Relativity using sound (not visuals)?

[Baby Astronaut]

If you were on earth, making a phone call to someone on a spaceship that's travelling near the speed of light, how would the speed of each converser's voice sound?

 

a. Quicker.

b. Slow as molasses.

 

This is assuming the phone conversation were transported instantly via wormholes to each other?

[Kyrisch]

If you were on earth, making a phone call to someone on a spaceship that's travelling near the speed of light, how would the speed of each converser's voice sound?

 

a. Quicker.

b. Slow as molasses.

 

This is assuming the phone conversation were transported instantly via wormholes to each other?

 

Your P.S. invalidates the question. The whole point is that the phone signal can only travel at the speed of light. You're asking a question regarding relativity with an assumption that breaks the main tenet of relativity.

[Baby Astronaut]

Your P.S. invalidates the question. The whole point is that the phone signal can only travel at the speed of light. You're asking a question regarding relativity with an assumption that breaks the main tenet of relativity.

Can you explain how please?

 

The two conversers would experience time differently. Will that reveal itself as a difference of pace in their conversation? The phone signal isn't the point at all (the reason for my P.S.)

[Kyrisch]

Your question is not answerable because the scenario is impossible. Nothing can be transported instantaneously. The only relativistic effects that would occur can only occur if the phone signal traveled at its proper speed.

[Baby Astronaut]

Your question is not answerable because the scenario is impossible.

Would you say that to whoever made the following scenario?

 

If an observer watches a person on a train going near the speed of light....

 

Nothing can be transported instantaneously.

Using wormholes, string theory...it's a possibility. Yet I'm only asking the same level of "let's pretend" as the scenario above.

 

The only relativistic effects that would occur can only occur if the phone signal traveled at its proper speed.

The instantaneous phone exists only to avoid comments like "it's a moot point since the signal couldn't reach a spacecraft travelling near the speed of light".

 

A more valid answer would be "I don't know"

Edited August 20, 2008 by Baby Astronaut

[ajb]

Information cannot be transmitted instantaneously. At best it can be transmitted at the speed of light.

 

Now, you can set up a configuration using a wormhole* such that one has apparent faster than light travel of information. It is apparent because you sent it via the wormhole at the speed of light, but it looks like it is going faster compared to a signal sent through "normal space". There is no violation of relativity here.

 

Such configurations will lead to closed time-like curves (CTC's) better known as "time machines".

 

So, one could in principle send a message that appears instantaneous or even it could arrive before you sent it!. Again, this would not violate relativity as the information was actually sent with a speed less than the speed of light via a wormhole.

 

______________________________________________

* Lets ignore any issue as to the existence of wormholes and how to support them. Also lets ignore any technical issues with time travel.

[Kyrisch]

Would you say that to whoever made the following scenario?

 

If an observer watches a person on a train going near the speed of light....

 

That's not impossible. It's just not an attainable circumstance given present technology. Let me stress again that you're asking a question concerning the nature of relativity with an added assumption that violates relativity.

 

Using wormholes, string theory...it's a possibility. Yet I'm only asking the same level of "let's pretend" as the scenario above.

No one knows how wormholes really work, if they even exist. The signal could even arrive before it was sent, as ajb pointed out.

 

The instantaneous phone exists only to avoid comments like "it's a moot point since the signal couldn't reach a spacecraft travelling near the speed of light".

But it could... Velocity transformation is a calculable phenomenon within the maths of relativity.

[Baby Astronaut]

OK, would anyone mind answering the question if re-edited without the offending "P.S."?

 

If you were on earth, making a phone call to someone on a spaceship that's travelling near the speed of light, how would the speed of each converser's voice sound?

 

a. Quicker.

b. Slow as molasses.

 

[invalidating P.S. removed]

[swansont]

Slow. If it's analog, the signal is red-shifted, i.e. a lower frequency. If it's digital, the clock rate of the sender is slow, so your data transmission rate is slow as measured by the recipient.

[Kyrisch]

OK, would anyone mind answering the question if re-edited without the offending "P.S."?

 

I didn't want to provoke hostility. I just wanted to point out that the signal IS the point. Simultaneity is relative in SR, so instantaneous transmission is hard to handle as it dives into the ill-defined world of hypothetical wormholes.

 

Slow. If it's analog, the signal is red-shifted, i.e. a lower frequency. If it's digital, the clock rate of the sender is slow, so your data transmission rate is slow as measured by the recipient.

 

Great, simple answer by Swansont that thoroughly illustrates the point that the phenomenon is, in fact, due to the fact that the signal travels at a specific velocity, that being c.

[Pete]

OK, would anyone mind answering the question if re-edited without the offending "P.S."?

Your question as stated could have been rephrased in such a way so as to provide you with the response that you were seeking. All we have to do is cheat.

 

Here's how I'd do it: Suppose we first make a recording of the vocal message on a digital recording device. The recording is duplicated. One copy of the message is left on the earth and the other is placed on player which is comoving with the ship. At a later date the ship is moving relative to the earth and at t = 0 as measured in frame S, the rest frame of the earth, the recording starts to play on the earth and the ship. The player on the ship is synchronized with the player on the ship, as measured in S, and each player runs at the same rate as measured in S.

 

This exactly duplicates what would happen if the signal was relayed instantaneously.

 

The answer to your question is that the voice sounds slower.

 

Pete

[Baby Astronaut]

No hostility provoked Kyrisch. Heck, you might've just been trying to deter the possible spread of a misperception.

 

I probably should have elaborated on my reason for asking the original question. See, if time passes differently for person #1 on Earth than for Person #2 on the spacecraft, it'd be cool to perceive that difference in real time.

 

I'm not sure if anyone understood the scenario I aimed for. That is, if both parties can detect, in real time, the slowing or quickening of time for the other party (time passage isn't equal because of their great difference in speed). So one person might sound like a vinyl record being slowed, while the other sounds like a sped-up vinyl record (due to experiencing time faster).

 

P.S. If not in real time, some viable method then.

 

The player on the ship is synchronized with the player on the ship

Did you mean to say that?

Edited August 21, 2008 by Baby Astronaut

[Pete]

Did you mean to say that?

Nope.

 

I meant to say that the Earth player is synchronized with the ship player as measured in the Earth frame. Of course this means that the players are not snychronized in the ship frame. And it also possible that, according to the ship obervers, the ship will start to recieve the message before it is sent.

 

That's the problem with instantaneous communication in relativity!

 

Pete

[Jacques]

What if the astronaute is comming back to earth ?

Relativity time dilatation + blue shift = ???

Maybe he would sound normal .

[Pete]

What if the astronaute is comming back to earth ?

Relativity time dilatation + blue shift = ???

Maybe he would sound normal .

Excellant point. I neglected to mention that the vpoice would sound slow if the ship was moving away and sound higher if it was higher if the ship was getting closer. It would sound slower if the distance remained constant such as if the ship was moving near c in a circle with the earth at the center of the circle.

 

Pete

[Baby Astronaut]

I feel the need to start over. I'm not even certain if swansont's reply addresses each person (ie, both conversers), or just the recipeint on Earth. Plus, aren't the red-shifted signals like a doppler type effect? If so, we've definitely veered off-course from what I seek to know.

 

So, let's completely disregard what came before. I'm not interested in phone signals, distances, or travelling away/to.

 

Below, I've re-engineered my original question from the ground up. It's how I should've asked it the first time around.

 

You know in movies, how when a person moves super fast (like Clark Kent in Smallville), or their molecules have been sped up, and out on the street the normal-moving crowds of people are "frozen" motionless, indicating that's how slow they're moving in comparison to Mr Quick?

 

Well it's not scientifically correct, and not even relativity, but the scenes are handy for illustrating how a person travelling near light speed might see others travelling at Earth speed.

 

Thus my question is, if a person travelling pretty fast -- just enough that others doing Earth speed aren't motionless but rather "slowed" by 1/4 or so -- if that person were to somehow be heard speaking by those on the Earth speed frame of reference, and vice versa, would it come across to each other as if one is speaking very quickly and the other slowly?

 

After all, one is experiencing time faster, and the others slower.

That quote above is ultimately want I seek the answer to. And while it might seem its answer is obvious, I just like to double check.

Edited August 21, 2008 by Baby Astronaut

[Pete]

In responding to a question about relativity one must ask about what is actually measuring. Even traveling a slow speeds in an atmosphere there is a doppler effect which makes sounds sound higher/lower and thus voices speaking faster/slower. This is caused by the increasing/decreasing distance between source and observer. If the source is moving in a circle there is no doppler effect. However there will still be an additional relativistic effect in each case due to time actually slowing down with the relative speed of source and observer. By that its meant that processes which occur in one frame run at different rates as measured from a moving frame. If the observer is at rest and a source remains at a fixed distance then the time in hte moving frame will be observed to be running slower compared to the time in the stationary frame. Thus even though there is zero doppler effect there is still a time dilation effect. In this case the "sound" waves will still result in the person's speach sounding slower, in this case because they are actually speaking slower.

 

Pete

 

ps - I've ingored things like what happens when a body moves through air at relativistic speeds.

[Baby Astronaut]

That cleared it up quite a bit, Pete. Thanks.

 

I'm amazed. Does going in a circle really prevent a doppler effect? It makes sense now thinking about it, but I didn't know that before.

 

One last thing. If the person in the stationary frame were to speak, I'd guess that the person in the moving frame (the one going in a circle) would hear a very fast voice, because the stationary person would actually be speaking faster. Am I correct?

 

I really like your explanation.

 

P.S. I realize I messed up the physics in my "re-engineered" question. The fast/slow should've been in reverse order.

[Baby Astronaut]

(A few days ago this necromancer showed me a cool trick )*

 

 

 

OK let's modify the scenario a wee bit: the time dilation's still experienced between the phone callers, except now it's due to gravity instead of speed.

 

That way, the distance between each phone converser only needs to be in the neighborhood of a few thousand/hundred yards, while near enough to a black hole that it makes a substantial difference.

 

Will either person notice the other's talking get quicker/slower?

 

 

*And thanks to everyone who helped shape the obvious difference between what I knew then (my first post here) and now.

[Janus]

(A few days ago this necromancer showed me a cool trick )*

 

 

 

OK let's modify the scenario a wee bit: the time dilation's still experienced between the phone callers, except now it's due to gravity instead of speed.

 

That way, the distance between each phone converser only needs to be in the neighborhood of a few thousand/hundred yards, while near enough to a black hole that it makes a substantial difference.

 

Will either person notice the other's talking get quicker/slower?

Yes, the higher person will hear the lower one talking slower, and the lower one will hear the upper one talking faster. However, unless the gravitational potential between them is really large, this difference is going to be really small.