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One interesting question of this is if science changes once the other galaxy groups disappear. By that I mean if a human was to redo all previous experiments h

One interesting question of this is if science changes once the other galaxy groups disappear. By that I mean if a human was to redo all previous experiments have we lost any data that would result in us building a different model of the universe than what we've built with the other galaxy groups present. Sure, we will have records of evidence from the past, but records of evidence from experiments that can no longer be repeated is no longer reliable data. This is ignoring the whole development of humanity and science in the intervening 150 billion years which may change what options are available to use then. I'm also not sure if this is the most up to date model of the universe. I've recently dived deep into quantum field theory and theoretical physics (well as deep as one can without understanding a field of spinors) and I've watched a number of lectures given over the last decade that include alternate takes on expansion. I could be completely misunderstanding what was being spoken about, but it appears one possible model of reality is a sort of bubble in hyperexpanding space that gives rise to a big bang event that eventually leads to the bubble becoming hyper expanding space itself that can give rise to further bubbles. Here is one talk. https://www.youtube.com/watch?v=jhnKBKZvb_U https://www.youtube.com/watch?v=jhnKBKZvb_U I recommend the whole thing if you aren't familiar with Boltzmann brains and boxes, but if you want to see the issue with the current model presented in this article go to 41 minute mark and to see a possible alternate model go to about 44:50.

raattgift 5y ago
The galaxies of the local group won't recede from us. Telescopes as recently as the early 20th century could not resolve the sky well enough to determine which nebulae are in the Milky Way, are satellites of the Milky Way, are in the local group, or are outside it. This lack of observation allowed the Shapeley-Curtis https://en.wikipedia.org/wiki/Great_Debate_(astronomy) https://en.wikipedia.org/wiki/Great_Debate_(astronomy) to last as long as it did -- it ended with clear observations of light curves within M31 and other galaxies in the local group. Those observations will remain available for a lonnnnnnnnnnng time after there are no other galaxy groups in the view of anything in the local group. Moreover, the relic fields (cosmic microwave background and cosmic neutrino background) will be detectable (at least in principle) as they grow ever colder in the far future, so at least the radiation and dark energy sectors can be rediscovered in the distant future when there are no highly redshifted galaxies left to see. We are lucky to have clear views of redshifted, dimmed, smaller-on-the-sky spiral galaxies at all sorts of orientations to us (including face on). Those certainly help us to understand galactic evolution, and also provide us lots of interesting objects (gas and dust clouds, active nuclei, stars, supernovae) "in the past". In the far future, the local group will have fewer spirals, fewer stars, almost no low-metallicity stars, and so on, and recovering those from observation of what's left in the distant future will be more difficult. But around the garganguan black holes left in the local group in the very far future there will still be plenty of dust and gas and cooling stellar remnants; the occasional star will probably form, but not often. Still, the volume will be large enough far into the future that "not often" simply invites wider searches of the sky. Supernovae don't happen often, but thanks to all-sky surveys like http://www.astronomy.ohio-state.edu/~assassin/index.shtml http://www.astronomy.ohio-state.edu/~assassin/index.shtml we see A LOT more of them than could have been hoped for a hundred years ago. Far future astronomers might have a super-hyper-ultra ASAS-SN type programme to look for the earliest signs of star formation in what's left of the local group. Of course as you note, even better would be if the far future astronomers can recover the records of earlier astronomers, rather than having to rediscover everything from scratch using the "records" provided by nature at astronomical scales. The far far future where one cannot see distant galaxies from the local group is very very very very very much earlier than the epoch of fluctuations into Boltzmann brains, vacuum decay, etc. etc., none of which is a really reliable prediction of well-tested theory. (In fact, they are diagnostic of theoretical deficiencies: how do we prevent objects that can happen according to a theory from happening according to that theory, given that we do not see those objects? This recurs a lot at the edges of theoretical physics: in General Relativity it's the basis for developing the https://en.wikipedia.org/wiki/Energy_condition https://en.wikipedia.org/wiki/Energy_condition (s) for instance).

raattgift 5y ago

The galaxies of the local group won't recede from us. Telescopes as recently as the early 20th century could not resolve the sky well enough to determine which nebulae are in the Milky Way, are satellites of the Milky Way, are in the local group, or are outside it. This lack of observation allowed the Shapeley-Curtis https://en.wikipedia.org/wiki/Great_Debate_(astronomy) https://en.wikipedia.org/wiki/Great_Debate_(astronomy) to last as long as it did -- it ended with clear observations of light curves within M31 and other galaxies in the local group. Those observations will remain available for a lonnnnnnnnnnng time after there are no other galaxy groups in the view of anything in the local group. Moreover, the relic fields (cosmic microwave background and cosmic neutrino background) will be detectable (at least in principle) as they grow ever colder in the far future, so at least the radiation and dark energy sectors can be rediscovered in the distant future when there are no highly redshifted galaxies left to see. We are lucky to have clear views of redshifted, dimmed, smaller-on-the-sky spiral galaxies at all sorts of orientations to us (including face on). Those certainly help us to understand galactic evolution, and also provide us lots of interesting objects (gas and dust clouds, active nuclei, stars, supernovae) "in the past". In the far future, the local group will have fewer spirals, fewer stars, almost no low-metallicity stars, and so on, and recovering those from observation of what's left in the distant future will be more difficult. But around the garganguan black holes left in the local group in the very far future there will still be plenty of dust and gas and cooling stellar remnants; the occasional star will probably form, but not often. Still, the volume will be large enough far into the future that "not often" simply invites wider searches of the sky. Supernovae don't happen often, but thanks to all-sky surveys like http://www.astronomy.ohio-state.edu/~assassin/index.shtml http://www.astronomy.ohio-state.edu/~assassin/index.shtml we see A LOT more of them than could have been hoped for a hundred years ago. Far future astronomers might have a super-hyper-ultra ASAS-SN type programme to look for the earliest signs of star formation in what's left of the local group. Of course as you note, even better would be if the far future astronomers can recover the records of earlier astronomers, rather than having to rediscover everything from scratch using the "records" provided by nature at astronomical scales. The far far future where one cannot see distant galaxies from the local group is very very very very very much earlier than the epoch of fluctuations into Boltzmann brains, vacuum decay, etc. etc., none of which is a really reliable prediction of well-tested theory. (In fact, they are diagnostic of theoretical deficiencies: how do we prevent objects that can happen according to a theory from happening according to that theory, given that we do not see those objects? This recurs a lot at the edges of theoretical physics: in General Relativity it's the basis for developing the https://en.wikipedia.org/wiki/Energy_condition https://en.wikipedia.org/wiki/Energy_condition (s) for instance).