5
$\begingroup$

Gravitational time dilation like the one shown in the movie Interstellar, causes time to move slowly for someone within the high gravity reference frame. Now let's say that from such a place, I was able to view through a telescope somewhere far away which is not gravitationally dilated. And assume that I am able to view the near live video stream of it. Would those people look fast moving?

$\endgroup$
  • 1
    $\begingroup$ I don't think it really makes sense to talk about a "gravitational time dilated place". Time dilation is a relative phenomenon, in which different observers calculate different intervals between the same two events. In special relativity, for instance, two moving observers will each calculate that the others clock is "running slow". $\endgroup$ – Steve Linton Jun 27 at 10:24
  • $\begingroup$ I'm pretty sure there was a film narrated by Albert Einstein that describes exactly this. I even remember Einstein joking he saw who won a future World Series, but he wasn't going to tell. $\endgroup$ – barrycarter Jun 27 at 16:18
  • $\begingroup$ Similar to (possibly duplicate of) astronomy.stackexchange.com/questions/8136/… $\endgroup$ – Florin Andrei Jun 27 at 19:08
  • $\begingroup$ Time dilation is one of the more fantastical postulates from the messy minds of theoretical physicists. It's based utterly on the belief that time is an actual property, as opposed to what it really is: entirely a human construct/concept. $\endgroup$ – White Prime Jun 28 at 14:34
3
$\begingroup$

a Gravitational-Time dilated place to somewhere far which is not dilated

"Dilated" or "not dilated" are not absolutes. It's always a relative thing. "Dilated" relative to me, but perhaps "not dilated" relative to you. There is no dilation that happens "in general"; it's always relative to another place/observer/reference.

Would those people look fast moving?

Yes.

Now, everything coming out of that place would seem like it's "speeding up time" relative to you. If you're looking at them through a telescope, all light would be blue-shifted. If you're receiving a TV transmission, the frequency of the carrier would also be higher.

Keep in mind, this time dilation is not an illusion. It's not just "how you see things". Their flow of time, as measured by you, is indeed faster. This affects everything in that place, as measured by you.

But it's also relative. Some other observer may be in a place where time flows differently from yours - they would look through the telescope and would see a different rate of change. And it's not an illusion for them either.

Time dilation is real. What's not real is a unique time, ticking the same for everyone - that's the actual illusion.

Time is a local thing. (more precisely, the rate of ticking for a clock is a local thing)

$\endgroup$
  • $\begingroup$ Nice answer. Thanks. I think it was possible in an Interstellar like scenario for people on Miller's planet to look at the mother ship where Romilly aged 28 years. $\endgroup$ – Sid Jun 28 at 8:24
1
$\begingroup$

Yes they would. In fact, you can interpret cosmological observations we now do as precisely this phenomenon, only backward-- we are looking from a less dilated place to more dilated places, and they appear to be moving slowly as a result. For example, cosmologically distant supernovae seem to play out in slow motion as we watch them. So to have a situation as in your question, we only would have needed a universe that is contracting instead of expanding, and we'd be seeing things playing out in fast motion at large distance.

Note this general relativistic effect, which appears at order (v/c)^2 where v is a measure of the strength of gravity in velocity units (similar to an escape speed, for example), is not to be confused with a time-of-flight effect, which appears to order (v/c) for some actual v, and also can make things appear like they are moving fast or slow depending on the sign of v. For example, if you drive toward a drive-in movie screen, the movie will appear to play out slightly faster, but this is just a time-of-flight effect and would happen for a sound concert as well. It is also not to be confused with the special relativistic effect of time dilation, which always makes everything else outside of you appear to play out slower than it would have otherwise, regardless of whether it is moving toward you or away from you. The general relativistic effect is a gravity effect, and cosmological effects can be interpreted similarly to gravity effects as the gravity of the universe as a while evolves.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.