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Groups > sci.physics.relativity > #626504
| From | Thomas Heger <ttt_heg@web.de> |
|---|---|
| Newsgroups | sci.physics.relativity |
| Subject | Re: Ehrenfest paradox |
| Date | 2023-12-27 06:39 +0100 |
| Message-ID | <kv1rdhF6ggvU1@mid.individual.net> (permalink) |
| References | <kuq7ihFpeblU1@mid.individual.net> <1qm8va9.1qil74z1wc3rlbN%nospam@de-ster.demon.nl> <ZsjXr9bgTTCYAO4oJQtdLu_p5EQ@jntp> <kT_ns34ezkf-xf-FRXFdauTG6sE@jntp> |
Am 27.12.2023 um 03:21 schrieb Richard Hachel: > Le 25/12/2023 à 17:26, Richard Hachel a écrit : >> Le 24/12/2023 à 13:18, nospam@de-ster.demon.nl (J. J. Lodder) a écrit : >>> Thomas Heger <ttt_heg@web.de> wrote: >>> >>>> Hi NG >>>> >>>> I had recently read a book about GR and found it astonishing, what >>>> Einstein and Ehrenfest said about observers on a rotating disk. >>>> >>>> https://en.wikipedia.org/wiki/Ehrenfest_paradox >>>> >>>> >>>> >>>> To me it is selfevident, that observers on a rotating disk would >>>> encounter some kind of outwards acceleration, if that disk rotates. >>> >>> It was evident then, and it should be evident now, >>> is that special relativity by itself >>> is not adequate to deal with the situation. >>> That's all there is to it, >>> >>> Jan >> >> Coward, coward! >> >> R.H. > > For me, no matter how many times I tossed the problem around for > decades, it always ended up that both the circumference AND the radius > contracted. > > Let's take for example a point A which passes at the top of the record > at 12 o'clock position. > > It has practically zero velocity in "y" at this instant, and its > entire velocity vector is practically in "x". > > But we are in a rotating frame of reference, and not in a purely > Galilean frame of reference. Sure, a rotating frame of reference is not inertial. The reason: rotation is causing acceleration and that is measurable without any reference. So, rotation is 'absolute', while inertial movement is 'relative'. We know this 'absoluteness' from the realm of missile guidence or satelite control. They use laser gyroscopes, which can detect very small rotations. For rotation you don't need to see a reference point, because rotation causes acceleration. And acceleration is not inertial. > This mini component in y still exists, and it should be noted that > this small Δy does not undergo any obvious contraction, as its speed is > low compared to the tangential speed. Sure. But you certainly don't want to be an observer on a rotating disk, which has tangential velocity in the relativistic realm. That would be like sitting on a carussel, which runs insanely fast. You will be shot from that disk like a cannon ball. Therefore only very slow rotation is somehow feasable (for human observers), which is far far far from relativity velocity. > If we decompose the movement, we then understand that the part Δy does > not contract or only slightly, and that the part Δx contracts greatly at > relativistic speed. If you want to enter the realm of special relativity, you need extremely high angular velocity or extremely large disks (or both). This will bring the 'rigid' disk into its critical realm, where tensions are far greater than the strength of the material could possibly be. But at least: the radius will not shrink nor will the circumference. (more likely: that disk will break) > The observable residual velocity vector is therefore deviated inwards. > > This can explain why the disk ALSO contracts at the level of the > radius, and why there is no paradox, since pi remains invariant in this > case. I have absolutely no idea, what Einstein and Ehrenfest actually wanted to say. To me this 'paradox' is just nuts. TH
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Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2023-12-24 09:17 +0100
Re: Ehrenfest paradox nospam@de-ster.demon.nl (J. J. Lodder) - 2023-12-24 13:18 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-25 16:26 +0000
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-27 02:21 +0000
Re: Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2023-12-27 06:39 +0100
Re: Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2023-12-28 09:04 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-28 08:31 +0000
Re: Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2024-01-03 08:51 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2024-01-03 10:56 +0000
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2024-01-03 09:53 -0800
Re: Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2024-01-04 08:23 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2024-01-04 10:05 +0000
Re: Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2024-01-05 07:26 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2024-01-05 12:33 +0000
Re: Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2024-01-06 08:47 +0100
Re: Ehrenfest paradox nospam@de-ster.demon.nl (J. J. Lodder) - 2023-12-28 13:18 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-28 04:46 -0800
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-28 14:19 +0000
Re: Ehrenfest paradox Python <python@invalid.org> - 2023-12-28 16:10 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-28 16:16 +0000
Re: Ehrenfest paradox JanPB <filmart@gmail.com> - 2023-12-28 15:03 -0800
Re: Ehrenfest paradox Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-12-28 19:34 -0800
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-28 21:05 -0800
Re: Ehrenfest paradox Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-12-28 10:14 -0800
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-28 11:04 -0800
Re: Ehrenfest paradox Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-12-28 11:08 -0800
Re: Ehrenfest paradox Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-12-28 19:32 -0800
Re: Ehrenfest paradox Thomas Heger <ttt_heg@web.de> - 2023-12-31 08:08 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-31 09:38 +0000
Re: Ehrenfest paradox nospam@de-ster.demon.nl (J. J. Lodder) - 2024-01-04 12:00 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2024-01-04 11:24 +0000
Re: Ehrenfest paradox Tom Roberts <tjoberts137@sbcglobal.net> - 2024-01-04 12:18 -0600
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2024-01-04 22:18 +0000
Re: Ehrenfest paradox pnalsing@gmail.com (palsing) - 2024-01-04 23:07 +0000
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2024-01-04 21:56 -0800
Re: Ehrenfest paradox pnalsing@gmail.com (palsing) - 2024-01-05 06:36 +0000
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2024-01-04 23:45 -0800
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2024-01-05 12:18 +0000
Re: Ehrenfest paradox nospam@de-ster.demon.nl (J. J. Lodder) - 2024-01-05 13:54 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2024-01-05 05:20 -0800
Re: Ehrenfest paradox Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-12-28 01:15 -0800
Re: Ehrenfest paradox JanPB <filmart@gmail.com> - 2023-12-28 15:00 -0800
Re: Ehrenfest paradox nospam@de-ster.demon.nl (J. J. Lodder) - 2024-01-03 14:28 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2024-01-03 09:54 -0800
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2024-01-03 18:09 +0000
Re: Ehrenfest paradox Athel Cornish-Bowden <me@yahoo.com> - 2024-01-03 19:48 +0100
Re: Ehrenfest paradox Adolf Göbel <adolfgoebel@aol.com> - 2024-01-03 22:21 +0100
Re: Ehrenfest paradox JanPB <filmart@gmail.com> - 2024-01-03 11:25 -0800
Re: Ehrenfest paradox wugi <wugi@brol.invalid> - 2023-12-28 22:31 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-29 07:42 +0000
Re: Ehrenfest paradox wugi <wugi@brol.invalid> - 2023-12-29 12:51 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-29 12:58 +0000
Re: Ehrenfest paradox Ross Finlayson <ross.a.finlayson@gmail.com> - 2023-12-29 07:55 -0800
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-29 13:25 +0000
Re: Ehrenfest paradox Python <python@invalid.org> - 2023-12-29 14:36 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-29 13:43 +0000
Re: Ehrenfest paradox Python <python@invalid.org> - 2023-12-29 14:45 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-29 06:48 -0800
Re: Ehrenfest paradox Athel Cornish-Bowden <me@yahoo.com> - 2023-12-29 16:24 +0100
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-29 15:29 +0000
Re: Ehrenfest paradox Python <python@invalid.org> - 2023-12-29 20:33 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-29 12:11 -0800
Re: Ehrenfest paradox Python <python@invalid.org> - 2023-12-29 21:22 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-30 01:34 -0800
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-30 10:02 +0000
Re: Ehrenfest paradox Athel Cornish-Bowden <me@yahoo.com> - 2023-12-30 11:06 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-30 02:33 -0800
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-30 11:07 +0000
Re: Ehrenfest paradox Python <python@invalid.org> - 2023-12-29 16:53 +0100
Re: Ehrenfest paradox wugi <wugi@brol.invalid> - 2023-12-29 23:59 +0100
Re: Ehrenfest paradox Maciej Wozniak <maluwozniak@gmail.com> - 2023-12-30 01:37 -0800
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-30 17:59 +0000
Re: Ehrenfest paradox Volney <volney@invalid.invalid> - 2024-01-03 23:30 -0500
Re: Ehrenfest paradox Richard Hachel <r.hachel@tiscali.fr> - 2023-12-29 07:44 +0000
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