# Another "Relativity from the photon's viewpoint" question

**URL:** <https://boards.straightdope.com/t/another-relativity-from-the-photons-viewpoint-question/982344>\
**Category:** Factual Questions\
**Created:** [April 7, 2023, 10:54pm UTC](https://boards.straightdope.com/t/another-relativity-from-the-photons-viewpoint-question/982344 "2023-04-07T22:54:36Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\
**Post date:** [April 7, 2023, 10:54pm UTC](https://boards.straightdope.com/t/another-relativity-from-the-photons-viewpoint-question/982344/1 "2023-04-07T22:54:36Z")

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If from a photon’s perspective the rest of the universe is traveling at C, how does that not mean that all the objects with rest mass in the universe appear to have infinite relativistic mass?

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [April 7, 2023, 11:12pm UTC](https://boards.straightdope.com/t/another-relativity-from-the-photons-viewpoint-question/982344/2 "2023-04-07T23:12:05Z")

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First off, part of the point of relativity is that a photon does not, cannot, have a viewpoint, so any question that starts off with “from the photon’s viewpoint” is inherently meaningless.

But I think we can get past that. Let’s, instead of a photon, consider the viewpoint of the Oh-my-God Particle. From that particle’s viewpoint, wouldn’t the rest of the objects in the Universe all have a finite but ludicrously huge relativistic mass? Yes, they would. And so what?

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**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\
**Post date:** [April 8, 2023, 2:46am UTC](https://boards.straightdope.com/t/another-relativity-from-the-photons-viewpoint-question/982344/3 "2023-04-08T02:46:35Z")

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> [@Chronos](#):
>
> First off, part of the point of relativity is that a photon does not, cannot, have a viewpoint, so any question that starts off with “from the photon’s viewpoint” is inherently meaningless.

But wasn’t that exactly the viewpoint of Einstein’s original _Gedankenexperiment_?

> If I pursue a beam of light with the velocity c (velocity of light in a vacuum), I should observe such a beam of light as an electromagnetic field at rest though spatially oscillating. There seems to be no such thing, however, neither on the basis of experience nor according to Maxwell’s equations. From the very beginning it appeared to me intuitively clear that, judged from the standpoint of such an observer, everything would have to happen according to the same laws as for an observer who, relative to the earth, was at rest. For how should the first observer know or be able to determine, that he is in a state of fast uniform motion?

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**Author:** ![Buck\_Godot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/buck_godot/32/6573_2.png) [@Buck\_Godot](https://boards.straightdope.com/u/Buck_Godot)\
**Post date:** [April 8, 2023, 4:12am UTC](https://boards.straightdope.com/t/another-relativity-from-the-photons-viewpoint-question/982344/4 "2023-04-08T04:12:31Z")

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I believe that the problem is that “from the photons point of view” there is no such thing as space and time, which makes is hard to have a point of view. The universe is a infinitely thin plane which it would transverse instantaneously, except for the fact that the universe is also expanding infinitely fast.

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [April 8, 2023, 1:25pm UTC](https://boards.straightdope.com/t/another-relativity-from-the-photons-viewpoint-question/982344/5 "2023-04-08T13:25:11Z")

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> [@Lumpy](#):
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> But wasn’t that exactly the viewpoint of Einstein’s original _Gedankenexperiment_?

Yes, exactly. He started by assuming that a photon had a point of view, and from that deduced a logical impossibility, and thus concluded that photons don’t have a point of view.