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Groups > sci.physics.relativity > #423045 > unrolled thread
| Started by | Pentcho Valev <pvalev@yahoo.com> |
|---|---|
| First post | 2017-06-19 14:30 -0700 |
| Last post | 2017-06-23 11:43 +0000 |
| Articles | 20 on this page of 92 — 19 participants |
Back to article view | Back to sci.physics.relativity
The Secret to Einstein's Twin Paradox Pentcho Valev <pvalev@yahoo.com> - 2017-06-19 14:30 -0700
Re: The Secret to Einstein's Twin Paradox Gary Harnagel <hitlong@yahoo.com> - 2017-06-19 14:48 -0700
Re: The Secret to Einstein's Twin Paradox Eshiki Orakut <usa@iwikuh.ki> - 2017-06-20 13:45 +0000
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-06-20 09:49 -0600
Re: The Secret to Einstein's Twin Paradox Eshiki Orakut <usa@iwikuh.ki> - 2017-06-20 21:10 +0000
Re: The Secret to Einstein's Twin Paradox mlwozniak@wp.pl - 2017-06-21 02:40 -0700
Re: The Secret to Einstein's Twin Paradox JanPB <filmart@gmail.com> - 2017-06-23 04:42 -0700
Re: The Secret to Einstein's Twin Paradox mlwozniak@wp.pl - 2017-06-23 04:48 -0700
Re: The Secret to Einstein's Twin Paradox JanPB <filmart@gmail.com> - 2017-06-23 13:51 -0700
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-22 04:30 -0700
Re: The Secret to Einstein's Twin Paradox JanPB <filmart@gmail.com> - 2017-06-23 04:44 -0700
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-27 07:06 -0700
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-06-27 12:22 -0600
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-27 22:44 -0500
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-06-28 07:40 -0600
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-29 00:26 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-29 04:01 -0700
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-29 04:14 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-29 08:30 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-29 06:54 -0700
Re: The Secret to Einstein's Twin Paradox Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-06-29 14:41 +0200
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-29 08:37 -0500
Re: The Secret to Einstein's Twin Paradox Poutnik <poutnik4nntp@gmail.com> - 2017-06-29 16:16 +0200
Re: The Secret to Einstein's Twin Paradox Jim Petroff <ruuri@twjotr.eo> - 2017-06-29 14:29 +0000
Re: The Secret to Einstein's Twin Paradox Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-06-29 16:45 +0200
Re: The Secret to Einstein's Twin Paradox Jim Petroff <ruuri@twjotr.eo> - 2017-06-29 15:00 +0000
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-29 08:11 -0700
Re: The Secret to Einstein's Twin Paradox Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-06-29 17:19 +0200
Re: The Secret to Einstein's Twin Paradox Jim Petroff <ruuri@twjotr.eo> - 2017-06-29 15:34 +0000
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-29 08:39 -0700
Re: The Secret to Einstein's Twin Paradox Jim Petroff <ruuri@twjotr.eo> - 2017-06-29 15:29 +0000
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-01 12:29 -0500
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-07-02 12:35 -0600
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-03 08:18 -0700
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-07-03 09:45 -0600
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-04 05:24 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-03 17:52 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-04 05:45 -0700
Re: The Secret to Einstein's Twin Paradox Poutnik <poutnik4nntp@gmail.com> - 2017-07-04 15:03 +0200
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-07 13:56 -0700
Re: The Secret to Einstein's Twin Paradox Poutnik <poutnik4nntp@gmail.com> - 2017-07-07 23:55 +0200
Re: The Secret to Einstein's Twin Paradox mlwozniak@wp.pl - 2017-07-08 00:15 -0700
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-10 08:43 -0700
Re: The Secret to Einstein's Twin Paradox Upech Bezradne <adeeia@bbzzeop.ic> - 2017-07-08 10:44 +0000
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-10 08:38 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-04 12:56 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-07 13:20 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-08 00:06 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-10 08:26 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-11 10:56 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-11 13:40 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-12 10:13 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-13 10:07 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-14 20:04 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-15 13:49 -0700
Re: The Secret to Einstein's Twin Paradox The Starmaker <starmaker@ix.netcom.com> - 2017-07-15 14:26 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-17 20:20 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-20 07:25 -0700
Re: The Secret to Einstein's Twin Paradox kenseto <setoken@att.net> - 2017-07-05 07:50 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-03 18:26 -0500
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-29 07:05 -0700
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-06-29 09:31 -0600
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-28 05:01 -0700
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-06-28 07:52 -0600
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-29 03:47 -0700
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-06-29 10:19 -0600
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-06-30 08:09 -0700
Re: The Secret to Einstein's Twin Paradox Lord Kronos Prime <fuller.david@hotmail.com> - 2017-06-30 08:39 -0700
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-01 08:33 -0700
Re: The Secret to Einstein's Twin Paradox Mike Fontenot <mlfasf@comcast.net> - 2017-06-30 11:30 -0600
Re: The Secret to Einstein's Twin Paradox Jonathan Doolin <good4usoul@gmail.com> - 2017-07-01 08:11 -0700
Re: The Secret to Einstein's Twin Paradox Pentcho Valev <pvalev@yahoo.com> - 2017-06-19 23:58 -0700
Re: The Secret to Einstein's Twin Paradox JanPB <filmart@gmail.com> - 2017-06-20 03:18 -0700
Re: The Secret to Einstein's Twin Paradox Lipek Mniak <iluka@sskwpiw.pp> - 2017-06-23 11:47 +0000
Re: The Secret to Einstein's Twin Paradox The Starmaker <starmaker@ix.netcom.com> - 2017-06-23 11:18 -0700
Re: The Secret to Einstein's Twin Paradox Eckard B <eckard.blumschein@arcor.de> - 2017-06-21 09:21 -0700
Re: The Secret to Einstein's Twin Paradox Poutnik <poutnik4nntp@gmail.com> - 2017-06-21 19:33 +0200
Re: The Secret to Einstein's Twin Paradox Poutnik <poutnik4nntp@gmail.com> - 2017-06-22 07:32 +0200
Re: The Secret to Einstein's Twin Paradox mlwozniak@wp.pl - 2017-06-21 23:16 -0700
Re: The Secret to Einstein's Twin Paradox Lipek Mniak <iluka@sskwpiw.pp> - 2017-06-23 11:33 +0000
Re: The Secret to Einstein's Twin Paradox Eckard B <eckard.blumschein@arcor.de> - 2017-06-22 08:14 -0700
Re: The Secret to Einstein's Twin Paradox Poutnik <poutnik4nntp@gmail.com> - 2017-06-22 18:13 +0200
Re: The Secret to Einstein's Twin Paradox Lipek Mniak <iluka@sskwpiw.pp> - 2017-06-23 11:35 +0000
Re: The Secret to Einstein's Twin Paradox The Starmaker <starmaker@ix.netcom.com> - 2017-06-23 11:15 -0700
Re: The Secret to Einstein's Twin Paradox Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-22 15:38 -0500
Re: The Secret to Einstein's Twin Paradox Eckard B <eckard.blumschein@arcor.de> - 2017-06-23 03:22 -0700
Re: The Secret to Einstein's Twin Paradox Lipek Mniak <iluka@sskwpiw.pp> - 2017-06-23 11:38 +0000
Re: The Secret to Einstein's Twin Paradox Poutnik <poutnik4nntp@gmail.com> - 2017-06-28 08:32 +0200
Re: The Secret to Einstein's Twin Paradox mlwozniak@wp.pl - 2017-06-23 03:37 -0700
Re: The Secret to Einstein's Twin Paradox bigal95210@gmail.com - 2017-06-21 16:48 -0700
Re: The Secret to Einstein's Twin Paradox John Gogo <jfgogo22@yahoo.com> - 2017-07-14 19:00 -0700
Re: The Secret to Einstein's Twin Paradox Lipek Mniak <iluka@sskwpiw.pp> - 2017-06-23 11:43 +0000
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| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Date | 2017-06-29 14:41 +0200 |
| Message-ID | <2227715.4XsnlVU6TS@PointedEars.de> |
| In reply to | #423590 |
Tom Roberts wrote: > From that information the observer knows the sender's age when the signal > was SENT, without reference to the CADO frame. But from that information > alone the observer cannot possibly know how old she is when it is > RECEIVED. > Because this is not a measurement of the distant person, it is a > measurement of a SIGNAL, and the observer does not know how long the > signal traveled from her to him. I presume it could be calculated if the sender time would be encoded in the signal (as with GPS), but it would only be trivial to do in flat spacetime and non-complex (e.g., one-time) acceleration (as in the twin paradox). One encloses words in *asterisks*, _underscores_, and /forward slashes/ in Usenet for emphasis and similar text formatting. By contrast, ALL-CAPS is considered shouting and impolite instead. -- PointedEars Twitter: @PointedEars2 Please do not cc me. / Bitte keine Kopien per E-Mail.
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| From | Tom Roberts <tjroberts137@sbcglobal.net> |
|---|---|
| Date | 2017-06-29 08:37 -0500 |
| Message-ID | <r8CdnSbEGLsNn8jEnZ2dnUU7_83NnZ2d@giganews.com> |
| In reply to | #423600 |
On 6/29/17 6/29/17 7:41 AM, Thomas 'PointedEars' Lahn wrote: > Tom Roberts wrote: > >> From that information the observer knows the sender's age when the signal >> was SENT, without reference to the CADO frame. But from that information >> alone the observer cannot possibly know how old she is when it is >> RECEIVED. >> Because this is not a measurement of the distant person, it is a >> measurement of a SIGNAL, and the observer does not know how long the >> signal traveled from her to him. > > I presume it could be calculated if the sender time would be encoded in the > signal (as with GPS), but it would only be trivial to do in flat spacetime > and non-complex (e.g., one-time) acceleration (as in the twin paradox). The sender's age is part of the signal, as Mike stated. But your PRESUMPTION that the receiver could calculate the time the signal was in transit is precisely at issue -- for arbitrary motion of the observer it cannot be done (except for the case of my exception, using the inertial frame, as the GPS does). > One encloses words in *asterisks*, _underscores_, and /forward slashes/ in > Usenet for emphasis and similar text formatting. By contrast, ALL-CAPS is > considered shouting and impolite instead. Some people do that, and others like me use capitals for emphasis. IMHO it better mimics the verbal stresses people use when speaking. Tom Roberts
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| From | Poutnik <poutnik4nntp@gmail.com> |
|---|---|
| Date | 2017-06-29 16:16 +0200 |
| Message-ID | <oj31sq$mcv$1@dont-email.me> |
| In reply to | #423604 |
Dne 29.6.2017 v 15:37 Tom Roberts napsal(a): > On 6/29/17 6/29/17 7:41 AM, Thomas 'PointedEars' Lahn wrote: > >> One encloses words in *asterisks*, _underscores_, and /forward >> slashes/ in >> Usenet for emphasis and similar text formatting. By contrast, >> ALL-CAPS is >> considered shouting and impolite instead. > > Some people do that, and others like me use capitals for emphasis. IMHO > it better mimics the verbal stresses people use when speaking. Aside of that, a single capitalized word is rarely considered as shouting or impoliteness. It applies rather to the whole sentences. -- Poutnik ( The Pilgrim, Der Wanderer ) A wise man guards words he says, as they say about him more, than he says about the subject.
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| From | Jim Petroff <ruuri@twjotr.eo> |
|---|---|
| Date | 2017-06-29 14:29 +0000 |
| Message-ID | <oj32rr$6bt$2@gioia.aioe.org> |
| In reply to | #423610 |
Poutnik wrote: > Dne 29.6.2017 v 15:37 Tom Roberts napsal(a): >> On 6/29/17 6/29/17 7:41 AM, Thomas 'PointedEars' Lahn wrote: > > >>> One encloses words in *asterisks*, _underscores_, and /forward >>> slashes/ >>> in Usenet for emphasis and similar text formatting. By contrast, >>> ALL-CAPS is considered shouting and impolite instead. >> >> Some people do that, and others like me use capitals for emphasis. IMHO >> it better mimics the verbal stresses people use when speaking. > > Aside of that, a single capitalized word is rarely considered as > shouting or impoliteness. > It applies rather to the whole sentences. Potty just realized pointedhead is an imbecile.
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| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Date | 2017-06-29 16:45 +0200 |
| Message-ID | <2349894.q0ZmV6gNhb@PointedEars.de> |
| In reply to | #423604 |
Tom Roberts wrote: > On 6/29/17 6/29/17 7:41 AM, Thomas 'PointedEars' Lahn wrote: >> Tom Roberts wrote: >>> From that information the observer knows the sender's age when the >>> signal >>> was SENT, without reference to the CADO frame. But from that information >>> alone the observer cannot possibly know how old she is when it is >>> RECEIVED. >>> Because this is not a measurement of the distant person, it is a >>> measurement of a SIGNAL, and the observer does not know how long the >>> signal traveled from her to him. >> >> I presume it could be calculated if the sender time would be encoded in >> the signal (as with GPS), but it would only be trivial to do in flat >> spacetime and non-complex (e.g., one-time) acceleration (as in the twin >> paradox). > > The sender's age is part of the signal, as Mike stated. But your > PRESUMPTION that the receiver could calculate the time the signal was in > transit is precisely at issue -- for arbitrary motion of the observer it > cannot be done (except for the case of my exception, using the inertial > frame, as the GPS does). In flat spacetime: Suppose the receiver would synchronize their clock with the sender when the former is at relative rest to the latter, and the sender would from then on send a signal to the receiver all the times, so that the initial distance to the receiver could be determined by subtracting light travel time. Could the receiver determine from the Doppler shift of the signal at all times what their velocity relative to the sender is at all times (so even when accelerating), and from the information in the signals, do the Lorentz transformation to obtain the sender’s current spacetime position (assuming that the sender still exists)? -- PointedEars Twitter: @PointedEars2 Please do not cc me. / Bitte keine Kopien per E-Mail.
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| From | Jim Petroff <ruuri@twjotr.eo> |
|---|---|
| Date | 2017-06-29 15:00 +0000 |
| Message-ID | <oj34mt$bu1$1@gioia.aioe.org> |
| In reply to | #423615 |
Thomas 'PointedEars' Lahn wrote: > Tom Roberts wrote: >> The sender's age is part of the signal, as Mike stated. But your >> PRESUMPTION that the receiver could calculate the time the signal was >> in transit is precisely at issue -- for arbitrary motion of the >> observer it cannot be done (except for the case of my exception, using >> the inertial frame, as the GPS does). > > Suppose the receiver would synchronize their clock with the sender when > the former is at relative rest to the latter, and the sender would from > then on send a signal to the receiver all the times, so that the initial > distance to the receiver could be determined by subtracting light travel > time. You cannot suppose that, please suppose something else.
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| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-06-29 08:11 -0700 |
| Message-ID | <bbd445b9-cc28-4622-bfed-23a734abd226@googlegroups.com> |
| In reply to | #423615 |
On Thursday, June 29, 2017 at 9:45:30 AM UTC-5, Thomas 'PointedEars' Lahn wrote: > Tom Roberts wrote: > > > On 6/29/17 6/29/17 7:41 AM, Thomas 'PointedEars' Lahn wrote: > >> Tom Roberts wrote: > >>> From that information the observer knows the sender's age when the > >>> signal > >>> was SENT, without reference to the CADO frame. But from that information > >>> alone the observer cannot possibly know how old she is when it is > >>> RECEIVED. > >>> Because this is not a measurement of the distant person, it is a > >>> measurement of a SIGNAL, and the observer does not know how long the > >>> signal traveled from her to him. > >> > >> I presume it could be calculated if the sender time would be encoded in > >> the signal (as with GPS), but it would only be trivial to do in flat > >> spacetime and non-complex (e.g., one-time) acceleration (as in the twin > >> paradox). > > > > The sender's age is part of the signal, as Mike stated. But your > > PRESUMPTION that the receiver could calculate the time the signal was in > > transit is precisely at issue -- for arbitrary motion of the observer it > > cannot be done (except for the case of my exception, using the inertial > > frame, as the GPS does). > > In flat spacetime: > > Suppose the receiver would synchronize their clock with the sender when the > former is at relative rest to the latter, and the sender would from then on > send a signal to the receiver all the times, so that the initial distance to > the receiver could be determined by subtracting light travel time. > > Could the receiver determine from the Doppler shift of the signal at all > times what their velocity relative to the sender is at all times (so even > when accelerating), and from the information in the signals, do the Lorentz > transformation to obtain the sender’s current spacetime position (assuming > that the sender still exists)? > Of course not. The receiver would never get the sender's _current_ spacetime position from the signal, because there would always be a delay, as the signal has to traverse the distance, from the sender, to the receiver.
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| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Date | 2017-06-29 17:19 +0200 |
| Message-ID | <2053843.n0HT0TaD9V@PointedEars.de> |
| In reply to | #423618 |
Jonathan Doolin wrote: > […] Thomas 'PointedEars' Lahn wrote: It’s called attribution _line_, not attribution novel. >> In flat spacetime: >> >> Suppose the receiver would synchronize their clock with the sender when >> the former is at relative rest to the latter, and the sender would from >> then on send a signal to the receiver all the times, so that the initial >> distance to the receiver could be determined by subtracting light travel >> time. >> >> Could the receiver determine from the Doppler shift of the signal at all >> times what their velocity relative to the sender is at all times (so even >> when accelerating), and from the information in the signals, do the >> Lorentz transformation to obtain the sender’s current spacetime position >> (assuming that the sender still exists)? > > Of course not. > > The receiver would never get the sender's _current_ spacetime position > from the signal, because there would always be a delay, > as the signal has to traverse the distance, > from the sender, to the receiver. True, but it could be interpolated more precisely, could it not? -- PointedEars Twitter: @PointedEars2 Please do not cc me. / Bitte keine Kopien per E-Mail.
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| From | Jim Petroff <ruuri@twjotr.eo> |
|---|---|
| Date | 2017-06-29 15:34 +0000 |
| Message-ID | <oj36mn$g3q$1@gioia.aioe.org> |
| In reply to | #423619 |
Thomas 'PointedEars' Lahn wrote: >> The receiver would never get the sender's _current_ spacetime position >> from the signal, because there would always be a delay, >> as the signal has to traverse the distance, >> from the sender, to the receiver. > > True, but it could be interpolated more precisely, could it not? No, is not, pointy boy.
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| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-06-29 08:39 -0700 |
| Message-ID | <95cda5dd-4734-4e7f-89ff-b4bdd9c00e10@googlegroups.com> |
| In reply to | #423619 |
On Thursday, June 29, 2017 at 10:19:58 AM UTC-5, Thomas 'PointedEars' Lahn wrote: > > > > The receiver would never get the sender's _current_ spacetime position > > from the signal, because there would always be a delay, > > as the signal has to traverse the distance, > > from the sender, to the receiver. > > True, but it could be interpolated more precisely, could it not? The receiver (observer) could interpolate the current distance to the sender (observed) but the interpolation requires "knowledge" of the path the sender is going to follow. But the "knowledge" isn't measurement. It is based on an expectation that the observed object will follow some prescribed path, that the observer will only be able to confirm after some time passes and the currently transmitted event reaches the observer.
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| From | Jim Petroff <ruuri@twjotr.eo> |
|---|---|
| Date | 2017-06-29 15:29 +0000 |
| Message-ID | <oj36cd$f4j$1@gioia.aioe.org> |
| In reply to | #423618 |
Jonathan Doolin wrote: > The receiver would never get the sender's _current_ spacetime position > from the signal, because there would always be a delay, > as the signal has to traverse the distance, from the sender, to the > receiver. Easy to find out, once the distance, direction and speed of the satellite wrt to the receiver is known. Not even worth calculate, since the offset would be insignificant small.
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| From | Tom Roberts <tjroberts137@sbcglobal.net> |
|---|---|
| Date | 2017-07-01 12:29 -0500 |
| Message-ID | <Ff2dncPsl6R6RsrEnZ2dnUU7_83NnZ2d@giganews.com> |
| In reply to | #423615 |
On 6/29/17 6/29/17 9:45 AM, Thomas 'PointedEars' Lahn wrote: > In flat spacetime: > > Suppose the receiver would synchronize their clock with the sender when the > former is at relative rest to the latter, That is a more restricted instance of what I said, "as long as he knew [sender's age] at some earlier point along his path". > and the sender would from then on > send a signal to the receiver all the times, so that the initial distance to > the receiver could be determined by subtracting light travel time. That's extending the scenario, but OK. > Could the receiver determine from the Doppler shift of the signal at all > times what their velocity relative to the sender is at all times (so even > when accelerating), and from the information in the signals, do the Lorentz > transformation to obtain the sender’s current spacetime position (assuming > that the sender still exists)? No. There is ambiguity between relative speed and relative angle between signal and velocity. But as long as the observer keeps track of his speed relative to the original inertial frame [#], then from the value of his own watch he can continuously keep track of the time coordinate of the inertial frame (by inverting the equation for "time dilation" relative to an inertial frame). That time coordinate is, of course, also the age of the sender (who remains at rest in that frame). This uses the simultaneity of that inertial frame, not the observer's "CADO frame" (which I think is irrelevant and useless here). In some distant future in which spaceships travel at relativistic speeds, this is surely what an astronaut would want to know about the age of relatives back on earth, not anything related to the "CADO frame". Moreover, it is more straightforward to calculate. [#] Any astronaut would surely do this automatically. Tom Roberts
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| From | Mike Fontenot <mlfasf@comcast.net> |
|---|---|
| Date | 2017-07-02 12:35 -0600 |
| Message-ID | <ace3aa26-2f77-fbc1-8a97-2b60988343f5@comcast.net> |
| In reply to | #423762 |
On 7/1/17 11:29 AM, Tom Roberts wrote: > > But as long as the observer keeps track of his speed relative to the > original inertial frame [#], then from the value of his own watch he can > continuously keep track of the time coordinate of the inertial frame (by > inverting the equation for "time dilation" relative to an inertial > frame). That time coordinate is, of course, also the age of the sender > (who remains at rest in that frame). This uses the simultaneity of that > inertial frame, not the observer's "CADO frame" (which I think is > irrelevant and useless here). > > In some distant future in which spaceships travel at relativistic > speeds, this is surely what an astronaut would want to know about > the age of relatives back on earth, not anything related to the > "CADO frame". Moreover, it is more straightforward to calculate. > > [#] Any astronaut would surely do this automatically. > In terms of the CADO terminology, you're proposing to use CADO_H(t) for the TRAVELER'S conclusion about the current age of the home twin (she) when his age is "t". In the CADO formalism, CADO_H(t) is the age of the home twin, when the traveler's age is "t", according to the HOME twin. In contrast, the CADO formalism says that the traveler's "viewpoint" should be CADO_T(t), which is the age of the home twin when the traveler's age is "t", according to the TRAVELER. CADO_T(t) is easily and quickly obtained via the CADO equation, using CADO_H(t) and a couple of other quantities as input. Your astronaut COULD choose to use CADO_H(t) as his "viewpoint" if he wants to, but there's a BIG disadvantage to that choice. Suppose that for most of the voyage, his rocket motor is off ... suppose it's only used for a short time at the beginning of the trip, and at the turnaround, and at the end of the trip. During the (long) inertial portions of the trip, the astronaut won't be able to use the standard time-dilation result that says that moving clocks run slower than his own clocks ... or equivalently, that the home twin should be ageing more slowly than he is. But CADO_H(t) says that the home twin is ageing more quickly than he is ... the opposite of the time dilation result. And, even more disturbing, if the astronaut uses his own measurements and elementary calculations, he will find that the home twin is indeed ageing more slowly than he is, during the inertial portions of his trip, which contradicts what CADO_H(t) tells him. I don't think most astronauts would be happy with that situation. -- https://sites.google.com/site/cadoequation/cado-reference-frame "Accelerated Observers in Special Relativity", PHYSICS ESSAYS, December 1999, p629. All you ever need to know about the twin "paradox".
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| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-07-03 08:18 -0700 |
| Message-ID | <c148b865-273b-454b-a1b9-0a8f80f24fd4@googlegroups.com> |
| In reply to | #423826 |
On Sunday, July 2, 2017 at 1:35:04 PM UTC-5, Mike_Fontenot wrote: > On 7/1/17 11:29 AM, Tom Roberts wrote: > > > > But as long as the observer keeps track of his speed relative to the > > original inertial frame [#], then from the value of his own watch he can > > continuously keep track of the time coordinate of the inertial frame (by > > inverting the equation for "time dilation" relative to an inertial > > frame). I think it is confusing here, Tom, that you refer to "the time coordinate of the inertial frame". I think, below, Mike guessed that you mean "the time coordinate of the inertial frame AT the position of the traveling twin." Mike then correctly points out, if this is what you meant, then that time would be proceeding, not SLOWER than the traveling twin's clock, but FASTER than the traveling twin's clock. > > That time coordinate is, of course, also the age of the sender > > (who remains at rest in that frame). This uses the simultaneity of that > > inertial frame, not the observer's "CADO frame" (which I think is > > irrelevant and useless here). > > > > In some distant future in which spaceships travel at relativistic > > speeds, this is surely what an astronaut would want to know about > > the age of relatives back on earth, not anything related to the > > "CADO frame". Moreover, it is more straightforward to calculate. > > > > [#] Any astronaut would surely do this automatically. > > > > In terms of the CADO terminology, you're proposing to use CADO_H(t) for > the TRAVELER'S conclusion about the current age of the home twin (she) > when his age is "t". In the CADO formalism, CADO_H(t) is the age of the > home twin, when the traveler's age is "t", according to the HOME twin. > In contrast, the CADO formalism says that the traveler's "viewpoint" > should be CADO_T(t), which is the age of the home twin when the > traveler's age is "t", according to the TRAVELER. CADO_T(t) is easily > and quickly obtained via the CADO equation, using CADO_H(t) and a couple > of other quantities as input. > > Your astronaut COULD choose to use CADO_H(t) as his "viewpoint" if he > wants to, but there's a BIG disadvantage to that choice. Suppose that > for most of the voyage, his rocket motor is off ... suppose it's only > used for a short time at the beginning of the trip, and at the > turnaround, and at the end of the trip. During the (long) inertial > portions of the trip, the astronaut won't be able to use the standard > time-dilation result that says that moving clocks run slower than his > own clocks ... or equivalently, that the home twin should be ageing more > slowly than he is. But CADO_H(t) says that the home twin is ageing more > quickly than he is ... the opposite of the time dilation result. And, > even more disturbing, if the astronaut uses his own measurements and > elementary calculations, he will find that the home twin is indeed > ageing more slowly than he is, during the inertial portions of his trip, > which contradicts what CADO_H(t) tells him. I don't think most > astronauts would be happy with that situation. > I think I see what you're saying here Mike: If the traveling twin is constantly thinking about "what time is it *here-where-I-am* in the reference frame of the home twin?" He would agree that the home-twin's *system* of clocks is indeed going faster than his own clock. Though each independent clock in the home twin's system is going slower than the traveling twin's clock, each clock the traveling twin passes is slightly ahead, of the clock he passed just before. If your hypothetical astronaut bothers to make such calculations he should calculate that both facts are true. But since both facts are simultaneously true, and not a matter of opinion, I don't think either one would make the astronaut more disturbed or unhappy than the other.
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| From | Mike Fontenot <mlfasf@comcast.net> |
|---|---|
| Date | 2017-07-03 09:45 -0600 |
| Message-ID | <91ebc5a9-2d31-d284-c871-bcc09b384b23@comcast.net> |
| In reply to | #423864 |
On 7/3/17 9:18 AM, Jonathan Doolin wrote: > > But since both facts are simultaneously true, and not a matter of opinion, > I don't think either one would make the astronaut > more disturbed or unhappy than the other. > What would make the astronaut unhappy would be to have to adopt a "viewpoint" for himself about the home twin's current age that disagrees with his own measurements and elementary calculations. -- https://sites.google.com/site/cadoequation/cado-reference-frame "Accelerated Observers in Special Relativity", PHYSICS ESSAYS, December 1999, p629. All you ever need to know about the twin "paradox".
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| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-07-04 05:24 -0700 |
| Message-ID | <afd2858f-ff44-4807-bfa1-690ff914bad6@googlegroups.com> |
| In reply to | #423866 |
On Monday, July 3, 2017 at 10:45:17 AM UTC-5, Mike_Fontenot wrote: > On 7/3/17 9:18 AM, Jonathan Doolin wrote: > > > > But since both facts are simultaneously true, and not a matter of > opinion, > > I don't think either one would make the astronaut > > more disturbed or unhappy than the other. > > > > What would make the astronaut unhappy would be to have to adopt a > "viewpoint" for himself about the home twin's current age that disagrees > with his own measurements and elementary calculations. > If the astronaut were measuring the same thing in two different ways, and came up with two different answers, I could see saying, this would make the astronaut unhappy. But if you are measuring two different things (1) The "home twin's current age" at the home twin's location (with "current" being defined with the traveling twin's simultaneity) and (2) the "age of a clock synchronized with the twin" (with "synchronized" being defined with the home twin's simultaneity) at the traveling twin's location You're measuring two different rates, and it should cause no unhappiness or disturbance that the two different rates come to two different things. Mathematically, the first (1) is a partial derivative dt/dt' with the x' held constant, which evaluates to 1/sqrt(1-v^2/c^2) > 1 and the second (2) is a partial derivative dt/dt' with the x held constant, which evaluates to sqrt(1-v^2/c^2) < 1. The two "elementary calculations" will disagree because they're not calculating the same quantity.
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| From | Tom Roberts <tjroberts137@sbcglobal.net> |
|---|---|
| Date | 2017-07-03 17:52 -0500 |
| Message-ID | <PrudnUXQI78KV8fEnZ2dnUU7_8zNnZ2d@giganews.com> |
| In reply to | #423864 |
On 7/3/17 7/3/17 10:18 AM, Jonathan Doolin wrote: > On Sunday, July 2, 2017 at 1:35:04 PM UTC-5, Mike_Fontenot wrote: >> On 7/1/17 11:29 AM, Tom Roberts wrote: >>> But as long as the observer keeps track of his speed relative to the >>> original inertial frame [#], then from the value of his own watch he can >>> continuously keep track of the time coordinate of the inertial frame (by >>> inverting the equation for "time dilation" relative to an inertial >>> frame). > > I think it is confusing here, Tom, that you refer to "the time coordinate of > the inertial frame". I think, below, Mike guessed that you mean "the time > coordinate of the inertial frame AT the position of the traveling twin." But the value of the time coordinate of an inertial frame is independent of location -- it has the same value everywhere, because that's what those words mean (when applied to an inertial frame, which is one of the main reason inertial frames are so useful). So your addition adds nothing. > Mike then correctly points out, if this is what you meant, then that time > would be proceeding, not SLOWER than the traveling twin's clock, but FASTER > than the traveling twin's clock. Yes, of course (unless the traveling twin stops somewhere at rest in that inertial frame). Any astronaut capable of traveling at relativistic speed would know this. Tom Roberts
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| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-07-04 05:45 -0700 |
| Message-ID | <927843b4-97ac-4b7b-9e52-4a0b4877c2e0@googlegroups.com> |
| In reply to | #423903 |
On Monday, July 3, 2017 at 5:52:14 PM UTC-5, tjrob137 wrote: > On 7/3/17 7/3/17 10:18 AM, Jonathan Doolin wrote: > > On Sunday, July 2, 2017 at 1:35:04 PM UTC-5, Mike_Fontenot wrote: > >> On 7/1/17 11:29 AM, Tom Roberts wrote: > >>> But as long as the observer keeps track of his speed relative to the > >>> original inertial frame [#], then from the value of his own watch he can > >>> continuously keep track of the time coordinate of the inertial frame (by > >>> inverting the equation for "time dilation" relative to an inertial > >>> frame). > > > > I think it is confusing here, Tom, that you refer to "the time coordinate of > > the inertial frame". I think, below, Mike guessed that you mean "the time > > coordinate of the inertial frame AT the position of the traveling twin." > > But the value of the time coordinate of an inertial frame is independent of > location -- it has the same value everywhere, because that's what those words > mean (when applied to an inertial frame, which is one of the main reason > inertial frames are so useful). So your addition adds nothing. > I'm not sure what scenario you're thinking of, But it's certainly not generally true. Recall the Lorentz Transformation for t': t' = (t - vx/c^2)/sqrt(1-v^2/c^2) Here, you can see that the time, t', is NOT independent of location, x. Rather, it is a linear function of the location, x. > > Mike then correctly points out, if this is what you meant, then that time > > would be proceeding, not SLOWER than the traveling twin's clock, but FASTER > > than the traveling twin's clock. > > Yes, of course (unless the traveling twin stops somewhere at rest in that > inertial frame). Any astronaut capable of traveling at relativistic speed would > know this. > > Tom Roberts Sure, but he would also understand that the time coordinate of the home twin's frame would not be the same at his own position, and at the home twin's position.
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| From | Poutnik <poutnik4nntp@gmail.com> |
|---|---|
| Date | 2017-07-04 15:03 +0200 |
| Message-ID | <ojg3fd$aoj$1@dont-email.me> |
| In reply to | #423925 |
Dne 4.7.2017 v 14:45 Jonathan Doolin napsal(a): > On Monday, July 3, 2017 at 5:52:14 PM UTC-5, tjrob137 wrote: >> >> But the value of the time coordinate of an inertial frame is independent of >> location -- it has the same value everywhere, because that's what those words >> mean (when applied to an inertial frame, which is one of the main reason >> inertial frames are so useful). So your addition adds nothing. >> > > I'm not sure what scenario you're thinking of, > But it's certainly not generally true. > > Recall the Lorentz Transformation for t': > t' = (t - vx/c^2)/sqrt(1-v^2/c^2) > > Here, you can see that the time, t', is NOT > independent of location, x. > Rather, it is a linear function of the location, x. > You get it wrong. Time t' does not belong to the same frame as location x. It is transformation t->t', what is linear function of location x. Not t' itself. When there is in coordinate system O' time t', there is time t' in the whose system. -- Poutnik ( The Pilgrim, Der Wanderer ) A wise man guards words he says, as they say about him more, than he says about the subject.
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| From | Jonathan Doolin <good4usoul@gmail.com> |
|---|---|
| Date | 2017-07-07 13:56 -0700 |
| Message-ID | <7d29a4b0-ca42-4661-a27a-9d7329ce16d5@googlegroups.com> |
| In reply to | #423926 |
On Tuesday, July 4, 2017 at 8:03:17 AM UTC-5, Poutnik wrote: > Dne 4.7.2017 v 14:45 Jonathan Doolin napsal(a): > > On Monday, July 3, 2017 at 5:52:14 PM UTC-5, tjrob137 wrote: > > >> > >> But the value of the time coordinate of an inertial frame is independent of > >> location -- it has the same value everywhere, because that's what those words > >> mean (when applied to an inertial frame, which is one of the main reason > >> inertial frames are so useful). So your addition adds nothing. > >> > > > > I'm not sure what scenario you're thinking of, > > But it's certainly not generally true. > > > > Recall the Lorentz Transformation for t': > > t' = (t - vx/c^2)/sqrt(1-v^2/c^2) > > > > Here, you can see that the time, t', is NOT > > independent of location, x. > > Rather, it is a linear function of the location, x. > > > > You get it wrong. > Time t' does not belong to the same frame as location x. > But if you can read rulers and clocks from a frame, you can see the clocks and rulers of each frame from any position. t' would be a measure of the time of events on clocks comoving with the origin of the primed frame. t is the measure of time of events on clocks comoving with the origin of the unprimed frame x is the measure of positions of events by rulers comoving with the origin of the unprimed frame. x' is the measure of positions of events by rulers comoving with the origin of the primed frame.
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