Sound in space and the end of the universe

In summary: Yes, that is basically how it works. We see the light as it is emitted, but because the light is travelling to us from a point in the past, it has been "red shifted".
  • #1
GreatScot
5
0
Hello

I am trying to get into physics and astronomy as a hobby so please excuse the crudity of my posts, I regrettably have no physics education past high school level but nevertheless I aim to slowly but surely learn either self-taught or through some further eduction whether at college or university level.

I have a few questions I'd like to ask of those much more learned than I:

Say an astronaut is in space without a space suit. The astronaut starts a song on his iPod and puts his earphones in; will he hear anything? I assume there would still need to be air (or another medium for the sound to travel) between the earphone and the astronaut's ear/eardrum?

Secondly, is it reasonable to assume that, given the magnitude of the universe, it could have already come to an end just, the light hasn't yet traveled to the Earth? I know that currently it is thought that the universe will end in some sort of big regression so therefore it's probably unlikely to already have happened (in this manner), or is it?

Thanks!
 
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  • #2
GreatScot said:
Say an astronaut is in space without a space suit. The astronaut starts a song on his iPod and puts his earphones in; will he hear anything? I assume there would still need to be air (or another medium for the sound to travel) between the earphone and the astronaut's ear/eardrum?

Good question. There might be enough conduction by the skin to allow some sound to be heard. Probably depends on how far into the ear the buds get. Of course, in any case, the astronaut isn't going to care since he'll be busy suffocating to death.

Secondly, is it reasonable to assume that, given the magnitude of the universe, it could have already come to an end just, the light hasn't yet traveled to the Earth? I know that currently it is thought that the universe will end in some sort of big regression so therefore it's probably unlikely to already have happened (in this manner), or is it?

This is so far off base that I can only suggest that you pursue your studies some more. The universe might or might not be infinite in size but even if it is finite and unbounded, the consensus is that is is enormously larger than the observable universe. "Big crunch" theories pretty much went out long ago. The universe is expanding and is expected to continue to do so.
 
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  • #3
phinds said:
This is so far off base that I can only suggest that you pursue your studies some more. The universe might or might not be infinite in size but even if it is finite and unbounded, the consensus is that is is enormously larger than the observable universe. "Big crunch" theories pretty much went out long ago. The universe is expanding and is expected to continue to do so.

Thanks for replying, I appreciate it! I do recall reading about the expansion apparently going on forever to the point where no other galaxies will be visible to observers on Earth, but is it not true that it's thought that at some point further in the future the universe will consist of nothing more than helium and hydrogen atoms? Perhaps I am not remembering something correctly.
 
  • #4
GreatScot said:
... is it not true that it's thought that at some point further in the future the universe will consist of nothing more than helium and hydrogen atoms? Perhaps I am not remembering something correctly.

That is the "big rip" scenario and has been pretty much discredited.

It is even possible that galaxies within local clusters will not be disturbed by the expansion, and certainly galaxies themselves are not likely to be disturbed.
 
  • #6
Ah I see, thank you. I will certainly give those links a look. So it is currently held that the universe will continue to expand forever with no real "end"?

On the topic of expansion, IIRC it was originally demonstrated through spectroscopy by Edwin Hubble showing the fact that light from celestial objects were red shifted. This is probably quite an easy question to answer but, how is it we know the light has been red shifted? How do we know that the light isn't emitted in the way we observe it and wasn't streched?

Perhaps I don't quite understand red shifted light. What I mean to say is, if we observe a blue star, are we to expect it to look to the naked eye more red if it's moving away from us when we observe it? Or, are these observations made over a finite period of time? So take a spectrum on day x, wait until day y and do another and if the object appears more red/spectrum has more red light, we can assume it's moving away from us?
 
  • #8
Depending on the headphones, there could be significant sound transmitted through the bones in the head.

I think that the general consensus, or at least the majority opinion, is that the universe will not end. It is expanding and accelerating in its expansion, so there's no reason to not expect it to expand forever.

If the universe does come to a sudden end, then I suppose the end would happen everywhere in the universe, separated by spacelike intervals, so it wouldn't be possible to see the end of the universe in your past light cone no matter where you are.
 
  • #9
GreatScot said:
On the topic of expansion, IIRC it was originally demonstrated through spectroscopy by Edwin Hubble showing the fact that light from celestial objects were red shifted. This is probably quite an easy question to answer but, how is it we know the light has been red shifted?

The redshift correlates pretty much exactly to the distance away from us. It would be an impossible coincidence if all the stars one distance from us emitted light one color of red and those twice that far away all emitted light of a different (but the same as each other) color of red.
 

What is sound in space?

Sound in space refers to the propagation of mechanical waves through a medium, such as the interstellar medium. In the vacuum of space, sound cannot travel as there is no medium for the waves to travel through. However, there are other forms of electromagnetic radiation, such as radio waves, that can travel through space and be detected by instruments.

Why can't sound travel in space?

Sound waves require a medium, such as air or water, to travel through. In the vacuum of space, there is no medium for sound waves to vibrate and propagate. Without a medium, there can be no sound.

Can we hear anything in space?

No, we cannot hear anything in space because there is no medium for sound to travel through. However, astronauts can hear sounds inside their spacesuits or spacecraft, as these are enclosed environments with air for the sound waves to travel through.

What happens to sound at the end of the universe?

As the universe continues to expand, the distance between galaxies and other objects will increase. This means that sound waves from other galaxies will eventually be unable to reach us, resulting in a "silent" universe. However, it is important to note that the end of the universe is a theoretical concept and the fate of sound in the distant future is still unknown.

How do we study sound in space?

We can study sound in space indirectly through the use of instruments that can detect other forms of electromagnetic radiation, such as radio waves. These instruments can provide us with valuable information about the composition and movement of objects in space, including stars and galaxies. Additionally, we can also study the effects of sound on astronauts and spacecraft in the enclosed environments of space missions.

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