev page 1 … 5 6 [7] 8 9 … 13 Next page →
| From | The Starmaker <starmaker@ix.netcom.com> |
|---|---|
| Date | 2017-03-22 12:06 -0800 |
| Message-ID | <58D2D92F.4337@ix.netcom.com> |
| In reply to | #413752 |
The Starmaker wrote: > > The Starmaker wrote: > > > > The Starmaker wrote: > > > > > > The Starmaker wrote: > > > > > > > > The Starmaker wrote: > > > > > > > > > > one needs to define ..."ageing" before one > > > > > can say a twin aged or a clock aged. > > > > > > > > > > If you stop the ageing process.. > > > > > > > > > > time still flows. > > > > > > > > but here is the real problem... > > > > > > > > one twin stays on earth > > > > > > > > the other travels.. > > > > > > > > it is not necessary for the traveling > > > > twin to come back. > > > > > > > > You can look at his clock without > > > > the twin returning since it is only...a thought experiment. > > > > > > so, one twin looks at his clock and > > > the other twin looks at his clock.. > > > which twin had the real time???? > > > > > > > The minute one has the twin 'returning'... > > > > you run into problems that cannot be...fixed. > > > > patched up maybe..a bandage maybe...but no cure. > > When the train arrives at the station...are you going to turn it around > and go back???? > > If you look above at the title of this newsgroups: relativity > > That means, a twin returning has nothing to do with Relativity. > > The Earth travels in a straight line...but > the Sun makes it return. > > That falls under Gravity, not Relativity. Let me put it this way... the traveling twin in a rocket ship is traveling in a straight line... the minute he turns around and goes back.. it gets too complicated for me. I didn't get to the G word yet in the dictionary. i'm no einstein.
[toc] | [prev] | [next] | [standalone]
| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-03-15 04:16 -0700 |
| Message-ID | <039f8379-d832-4d1e-93df-b971c8465d47@googlegroups.com> |
| In reply to | #412806 |
On Tuesday, March 14, 2017 at 10:50:14 AM UTC-5, tjrob137 wrote:
> On 3/13/17 3/13/17 - 10:33 AM, Jonathan Doolin wrote:
> > On Monday, March 13, 2017 at 9:54:04 AM UTC-5, tjrob137 wrote:
> >> In physics we use the term "event" to mean a single happening at a definite
> >> place and time. So events cannot "move" -- they have zero spatial extent
> >> and zero duration; each event is a single point in the spacetime manifold.
> >>
> >> Apparently you are confused about what "event" means. A simple snap of the
> >> fingers is an event (abstracting it to zero extent and duration). A clock
> >> displaying a specific value of time is an event -- it happens at a definite
> >> place (where the clock is located at that time), and a definite time (as
> >> specified), and has zero duration (the clock is continually ticking [#]).
> >>
> >> [#] We consider a tick to be of zero duration, with ticks being separated
> >> by a time interval that is not part of the tick.
> >
> > I think that you seem to be saying that my argument "sounds absurd" to you.
>
> No. I'm saying that the words you use do not mean what you apparently think they
> mean.
>
> > You're saying events cannot move.
>
> I'm saying that "motion" does not apply to events. The concepts are
> irreconcilable. OBJECTS move, not events (aka points in the manifold).
>
If I am looking straight ahead, and I turn to the left, then all of the objects move to the right, within my view. In the same fashion, if I am looking straight ahead, and I accelerate forward, all of the events that I am seeing, move forward, and into the past in my view.
> > You argue, "Once one has specified a coordinate system {x,y,z,t}, an event
> > has specific values of the coordinates. A SINGLE value of each of the four
> > coordinates."
>
> That is not an "argument", that is part of the definition of what a coordinate
> system is.
>
> > But when an observer accelerates, and changes his perspective from a S
> > coordinate system to an S' coordinate system, of course, he is no longer
> > measuring distance and time in the {x,y,z,t} coordinate system, but in the
> > {x',y',z',t'} coordinate system.
> >
> > Surely you can see that before and after a Lorentz transformation x' for a
> > particular event is not equal to x for the same event. t' for a particular
> > event is not equal to t for the same event.
>
> Sure. This is not "motion", this is simply applying a different coordinate
> system to the same manifold.
>
> > In the view of the accelerating observer, the event has moved forward or
> > backward in space from x to x', and forward or backward in time, from t to
> > t'.
>
> NO. In the view of the accelerating observer, the new coordinates apply rather
> than the old ones. This is not "motion" in any sense of the word.
>
> Analogy: I label my house "Tom's house". When I sell it the new
> owner labels it "Mary's house"; did the house move? -- no.
>
It's not mere relabeling. When one person says "That event happened one second ago and 1 light-second away" and another person, at the same location says "That event happened 10 seconds ago, and 10 light-seconds away" it is not a matter of one labeling it one thing, and another calls it a different thing.
They are seeing the same event, at different locations.
> Coordinate N-tuples (x,y,z,t) and (x',y',z',t') are merely DIFFERENT LABELS FOR
> THE SAME EVENT. Just like the house, re-labeling events is not any sort of "motion".
>
> IOW: the labels (x,y,z,t) and (x',y',z',t') can both apply to a given event.
> Such labels do not imply any sort of "motion".
>
You, (like Dolby and Gull), can label events whatever you want, but that won't prevent their coordinates from changing under a Lorentz Transformation.
>
> > But I realize that you are taking a seemingly conventional position that
> > "events don't move" and I am taking what sounds like an absurd position,
> > that "events DO move with respect to accelerating observers." But I would
> > argue that in fact, the common convention to say "events don't move" is
> > actually incorrect, and the unconventional claim that "events move when you
> > accelerate" is correct, regardless of how absurd that seems to you.
>
> Nope. Your claims contradict the definitions of what these words actually mean.
> This is not a "conventional position", this is merely acknowledging the
> meanings of words.
>
> > I have a working paper that addresses this topic, at
> > https://www.researchgate.net/publication/314235352_Radar_Time_and_Temporal_Facing_A_Distinction_of_Two_Compatible_Ideas
>
> I'll discuss here, but rarely visit webpages. If it reflects the misconceptions
> you display here, visiting it would be useless.
>
> Tom Roberts
[toc] | [prev] | [next] | [standalone]
| From | someone <glenn.spigel@googlemail.com> |
|---|---|
| Date | 2017-03-06 09:34 -0800 |
| Message-ID | <c368b71f-9d98-466c-b357-7e1dc78fc3fc@googlegroups.com> |
| In reply to | #411804 |
On Sunday, March 5, 2017 at 8:31:38 PM UTC, Paul B. Andersen wrote: > On 03.03.2017 16:04, someone wrote: > > The twin paradox is as I understand it that there are twins, > > and one goes off in a spaceship, and as it does from its > > perspective the other twins clock is going slower, > > but from the twin on Earths perspective the twin going > > off in a spaceships clock is going slower. > > But when they come back to meet it cannot be that both clocks were going slower. > > It is then claimed that the one that was on the spaceship will be the one that > > aged for some reason. https://en.wikipedia.org/wiki/Twin_paradox states: > > --- > > Max von Laue argued in 1913 that since the traveling twin must be in two > > separate inertial frames, one on the way out and another on the way back, > > this frame switch is the reason for the aging difference, > > not the acceleration per se.[7] Explanations put forth by Albert Einstein > > and Max Born invoked gravitational time dilation to explain the aging as > > a direct effect of acceleration.[8] > > When both twin's are inertial, mutual time dilation applies > (the other twin ages less). So the travelling twin will > then conclude that home twin is ageing less than herself. > But while the travelling twin is accelerating at turn around, > it will appear to her that the 'home twin's' clock are running fast, > so much so that the home twin ends up older than herself when they > are back. > What is relevant about the turn around? For example imagine there were two sets of twins, one from one set travelled for 1 year, and one from the other set travelled for a thousand years (imagine average lifespan at 10,000 years when this happened) at the same constant velocities. They both decelerate and and accelerate the same at their turn around. Will the identical turnarounds result in a significant difference in the amount the 'home twin's' clock appears to be running? > Note however that there is no practical way the travelling twin > can measure the rate of the home twin's clock, it is a question of > how simultaneity is defined. So when the travelling twin is > accelerating, she will continuously change her opinion of what > is simultaneous (according to the definition in SR) at > the home twin's clock. That's why the home twin's clock for > the travelling twin (according to SR) will appear to run fast > during the acceleration. > But both clocks are running at normal rate all the time. > > The 'twin paradox' is that the travelling twin really _is_ > younger than the home twin when the travelling twin > has returned, it is nothing apparent about that. > The proper time of a clock between two events is a measure > of the 'length' of the path in space-time travelled by the clock. > So the proper time of the home twin is longer than the proper > time of the travelling twin because the lengths of their > paths through space time are different, not because their > clocks are ticking at different rate. > I think the paradox is that they cannot both be younger than each other. The solution to the paradox was that only one had aged. > You can see a simulation of the twin paradox here. > You can see it from both twin's point of view. > Note the strange things that appear to happen from > twin B's point of view when she is accelerating. > But remember that much of it really are artefacts which > follows from the definition of relativity. For example, > twin A is never really travelling faster than c relative > to B, even if it appears so for twin B. > > https://paulba.no/twins.html > > Se also: > https://paulba.no/pdf/TwinsByMetric.pdf > > What could be measured, is the Doppler shift: > https://paulba.no/pdf/TwinsByDoppler.pdf > Thanks for the links. > > > > But wouldn't the amount of ageing be dependent on how far > > the spaceship was travelling at constant velocity once it had reached it, > > Yes. > > > and wouldn't there be hardly any gravitational time dilation at that point > > (assuming it is at a suitable distance away from any objects of significant > > mass and undergoing no proper acceleration)? > > All I have said above is according to SR in flat space-time. > > You can however have 'twin paradox' in Earth's gravitation as well. > A couple of much more realistic scenarios can be seen here: > https://paulba.no/Satellites.html > > scenario: "Twin scenario - kind of" > ---------------------------------- > The green and red clocks are in different > orbits, but are meeting periodically. > The green clock ages 16.6 us more than the red clock > between each time they meet. > > scenario: "Two ballistic rockets" > -------------------------------- > This could be a "triple paradox". > Three clocks (ground clock, red clock, green clock) > are travelling between the same two events. > The red clock ages 1.774 us more than the ground clock > The green clock ages 0.845 us less than the ground clock. > > (The path of the red clock is almost identical to gravity probe A) > If you pause the run when the red clock is at the top, you will > see that the apparent relative rate difference observed from > the ground is ca. 4.25E-10. > Compare that to fig 3 in this: > https://paulba.no/paper/Vessot.pdf > thanks for the links again. > > > > Also what difference is it supposed to make to the relevant ageing whether > > the ship turns back or not? > > There is no "twin paradox" if the twins don't meet again. > There is in the sense that they cannot both be ageing more than the other. I have assumed that no one is suggesting that any ageing the twin undergoes on the outward journey is dependent on whether the ship is going to turn around or not. > > Lastly supposing the twin in the spaceship had taken off from some giant > > Death Star type structure, and had been in some unconscious in some sleep > > inducing machine at takeoff until a day before the spaceship was to turn around. > > And that an hour after the twin awakes it passes another spaceship with a person > > on board which had also just awaken. Their ships would pass, and if neither knew > > what their ship's program was, neither would be able to tell who was moving. > > But imagine that the second ship was at rest with the Death Star structure. > > So both could be thinking that the other's clock was running slower than its own, > > if they thought it was all relative, but wouldn't the one in the ship at rest with > > the Death Star be wrong (the clock on the ship that had left earth was going slower > > relative to any clock in the Death Star's restframe)? > > > > What's the point with this nonsense? > I have no idea of what a "Death Star" might be. > Never mind, I had assumed that you had seen the first Star Wars movie. Just substitute the "Death Star" as a small planet sized spaceship. I perhaps should have made the point to that clearer. The point was regarding mutual time dilation. To do that I embedded another scenario into the twin paradox. The embedded scenario was the twin in the spaceship passing or being passed by another spaceship (for all the twin, or the person in the other spaceship knows). In such a scenario it is often stated that they are undergoing mutual time dilation, and that it is relative, but here seeing the wider context (of the twin paradox). There often is no distinction between whether the observations of time dilation would be mutual, and whether actual time dilation would be mutual. In this scenario though, presumably they would both observe the clock on the other ship to appear to be going slower than their own, thus mutually observed time dilation. Though as I currently understand it, despite perhaps their belief that any time dilation was mutual as observed, the actual time dilation wasn't. I mean that in the sense that if there had been a series of space ships at rest with the Earth along the outward journey each synched with the one on Earth, and the twin stopped at any one, it would observe that its clock had ticked less times than theirs since the launch. They cannot say the same so it wasn't mutual. This could include a silly misunderstanding on my part, so thanks for participating on the forum, helping those that aren't as conversant with the theories as yourself. > -- > Paul > > https://paulba.no/
[toc] | [prev] | [next] | [standalone]
| From | "Paul B. Andersen" <relativity@paulba.no> |
|---|---|
| Date | 2017-03-06 23:01 +0100 |
| Message-ID | <o9km6t$trt$1@news.albasani.net> |
| In reply to | #411919 |
On 06.03.2017 18:34, someone wrote: > On Sunday, March 5, 2017 at 8:31:38 PM UTC, Paul B. Andersen wrote: >> On 03.03.2017 16:04, someone wrote: >>> The twin paradox is as I understand it that there are twins, >>> and one goes off in a spaceship, and as it does from its >>> perspective the other twins clock is going slower, >>> but from the twin on Earths perspective the twin going >>> off in a spaceships clock is going slower. >>> But when they come back to meet it cannot be that both clocks were going slower. >>> It is then claimed that the one that was on the spaceship will be the one that >>> aged for some reason. https://en.wikipedia.org/wiki/Twin_paradox states: >>> --- >>> Max von Laue argued in 1913 that since the traveling twin must be in two >>> separate inertial frames, one on the way out and another on the way back, >>> this frame switch is the reason for the aging difference, >>> not the acceleration per se.[7] Explanations put forth by Albert Einstein >>> and Max Born invoked gravitational time dilation to explain the aging as >>> a direct effect of acceleration.[8] >> >> When both twin's are inertial, mutual time dilation applies >> (the other twin ages less). So the travelling twin will >> then conclude that home twin is ageing less than herself. >> But while the travelling twin is accelerating at turn around, >> it will appear to her that the 'home twin's' clock are running fast, >> so much so that the home twin ends up older than herself when they >> are back. >> > > What is relevant about the turn around? For example imagine > there were two sets of twins, one from one set travelled for 1 year, > and one from the other set travelled for a thousand years > (imagine average lifespan at 10,000 years when this happened) > at the same constant velocities. They both decelerate and and accelerate > the same at their turn around. Will the identical turnarounds result in > a significant difference in the amount the 'home twin's' clock appears to be running? Yes indeed. In the simplest scenario, when the turnaround is done with an infinite high acceleration for zero time. (See 2.2. in https://paulba.no/pdf/TwinsByMetric.pdf ) we have: T_B = T_A sqrt(1-v^2/c^2) where T_A is the proper time of the home twin A, and T_B is the proper time of the travelling twin B. Let's for simplicity set v = 0.866c so sqrt(1-v^2/c^2) = 0.5. If B travelled for 1 year as measured by A, T_A = 1 year and T_B = 0.5 year. If B travelled for 1000 years, then T_A = 1000 years and T_B = 500 years. So even if the acceleration is the same, the different travelled times will indeed result in different travelled times. Rather obvious, if you think about it, isn't it? :-) But let's see it from B's point of view: Immediately before B turns around her clock will show 0.25 year, and according to SR A will simultaneously show 0.125 year (why?). Immediately after B turned around her clock will still show 0.25 years and according to SR A will simultaneously show 0.825 year. So when B abruptly turns around it will appear to her that clock A jumps 0.75 years forward in time. But both clocks always run at proper rate, and no clock jumps in time. There is no practical way B can measure what clock A simultaneously shows. But she can use SR to calculate it, using the definition of simultaneity. The apparent jump of A's clock is a consequence of the definition of simultaneity, B suddenly changes her mind about what is simultaneous at A. In the more realistic case when the acceleration is limited a, clock A will not from B's point of view appear to jump in time, but to run very fast while B is accelerating. At the moment when B is stationary to A at a distance d, clock A will appear to run at the rate (1 + ad/c^2) (Note that this equation is the same as the approximated gravitational time dilation when h << R : (1 + gh/c^2) ) See: https://paulba.no/twins.html > >> Note however that there is no practical way the travelling twin >> can measure the rate of the home twin's clock, it is a question of >> how simultaneity is defined. So when the travelling twin is >> accelerating, she will continuously change her opinion of what >> is simultaneous (according to the definition in SR) at >> the home twin's clock. That's why the home twin's clock for >> the travelling twin (according to SR) will appear to run fast >> during the acceleration. >> But both clocks are running at normal rate all the time. >> >> The 'twin paradox' is that the travelling twin really _is_ >> younger than the home twin when the travelling twin >> has returned, it is nothing apparent about that. >> The proper time of a clock between two events is a measure >> of the 'length' of the path in space-time travelled by the clock. >> So the proper time of the home twin is longer than the proper >> time of the travelling twin because the lengths of their >> paths through space time are different, not because their >> clocks are ticking at different rate. >> > > I think the paradox is that they cannot both be younger > than each other. The solution to the paradox was that only one had aged. There is no paradox. But the apparent paradox in the phrase "twin paradox" is that the travelling twin really is younger, because this seems impossible. > >> You can see a simulation of the twin paradox here. >> You can see it from both twin's point of view. >> Note the strange things that appear to happen from >> twin B's point of view when she is accelerating. >> But remember that much of it really are artefacts which >> follows from the definition of relativity. For example, >> twin A is never really travelling faster than c relative >> to B, even if it appears so for twin B. >> >> https://paulba.no/twins.html >> >> Se also: >> https://paulba.no/pdf/TwinsByMetric.pdf >> >> What could be measured, is the Doppler shift: >> https://paulba.no/pdf/TwinsByDoppler.pdf >> > > Thanks for the links. > >>> >>> But wouldn't the amount of ageing be dependent on how far >>> the spaceship was travelling at constant velocity once it had reached it, >> >> Yes. >> >>> and wouldn't there be hardly any gravitational time dilation at that point >>> (assuming it is at a suitable distance away from any objects of significant >>> mass and undergoing no proper acceleration)? >> >> All I have said above is according to SR in flat space-time. >> >> You can however have 'twin paradox' in Earth's gravitation as well. >> A couple of much more realistic scenarios can be seen here: >> https://paulba.no/Satellites.html >> >> scenario: "Twin scenario - kind of" >> ---------------------------------- >> The green and red clocks are in different >> orbits, but are meeting periodically. >> The green clock ages 16.6 us more than the red clock >> between each time they meet. >> >> scenario: "Two ballistic rockets" >> -------------------------------- >> This could be a "triple paradox". >> Three clocks (ground clock, red clock, green clock) >> are travelling between the same two events. >> The red clock ages 1.774 us more than the ground clock >> The green clock ages 0.845 us less than the ground clock. >> >> (The path of the red clock is almost identical to gravity probe A) >> If you pause the run when the red clock is at the top, you will >> see that the apparent relative rate difference observed from >> the ground is ca. 4.25E-10. >> Compare that to fig 3 in this: >> https://paulba.no/paper/Vessot.pdf >> > > thanks for the links again. > >>> >>> Also what difference is it supposed to make to the relevant ageing whether >>> the ship turns back or not? >> >> There is no "twin paradox" if the twins don't meet again. >> > > There is in the sense that they cannot both be ageing more than the other. But this is irrelevant becuse the apparent paradox is not that both is ageing less than the other, they are not! > I have assumed that no one is suggesting that any ageing the twin undergoes > on the outward journey is dependent on whether the ship is going to turn around or not. Look: The 'twin paradox' is that the twins seperate and meet again, and have experienced different proper times when they are co-located and compare their clocks. That's the only way the different ageing can be measured in an objective way, not depending on points of view. Any comparison of the ageing when they are not colocated is apparent, it is different projections in different frames of references. > >>> Lastly supposing the twin in the spaceship had taken off from some giant >>> Death Star type structure, and had been in some unconscious in some sleep >>> inducing machine at takeoff until a day before the spaceship was to turn around. >>> And that an hour after the twin awakes it passes another spaceship with a person >>> on board which had also just awaken. Their ships would pass, and if neither knew >>> what their ship's program was, neither would be able to tell who was moving. >>> But imagine that the second ship was at rest with the Death Star structure. >>> So both could be thinking that the other's clock was running slower than its own, >>> if they thought it was all relative, but wouldn't the one in the ship at rest with >>> the Death Star be wrong (the clock on the ship that had left earth was going slower >>> relative to any clock in the Death Star's restframe)? >>> >> >> What's the point with this nonsense? >> I have no idea of what a "Death Star" might be. >> > > Never mind, I had assumed that you had seen the first Star Wars movie. > Just substitute the "Death Star" as a small planet sized spaceship. > > I perhaps should have made the point to that clearer. > The point was regarding mutual time dilation. > To do that I embedded another scenario into the twin paradox. You seem obsessed with the mutual time dilation. It is irrelevant to the 'twin paradox'. > The embedded scenario was the twin in the spaceship passing > or being passed by another spaceship (for all the twin, or > the person in the other spaceship knows). Sure. When two clocks pass each other, and each of them measure the apparent rate of the other clocks as I now have explained several times, there is 'mutual time dilation'. Even if there is a gravitational field, there is _locally_ mutual time dilation when they pass each other. But mutual time dilation is only different projections of the proper time of a clock into different frames of reference. For the last time: The apparent rate of a clock will be different when measured in different frames of references. It is a frame dependent entity which has no objective value which everybody will agree about. But the proper time of a clock between two events is invariant, it is an objective value which everybody will agree about. The twin paradox is that the proper times of two clocks between _the same two events_ may be different. Any comparison of the rate and readings of the clocks when they are not co-located is frame dependent, and can have an infinite number of different results. > In such a scenario it is often stated that they are undergoing > mutual time dilation, and that it is relative, but here seeing > the wider context (of the twin paradox). > There often is no distinction between whether the observations > of time dilation would be mutual, and whether actual time dilation > would be mutual. In this scenario though, presumably they would both > observe the clock on the other ship to appear to be going slower > than their own, thus mutually observed time dilation. > Though as I currently understand it, despite perhaps their belief > that any time dilation was mutual as observed, the actual time dilation wasn't. > I mean that in the sense that if there had been a series of space ships at rest > with the Earth along the outward journey each synched with the one on Earth, > and the twin stopped at any one, it would observe that its clock had ticked > less times than theirs since the launch. They cannot say the same so it wasn't mutual. > > This could include a silly misunderstanding on my part, so thanks for participating on the forum, helping those that aren't as conversant with the theories as yourself. > >> -- >> Paul >> >> https://paulba.no/ > -- Paul https://paulba.no/
[toc] | [prev] | [next] | [standalone]
| From | alsor@interia.pl |
|---|---|
| Date | 2017-03-06 15:09 -0800 |
| Message-ID | <13fb30d5-fcf1-40cd-bf97-d94bdf870e3f@googlegroups.com> |
| In reply to | #411955 |
W dniu poniedziałek, 6 marca 2017 23:01:03 UTC+1 użytkownik Paul B. Andersen > Any comparison of the rate and readings of the clocks when > they are not co-located is frame dependent, and can have > an infinite number of different results. Sorry babe, but in the reality you just must compare and permanently. See the GPS: there are plenty of distant clocks, and the system still works good, unfortunately to your stupid claims.
[toc] | [prev] | [next] | [standalone]
| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-03-07 09:49 -0800 |
| Message-ID | <352a5e96-b9af-4c40-8abb-7bd24d31ddc3@googlegroups.com> |
| In reply to | #411955 |
On Monday, March 6, 2017 at 4:01:03 PM UTC-6, Paul B. Andersen wrote: > On 06.03.2017 18:34, someone wrote: > > On Sunday, March 5, 2017 at 8:31:38 PM UTC, Paul B. Andersen wrote: > >> On 03.03.2017 16:04, someone wrote: > >>> The twin paradox is as I understand it that there are twins, > >>> and one goes off in a spaceship, and as it does from its > >>> perspective the other twins clock is going slower, > >>> but from the twin on Earths perspective the twin going > >>> off in a spaceships clock is going slower. > >>> But when they come back to meet it cannot be that both clocks were going slower. > >>> It is then claimed that the one that was on the spaceship will be the one that > >>> aged for some reason. https://en.wikipedia.org/wiki/Twin_paradox states: > >>> --- > >>> Max von Laue argued in 1913 that since the traveling twin must be in two > >>> separate inertial frames, one on the way out and another on the way back, > >>> this frame switch is the reason for the aging difference, > >>> not the acceleration per se.[7] Explanations put forth by Albert Einstein > >>> and Max Born invoked gravitational time dilation to explain the aging as > >>> a direct effect of acceleration.[8] > >> > >> When both twin's are inertial, mutual time dilation applies > >> (the other twin ages less). So the travelling twin will > >> then conclude that home twin is ageing less than herself. > >> But while the travelling twin is accelerating at turn around, > >> it will appear to her that the 'home twin's' clock are running fast, > >> so much so that the home twin ends up older than herself when they > >> are back. > >> > > > > What is relevant about the turn around? For example imagine > > there were two sets of twins, one from one set travelled for 1 year, > > and one from the other set travelled for a thousand years > > (imagine average lifespan at 10,000 years when this happened) > > at the same constant velocities. They both decelerate and and accelerate > > the same at their turn around. Will the identical turnarounds result in > > a significant difference in the amount the 'home twin's' clock appears to be running? > > Yes indeed. > In the simplest scenario, when the turnaround is done with > an infinite high acceleration for zero time. > (See 2.2. in https://paulba.no/pdf/TwinsByMetric.pdf ) > we have: > T_B = T_A sqrt(1-v^2/c^2) > where T_A is the proper time of the home twin A, > and T_B is the proper time of the travelling twin B. > > Let's for simplicity set v = 0.866c so sqrt(1-v^2/c^2) = 0.5. > > If B travelled for 1 year as measured by A, > T_A = 1 year and T_B = 0.5 year. > If B travelled for 1000 years, then > T_A = 1000 years and T_B = 500 years. > > So even if the acceleration is the same, the different > travelled times will indeed result in different travelled times. > Rather obvious, if you think about it, isn't it? :-) > > But let's see it from B's point of view: > Immediately before B turns around her clock will show 0.25 year, > and according to SR A will simultaneously show 0.125 year (why?). > Immediately after B turned around her clock will still show 0.25 years > and according to SR A will simultaneously show 0.825 year. > So when B abruptly turns around it will appear to her that clock > A jumps 0.75 years forward in time. > > But both clocks always run at proper rate, and no clock jumps in time. > There is no practical way B can measure what clock A simultaneously > shows. But she can use SR to calculate it, using the definition of > simultaneity. The apparent jump of A's clock is a consequence of > the definition of simultaneity, B suddenly changes her mind about > what is simultaneous at A. > > In the more realistic case when the acceleration is limited a, > clock A will not from B's point of view appear to jump in time, > but to run very fast while B is accelerating. > At the moment when B is stationary to A at a distance d, > clock A will appear to run at the rate (1 + ad/c^2) > So the short answer... If d1 is 1 light year, and d2 is 1000 light-years, and the traveling twin accelerates at 1 light-year per year^2. Then the rate of the clock at distance d1 is 1+(1*1)/1^2 = 2, and the rate of the clock at distance d2 is 1+(1*1000)/1^2 = 1001. I might want to check this, for whether it's exactly the same formula, but I think, this is essentially what goes on in the Rindler coordinate system. The further you get from the Rindler horizon, the faster time goes. If you look toward the Rindler horizon, and beyond it, the rate of clocks in that region is negative. (Going backwards) In the case of instantaneous acceleration, you're at the rindler horizon. Here, in this image the acceleration appears essentially instantaneous at this scale--so the rindler horizon is approximately zero-to-one pixel away from the acceleration event. https://upload.wikimedia.org/wikipedia/commons/c/ce/Twin_Paradox_Minkowski_Diagram.svg ...the speed of time is essentially proportional to the distance that the red line is above the blue line. To the left,(the direction the traveling twin is traveling toward) the time is going forward. To the right, (the direction that the traveling twin is accelerating away from) the time is going backwards. In any case, the aging that you are looking at is the time passed "during the twin's acceleration" and by "during" you mean "simultaneous from the point-of-view of the traveling twin" But if you constrained yourself to "the events that I literally see during my acceleration, with my eyes, without doing any calculations" you would not see any objects aging backwards, or suddenly jumping forward in age. But you would see them shift, so the objects you're accelerating toward would stretch out away from you, and the distance to objects behind you would appear to contract, and loom dark and redshifted behind you. And the objects to your right and left would swing forward. > (Note that this equation is the same as the approximated > gravitational time dilation when h << R : (1 + gh/c^2) ) > > See: > https://paulba.no/twins.html > > > > >> Note however that there is no practical way the travelling twin > >> can measure the rate of the home twin's clock, it is a question of > >> how simultaneity is defined. So when the travelling twin is > >> accelerating, she will continuously change her opinion of what > >> is simultaneous (according to the definition in SR) at > >> the home twin's clock. That's why the home twin's clock for > >> the travelling twin (according to SR) will appear to run fast > >> during the acceleration. > >> But both clocks are running at normal rate all the time. > >> > >> The 'twin paradox' is that the travelling twin really _is_ > >> younger than the home twin when the travelling twin > >> has returned, it is nothing apparent about that. > >> The proper time of a clock between two events is a measure > >> of the 'length' of the path in space-time travelled by the clock. > >> So the proper time of the home twin is longer than the proper > >> time of the travelling twin because the lengths of their > >> paths through space time are different, not because their > >> clocks are ticking at different rate. > >> > > > > I think the paradox is that they cannot both be younger > > than each other. The solution to the paradox was that only one had aged. > > There is no paradox. > But the apparent paradox in the phrase "twin paradox" > is that the travelling twin really is younger, > because this seems impossible. > > > > >> You can see a simulation of the twin paradox here. > >> You can see it from both twin's point of view. > >> Note the strange things that appear to happen from > >> twin B's point of view when she is accelerating. > >> But remember that much of it really are artefacts which > >> follows from the definition of relativity. For example, > >> twin A is never really travelling faster than c relative > >> to B, even if it appears so for twin B. > >> > >> https://paulba.no/twins.html > >> > >> Se also: > >> https://paulba.no/pdf/TwinsByMetric.pdf > >> > >> What could be measured, is the Doppler shift: > >> https://paulba.no/pdf/TwinsByDoppler.pdf > >> > > > > Thanks for the links. > > > >>> > >>> But wouldn't the amount of ageing be dependent on how far > >>> the spaceship was travelling at constant velocity once it had reached it, > >> > >> Yes. > >> > >>> and wouldn't there be hardly any gravitational time dilation at that point > >>> (assuming it is at a suitable distance away from any objects of significant > >>> mass and undergoing no proper acceleration)? > >> > >> All I have said above is according to SR in flat space-time. > >> > >> You can however have 'twin paradox' in Earth's gravitation as well. > >> A couple of much more realistic scenarios can be seen here: > >> https://paulba.no/Satellites.html > >> > >> scenario: "Twin scenario - kind of" > >> ---------------------------------- > >> The green and red clocks are in different > >> orbits, but are meeting periodically. > >> The green clock ages 16.6 us more than the red clock > >> between each time they meet. > >> > >> scenario: "Two ballistic rockets" > >> -------------------------------- > >> This could be a "triple paradox". > >> Three clocks (ground clock, red clock, green clock) > >> are travelling between the same two events. > >> The red clock ages 1.774 us more than the ground clock > >> The green clock ages 0.845 us less than the ground clock. > >> > >> (The path of the red clock is almost identical to gravity probe A) > >> If you pause the run when the red clock is at the top, you will > >> see that the apparent relative rate difference observed from > >> the ground is ca. 4.25E-10. > >> Compare that to fig 3 in this: > >> https://paulba.no/paper/Vessot.pdf > >> > > > > thanks for the links again. > > > >>> > >>> Also what difference is it supposed to make to the relevant ageing whether > >>> the ship turns back or not? > >> > >> There is no "twin paradox" if the twins don't meet again. > >> > > > > There is in the sense that they cannot both be ageing more than the other. > > But this is irrelevant becuse the apparent paradox is not > that both is ageing less than the other, they are not! > > > I have assumed that no one is suggesting that any ageing the twin undergoes > > on the outward journey is dependent on whether the ship is going to turn around or not. > > Look: > The 'twin paradox' is that the twins seperate and meet again, > and have experienced different proper times when they are > co-located and compare their clocks. > That's the only way the different ageing can be measured > in an objective way, not depending on points of view. > > Any comparison of the ageing when they are not colocated > is apparent, it is different projections in different frames > of references. > > > > > >>> Lastly supposing the twin in the spaceship had taken off from some giant > >>> Death Star type structure, and had been in some unconscious in some sleep > >>> inducing machine at takeoff until a day before the spaceship was to turn around. > >>> And that an hour after the twin awakes it passes another spaceship with a person > >>> on board which had also just awaken. Their ships would pass, and if neither knew > >>> what their ship's program was, neither would be able to tell who was moving. > >>> But imagine that the second ship was at rest with the Death Star structure. > >>> So both could be thinking that the other's clock was running slower than its own, > >>> if they thought it was all relative, but wouldn't the one in the ship at rest with > >>> the Death Star be wrong (the clock on the ship that had left earth was going slower > >>> relative to any clock in the Death Star's restframe)? > >>> > >> > >> What's the point with this nonsense? > >> I have no idea of what a "Death Star" might be. > >> > > > > Never mind, I had assumed that you had seen the first Star Wars movie. > > Just substitute the "Death Star" as a small planet sized spaceship. > > > > I perhaps should have made the point to that clearer. > > The point was regarding mutual time dilation. > > To do that I embedded another scenario into the twin paradox. > > You seem obsessed with the mutual time dilation. > It is irrelevant to the 'twin paradox'. > > > The embedded scenario was the twin in the spaceship passing > > or being passed by another spaceship (for all the twin, or > > the person in the other spaceship knows). > > Sure. When two clocks pass each other, and each of them > measure the apparent rate of the other clocks as I now > have explained several times, there is 'mutual time dilation'. > Even if there is a gravitational field, there is _locally_ > mutual time dilation when they pass each other. > But mutual time dilation is only different projections > of the proper time of a clock into different frames of reference. > > For the last time: > The apparent rate of a clock will be different when measured > in different frames of references. It is a frame dependent > entity which has no objective value which everybody will agree > about. > > But the proper time of a clock between two events is invariant, > it is an objective value which everybody will agree about. > The twin paradox is that the proper times of two clocks between > _the same two events_ may be different. > > Any comparison of the rate and readings of the clocks when > they are not co-located is frame dependent, and can have > an infinite number of different results. > > > > In such a scenario it is often stated that they are undergoing > > mutual time dilation, and that it is relative, but here seeing > > the wider context (of the twin paradox). > > There often is no distinction between whether the observations > > of time dilation would be mutual, and whether actual time dilation > > would be mutual. In this scenario though, presumably they would both > > observe the clock on the other ship to appear to be going slower > > than their own, thus mutually observed time dilation. > > Though as I currently understand it, despite perhaps their belief > > that any time dilation was mutual as observed, the actual time dilation wasn't. > > I mean that in the sense that if there had been a series of space ships at rest > > with the Earth along the outward journey each synched with the one on Earth, > > and the twin stopped at any one, it would observe that its clock had ticked > > less times than theirs since the launch. They cannot say the same so it wasn't mutual. > > > > This could include a silly misunderstanding on my part, so thanks for participating on the forum, helping those that aren't as conversant with the theories as yourself. > > > >> -- > >> Paul > >> > >> https://paulba.no/ > > > > > -- > Paul > > https://paulba.no/
[toc] | [prev] | [next] | [standalone]
| From | someone <glenn.spigel@googlemail.com> |
|---|---|
| Date | 2017-03-07 14:04 -0800 |
| Message-ID | <b8359dff-1c43-4f13-b130-5447d610b5cf@googlegroups.com> |
| In reply to | #411955 |
On Monday, March 6, 2017 at 10:01:03 PM UTC, Paul B. Andersen wrote: > On 06.03.2017 18:34, someone wrote: > > On Sunday, March 5, 2017 at 8:31:38 PM UTC, Paul B. Andersen wrote: > >> On 03.03.2017 16:04, someone wrote: > >>> The twin paradox is as I understand it that there are twins, > >>> and one goes off in a spaceship, and as it does from its > >>> perspective the other twins clock is going slower, > >>> but from the twin on Earths perspective the twin going > >>> off in a spaceships clock is going slower. > >>> But when they come back to meet it cannot be that both clocks were going slower. > >>> It is then claimed that the one that was on the spaceship will be the one that > >>> aged for some reason. https://en.wikipedia.org/wiki/Twin_paradox states: > >>> --- > >>> Max von Laue argued in 1913 that since the traveling twin must be in two > >>> separate inertial frames, one on the way out and another on the way back, > >>> this frame switch is the reason for the aging difference, > >>> not the acceleration per se.[7] Explanations put forth by Albert Einstein > >>> and Max Born invoked gravitational time dilation to explain the aging as > >>> a direct effect of acceleration.[8] > >> > >> When both twin's are inertial, mutual time dilation applies > >> (the other twin ages less). So the travelling twin will > >> then conclude that home twin is ageing less than herself. > >> But while the travelling twin is accelerating at turn around, > >> it will appear to her that the 'home twin's' clock are running fast, > >> so much so that the home twin ends up older than herself when they > >> are back. > >> > > > > What is relevant about the turn around? For example imagine > > there were two sets of twins, one from one set travelled for 1 year, > > and one from the other set travelled for a thousand years > > (imagine average lifespan at 10,000 years when this happened) > > at the same constant velocities. They both decelerate and and accelerate > > the same at their turn around. Will the identical turnarounds result in > > a significant difference in the amount the 'home twin's' clock appears to be running? > > Yes indeed. > In the simplest scenario, when the turnaround is done with > an infinite high acceleration for zero time. > (See 2.2. in https://paulba.no/pdf/TwinsByMetric.pdf ) > we have: > T_B = T_A sqrt(1-v^2/c^2) > where T_A is the proper time of the home twin A, > and T_B is the proper time of the travelling twin B. > > Let's for simplicity set v = 0.866c so sqrt(1-v^2/c^2) = 0.5. > > If B travelled for 1 year as measured by A, > T_A = 1 year and T_B = 0.5 year. > If B travelled for 1000 years, then > T_A = 1000 years and T_B = 500 years. > > So even if the acceleration is the same, the different > travelled times will indeed result in different travelled times. > Rather obvious, if you think about it, isn't it? :-) > > But let's see it from B's point of view: > Immediately before B turns around her clock will show 0.25 year, > and according to SR A will simultaneously show 0.125 year (why?). > Immediately after B turned around her clock will still show 0.25 years > and according to SR A will simultaneously show 0.825 year. > So when B abruptly turns around it will appear to her that clock > A jumps 0.75 years forward in time. > > But both clocks always run at proper rate, and no clock jumps in time. > There is no practical way B can measure what clock A simultaneously > shows. But she can use SR to calculate it, using the definition of > simultaneity. The apparent jump of A's clock is a consequence of > the definition of simultaneity, B suddenly changes her mind about > what is simultaneous at A. > > In the more realistic case when the acceleration is limited a, > clock A will not from B's point of view appear to jump in time, > but to run very fast while B is accelerating. > At the moment when B is stationary to A at a distance d, > clock A will appear to run at the rate (1 + ad/c^2) > > (Note that this equation is the same as the approximated > gravitational time dilation when h << R : (1 + gh/c^2) ) > > See: > https://paulba.no/twins.html > > > > >> Note however that there is no practical way the travelling twin > >> can measure the rate of the home twin's clock, it is a question of > >> how simultaneity is defined. So when the travelling twin is > >> accelerating, she will continuously change her opinion of what > >> is simultaneous (according to the definition in SR) at > >> the home twin's clock. That's why the home twin's clock for > >> the travelling twin (according to SR) will appear to run fast > >> during the acceleration. > >> But both clocks are running at normal rate all the time. > >> > >> The 'twin paradox' is that the travelling twin really _is_ > >> younger than the home twin when the travelling twin > >> has returned, it is nothing apparent about that. > >> The proper time of a clock between two events is a measure > >> of the 'length' of the path in space-time travelled by the clock. > >> So the proper time of the home twin is longer than the proper > >> time of the travelling twin because the lengths of their > >> paths through space time are different, not because their > >> clocks are ticking at different rate. > >> > > > > I think the paradox is that they cannot both be younger > > than each other. The solution to the paradox was that only one had aged. > > There is no paradox. > But the apparent paradox in the phrase "twin paradox" > is that the travelling twin really is younger, > because this seems impossible. > > > > >> You can see a simulation of the twin paradox here. > >> You can see it from both twin's point of view. > >> Note the strange things that appear to happen from > >> twin B's point of view when she is accelerating. > >> But remember that much of it really are artefacts which > >> follows from the definition of relativity. For example, > >> twin A is never really travelling faster than c relative > >> to B, even if it appears so for twin B. > >> > >> https://paulba.no/twins.html > >> > >> Se also: > >> https://paulba.no/pdf/TwinsByMetric.pdf > >> > >> What could be measured, is the Doppler shift: > >> https://paulba.no/pdf/TwinsByDoppler.pdf > >> > > > > Thanks for the links. > > > >>> > >>> But wouldn't the amount of ageing be dependent on how far > >>> the spaceship was travelling at constant velocity once it had reached it, > >> > >> Yes. > >> > >>> and wouldn't there be hardly any gravitational time dilation at that point > >>> (assuming it is at a suitable distance away from any objects of significant > >>> mass and undergoing no proper acceleration)? > >> > >> All I have said above is according to SR in flat space-time. > >> > >> You can however have 'twin paradox' in Earth's gravitation as well. > >> A couple of much more realistic scenarios can be seen here: > >> https://paulba.no/Satellites.html > >> > >> scenario: "Twin scenario - kind of" > >> ---------------------------------- > >> The green and red clocks are in different > >> orbits, but are meeting periodically. > >> The green clock ages 16.6 us more than the red clock > >> between each time they meet. > >> > >> scenario: "Two ballistic rockets" > >> -------------------------------- > >> This could be a "triple paradox". > >> Three clocks (ground clock, red clock, green clock) > >> are travelling between the same two events. > >> The red clock ages 1.774 us more than the ground clock > >> The green clock ages 0.845 us less than the ground clock. > >> > >> (The path of the red clock is almost identical to gravity probe A) > >> If you pause the run when the red clock is at the top, you will > >> see that the apparent relative rate difference observed from > >> the ground is ca. 4.25E-10. > >> Compare that to fig 3 in this: > >> https://paulba.no/paper/Vessot.pdf > >> > > > > thanks for the links again. > > > >>> > >>> Also what difference is it supposed to make to the relevant ageing whether > >>> the ship turns back or not? > >> > >> There is no "twin paradox" if the twins don't meet again. > >> > > > > There is in the sense that they cannot both be ageing more than the other. > > But this is irrelevant becuse the apparent paradox is not > that both is ageing less than the other, they are not! > What would be paradoxical about that? I can see no contradiction in one being younger than the other. Which is why I thought the idea was that with Relativity, inertial frame motion is relative. So if either frame could be considered to be an inertial frame, then their should be symmetry, and they should both be younger than each other which does involve a contradiction, thus a paradox. Which is why I thought the solution to the paradox (or rather the answer as to why it was not a paradox) was that they aren't both inertial frames as there is acceleration in one, and so it is not symmetrical. > > I have assumed that no one is suggesting that any ageing the twin undergoes > > on the outward journey is dependent on whether the ship is going to turn around or not. > > Look: > The 'twin paradox' is that the twins seperate and meet again, > and have experienced different proper times when they are > co-located and compare their clocks. > That's the only way the different ageing can be measured > in an objective way, not depending on points of view. > Yes I understood that, but that does not contradict what I wrote. Imagine that the experiment was done and the twin in the spaceship was found to have aged less. You presumably are not suggesting that it wasn't ageing slower on the outward journey, or that the slower ageing on the outward journey was dependent on whether the ship turned around. > Any comparison of the ageing when they are not colocated > is apparent, it is different projections in different frames > of references. > > > > > >>> Lastly supposing the twin in the spaceship had taken off from some giant > >>> Death Star type structure, and had been in some unconscious in some sleep > >>> inducing machine at takeoff until a day before the spaceship was to turn around. > >>> And that an hour after the twin awakes it passes another spaceship with a person > >>> on board which had also just awaken. Their ships would pass, and if neither knew > >>> what their ship's program was, neither would be able to tell who was moving. > >>> But imagine that the second ship was at rest with the Death Star structure. > >>> So both could be thinking that the other's clock was running slower than its own, > >>> if they thought it was all relative, but wouldn't the one in the ship at rest with > >>> the Death Star be wrong (the clock on the ship that had left earth was going slower > >>> relative to any clock in the Death Star's restframe)? > >>> > >> > >> What's the point with this nonsense? > >> I have no idea of what a "Death Star" might be. > >> > > > > Never mind, I had assumed that you had seen the first Star Wars movie. > > Just substitute the "Death Star" as a small planet sized spaceship. > > > > I perhaps should have made the point to that clearer. > > The point was regarding mutual time dilation. > > To do that I embedded another scenario into the twin paradox. > > You seem obsessed with the mutual time dilation. > It is irrelevant to the 'twin paradox'. > I think they are linked. From https://www.thoughtco.com/twin-paradox-real-time-travel-2699432, I have added capital letters in brackets to annotate the text. --- The twin paradox is a thought experiment that demonstrates the curious manifestation of time dilation in modern physics, as it was introduced by Albert Einstein through the theory of relativity. Answer: Consider two twins, named Biff and Cliff. On their twentieth birthday, Biff decides to get in a spaceship and take off into outer space, traveling at nearly the speed of light. He journeys around the cosmos at this speed for about 5 years, returning to the Earth when he is 25 years old. Cliff, on the other hand, remains on the Earth. When Biff returns, it turns out that Cliff is 95 years old. WHAT HAPPENED? According to relativity, two frames of reference that move differently from each other experience time differently, a process known as time dilation. Because Biff was moving so rapidly, time was in effect moving slower for him. This can be calculated precisely using Lorentz transformations, which are a standard part of relativity. TWIN PARADOX ONE The first twin paradox isn't really a scientific paradox, but a logical one: How old is Biff? Biff has experienced 25 years of life, but he was also born the same moment as Cliff, which was 90 years ago. So is he 25 years old or 90 years old? In this case, the answer is "both" ... depending on which way you're measuring age. According to his driver's license, which measures Earth time (and is no doubt expired), he's 90. According to his body, he's 25. Neither age is "right" or "wrong," although the social security administration might take exception if he tries to claim benefits. TWIN PARADOX TWO The second paradox is a bit more technical, and really comes to the heart of what physicists mean when they talk about relativity. The entire scenario is based on the idea that Biff was traveling very fast, so time slowed down for him. The problem is that in relativity, only the relative motion is involved. So what if you considered things from Biff's point of view, then he stayed stationary the whole time, and it was Cliff who was moving away at rapid speeds. Shouldn't calculations performed in this way mean that Cliff is the one who ages more slowly? Doesn't relativity imply that these situations are symmetrical [AS IS SUPPOSED WITH MUTUAL TIME DILATION]? Now, if Biff and Cliff were on spaceships traveling at constant speeds in opposite directions [THEY WOULD EXPERIENCE MUTUAL TIME DILATION], this argument would be perfectly true. The rules of special relativity, which govern constant speed (inertial) frames of reference, indicate that only the relative motion between the two is what matters. In fact, if you're moving at a constant speed, there's not even an experiment that you can perform within your frame of reference which would distinguish you from being at rest. (Even if you looked outside the ship and compared yourself to some other constant frame of reference, you could only determine that one of you is moving, but not which one.) But there's one very important distinction here: Biff is accelerating during this process. --- > > The embedded scenario was the twin in the spaceship passing > > or being passed by another spaceship (for all the twin, or > > the person in the other spaceship knows). > > Sure. When two clocks pass each other, and each of them > measure the apparent rate of the other clocks as I now > have explained several times, there is 'mutual time dilation'. > Even if there is a gravitational field, there is _locally_ > mutual time dilation when they pass each other. > But mutual time dilation is only different projections > of the proper time of a clock into different frames of reference. > > For the last time: > The apparent rate of a clock will be different when measured > in different frames of references. It is a frame dependent > entity which has no objective value which everybody will agree > about. > > But the proper time of a clock between two events is invariant, > it is an objective value which everybody will agree about. > The twin paradox is that the proper times of two clocks between > _the same two events_ may be different. > Different but invariant, like in the Hafele-Keating experiment you mean? If so, that would not be paradox. The situation would be the same with just Gravitational time dilation, and no one suggests gravitational time dilation involves a paradox. > Any comparison of the rate and readings of the clocks when > they are not co-located is frame dependent, and can have > an infinite number of different results. > > > > In such a scenario it is often stated that they are undergoing > > mutual time dilation, and that it is relative, but here seeing > > the wider context (of the twin paradox). > > There often is no distinction between whether the observations > > of time dilation would be mutual, and whether actual time dilation > > would be mutual. In this scenario though, presumably they would both > > observe the clock on the other ship to appear to be going slower > > than their own, thus mutually observed time dilation. > > Though as I currently understand it, despite perhaps their belief > > that any time dilation was mutual as observed, the actual time dilation wasn't. > > I mean that in the sense that if there had been a series of space ships at rest > > with the Earth along the outward journey each synched with the one on Earth, > > and the twin stopped at any one, it would observe that its clock had ticked > > less times than theirs since the launch. They cannot say the same so it wasn't mutual. > > You didn't reply to this part, was there a problem with it (you forgot what the scenario was for example)? > > This could include a silly misunderstanding on my part, so thanks for participating on the forum, helping those that aren't as conversant with the theories as yourself. > > > >> -- > >> Paul > >> > >> https://paulba.no/ > > > > > -- > Paul > > https://paulba.no/
[toc] | [prev] | [next] | [standalone]
| From | "Paul B. Andersen" <relativity@paulba.no> |
|---|---|
| Date | 2017-03-08 10:40 +0100 |
| Message-ID | <o9ojhs$aa8$1@news.albasani.net> |
| In reply to | #412094 |
On 07.03.2017 23:04, someone wrote: > On Monday, March 6, 2017 at 10:01:03 PM UTC, Paul B. Andersen wrote: >> On 06.03.2017 18:34, someone wrote: >>> On Sunday, March 5, 2017 at 8:31:38 PM UTC, Paul B. Andersen wrote: >>>> On 03.03.2017 16:04, someone wrote: >>>>> The twin paradox is as I understand it that there are twins, >>>>> and one goes off in a spaceship, and as it does from its >>>>> perspective the other twins clock is going slower, >>>>> but from the twin on Earths perspective the twin going >>>>> off in a spaceships clock is going slower. >>>>> But when they come back to meet it cannot be that both clocks were going slower. >>>>> It is then claimed that the one that was on the spaceship will be the one that >>>>> aged for some reason. https://en.wikipedia.org/wiki/Twin_paradox states: >>>>> --- >>>>> Max von Laue argued in 1913 that since the traveling twin must be in two >>>>> separate inertial frames, one on the way out and another on the way back, >>>>> this frame switch is the reason for the aging difference, >>>>> not the acceleration per se.[7] Explanations put forth by Albert Einstein >>>>> and Max Born invoked gravitational time dilation to explain the aging as >>>>> a direct effect of acceleration.[8] >>>> >>>> When both twin's are inertial, mutual time dilation applies >>>> (the other twin ages less). So the travelling twin will >>>> then conclude that home twin is ageing less than herself. >>>> But while the travelling twin is accelerating at turn around, >>>> it will appear to her that the 'home twin's' clock are running fast, >>>> so much so that the home twin ends up older than herself when they >>>> are back. >>>> >>> >>> What is relevant about the turn around? For example imagine >>> there were two sets of twins, one from one set travelled for 1 year, >>> and one from the other set travelled for a thousand years >>> (imagine average lifespan at 10,000 years when this happened) >>> at the same constant velocities. They both decelerate and and accelerate >>> the same at their turn around. Will the identical turnarounds result in >>> a significant difference in the amount the 'home twin's' clock appears to be running? >> >> Yes indeed. >> In the simplest scenario, when the turnaround is done with >> an infinite high acceleration for zero time. >> (See 2.2. in https://paulba.no/pdf/TwinsByMetric.pdf ) >> we have: >> T_B = T_A sqrt(1-v^2/c^2) >> where T_A is the proper time of the home twin A, >> and T_B is the proper time of the travelling twin B. >> >> Let's for simplicity set v = 0.866c so sqrt(1-v^2/c^2) = 0.5. >> >> If B travelled for 1 year as measured by A, >> T_A = 1 year and T_B = 0.5 year. >> If B travelled for 1000 years, then >> T_A = 1000 years and T_B = 500 years. >> >> So even if the acceleration is the same, the different >> travelled times will indeed result in different travelled times. >> Rather obvious, if you think about it, isn't it? :-) >> >> But let's see it from B's point of view: >> Immediately before B turns around her clock will show 0.25 year, >> and according to SR A will simultaneously show 0.125 year (why?). >> Immediately after B turned around her clock will still show 0.25 years >> and according to SR A will simultaneously show 0.825 year. >> So when B abruptly turns around it will appear to her that clock >> A jumps 0.75 years forward in time. >> >> But both clocks always run at proper rate, and no clock jumps in time. >> There is no practical way B can measure what clock A simultaneously >> shows. But she can use SR to calculate it, using the definition of >> simultaneity. The apparent jump of A's clock is a consequence of >> the definition of simultaneity, B suddenly changes her mind about >> what is simultaneous at A. >> >> In the more realistic case when the acceleration is limited a, >> clock A will not from B's point of view appear to jump in time, >> but to run very fast while B is accelerating. >> At the moment when B is stationary to A at a distance d, >> clock A will appear to run at the rate (1 + ad/c^2) >> >> (Note that this equation is the same as the approximated >> gravitational time dilation when h << R : (1 + gh/c^2) ) >> >> See: >> https://paulba.no/twins.html >> >>> >>>> Note however that there is no practical way the travelling twin >>>> can measure the rate of the home twin's clock, it is a question of >>>> how simultaneity is defined. So when the travelling twin is >>>> accelerating, she will continuously change her opinion of what >>>> is simultaneous (according to the definition in SR) at >>>> the home twin's clock. That's why the home twin's clock for >>>> the travelling twin (according to SR) will appear to run fast >>>> during the acceleration. >>>> But both clocks are running at normal rate all the time. >>>> >>>> The 'twin paradox' is that the travelling twin really _is_ >>>> younger than the home twin when the travelling twin >>>> has returned, it is nothing apparent about that. >>>> The proper time of a clock between two events is a measure >>>> of the 'length' of the path in space-time travelled by the clock. >>>> So the proper time of the home twin is longer than the proper >>>> time of the travelling twin because the lengths of their >>>> paths through space time are different, not because their >>>> clocks are ticking at different rate. >>>> >>> >>> I think the paradox is that they cannot both be younger >>> than each other. The solution to the paradox was that only one had aged. >> >> There is no paradox. >> But the apparent paradox in the phrase "twin paradox" >> is that the travelling twin really is younger, >> because this seems impossible. >> >>> >>>> You can see a simulation of the twin paradox here. >>>> You can see it from both twin's point of view. >>>> Note the strange things that appear to happen from >>>> twin B's point of view when she is accelerating. >>>> But remember that much of it really are artefacts which >>>> follows from the definition of relativity. For example, >>>> twin A is never really travelling faster than c relative >>>> to B, even if it appears so for twin B. >>>> >>>> https://paulba.no/twins.html >>>> >>>> Se also: >>>> https://paulba.no/pdf/TwinsByMetric.pdf >>>> >>>> What could be measured, is the Doppler shift: >>>> https://paulba.no/pdf/TwinsByDoppler.pdf >>>> >>> >>> Thanks for the links. >>> >>>>> >>>>> But wouldn't the amount of ageing be dependent on how far >>>>> the spaceship was travelling at constant velocity once it had reached it, >>>> >>>> Yes. >>>> >>>>> and wouldn't there be hardly any gravitational time dilation at that point >>>>> (assuming it is at a suitable distance away from any objects of significant >>>>> mass and undergoing no proper acceleration)? >>>> >>>> All I have said above is according to SR in flat space-time. >>>> >>>> You can however have 'twin paradox' in Earth's gravitation as well. >>>> A couple of much more realistic scenarios can be seen here: >>>> https://paulba.no/Satellites.html >>>> >>>> scenario: "Twin scenario - kind of" >>>> ---------------------------------- >>>> The green and red clocks are in different >>>> orbits, but are meeting periodically. >>>> The green clock ages 16.6 us more than the red clock >>>> between each time they meet. >>>> >>>> scenario: "Two ballistic rockets" >>>> -------------------------------- >>>> This could be a "triple paradox". >>>> Three clocks (ground clock, red clock, green clock) >>>> are travelling between the same two events. >>>> The red clock ages 1.774 us more than the ground clock >>>> The green clock ages 0.845 us less than the ground clock. >>>> >>>> (The path of the red clock is almost identical to gravity probe A) >>>> If you pause the run when the red clock is at the top, you will >>>> see that the apparent relative rate difference observed from >>>> the ground is ca. 4.25E-10. >>>> Compare that to fig 3 in this: >>>> https://paulba.no/paper/Vessot.pdf >>>> >>> >>> thanks for the links again. >>> >>>>> >>>>> Also what difference is it supposed to make to the relevant ageing whether >>>>> the ship turns back or not? >>>> >>>> There is no "twin paradox" if the twins don't meet again. >>>> >>> >>> There is in the sense that they cannot both be ageing more than the other. >> >> But this is irrelevant becuse the apparent paradox is not >> that both is ageing less than the other, they are not! >> > > What would be paradoxical about that? I can see no contradiction in one being younger than the other. > > Which is why I thought the idea was that with Relativity, inertial frame motion is relative. So if either frame could be considered to be an inertial frame, then their should be symmetry, and they should both be younger than each other which does involve a contradiction, thus a paradox. Which is why I thought the solution to the paradox (or rather the answer as to why it was not a paradox) was that they aren't both inertial frames as there is acceleration in one, and so it is not symmetrical. > >>> I have assumed that no one is suggesting that any ageing the twin undergoes >>> on the outward journey is dependent on whether the ship is going to turn around or not. >> >> Look: >> The 'twin paradox' is that the twins seperate and meet again, >> and have experienced different proper times when they are >> co-located and compare their clocks. >> That's the only way the different ageing can be measured >> in an objective way, not depending on points of view. >> > > Yes I understood that, but that does not contradict what I wrote. Imagine that the experiment was done and the twin in the spaceship was found to have aged less. You presumably are not suggesting that it wasn't ageing slower on the outward journey, or that the slower ageing on the outward journey was dependent on whether the ship turned around. > > >> Any comparison of the ageing when they are not colocated >> is apparent, it is different projections in different frames >> of references. >> >> >>> >>>>> Lastly supposing the twin in the spaceship had taken off from some giant >>>>> Death Star type structure, and had been in some unconscious in some sleep >>>>> inducing machine at takeoff until a day before the spaceship was to turn around. >>>>> And that an hour after the twin awakes it passes another spaceship with a person >>>>> on board which had also just awaken. Their ships would pass, and if neither knew >>>>> what their ship's program was, neither would be able to tell who was moving. >>>>> But imagine that the second ship was at rest with the Death Star structure. >>>>> So both could be thinking that the other's clock was running slower than its own, >>>>> if they thought it was all relative, but wouldn't the one in the ship at rest with >>>>> the Death Star be wrong (the clock on the ship that had left earth was going slower >>>>> relative to any clock in the Death Star's restframe)? >>>>> >>>> >>>> What's the point with this nonsense? >>>> I have no idea of what a "Death Star" might be. >>>> >>> >>> Never mind, I had assumed that you had seen the first Star Wars movie. >>> Just substitute the "Death Star" as a small planet sized spaceship. >>> >>> I perhaps should have made the point to that clearer. >>> The point was regarding mutual time dilation. >>> To do that I embedded another scenario into the twin paradox. >> >> You seem obsessed with the mutual time dilation. >> It is irrelevant to the 'twin paradox'. >> > > I think they are linked. From https://www.thoughtco.com/twin-paradox-real-time-travel-2699432, I have added capital letters in brackets to annotate the text. > > --- > The twin paradox is a thought experiment that demonstrates the curious manifestation of time dilation in modern physics, as it was introduced by Albert Einstein through the theory of relativity. > > Answer: Consider two twins, named Biff and Cliff. On their twentieth birthday, Biff decides to get in a spaceship and take off into outer space, traveling at nearly the speed of light. > > > He journeys around the cosmos at this speed for about 5 years, returning to the Earth when he is 25 years old. > > Cliff, on the other hand, remains on the Earth. When Biff returns, it turns out that Cliff is 95 years old. > > WHAT HAPPENED? > According to relativity, two frames of reference that move differently from each other experience time differently, a process known as time dilation. Because Biff was moving so rapidly, time was in effect moving slower for him. This can be calculated precisely using Lorentz transformations, which are a standard part of relativity. > > TWIN PARADOX ONE > The first twin paradox isn't really a scientific paradox, but a logical one: How old is Biff? > > Biff has experienced 25 years of life, but he was also born the same moment as Cliff, which was 90 years ago. So is he 25 years old or 90 years old? > > In this case, the answer is "both" ... depending on which way you're measuring age. > > According to his driver's license, which measures Earth time (and is no doubt expired), he's 90. According to his body, he's 25. Neither age is "right" or "wrong," although the social security administration might take exception if he tries to claim benefits. > > TWIN PARADOX TWO > The second paradox is a bit more technical, and really comes to the heart of what physicists mean when they talk about relativity. > > > The entire scenario is based on the idea that Biff was traveling very fast, so time slowed down for him. > > The problem is that in relativity, only the relative motion is involved. So what if you considered things from Biff's point of view, then he stayed stationary the whole time, and it was Cliff who was moving away at rapid speeds. Shouldn't calculations performed in this way mean that Cliff is the one who ages more slowly? Doesn't relativity imply that these situations are symmetrical [AS IS SUPPOSED WITH MUTUAL TIME DILATION]? > > Now, if Biff and Cliff were on spaceships traveling at constant speeds in opposite directions [THEY WOULD EXPERIENCE MUTUAL TIME DILATION], this argument would be perfectly true. The rules of special relativity, which govern constant speed (inertial) frames of reference, indicate that only the relative motion between the two is what matters. In fact, if you're moving at a constant speed, there's not even an experiment that you can perform within your frame of reference which would distinguish you from being at rest. (Even if you looked outside the ship and compared yourself to some other constant frame of reference, you could only determine that one of you is moving, but not which one.) > > But there's one very important distinction here: Biff is accelerating during this process. > --- > >>> The embedded scenario was the twin in the spaceship passing >>> or being passed by another spaceship (for all the twin, or >>> the person in the other spaceship knows). >> >> Sure. When two clocks pass each other, and each of them >> measure the apparent rate of the other clocks as I now >> have explained several times, there is 'mutual time dilation'. >> Even if there is a gravitational field, there is _locally_ >> mutual time dilation when they pass each other. >> But mutual time dilation is only different projections >> of the proper time of a clock into different frames of reference. >> >> For the last time: >> The apparent rate of a clock will be different when measured >> in different frames of references. It is a frame dependent >> entity which has no objective value which everybody will agree >> about. >> >> But the proper time of a clock between two events is invariant, >> it is an objective value which everybody will agree about. >> The twin paradox is that the proper times of two clocks between >> _the same two events_ may be different. >> > > Different but invariant, like in the Hafele-Keating experiment you mean? If so, that would not be paradox. The situation would be the same with just Gravitational time dilation, and no one suggests gravitational time dilation involves a paradox. > >> Any comparison of the rate and readings of the clocks when >> they are not co-located is frame dependent, and can have >> an infinite number of different results. >> >> >>> In such a scenario it is often stated that they are undergoing >>> mutual time dilation, and that it is relative, but here seeing >>> the wider context (of the twin paradox). >>> There often is no distinction between whether the observations >>> of time dilation would be mutual, and whether actual time dilation >>> would be mutual. In this scenario though, presumably they would both >>> observe the clock on the other ship to appear to be going slower >>> than their own, thus mutually observed time dilation. >>> Though as I currently understand it, despite perhaps their belief >>> that any time dilation was mutual as observed, the actual time dilation wasn't. >>> I mean that in the sense that if there had been a series of space ships at rest >>> with the Earth along the outward journey each synched with the one on Earth, >>> and the twin stopped at any one, it would observe that its clock had ticked >>> less times than theirs since the launch. They cannot say the same so it wasn't mutual. >>> > > You didn't reply to this part, was there a problem with it (you forgot what the scenario was for example)? > > >>> This could include a silly misunderstanding on my part, so thanks for participating on the forum, helping those that aren't as conversant with the theories as yourself. >>> >>>> -- >>>> Paul >>>> >>>> https://paulba.no/ >>> >> >> >> -- >> Paul >> >> https://paulba.no/ > I think I have said what I have to say; I see no point in repeating the same over and over. You can find the answer to most (all?) of your question in what I have written. You can read it again. -- Paul https://paulba.no/
[toc] | [prev] | [next] | [standalone]
| From | someone <glenn.spigel@googlemail.com> |
|---|---|
| Date | 2017-03-08 07:11 -0800 |
| Message-ID | <da7bba07-d69f-46b5-8eae-5d89a1dff212@googlegroups.com> |
| In reply to | #412133 |
On Wednesday, March 8, 2017 at 9:40:13 AM UTC, Paul B. Andersen wrote:
> On 07.03.2017 23:04, someone wrote:
> > On Monday, March 6, 2017 at 10:01:03 PM UTC, Paul B. Andersen wrote:
> >> On 06.03.2017 18:34, someone wrote:
> >>> On Sunday, March 5, 2017 at 8:31:38 PM UTC, Paul B. Andersen wrote:
> >>>> On 03.03.2017 16:04, someone wrote:
> >>>>> The twin paradox is as I understand it that there are twins,
> >>>>> and one goes off in a spaceship, and as it does from its
> >>>>> perspective the other twins clock is going slower,
> >>>>> but from the twin on Earths perspective the twin going
> >>>>> off in a spaceships clock is going slower.
> >>>>> But when they come back to meet it cannot be that both clocks were going slower.
> >>>>> It is then claimed that the one that was on the spaceship will be the one that
> >>>>> aged for some reason. https://en.wikipedia.org/wiki/Twin_paradox states:
> >>>>> ---
> >>>>> Max von Laue argued in 1913 that since the traveling twin must be in two
> >>>>> separate inertial frames, one on the way out and another on the way back,
> >>>>> this frame switch is the reason for the aging difference,
> >>>>> not the acceleration per se.[7] Explanations put forth by Albert Einstein
> >>>>> and Max Born invoked gravitational time dilation to explain the aging as
> >>>>> a direct effect of acceleration.[8]
> >>>>
> >>>> When both twin's are inertial, mutual time dilation applies
> >>>> (the other twin ages less). So the travelling twin will
> >>>> then conclude that home twin is ageing less than herself.
> >>>> But while the travelling twin is accelerating at turn around,
> >>>> it will appear to her that the 'home twin's' clock are running fast,
> >>>> so much so that the home twin ends up older than herself when they
> >>>> are back.
> >>>>
> >>>
> >>> What is relevant about the turn around? For example imagine
> >>> there were two sets of twins, one from one set travelled for 1 year,
> >>> and one from the other set travelled for a thousand years
> >>> (imagine average lifespan at 10,000 years when this happened)
> >>> at the same constant velocities. They both decelerate and and accelerate
> >>> the same at their turn around. Will the identical turnarounds result in
> >>> a significant difference in the amount the 'home twin's' clock appears to be running?
> >>
> >> Yes indeed.
> >> In the simplest scenario, when the turnaround is done with
> >> an infinite high acceleration for zero time.
> >> (See 2.2. in https://paulba.no/pdf/TwinsByMetric.pdf )
> >> we have:
> >> T_B = T_A sqrt(1-v^2/c^2)
> >> where T_A is the proper time of the home twin A,
> >> and T_B is the proper time of the travelling twin B.
> >>
> >> Let's for simplicity set v = 0.866c so sqrt(1-v^2/c^2) = 0.5.
> >>
> >> If B travelled for 1 year as measured by A,
> >> T_A = 1 year and T_B = 0.5 year.
> >> If B travelled for 1000 years, then
> >> T_A = 1000 years and T_B = 500 years.
> >>
> >> So even if the acceleration is the same, the different
> >> travelled times will indeed result in different travelled times.
> >> Rather obvious, if you think about it, isn't it? :-)
> >>
> >> But let's see it from B's point of view:
> >> Immediately before B turns around her clock will show 0.25 year,
> >> and according to SR A will simultaneously show 0.125 year (why?).
> >> Immediately after B turned around her clock will still show 0.25 years
> >> and according to SR A will simultaneously show 0.825 year.
> >> So when B abruptly turns around it will appear to her that clock
> >> A jumps 0.75 years forward in time.
> >>
> >> But both clocks always run at proper rate, and no clock jumps in time.
> >> There is no practical way B can measure what clock A simultaneously
> >> shows. But she can use SR to calculate it, using the definition of
> >> simultaneity. The apparent jump of A's clock is a consequence of
> >> the definition of simultaneity, B suddenly changes her mind about
> >> what is simultaneous at A.
> >>
> >> In the more realistic case when the acceleration is limited a,
> >> clock A will not from B's point of view appear to jump in time,
> >> but to run very fast while B is accelerating.
> >> At the moment when B is stationary to A at a distance d,
> >> clock A will appear to run at the rate (1 + ad/c^2)
> >>
> >> (Note that this equation is the same as the approximated
> >> gravitational time dilation when h << R : (1 + gh/c^2) )
> >>
> >> See:
> >> https://paulba.no/twins.html
> >>
> >>>
> >>>> Note however that there is no practical way the travelling twin
> >>>> can measure the rate of the home twin's clock, it is a question of
> >>>> how simultaneity is defined. So when the travelling twin is
> >>>> accelerating, she will continuously change her opinion of what
> >>>> is simultaneous (according to the definition in SR) at
> >>>> the home twin's clock. That's why the home twin's clock for
> >>>> the travelling twin (according to SR) will appear to run fast
> >>>> during the acceleration.
> >>>> But both clocks are running at normal rate all the time.
> >>>>
> >>>> The 'twin paradox' is that the travelling twin really _is_
> >>>> younger than the home twin when the travelling twin
> >>>> has returned, it is nothing apparent about that.
> >>>> The proper time of a clock between two events is a measure
> >>>> of the 'length' of the path in space-time travelled by the clock.
> >>>> So the proper time of the home twin is longer than the proper
> >>>> time of the travelling twin because the lengths of their
> >>>> paths through space time are different, not because their
> >>>> clocks are ticking at different rate.
> >>>>
> >>>
> >>> I think the paradox is that they cannot both be younger
> >>> than each other. The solution to the paradox was that only one had aged.
> >>
> >> There is no paradox.
> >> But the apparent paradox in the phrase "twin paradox"
> >> is that the travelling twin really is younger,
> >> because this seems impossible.
> >>
> >>>
> >>>> You can see a simulation of the twin paradox here.
> >>>> You can see it from both twin's point of view.
> >>>> Note the strange things that appear to happen from
> >>>> twin B's point of view when she is accelerating.
> >>>> But remember that much of it really are artefacts which
> >>>> follows from the definition of relativity. For example,
> >>>> twin A is never really travelling faster than c relative
> >>>> to B, even if it appears so for twin B.
> >>>>
> >>>> https://paulba.no/twins.html
> >>>>
> >>>> Se also:
> >>>> https://paulba.no/pdf/TwinsByMetric.pdf
> >>>>
> >>>> What could be measured, is the Doppler shift:
> >>>> https://paulba.no/pdf/TwinsByDoppler.pdf
> >>>>
> >>>
> >>> Thanks for the links.
> >>>
> >>>>>
> >>>>> But wouldn't the amount of ageing be dependent on how far
> >>>>> the spaceship was travelling at constant velocity once it had reached it,
> >>>>
> >>>> Yes.
> >>>>
> >>>>> and wouldn't there be hardly any gravitational time dilation at that point
> >>>>> (assuming it is at a suitable distance away from any objects of significant
> >>>>> mass and undergoing no proper acceleration)?
> >>>>
> >>>> All I have said above is according to SR in flat space-time.
> >>>>
> >>>> You can however have 'twin paradox' in Earth's gravitation as well.
> >>>> A couple of much more realistic scenarios can be seen here:
> >>>> https://paulba.no/Satellites.html
> >>>>
> >>>> scenario: "Twin scenario - kind of"
> >>>> ----------------------------------
> >>>> The green and red clocks are in different
> >>>> orbits, but are meeting periodically.
> >>>> The green clock ages 16.6 us more than the red clock
> >>>> between each time they meet.
> >>>>
> >>>> scenario: "Two ballistic rockets"
> >>>> --------------------------------
> >>>> This could be a "triple paradox".
> >>>> Three clocks (ground clock, red clock, green clock)
> >>>> are travelling between the same two events.
> >>>> The red clock ages 1.774 us more than the ground clock
> >>>> The green clock ages 0.845 us less than the ground clock.
> >>>>
> >>>> (The path of the red clock is almost identical to gravity probe A)
> >>>> If you pause the run when the red clock is at the top, you will
> >>>> see that the apparent relative rate difference observed from
> >>>> the ground is ca. 4.25E-10.
> >>>> Compare that to fig 3 in this:
> >>>> https://paulba.no/paper/Vessot.pdf
> >>>>
> >>>
> >>> thanks for the links again.
> >>>
> >>>>>
> >>>>> Also what difference is it supposed to make to the relevant ageing whether
> >>>>> the ship turns back or not?
> >>>>
> >>>> There is no "twin paradox" if the twins don't meet again.
> >>>>
> >>>
> >>> There is in the sense that they cannot both be ageing more than the other.
> >>
> >> But this is irrelevant becuse the apparent paradox is not
> >> that both is ageing less than the other, they are not!
> >>
> >
> > What would be paradoxical about that? I can see no contradiction in one being younger than the other.
> >
> > Which is why I thought the idea was that with Relativity, inertial frame motion is relative. So if either frame could be considered to be an inertial frame, then their should be symmetry, and they should both be younger than each other which does involve a contradiction, thus a paradox. Which is why I thought the solution to the paradox (or rather the answer as to why it was not a paradox) was that they aren't both inertial frames as there is acceleration in one, and so it is not symmetrical.
> >
> >>> I have assumed that no one is suggesting that any ageing the twin undergoes
> >>> on the outward journey is dependent on whether the ship is going to turn around or not.
> >>
> >> Look:
> >> The 'twin paradox' is that the twins seperate and meet again,
> >> and have experienced different proper times when they are
> >> co-located and compare their clocks.
> >> That's the only way the different ageing can be measured
> >> in an objective way, not depending on points of view.
> >>
> >
> > Yes I understood that, but that does not contradict what I wrote. Imagine that the experiment was done and the twin in the spaceship was found to have aged less. You presumably are not suggesting that it wasn't ageing slower on the outward journey, or that the slower ageing on the outward journey was dependent on whether the ship turned around.
> >
> >
> >> Any comparison of the ageing when they are not colocated
> >> is apparent, it is different projections in different frames
> >> of references.
> >>
> >>
> >>>
> >>>>> Lastly supposing the twin in the spaceship had taken off from some giant
> >>>>> Death Star type structure, and had been in some unconscious in some sleep
> >>>>> inducing machine at takeoff until a day before the spaceship was to turn around.
> >>>>> And that an hour after the twin awakes it passes another spaceship with a person
> >>>>> on board which had also just awaken. Their ships would pass, and if neither knew
> >>>>> what their ship's program was, neither would be able to tell who was moving.
> >>>>> But imagine that the second ship was at rest with the Death Star structure.
> >>>>> So both could be thinking that the other's clock was running slower than its own,
> >>>>> if they thought it was all relative, but wouldn't the one in the ship at rest with
> >>>>> the Death Star be wrong (the clock on the ship that had left earth was going slower
> >>>>> relative to any clock in the Death Star's restframe)?
> >>>>>
> >>>>
> >>>> What's the point with this nonsense?
> >>>> I have no idea of what a "Death Star" might be.
> >>>>
> >>>
> >>> Never mind, I had assumed that you had seen the first Star Wars movie.
> >>> Just substitute the "Death Star" as a small planet sized spaceship.
> >>>
> >>> I perhaps should have made the point to that clearer.
> >>> The point was regarding mutual time dilation.
> >>> To do that I embedded another scenario into the twin paradox.
> >>
> >> You seem obsessed with the mutual time dilation.
> >> It is irrelevant to the 'twin paradox'.
> >>
> >
> > I think they are linked. From https://www.thoughtco.com/twin-paradox-real-time-travel-2699432, I have added capital letters in brackets to annotate the text.
> >
> > ---
> > The twin paradox is a thought experiment that demonstrates the curious manifestation of time dilation in modern physics, as it was introduced by Albert Einstein through the theory of relativity.
> >
> > Answer: Consider two twins, named Biff and Cliff. On their twentieth birthday, Biff decides to get in a spaceship and take off into outer space, traveling at nearly the speed of light.
> >
> >
> > He journeys around the cosmos at this speed for about 5 years, returning to the Earth when he is 25 years old.
> >
> > Cliff, on the other hand, remains on the Earth. When Biff returns, it turns out that Cliff is 95 years old.
> >
> > WHAT HAPPENED?
> > According to relativity, two frames of reference that move differently from each other experience time differently, a process known as time dilation. Because Biff was moving so rapidly, time was in effect moving slower for him. This can be calculated precisely using Lorentz transformations, which are a standard part of relativity.
> >
> > TWIN PARADOX ONE
> > The first twin paradox isn't really a scientific paradox, but a logical one: How old is Biff?
> >
> > Biff has experienced 25 years of life, but he was also born the same moment as Cliff, which was 90 years ago. So is he 25 years old or 90 years old?
> >
> > In this case, the answer is "both" ... depending on which way you're measuring age.
> >
> > According to his driver's license, which measures Earth time (and is no doubt expired), he's 90. According to his body, he's 25. Neither age is "right" or "wrong," although the social security administration might take exception if he tries to claim benefits.
> >
> > TWIN PARADOX TWO
> > The second paradox is a bit more technical, and really comes to the heart of what physicists mean when they talk about relativity.
> >
> >
> > The entire scenario is based on the idea that Biff was traveling very fast, so time slowed down for him.
> >
> > The problem is that in relativity, only the relative motion is involved. So what if you considered things from Biff's point of view, then he stayed stationary the whole time, and it was Cliff who was moving away at rapid speeds. Shouldn't calculations performed in this way mean that Cliff is the one who ages more slowly? Doesn't relativity imply that these situations are symmetrical [AS IS SUPPOSED WITH MUTUAL TIME DILATION]?
> >
> > Now, if Biff and Cliff were on spaceships traveling at constant speeds in opposite directions [THEY WOULD EXPERIENCE MUTUAL TIME DILATION], this argument would be perfectly true. The rules of special relativity, which govern constant speed (inertial) frames of reference, indicate that only the relative motion between the two is what matters. In fact, if you're moving at a constant speed, there's not even an experiment that you can perform within your frame of reference which would distinguish you from being at rest. (Even if you looked outside the ship and compared yourself to some other constant frame of reference, you could only determine that one of you is moving, but not which one.)
> >
> > But there's one very important distinction here: Biff is accelerating during this process.
> > ---
> >
> >>> The embedded scenario was the twin in the spaceship passing
> >>> or being passed by another spaceship (for all the twin, or
> >>> the person in the other spaceship knows).
> >>
> >> Sure. When two clocks pass each other, and each of them
> >> measure the apparent rate of the other clocks as I now
> >> have explained several times, there is 'mutual time dilation'.
> >> Even if there is a gravitational field, there is _locally_
> >> mutual time dilation when they pass each other.
> >> But mutual time dilation is only different projections
> >> of the proper time of a clock into different frames of reference.
> >>
> >> For the last time:
> >> The apparent rate of a clock will be different when measured
> >> in different frames of references. It is a frame dependent
> >> entity which has no objective value which everybody will agree
> >> about.
> >>
> >> But the proper time of a clock between two events is invariant,
> >> it is an objective value which everybody will agree about.
> >> The twin paradox is that the proper times of two clocks between
> >> _the same two events_ may be different.
> >>
> >
> > Different but invariant, like in the Hafele-Keating experiment you mean? If so, that would not be paradox. The situation would be the same with just Gravitational time dilation, and no one suggests gravitational time dilation involves a paradox.
> >
> >> Any comparison of the rate and readings of the clocks when
> >> they are not co-located is frame dependent, and can have
> >> an infinite number of different results.
> >>
> >>
> >>> In such a scenario it is often stated that they are undergoing
> >>> mutual time dilation, and that it is relative, but here seeing
> >>> the wider context (of the twin paradox).
> >>> There often is no distinction between whether the observations
> >>> of time dilation would be mutual, and whether actual time dilation
> >>> would be mutual. In this scenario though, presumably they would both
> >>> observe the clock on the other ship to appear to be going slower
> >>> than their own, thus mutually observed time dilation.
> >>> Though as I currently understand it, despite perhaps their belief
> >>> that any time dilation was mutual as observed, the actual time dilation wasn't.
> >>> I mean that in the sense that if there had been a series of space ships at rest
> >>> with the Earth along the outward journey each synched with the one on Earth,
> >>> and the twin stopped at any one, it would observe that its clock had ticked
> >>> less times than theirs since the launch. They cannot say the same so it wasn't mutual.
> >>>
> >
> > You didn't reply to this part, was there a problem with it (you forgot what the scenario was for example)?
> >
> >
> >>> This could include a silly misunderstanding on my part, so thanks for participating on the forum, helping those that aren't as conversant with the theories as yourself.
> >>>
> >>>> --
> >>>> Paul
> >>>>
> >>>> https://paulba.no/
> >>>
> >>
> >>
> >> --
> >> Paul
> >>
> >> https://paulba.no/
> >
>
> I think I have said what I have to say; I see no point in
> repeating the same over and over. You can find the answer
> to most (all?) of your question in what I have written.
> You can read it again.
>
From what I had read you didn't not think the twin paradox was built on the idea of mutual dilation. You thought that one twin being younger made it a paradox, but as I pointed out, gravitational time dilation would do that, and no one suggests it involves a paradox. I even quoted from https://www.thoughtco.com/twin-paradox-real-time-travel-2699432 but you did not respond at all to the annotated quote I supplied. And extract is below:
---
The entire scenario is based on the idea that Biff was traveling(sic) very fast, so time slowed down for him.
The problem is that in relativity, only the relative motion is involved. So what if you considered things from Biff's point of view, then he stayed stationary the whole time, and it was Cliff who was moving away at rapid speeds. Shouldn't calculations performed in this way mean that Cliff is the one who ages more slowly? Doesn't relativity imply that these situations are symmetrical [AS IS SUPPOSED WITH MUTUAL TIME DILATION]?
Now, if Biff and Cliff were on spaceships traveling at constant speeds in opposite directions [THEY WOULD EXPERIENCE MUTUAL TIME DILATION], this argument would be perfectly true.
---
The point was that if the asymmetry in the time dilation in the supposed paradox is due to both frames not being inertial, there is still the issue with the other spaceship ship at rest with the small planet sized spaceship.
You did not seem to be denying that there would be actual verifiable (bringing the clocks together) asymmetrical time dilation between the clock with the twin on the small planet sized spaceship and the twin in the small spaceship.
You did not suggest that the actual verifiable asymmetrical time dilation would not be occurring on the outward journey, nor did you suggest that its occurrence was dependent upon the twins space ship turning back.
You did mention that unless it turned back the asymmetrical time dilation couldn't be verified ("The 'twin paradox' is that the twins seperate and meet again, and have experienced different proper times when they are co-located and compare their clocks.
That's the only way the different ageing can be measured in an objective way, not depending on points of view.").
You considered there to be symmetrical (mutual) time dilation between the other spaceship which was at rest with the small planet size and the twin's spaceship ("Sure. When two clocks pass each other, and each of them measure the apparent rate of the other clocks as I now have explained several times, there is 'mutual time dilation'").
So did it only appear like there was symmetrical (mutual) time dilation between the spaceship which was at rest with the small planet size and the twin's spaceship, when actually the time dilation was asymmetrical (as was later verified back on the small planet sized spaceship when the twin's spaceship returned)?
I didn't see you answer that. If you did could you please point out where.
(Me quoting you shows that I have taken look back over the conversation)
> Paul
>
> https://paulba.no/
[toc] | [prev] | [next] | [standalone]
| From | Tom Roberts <tjroberts137@sbcglobal.net> |
|---|---|
| Date | 2017-03-08 15:04 -0600 |
| Message-ID | <a8ba489a-01ee-a931-d127-76c9fa75bdd6@sbcglobal.net> |
| In reply to | #412157 |
On 3/8/17 3/8/17 - 9:11 AM, someone wrote: > The problem is that in relativity, only the relative motion is involved. This is not true, it is only a broad generalization. > So > what if you considered things from Biff's point of view, then he stayed > stationary the whole time, and it was Cliff who was moving away at rapid > speeds. Shouldn't calculations performed in this way mean that Cliff is the > one who ages more slowly? Doesn't relativity imply that these situations are > symmetrical [AS IS SUPPOSED WITH MUTUAL TIME DILATION]? No. Because Cliff was at rest in an inertial frame and Buff was not. This is a case where more than just relative motion is involved. In SR, inertial frames are important, and results based on non-inertial frames can differ. Tom Roberts
[toc] | [prev] | [next] | [standalone]
| From | someone <glenn.spigel@googlemail.com> |
|---|---|
| Date | 2017-03-08 14:30 -0800 |
| Message-ID | <e068a7c3-0fd1-4c72-bab4-098432ff4c73@googlegroups.com> |
| In reply to | #412195 |
On Wednesday, March 8, 2017 at 9:04:09 PM UTC, tjrob137 wrote: > On 3/8/17 3/8/17 - 9:11 AM, someone wrote: > > The problem is that in relativity, only the relative motion is involved. > > This is not true, it is only a broad generalization. > > > So > > what if you considered things from Biff's point of view, then he stayed > > stationary the whole time, and it was Cliff who was moving away at rapid > > speeds. Shouldn't calculations performed in this way mean that Cliff is the > > one who ages more slowly? Doesn't relativity imply that these situations are > > symmetrical [AS IS SUPPOSED WITH MUTUAL TIME DILATION]? > > No. Because Cliff was at rest in an inertial frame and Buff was not. This is a > case where more than just relative motion is involved. In SR, inertial frames > are important, and results based on non-inertial frames can differ. > > Tom Roberts I assume you were responding to https://groups.google.com/d/msg/sci.physics.relativity/nFIZ9q3DQmI/tQWi9lZ2AQAJ it mentions at the end "But there's one very important distinction here: Biff is accelerating during this process", and if you read the article in the link supplied https://www.thoughtco.com/twin-paradox-real-time-travel-2699432 you would have noticed the asymmetry was pointed out. I was just pointing out the link between the twin paradox and mutual time dilation. Though it isn't a paradox, because there is not mutual time dilation (because one frame is not inertial. What did you think about the issue about the asymmetrical dilation and symmetrical dilation made in this post https://groups.google.com/d/msg/sci.physics.relativity/nFIZ9q3DQmI/aQYDnF-uAQAJ ?
[toc] | [prev] | [next] | [standalone]
| From | Tom Roberts <tjroberts137@sbcglobal.net> |
|---|---|
| Date | 2017-03-09 10:39 -0600 |
| Message-ID | <Do6dnfhrfITVGFzFnZ2dnUU7_8zNnZ2d@giganews.com> |
| In reply to | #412202 |
On 3/8/17 3/8/17 - 4:30 PM, someone wrote: > On Wednesday, March 8, 2017 at 9:04:09 PM UTC, tjrob137 wrote: >> On 3/8/17 3/8/17 - 9:11 AM, someone wrote: >>> The problem is that in relativity, only the relative motion is involved. >> This is not true, it is only a broad generalization. >>> So what if you considered things from Biff's point of view, then he >>> stayed stationary the whole time, and it was Cliff who was moving away at >>> rapid speeds. Shouldn't calculations performed in this way mean that >>> Cliff is the one who ages more slowly? Doesn't relativity imply that >>> these situations are symmetrical [AS IS SUPPOSED WITH MUTUAL TIME >>> DILATION]? >> >> No. Because Cliff was at rest in an inertial frame and Biff was not. This >> is a case where more than just relative motion is involved. In SR, inertial >> frames are important, and results based on non-inertial frames can differ. > > I assume you were responding to > https://groups.google.com/d/msg/sci.physics.relativity/nFIZ9q3DQmI/tQWi9lZ2AQAJ I was responding to what I quoted above. > I was just pointing out > the link between the twin paradox and mutual time dilation. Though it isn't a > paradox, because there is not mutual time dilation (because one frame is not > inertial. Hmmmm. Attempts to "explain" the twin paradox via "time dilation" are doomed, because the physical situation does not illustrate "time dilation". Rather, it shows that different paths have different path lengths. > What did you think about the issue about the asymmetrical dilation and > symmetrical dilation made in this post > https://groups.google.com/d/msg/sci.physics.relativity/nFIZ9q3DQmI/aQYDnF-uAQAJ > ? That post is attempting to apply "time dilation" to the twin paradox, which is inappropriate. Discussing "time dilation" requires the measurement of clock tick rates (or equivalent), which requires describing HOW that is done; the twin paradox does not include such a description. Just about every attempt to discuss what one twin's clock shows as observed by the other twin does NOT describe HOW to do that; they are useless and tantamount to being wrong. To apply "time dilation" to a moving clock requires an assistant pre-positioned along the moving clock's path. This is so because "time dilation" refers to the specific physical situation using TWO SYNCHRONIZED CLOCKS to measure the tick rate of a moving clock. Of course no description of the twin paradox includes such assistants.... An alternative would be to have the twins send their clock ticks via light signals to the other twin; in this case it is Doppler shift that applies to the reception of those signals, not "time dilation". Tom Roberts
[toc] | [prev] | [next] | [standalone]
| From | someone <glenn.spigel@googlemail.com> |
|---|---|
| Date | 2017-03-09 13:20 -0800 |
| Message-ID | <860fa46a-2525-4d43-acf3-b322ad4b2b28@googlegroups.com> |
| In reply to | #412269 |
On Thursday, March 9, 2017 at 4:39:44 PM UTC, tjrob137 wrote: > On 3/8/17 3/8/17 - 4:30 PM, someone wrote: > > On Wednesday, March 8, 2017 at 9:04:09 PM UTC, tjrob137 wrote: > >> On 3/8/17 3/8/17 - 9:11 AM, someone wrote: > >>> The problem is that in relativity, only the relative motion is involved. > >> This is not true, it is only a broad generalization. > >>> So what if you considered things from Biff's point of view, then he > >>> stayed stationary the whole time, and it was Cliff who was moving away at > >>> rapid speeds. Shouldn't calculations performed in this way mean that > >>> Cliff is the one who ages more slowly? Doesn't relativity imply that > >>> these situations are symmetrical [AS IS SUPPOSED WITH MUTUAL TIME > >>> DILATION]? > >> > >> No. Because Cliff was at rest in an inertial frame and Biff was not. This > >> is a case where more than just relative motion is involved. In SR, inertial > >> frames are important, and results based on non-inertial frames can differ. > > > > I assume you were responding to > > https://groups.google.com/d/msg/sci.physics.relativity/nFIZ9q3DQmI/tQWi9lZ2AQAJ > > I was responding to what I quoted above. > Yes I was just trying to get the post it was from to give context. > > I was just pointing out > > the link between the twin paradox and mutual time dilation. Though it isn't a > > paradox, because there is not mutual time dilation (because one frame is not > > inertial. > > Hmmmm. Attempts to "explain" the twin paradox via "time dilation" are doomed, > because the physical situation does not illustrate "time dilation". Rather, it > shows that different paths have different path lengths. > Which results in time dilation does it not? > > What did you think about the issue about the asymmetrical dilation and > > symmetrical dilation made in this post > > https://groups.google.com/d/msg/sci.physics.relativity/nFIZ9q3DQmI/aQYDnF-uAQAJ > > ? > > That post is attempting to apply "time dilation" to the twin paradox, which is > inappropriate. Discussing "time dilation" requires the measurement of clock tick > rates (or equivalent), which requires describing HOW that is done; the twin > paradox does not include such a description. > > Just about every attempt to discuss what one twin's clock shows as observed by > the other twin does NOT describe HOW to do that; they are useless and tantamount > to being wrong. > > To apply "time dilation" to a moving clock requires an assistant pre-positioned > along the moving clock's path. This is so because "time dilation" refers to the > specific physical situation using TWO SYNCHRONIZED CLOCKS to measure the tick > rate of a moving clock. Of course no description of the twin paradox includes > such assistants.... > > An alternative would be to have the twins send their clock ticks via light > signals to the other twin; in this case it is Doppler shift that applies to the > reception of those signals, not "time dilation". > Your response makes it seem like you hadn't read it, and hadn't noticed that there was another scenario embedded which was a pretty much a standard one where mutual time dilation would be said to occur. > Tom Roberts
[toc] | [prev] | [next] | [standalone]
| From | Odd Bodkin <bodkinodd@gmail.com> |
|---|---|
| Date | 2017-03-10 07:27 -0600 |
| Message-ID | <o9u9kp$1uke$2@gioia.aioe.org> |
| In reply to | #412310 |
On 3/9/2017 3:20 PM, someone wrote: >> Hmmmm. Attempts to "explain" the twin paradox via "time dilation" are doomed, >> because the physical situation does not illustrate "time dilation". Rather, it >> shows that different paths have different path lengths. >> > Which results in time dilation does it not? > > I don't think that's really accurate. Time dilation is really about the rotation of a coordinate view of a pair of events, and it reflects the relativity of synchronization of clocks. -- Odd Bodkin -- maker of fine toys, tools, tables
[toc] | [prev] | [next] | [standalone]
| From | someone <glenn.spigel@googlemail.com> |
|---|---|
| Date | 2017-03-10 06:05 -0800 |
| Message-ID | <01739300-c95a-479b-ac42-bfe28be2df96@googlegroups.com> |
| In reply to | #412368 |
On Friday, March 10, 2017 at 1:27:56 PM UTC, Odd Bodkin wrote: > On 3/9/2017 3:20 PM, someone wrote: > >> Hmmmm. Attempts to "explain" the twin paradox via "time dilation" are doomed, > >> because the physical situation does not illustrate "time dilation". Rather, it > >> shows that different paths have different path lengths. > >> > > Which results in time dilation does it not? > > > > > I don't think that's really accurate. > Time dilation is really about the rotation of a coordinate view of a > pair of events, and it reflects the relativity of synchronization of clocks. > That wasn't the case in the Hafele-Keating experiment though was it? https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Overview "According to special relativity, the rate of a clock is greatest according to an observer who is at rest with respect to the clock. In a frame of reference in which the clock is not at rest, the clock runs more slowly, as expressed by the Lorentz factor." Would that not result in mutual (symmetrical) (kinematic) time dilation in cases where there is a constant relative difference in velocity between two spaceships. And the wiki article seems to experiment indicates that that is supposed to be real, rather than just in appearance, as in the estimates of kinematic time dilation being included with the prediction which was close to the result. The twin paradox seems to try to question how mutual (kinematic) time dilation could be real, as an attempt to create a scenario in which two twins would meet up after such mutual (kinematic) time dilation. The paradox being that they couldn't both be older than the other. The response though seems to be to suggest that the thought experiment doesn't do what was intended, as both frames of reference aren't symmetrical, one wasn't inertial but underwent acceleration, and in that case only one would have undergone kinematic time dilation. So the kinematic time dilation wasn't symmetrical. What I was trying to ask earlier, is if there was a spaceship with a physicist in out in space at a point the twin turned around, and the physicists spaceship was at rest with the Earth, then if the twin in the spaceship and the physicist had been in an induced sleep, and did not know the history of what had gone on, then if they were to follow Einstein's reasoning conclude mutual (kinematic) time dilation was taking place, when actually asymmetrical time dilation would be (as shown when the twin returned to Earth and compared its clock to one in the Earth's frame of reference. But I haven't recognised any answer to the question. > -- > Odd Bodkin -- maker of fine toys, tools, tables
[toc] | [prev] | [next] | [standalone]
| From | Odd Bodkin <bodkinodd@gmail.com> |
|---|---|
| Date | 2017-03-10 08:45 -0600 |
| Message-ID | <o9ue6n$8v0$1@gioia.aioe.org> |
| In reply to | #412374 |
On 3/10/2017 8:05 AM, someone wrote: > On Friday, March 10, 2017 at 1:27:56 PM UTC, Odd Bodkin wrote: >> On 3/9/2017 3:20 PM, someone wrote: >>>> Hmmmm. Attempts to "explain" the twin paradox via "time dilation" are doomed, >>>> because the physical situation does not illustrate "time dilation". Rather, it >>>> shows that different paths have different path lengths. >>>> >>> Which results in time dilation does it not? >>> >>> >> I don't think that's really accurate. >> Time dilation is really about the rotation of a coordinate view of a >> pair of events, and it reflects the relativity of synchronization of clocks. >> > > That wasn't the case in the Hafele-Keating experiment though was it? > > https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Overview > > "According to special relativity, the rate of a clock is greatest according to an observer who is at rest with respect > to the clock. In a frame of reference in which the clock is not at rest, the clock runs more slowly, as expressed by the > Lorentz factor." Yeah, that description in wikipedia is not the best. The Hafele-Keating experiment is actually fairly complicated, and isn't really well modeled by the twin paradox. But it's still true even for the HK experiment that the difference in time is more due to the difference in the paths through spacetime than the idealized concept of "time dilation". > > Would that not result in mutual (symmetrical) (kinematic) time dilation in cases where there is a constant relative > difference in velocity between two spaceships. Keep in mind that in the case of mutual time dilation there is no reunion possible. Two ships in inertial relative motion can meet at most once. So in this case you have to ask pretty carefully what it means to compare clock rates in the case of inertial relative motion, because it cannot possibly mean comparing clocks side-by-side on two occasions. What a lot of newbies then do is to say, "Well just turn one of the ships around real quick, it can't possibly matter." But it DOES matter, it matters a lot, and that's precisely the point to be learned in the twin paradox. > And the wiki article seems to experiment indicates that that is supposed > to be real, rather than just in appearance, as in the estimates of kinematic > time dilation being included with the > prediction which was close to the result. It's only a very rough and loose match to the concept of time dilation in this case. > > The twin paradox seems to try to question how mutual (kinematic) time dilation could be real, There's nothing mutual about it. Both observers agree that one of the clocks shows a lower elapsed time. That's exactly the OPPOSITE of what MUTUAL time dilation suggests, which is that the two observers will disagree which clock is running slow. So the twin paradox is a case where the elapsed time difference is NOT mutual, and the point of the exercise is to teach newbies what is wrong with their thinking that it SHOULD BE mutual. > as an attempt to create a > scenario in which two twins would meet up after such mutual (kinematic) time dilation. The paradox being that they > couldn't both be older than the other. The response though seems to be to suggest that the thought experiment doesn't > do what was intended, as both frames of reference aren't symmetrical, one wasn't inertial but underwent acceleration, > and in that case only one would have undergone kinematic time dilation. So the kinematic time dilation wasn't symmetrical. > > What I was trying to ask earlier, is if there was a spaceship with a physicist in out in space at a point > the twin turned around, and the physicists spaceship was at rest with the Earth, then if the twin in the > spaceship and the physicist had been in an induced sleep, and did not know the history of what had gone on, > then if they were to follow Einstein's reasoning conclude mutual (kinematic) time dilation was taking place, > when actually asymmetrical time dilation would be (as shown when the twin returned to Earth and compared its > clock to one in the Earth's frame of reference. But I haven't recognised any answer to the question. > >> -- >> Odd Bodkin -- maker of fine toys, tools, tables > -- Odd Bodkin -- maker of fine toys, tools, tables
[toc] | [prev] | [next] | [standalone]
| From | alsor@interia.pl |
|---|---|
| Date | 2017-03-14 13:19 -0700 |
| Message-ID | <ffa17a56-5d4d-49ca-9f2b-73e066f4c100@googlegroups.com> |
| In reply to | #412195 |
W dniu środa, 8 marca 2017 22:04:09 UTC+1 użytkownik tjrob137 napisał: > On 3/8/17 3/8/17 - 9:11 AM, someone wrote: > > The problem is that in relativity, only the relative motion is involved. > > This is not true, it is only a broad generalization. It's a limitation in fact. Your relative motion is unable to explain the motion in general. :) > No. Because Cliff was at rest in an inertial frame and Buff was not. This is a > case where more than just relative motion is involved. In SR, inertial frames > are important, and results based on non-inertial frames can differ. The physics/math is about the processes in the nature.. it is not about frames of reference at all.
[toc] | [prev] | [next] | [standalone]
| From | "Paul B. Andersen" <relativity@paulba.no> |
|---|---|
| Date | 2017-03-10 11:49 +0100 |
| Message-ID | <o9u0bc$kif$1@news.albasani.net> |
| In reply to | #412157 |
On 08.03.2017 16:11, someone wrote:
> On Wednesday, March 8, 2017 at 9:40:13 AM UTC, Paul B. Andersen wrote:
>>
>> I think I have said what I have to say; I see no point in
>> repeating the same over and over. You can find the answer
>> to most (all?) of your question in what I have written.
>> You can read it again.
>>
>
> From what I had read you didn't not think the twin paradox was built on the idea of mutual dilation. You thought that one twin being younger made it a paradox, but as I pointed out, gravitational time dilation would do that, and no one suggests it involves a paradox. I even quoted from https://www.thoughtco.com/twin-paradox-real-time-travel-2699432 but you did not respond at all to the annotated quote I supplied. And extract is below:
> ---
> The entire scenario is based on the idea that Biff was traveling(sic) very fast, so time slowed down for him.
>
> The problem is that in relativity, only the relative motion is involved. So what if you considered things from Biff's point of view, then he stayed stationary the whole time, and it was Cliff who was moving away at rapid speeds. Shouldn't calculations performed in this way mean that Cliff is the one who ages more slowly? Doesn't relativity imply that these situations are symmetrical [AS IS SUPPOSED WITH MUTUAL TIME DILATION]?
>
> Now, if Biff and Cliff were on spaceships traveling at constant speeds in opposite directions [THEY WOULD EXPERIENCE MUTUAL TIME DILATION], this argument would be perfectly true.
> ---
>
> The point was that if the asymmetry in the time dilation in the supposed paradox is due to both frames not being inertial, there is still the issue with the other spaceship ship at rest with the small planet sized spaceship.
>
> You did not seem to be denying that there would be actual verifiable (bringing the clocks together) asymmetrical time dilation between the clock with the twin on the small planet sized spaceship and the twin in the small spaceship.
>
> You did not suggest that the actual verifiable asymmetrical time dilation would not be occurring on the outward journey, nor did you suggest that its occurrence was dependent upon the twins space ship turning back.
>
> You did mention that unless it turned back the asymmetrical time dilation couldn't be verified ("The 'twin paradox' is that the twins seperate and meet again, and have experienced different proper times when they are co-located and compare their clocks.
> That's the only way the different ageing can be measured in an objective way, not depending on points of view.").
>
> You considered there to be symmetrical (mutual) time dilation between the other spaceship which was at rest with the small planet size and the twin's spaceship ("Sure. When two clocks pass each other, and each of them measure the apparent rate of the other clocks as I now have explained several times, there is 'mutual time dilation'").
>
> So did it only appear like there was symmetrical (mutual) time dilation between the spaceship which was at rest with the small planet size and the twin's spaceship, when actually the time dilation was asymmetrical (as was later verified back on the small planet sized spaceship when the twin's spaceship returned)?
>
> I didn't see you answer that.
But I have. The point is that if you had read what I wrote, you would
see that I had addressed most of your question before you asked them.
That was because you kept asking basically the same questions over
and over with only small variations.
> If you did could you please point out where.
I am not going to repeat it again.
Read the original.
Start with the first posting in the thread "Orbital time dilation".
--
Paul
https://paulba.no/
[toc] | [prev] | [next] | [standalone]
| From | wugi <brol@brol.be> |
|---|---|
| Date | 2017-03-17 17:37 +0100 |
| Message-ID | <oah3gi$s57$1@gioia.aioe.org> |
| In reply to | #412094 |
Op 7/03/2017 om 23:04 schreef someone: >> But this is irrelevant becuse the apparent paradox is not >> >that both is ageing less than the other, they are not! >> > > What would be paradoxical about that? I can see no contradiction in one > being younger than the other. > > Which is why I thought the idea was that with Relativity, inertial > frame motion is relative. So if either frame could be considered to be > an inertial frame, then their should be symmetry, and they should both > be younger than each other which does involve a contradiction, > thus a paradox. So you'd consider any relativistic inertial movement paradoxical? Because it implies mutual time dilation (and length contraction). > Which is why I thought the solution to the paradox > (or rather the answer as to why it was not a paradox) was that they > aren't both inertial frames as there is acceleration in one, and so > it is not symmetrical. Of course, since both twins meet again, at least one of them must have strayed away from inertial movement. Still, the main feature of the paradox, as has been stated elsewhere, is NOT (a difference in accumulated) DILATED TIME (although this part will occur also of course), BUT chiefly, a change in the travelling twin's horizon of SIMULTANEITY as he goes about swapping "instantaneous inertial frames" during his turn-around. See topic and many graphics at my page http://home.scarlet.be/~pin12499/paratwin.htm -- guido wugi
[toc] | [prev] | [next] | [standalone]
| From | Julio Di Egidio <julio@diegidio.name> |
|---|---|
| Date | 2017-03-19 21:33 -0700 |
| Message-ID | <3fc54e56-a9fd-477b-baee-18e98fc1b294@googlegroups.com> |
| In reply to | #413125 |
On Friday, March 17, 2017 at 5:39:52 PM UTC+1, wugi wrote: > Op 7/03/2017 om 23:04 schreef someone: > > Which is why I thought the solution to the paradox > > (or rather the answer as to why it was not a paradox) was that they > > aren't both inertial frames as there is acceleration in one, and so > > it is not symmetrical. > > Of course, since both twins meet again, at least one of them must have > strayed away from inertial movement. > Still, the main feature of the paradox, as has been stated elsewhere, is > NOT (a difference in accumulated) DILATED TIME (although this part will > occur also of course), BUT chiefly, a change in the travelling twin's > horizon of SIMULTANEITY as he goes about swapping "instantaneous > inertial frames" during his turn-around. Bullshit, you are making a distinction that does not have any value. Plus another aspect of that is the acceleration that the travelling twin FEELS. So, your diagrams are correct, your attempts at covering up the bullshit are noted, too. Julio
[toc] | [prev] | [next] | [standalone]
Page 7 of 13 — ← Prev page 1 … 5 6 [7] 8 9 … 13 Next page →
Back to top | Article view | sci.physics.relativity
csiph-web