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QuestionQuestion regarding time dilation and the light speed limit . (self.Physics)

Darktidemage が 投稿

Lets say I move really fast, or I go near a gravity source that is very great. We can get into a situation where for every 1 hour I'm experiencing you are experiencing 100 hours. Right?

So.... in that circumstance couldn't it appear to me as if things you are doing are happening faster than light?

Like in the movie Interstellar they say 1 hour for the woman on that planet = 7 years on Earth.

So, everything on Earth would appear to be traveling 61,320 times faster than it is actually traveling? That means a satellite orbiting at 40,000 miles per hour would appear to be orbiting at 2.4 billion miles per hour. Right?

That is faster than the speed of light. How does this work? Does the Satellite begin appearing as a probability wave form instead of as a physical object? and only when we measure it's position does the waveform collapse and then give us some specific position for that "moment" but then it vanishes again, as per the uncertainty principle?

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[–]Cassiterite 22 ポイント23 ポイント  (17子コメント)

Time dilation is relative. In other words, if I am looking at a spaceship traveling at relativistic velocities, I will see the inhabitants of the spaceship as moving slower through time than me, but from their perspective, they are moving normally and I am the one moving slowly. In other words you always see objects in motion relative to yourself in slow motion, never in "fast motion".

[–]vcdiag 8 ポイント9 ポイント  (2子コメント)

As others have explained, it doesn't quite work as you suggested in the examples you gave. But it's easy to come up with some other examples that also seem paradoxical. For example, if you spin on your chair at about 1 revolution per second, the moon appears to rotate around you up to 6 times faster than light. So what is going on?

Well, the truth is, coming up with a definition of "faster than light" that works in general is surprisingly tricky (see also section IIA here), particularly once you allow the geometry of spacetime or the matter distribution to be dynamical.

Fortunately, the basic, intuitive idea is simple for our purposes: we say that something is moving "slower than light" if it moves within its local light cone. The moon appears to be traversing a great distance according to you, but then again so does moonlight. What is important from the point of view of relativity is that causality be preserved, that effects don't precede their causes, and this depends only on whether messages can outrun light in their local environment. The perspective of someone far away, then, doesn't matter.

[–]Darktidemage[S] -2 ポイント-1 ポイント  (1子コメント)

That makes sense. My point wasn't "this should be impossible" though. I think it is possible, and must work this way. .

I'm just curious what it would look like. Seeing this through a telescope, when a satellite is going around Earth and it appears to be going 4.2 billion miles per hour. What if it went even faster? What if the speed it was going was such we stop being able to resolve it visually from moment to moment? Then it maybe it begins to look more like a quantum fluctuation, or a wave form, and not a classical object?

If at 61,000 times multiplication of how fast the satellite appears to be going around Earth you can see it at every point, is there some multiplication factor where that breaks down? Where you begin to see it as a "smear" on your measuring device? And only if you focus the measurement on one specific point at one specific time; then the satellite can actually be said to be in that spot, or not in that spot.

[–]sargeantbob 4 ポイント5 ポイント  (0子コメント)

Macroscopic objects don't behave like that. Things don't just become a "quantum fluctuation." Ignoring everything, if we speed up the unbreakable satellite to just under the speed of light, we still know where it is and how fast it's moving extremely well since it is a macroscopic object. In fact, just choose the boosted reference frame inside of the satellite and physics can be done at a stand still.

Edit: I suggested above you should read on relativity. You should also read on QM. I don't mean watching videos on the double slit experiment either. Crack open a modern physics text or Griffiths QM.

[–]jazzwhizParticle physics 12 ポイント13 ポイント  (3子コメント)

Velocities don't scale like that. The situation you've described is a somewhat complex one, but it is essentially the same as the standard special relativistic velocity. Check Wikipedia for relativistic velocity addition formula, and you will see that velocities scale in such a way that they never exceed c.

[–]Darktidemage[S] 1 ポイント2 ポイント  (2子コメント)

If Earth is moving at C around the sun it takes 500 seconds to orbit the sun.

Is that then the maximum possible ratio of time dilation? 1 year : 500 seconds?

I can't comprehend how it's possible.

I didn't think there was a maximum ratio of time dilation.

I thought if I went to .999C or .9999C or .99999C etc then the ratio of my time as compared to Earth time would keep becoming more and more skewed .... indefinitely. So that if I was "very close" to the speed of light I could get massive ratios like 1 second for me the Earth would go around the sun a billion times and the sun would swell up and whatnot.

But.... you are saying it's limited to me only ever seeing the Earth go around the sun at C?

[–]sargeantbob 3 ポイント4 ポイント  (0子コメント)

The Earth cannot have a velocity of the speed of light. Yes time dilation is indefinitely large as one moves at speeds closer and closer to c.

The comments have done a good job explaining things. I'd suggest popping open a book and reading more for yourself to supplement things. It seems like you just have some of the symmetries flipped in your head.

Also you probably won't see circular motion in relativity problems until you get knee deep. If you're interested, look up the Einstein disc.

[–]jazzwhizParticle physics 0 ポイント1 ポイント  (0子コメント)

The earth is moving towards you half the time and away from you half the time.

[–]MrSweetAndAwful 2 ポイント3 ポイント  (1子コメント)

ITT: OP thinks he's beaten physics and ignores all logical answers

[–]rhn94 0 ポイント1 ポイント  (0子コメント)

look at his post history, he's a trumpanzee and a fucking moron

[–]roshokaUndergraduate 1 ポイント2 ポイント  (12子コメント)

There are two ways to approach this.

The first is the easy way. Lets say I am on earth and you are in space traveling at a constant relativistic speed. Let's say I am the one observing you. So we know from time dilation, that I would observe a longer time interval than you would. Now, since you are traveling at a constant speed (inertial reference frame), we can flip it and look at me from your reference frame. So from your point of view, you are still and I am moving at a relativistic speed in the other direction. Now, applying the concept of time dilation to your point of view, it is clear that you would be the one observing a longer time interval.

The second way is more complicated (but the answer, when fully understood, may satisfy you more than the easy way I described earlier). The basic gist of it is that our clocks aren't actually in sync like you are thinking they are. If you want to read a full answer, look up "A first course in General Relativity 2nd ed" By Schutz. There is a free pdf of it online. Page 19 pretty much answers your exact question (the velocity part, at least) in the section "Failure of Relativity?" I can't use it's explanation here because it relies on a space-time diagram. But I recommend giving it a look (although you may have to skim through earlier pages of the book to get the notation).

[–]Darktidemage[S] 1 ポイント2 ポイント  (11子コメント)

Hm. perhaps I'm confused.

I get how velocity can be relative ; but is sitting in a gravitational field relative too?

I go in space and sit in a gravitational field, such that 50 years pass on Earth to my 1 year sitting in this gravitational field. I'm looking at Earth with a telescope.

Don't I see 50 years worth of light from Earth during the course of that 1 year collecting light in my telescope?

Would I not receive 50 years worth of programs on my TV in the gravity field? Would I not get 50 years worth of technological advancement downloaded off my internet connection?

i'm not going to feel like I'm experiencing the reverse and Earth is only producing at 1/50th speed. I will get 50x the information from Earth. That's what is going to occur. This will also happen if I am traveling relativistic speed ..... what would prevent me from getting signals sent from Earth during my flight? Voyager has been flying through space, and we have sent out signals. Those signals have reached it..... right? So.... voyager felt like X time passed. In reality very slightly MORE than X time passed, and it actually got MORE than x time worth of digital signals from Earth.

[–]roshokaUndergraduate 1 ポイント2 ポイント  (10子コメント)

Well, I guess my answer was answering the "going really fast" portion of your question instead of the gravity. I don't know as much about the gravity situation. Maybe someone else will reply with that part.

[–]Darktidemage[S] 0 ポイント1 ポイント  (9子コメント)

I can't see how "going really fast" is any different.

Say I travel in a straight line away from Earth at .9C.

1 year for me = 3 years on Earth.

Earth broadcasts the results of the "best picture of the year" from the oscars every year right? The TV signal goes off into space AT C.

SO.... I don't get those transmissions?

After I think 1 year has passed for me, you are saying "relativity makes me think Earth is moving very fast .... so I will see that 1 year passed for me, but only 1/3rd of a year passed on Earth". But in my computer it will have gotten the information and it will have told me three movies named which won best picture. I will know 3 years passed on Earth.

[–]Boccard 2 ポイント3 ポイント  (2子コメント)

Earth broadcasts the results of the "best picture of the year" from the oscars every year right? The TV signal goes off into space AT C.

SO.... I don't get those transmissions?

You get those transmissions every 3 years, as measured by you.

They send them off every year, but from their reference frame, your clocks are slow, so from their reference frame your clocks read the transmissions also every three years.

[–]Darktidemage[S] -2 ポイント-1 ポイント  (1子コメント)

I don't think that's true. I don't think I only get them once every 3 years.

Otherwise time wouldn't be dilated.

[–]Boccard 1 ポイント2 ポイント  (0子コメント)

Sure it would. Time dilation means that clocks that you are measuring appear to move slower. From your reference frame, the transmission of the signals appears to be slower (it only happens every 3 years) and from the earth's reference frame your measurement of the transmissions appears slower, so that you seem to be getting the transmissions every 3 years based on what they see as your clocks measuring.

[–]roshokaUndergraduate 1 ポイント2 ポイント  (4子コメント)

You'd get the transmission.

Going by what you said, Earth's first transmission would reach you on your third year.

[–]Darktidemage[S] 0 ポイント1 ポイント  (3子コメント)

and if Ithen saved Earth transmissions for 1 year after that I'd realize they did 3 best pictures in that year.

IE "everything on Earth is going 3x as fast as it is going for me".

Right? Not "earth has things going on 1/3rd as fast as I do because relative to me standing still they are moving away from me fast". . .

[–]roshokaUndergraduate 5 ポイント6 ポイント  (1子コメント)

I reread this conversation and I think your transmission analogy is throwing us off.

Time dilation works both ways in inertial reference frames. If I am on earth (and I'm the observer) and you are in space traveling very fast relative to me, and it takes you (from your perspective) 1 year to cross a certain distance, then I ( on earth) will have observed you crossing that same distance in 3 years.

Now if you switched it, making you the observer, then I would be traveling very fast the other way. Then I would be crossing that distance in 1 year (from my perspective) and you would observe me crossing that distance in 3 years.

It does seem weird that it works both ways, but it is the truth. It has been measured plenty of times in experiments.

You may be getting mixed up on your "1 year for me = 3 years for earth" bit. Keep in mind that "1 year for me = 3 years for earth" only works from earth's perspective. Because an earth observer would measure 3 years for you to cross the distance, while you would only measure 1 year. From your perspective it would be "3 years for me = 1 year for earth" since time dilation works both ways.

[–]sargeantbob 1 ポイント2 ポイント  (0子コメント)

Please think about symmetry. You're ignoring it. Imagine changing places in each situation you think of and imagine meeting in the middle. Measurements have to be the same for each frame but simultaneity doesn't.

[–]AnythingApplied 1 ポイント2 ポイント  (0子コメント)

Observing something going "really fast" or sped up would violate the speed of light. If everything looked like it was going super fast then photons would look like they were going faster than the speed of light, which doesn't work.

All of general relativity is derived from the fact that any observer from any location see light going the same speed. The rest of the weirdness of general relativity, like the time dilation, increasing mass, length contraction all come from holding the speed of light constant from all observers. Like someone standing still views a photon going the same speed as someone almost keeping up with it. Lots of variables have to be twisted in order to make that actually work, but it turns out to be what is needed.

[–]wilusa 4 ポイント5 ポイント  (2子コメント)

Commenting to remember i need to see answers on this.

[–]Xeno87Graduate 1 ポイント2 ポイント  (1子コメント)

You can use the RemindMe-bot for this.

[–]notatalker00 0 ポイント1 ポイント  (0子コメント)

In your example you wouldn't be able to tell exactly where the person was. If you were orbiting someone at. 9C and they were standing still - from the standing still person you would appear differently.

In your other example, where both are hitting buttons - let's say they play a blep every time they are pressed. So every like second they make a bip. Well to the one on the ground they would just hear the bip, but it'd be distorted because that same action took more physical space to accomplish. The person traveling would hear the bip, but it'd be slowed down tremendously - to point where it might not be able to bip.

[–]SILENTSAM69 0 ポイント1 ポイント  (0子コメント)

Take this even further. If you travel at the speed of light then time dilation has gotten to the point where it takes zero time to get anywhere. It also takes no distance to get there. So a photon does not exist, and doesn't travel any distance, as far as it is concerned.

[–]BTownPhD 0 ポイント1 ポイント  (0子コメント)

Read Schrödinger's cat and schrodigers kittens for a good and citable explanation.

Simply. In one scenario the author explains how two observers who at the speed of light away from each other, would still calculate the other observers velocity to be equal to the speed of light relative to them and defends the claim that nothing can ever travel faster than the speed of light relative to another object.

There are a lot of other good questions and answers in the books.

[–]thejaga 0 ポイント1 ポイント  (0子コメント)

In the case of a gravitational field, you are making a mistake of assuming what you can see is a true sight ignoring the effects of dilation. The light from an orbiting object will dilate as it reaches you and the appearance will not be that of increased speed

[–]gassy-e911 -2 ポイント-1 ポイント  (0子コメント)

Good question wish I could help you out with this one.