Why distant star's light can reach us?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Saint, Jun 24, 2022.

  1. James R Just this guy, you know? Staff Member

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    No. The Big Bang was not an explosion in space, but an explosion of space. It happened everywhere at once, including right where you are now. There is no "centre" to the universe.
     
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  3. Saint Valued Senior Member

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    Explosion of space? So you can imagine a 3D axis coordinate? Right?
    The cross section of X-Y-Z is the singularity?
     
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  5. James R Just this guy, you know? Staff Member

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    Saint:

    Don't imagine an explosion propagating outwards from a central point.

    Instead, visualise the expansion as like a baked loaf of raisin bread expanding. All the raisins move away from each other as the loaf expands. (The difference between this analogy and space, of course, is that the loaf of bread has a centre, while the universe does not, but the expansion works in a similar way.)
     
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  7. Saint Valued Senior Member

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    The universe is 93b light-year wide?
    How to measure that?
     
  8. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    A big ruler?
     
  9. Saint Valued Senior Member

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    Will Webb Telescope measure a bigger universe?
    Possibly.
     
  10. Janus58 Valued Senior Member

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    The observable universe is. But it doesn't look that big to us. What we see now is the light that left distant galaxies billions of years ago, But since that light left, the universe has expanded.
    There is a method called the Cosmic Ladder. It basically works like this. You have methods that can measure closer distances. These overlap with methods that can measure further distances, which in turn overlap with methods for measuring even further distances... We can use this to measure how big the universe looks to us now, take into account that this is old information, and extrapolate how much things have expanded in the time it took the light from these distant galaxies to reach us.
    However, we really have no idea how big the universe truly is, the observable universe could be just a small piece of it.

    But, that doesn't mean that we can just build better and and better telescopes and keep expanding the size of the observable universe forever. There is still the fact that as we look further and further away, we are looking at at younger and younger galaxies. Look far enough and you see things as they were before galaxies formed. Look even further, and you reach the time when the universe itself was opaque to light. We've then reached the limit as to what telescopes can reach.
    We build these better telescopes so that we can see closer to this limit, and thus get a better idea of the what the early universe was like, and to get better data on the universe as a whole.
     
  11. Beaconator Valued Senior Member

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    Twice light speed and I sat in dwfewf for all the things I’ve ✅ for
     
  12. Beaconator Valued Senior Member

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    The stars began at the same time as our universe. That is not the only reason we can see them
     

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