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Groups > sci.physics.relativity > #559000
| From | Thomas Heger <ttt_heg@web.de> |
|---|---|
| Newsgroups | sci.physics.relativity |
| Subject | Re: local time |
| Date | 2021-08-01 08:26 +0200 |
| Message-ID | <immt4qF36plU1@mid.individual.net> (permalink) |
| References | <imesinFdsmbU1@mid.individual.net> <b2ee5fec-8a22-41a8-8c4d-9c25092e91cdn@googlegroups.com> <imhn6nF15ugU1@mid.individual.net> <cd1317e1-2613-4ed8-af89-e05f5c8778bcn@googlegroups.com> |
Am 30.07.2021 um 18:19 schrieb Paparios: > El viernes, 30 de julio de 2021 a las 3:14:35 UTC-4, Thomas Heger escribió: >> Am 29.07.2021 um 15:29 schrieb Paparios: > >>> For physicists, time is what a clock reads. There is nothing we know about what time is and why it runs in one direction (from passed to future). >> OK >> >> But any clock must be somewhere by definition. >> >> This is actually the same idea as 'local time', because time is what >> clocks measure, this time is valid, where also the clock is located. >> > > Absolutely. The observer (or instrument) measures the readings of the clock at its location. Usually, the elapsed time is measured (ie, the time between two events). > > >> Now we allow an observer to construct clocks and to measure local time >> with them. >> >> This does not say, that other observers at other locations would measure >> the same time, because at other locations they would be somewhere else. > > Distant observers (or instruments) can only measure the clock ticking or the elapsed time through the reception of signals, informing the observer HERE of the clock reading THERE. > > >>> True, as every possible physics experiment uses clocks (to measure the passing of time and rulers to measure the locations of bodies). > >> Sure, but 'possible physics experiment' would require an experimenter, >> which could be called 'observer', too. >> > > As I said, the word observer implies the use of instruments at the location of the experiment. > >> This observer and his/her experiments need a location and that a local time. >> >> What happens at other places is not really known, unless some kind of >> contact is established to such an invisible realm. > > Not really. The only thing needed is the reception from signals, informing the observer HERE of the clock readings THERE. Astronomical observatories, for instance, use electromagnetic signals, like light, radio, X-rays, gamma rays, etc. to determine the physics of distant objects. > >>> >>> Clocks do not run backwards. The observation of the prince will always be of our clock to run slow and our observation of his clock will always be his clock is running slow. > >> Local clocks do not run backwards (by definition), if seen by a local >> observer. >> >> But other clocks at other locations could look like they would run >> backwards, because 'other location' means also 'other local time'. > > Wrong, as every clock, at a given location, just ticks in the positive direction at 1 second/second. The most extreme case would be that of a spacecraft approaching a black hole event horizon. In that case, an observer here on Earth would receive signals from the spacecraft clocks, which are severely time dilated with respect to our clocks. In the limit, when the spacecraft reaches the event horizon, the spacecraft clocks would be seen to completely stop, while the astronauts there would see no time dilation (ie their clocks would continue to tick at 1 second/second). The movie Interstellar shows this effect. 'Positive' is a relative measure. We all advance into the positive direction in time, whereever we are. But we cannot be everywhere. If we are somewhere, we advance into the positive direction in time. But this direction is positive only there and not necessarily everywhere else. Relativity uses Lorentz transformation. and a Lorentz transform could be imagined as complex rotation of the axis of time. Now every location has such an axis, because every location has a local time. Because two locations can have an axis of time in an angle, the angle could eventually exceed 180 °, what is actually a rotation into the opposite direction. This direction is still positive, because time is a local measure and only the time of an observed system could run backwards. > TH
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local time Thomas Heger <ttt_heg@web.de> - 2021-07-29 07:27 +0200
Re: local time Paparios <mrios@ing.puc.cl> - 2021-07-29 06:29 -0700
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-07-29 06:33 -0700
Re: local time Gary Harnagel <hitlong@yahoo.com> - 2021-07-29 08:02 -0700
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-07-29 08:10 -0700
Re: local time Uetake Matsumura <uetma@unijap2.jp> - 2021-07-29 19:04 +0000
Re: local time Uetake Matsumura <uetma@unijap2.jp> - 2021-07-29 19:35 +0000
Re: local time Thomas Heger <ttt_heg@web.de> - 2021-07-30 09:14 +0200
Re: local time Julio Di Egidio <julio@diegidio.name> - 2021-07-30 03:08 -0700
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-07-30 03:13 -0700
Re: local time Julio Di Egidio <julio@diegidio.name> - 2021-07-30 03:21 -0700
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-07-30 05:00 -0700
Re: local time Gabriella Bouttier <gabbo@nncastr2.au> - 2021-07-30 16:03 +0000
Re: local time Thomas Heger <ttt_heg@web.de> - 2021-08-01 08:34 +0200
Re: local time Paparios <mrios@ing.puc.cl> - 2021-07-30 09:19 -0700
Re: local time Thomas Heger <ttt_heg@web.de> - 2021-08-01 08:26 +0200
Re: local time Paparios <mrios@ing.puc.cl> - 2021-08-01 06:52 -0700
Re: local time Buck Ehler <buke@unicwta.pa> - 2021-08-01 14:29 +0000
Re: local time Thomas Heger <ttt_heg@web.de> - 2021-08-02 08:50 +0200
Re: local time Julio Di Egidio <julio@diegidio.name> - 2021-07-29 06:41 -0700
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-07-29 07:38 -0700
Re: local time Emmett Bradshaw <emmbs@nntunic.ki> - 2021-07-29 14:43 +0000
Re: local time Emmett Bradshaw <emmbs@nntunic.ki> - 2021-07-29 14:07 +0000
Re: local time Emmett Bradshaw <emmbs@nntunic.ki> - 2021-07-29 14:21 +0000
Re: local time Julio Di Egidio <julio@diegidio.name> - 2021-07-29 07:30 -0700
Re: local time Emmett Bradshaw <emmbs@nntunic.ki> - 2021-07-29 14:40 +0000
Re: local time "mitchr...@gmail.com" <mitchrae3323@gmail.com> - 2021-07-30 10:44 -0700
Re: local time Thomas Heger <ttt_heg@web.de> - 2021-08-01 08:32 +0200
Re: local time Ken Seto <setoken47@gmail.com> - 2021-07-31 04:07 -0700
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-01 10:45 -0400
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 06:02 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-02 13:08 +0000
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-02 06:12 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 06:26 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-02 14:31 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 08:28 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-02 15:37 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 10:04 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-02 17:36 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 12:50 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-02 20:01 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 14:06 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-02 21:34 +0000
Re: local time "mitchr...@gmail.com" <mitchrae3323@gmail.com> - 2021-08-02 15:38 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-03 04:57 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-03 13:04 +0000
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-03 13:35 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-03 07:48 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-03 15:46 +0000
Re: local time "mitchr...@gmail.com" <mitchrae3323@gmail.com> - 2021-08-03 11:47 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-04 07:28 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-04 14:54 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-04 08:46 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-04 17:31 +0000
Re: local time "mitchr...@gmail.com" <mitchrae3323@gmail.com> - 2021-08-04 11:03 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-04 13:20 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-04 21:15 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-05 05:30 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-05 14:45 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-05 08:59 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-05 16:17 +0000
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-05 09:48 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-05 17:09 +0000
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-05 10:20 -0700
Re: local time Python <python@python.invalid> - 2021-08-05 19:29 +0200
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-05 12:15 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-06 07:13 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-06 14:49 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-07 05:22 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-07 12:58 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-07 06:58 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-07 14:10 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-09 08:22 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-09 15:41 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-09 12:27 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-09 20:24 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-10 05:32 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-10 13:12 +0000
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-10 13:24 -0400
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-10 17:37 +0000
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-10 15:06 -0400
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-10 23:24 -0700
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-10 23:24 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-11 06:58 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-11 14:01 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-11 07:27 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-11 15:06 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-11 08:15 -0700
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-11 11:33 -0400
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-11 15:50 +0000
Re: local time "mitchr...@gmail.com" <mitchrae3323@gmail.com> - 2021-08-11 10:40 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-11 13:51 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-11 21:21 +0000
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-18 10:23 -0700
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-19 01:53 -0400
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-19 16:46 +0000
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-11 11:26 -0400
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-09 11:45 -0400
Re: local time "mitchr...@gmail.com" <mitchrae3323@gmail.com> - 2021-08-09 10:48 -0700
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-09 23:06 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-07 05:41 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-07 12:58 +0000
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-06 11:47 -0400
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-07 05:30 -0700
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-06 11:41 -0400
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-07 05:33 -0700
Re: local time Odd Bodkin <bodkinodd@gmail.com> - 2021-08-07 12:58 +0000
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-06 11:39 -0400
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-02 17:15 -0400
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-02 11:47 -0400
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-02 09:02 -0700
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 09:36 -0700
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-02 13:17 -0400
Re: local time Ken Seto <setoken47@gmail.com> - 2021-08-02 09:45 -0700
Re: local time Michael Moroney <moroney@world.std.spaamtrap.com> - 2021-08-02 13:31 -0400
Re: local time Thanh Walters <hwnta@uucnstv.cr> - 2021-08-02 18:00 +0000
Re: local time Maciej Wozniak <maluwozniak@gmail.com> - 2021-08-02 11:02 -0700
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