3 ms·

It’s early days on this, so let me ask again what I have asked previously: What does timescape do to estimates of the age of the universe?

sigmoid10 2y ago
It would mean that we literally can't calculate it anymore, because expansion and everything else we see might just be artefacts of inhomogeneities beyond the scale of the observable universe. But that would crash hard with our observation of the CMB and since this study only looks at supernovae, I would not bet on it holding up for long.
- geysersam 2y ago
  How would > that we literally can't calculate it (the age of the universe) anymore crash with our observation of the CMB? I don't see how us being unable to calculate a quantity from one set of observations could possibly clash with another set of observations (the cmb). What am I missing?
  - hnuser123456 2y ago
    The CMB suggests we get a picture of the entire early universe. However, other things are suggesting we might not be seeing the whole universe just by looking as far away as possible. It could be we can see some regions on the CMB that have already expanded outside of our observable universe. These regions aren't just "even fainter and we need a better telescope", they're "the last photon from that region that will ever reach us came and left billions of years ago." Therefore, there might not be one singular hubble constant, there might be two. One that applies to our local observable universe, and one that applies to the entire universe. It could be that the universe is 26 billion years old: https://academic.oup.com/mnras/article/524/3/3385/7221343?login=true https://academic.oup.com/mnras/article/524/3/3385/7221343?lo... And because at great enough distances(/times), expansion is faster than light, and we simply can't see a significantly different epoch of the universe just by looking deeper.
- User23 2y ago
  Even more fun, once you abandon isotropy you don't even need to posit matter inhomogenities. It could just be that spacetime itself has irregular topology. Which, incidentally, is probably a better theory than dark matter. For example it can produce the same results without the problem of undetectable matter.
  - cryptonector 2y ago
    Presumably we should be able to build a theory of spacetime that yields no need for dark matter, but we're not there yet. On the other hand, determining the local time dilation factor based on all mass beyond the local area is essentially not possible. We can talk about how the great voids have less time dilation than galaxy clusters, sure. But what about the universe as a whole? Our universe could be embedded in a larger one that contributes to time dilation in ours and we could never sense that. Time dilation at cosmological scales is relative for this reason.

sigmoid10 2y ago

It would mean that we literally can't calculate it anymore, because expansion and everything else we see might just be artefacts of inhomogeneities beyond the scale of the observable universe. But that would crash hard with our observation of the CMB and since this study only looks at supernovae, I would not bet on it holding up for long.

geysersam 2y ago
How would > that we literally can't calculate it (the age of the universe) anymore crash with our observation of the CMB? I don't see how us being unable to calculate a quantity from one set of observations could possibly clash with another set of observations (the cmb). What am I missing?
- hnuser123456 2y ago
  The CMB suggests we get a picture of the entire early universe. However, other things are suggesting we might not be seeing the whole universe just by looking as far away as possible. It could be we can see some regions on the CMB that have already expanded outside of our observable universe. These regions aren't just "even fainter and we need a better telescope", they're "the last photon from that region that will ever reach us came and left billions of years ago." Therefore, there might not be one singular hubble constant, there might be two. One that applies to our local observable universe, and one that applies to the entire universe. It could be that the universe is 26 billion years old: https://academic.oup.com/mnras/article/524/3/3385/7221343?login=true https://academic.oup.com/mnras/article/524/3/3385/7221343?lo... And because at great enough distances(/times), expansion is faster than light, and we simply can't see a significantly different epoch of the universe just by looking deeper.
User23 2y ago
Even more fun, once you abandon isotropy you don't even need to posit matter inhomogenities. It could just be that spacetime itself has irregular topology. Which, incidentally, is probably a better theory than dark matter. For example it can produce the same results without the problem of undetectable matter.
- cryptonector 2y ago
  Presumably we should be able to build a theory of spacetime that yields no need for dark matter, but we're not there yet. On the other hand, determining the local time dilation factor based on all mass beyond the local area is essentially not possible. We can talk about how the great voids have less time dilation than galaxy clusters, sure. But what about the universe as a whole? Our universe could be embedded in a larger one that contributes to time dilation in ours and we could never sense that. Time dilation at cosmological scales is relative for this reason.