High School Is it possible to see the history of space if it expands faster than light?

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SUMMARY

The discussion centers on the possibility of observing the history of the universe from the edge of space, particularly if the universe expands faster than light. Participants clarify that there is no physical edge to the universe, and observers would see a uniform distribution of galaxies similar to those seen from Earth. While it is possible to see back to events close to the Big Bang, visibility is limited to approximately 400,000 years post-Big Bang due to the opacity of the universe before this time. The cosmic microwave background radiation represents the limit of observable history using visible light.

PREREQUISITES
  • Understanding of cosmology principles, including the Big Bang theory
  • Familiarity with the concept of cosmic microwave background radiation
  • Knowledge of light propagation and redshift in an expanding universe
  • Basic grasp of gravitational waves and their significance in astrophysics
NEXT STEPS
  • Research the implications of cosmic microwave background radiation on our understanding of the universe
  • Explore the concept of gravitational waves and their detection methods
  • Study the principles of cosmological redshift and its effects on light from distant galaxies
  • Investigate the concept of co-moving coordinates in cosmology and their relevance to time measurement
USEFUL FOR

Astronomers, cosmologists, physics students, and anyone interested in the fundamental nature of the universe and its expansion.

ramim
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TL;DR
Can we view the history of space from the edge of expansion as it was expanding faster than the speed of light?
I was wondering if it would be possible to see the history of space if one was to stand at the edge of the universe as it expanded faster than the speed of light. If the universe was to be expanding faster than the speed of light right now, and I was able to somehow go there and keep up with it, what would I see if I turned around? I have thought about this and I was wondering if you would be able to see the history of the universe. Since the universe would be moving faster than the speed of light, all the light traveling to the edge of the universe would lag behind it and thus if you turned around and stopped, eventually all of that light would reach you. So what exactly would you see? Would you just see light from galaxies, etc., or would you be able to see the the formation of the universe?
This also leads me into a side question. Since the universe is not expanding at the speed of light, what happens to the light that reaches the edge of space? Does it just move at the speed of the universe expansion? If that is the case, this is why I reached the conclusion above (that you can see the formation of the universe). If the Big Bang is true then as the universe started expanding, that light being emitted is just following the edge and so you would see it if you were at the edge.
Have I made a mistake in my thinking or is this certainly true?
 
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ramim said:
If the Big Bang is true then as the universe started expanding, that light being emitted is just following the edge and so you would see it if you were at the edge.
Have I made a mistake in my thinking or is this certainly true?
There is no edge (and the Big Bang didn’t happen at the center either). Many previous threads here explaining this...
 
A fundamental principle of our understanding of cosmology is that, on large scales, everything is the same everywhere. So an observer in a galaxy at the very edge of what we can see would see everything around him/her/it looking much the same as it looks here (as Nugatory notes, there's no edge to the universe - but the finite speed of light limits how far we can see to how far light can have traveled since the beginning of the universe). There would be different stars and galaxies, of course, but they would be just stars and galaxies like we see around us here.
 
ramim said:
Would you just see light from galaxies, etc., or would you be able to see the the formation of the universe?
If you could see far enough, assuming our models of the universe are correct then you could indeed see back to events arbitrarily close to the formation of the universe, yes. The farther away you look, the farther back in time(1) are the things you see.

However, there is a limit to how far away/back in time you can look. If you look back to around 400,000 years after the big bang, you see the surface of last scattering -- this is where the cosmic microwave background radiation comes from. Prior to this time, the universe was opaque to visible light. So you cannot see past this point using visible light (which, due to cosmological red shift now manifests as microwaves in your radio dish).

(1) Here I am implicitly using standard "co-moving" coordinates to establish a standard of cosmological time.
 
Last edited:
ramim said:
... or would you be able to see the the formation of the universe?
In addition to what @jbriggs444 already said astronomers could in principle detect gravitational waves produced during inflation, the super-fast expansion almost at the beginning of the universe.
 

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