What is the Universe expanding into..

Do you think there was anything before the big bang?

  • I don't think there was anything before the Big Bang

    Votes: 56 12.5%

  • I think something existed before the Big Bang

    Votes: 200 44.7%

  • I don't think the big bang happened

    Votes: 54 12.1%

  • I think the universe is part of a mutiverse

    Votes: 201 45.0%
  • Total voters
    447
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#2,042
One possible way to think about the why the universe is expanding is to consider time and energy as being two sides of the same coin. Energy can only be converted from one form to another, through time. Stated differently, time can only pass if there is a change in energy - either through expenditure or a gain.

To illustrate this, consider two bodies falling freely through space and in close proximity. Both will experience the passage of time at the same rate. If we then apply a force to one of the bodies, we expend energy to do so and we set that body off on an altered trajectory and the distance between the bodies increases. We can see distance therefore as a proxy for time: you cannot have a difference in time without there being some expenditure of energy - ie you trade one for the other.

So, in the visible universe, we have a huge amount of energy, that under the laws of entropy, is moving towards a net uniform state ultimately across the entire universe - the cold dark hypothesis. This process can only happen through the mechanism of time and in fact ‘drives’ time which is manifest as distance between objects hence we see it as an expanding universe.
 
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#2,045
Just Dave said:
Skipping past the "near universe", such as our galaxy, and go out to seriously deep space - other galaxies, where does it end? Does it end?
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We can only see as far as nature allows us.

Light from galaxies in the universe beyond our observable universe has not yet had time to reach us, and its journey time is made even longer by the expansion of space.

There's more of the same beyond our observable universe, we simply can't see it and no one knows how far it stretches. Well, that's one hypothesis anyway. 😉
 
#2,046
Bonsai said:
One possible way to think about the why the universe is expanding is to consider time and energy as being two sides of the same coin. Energy can only be converted from one form to another, through time. Stated differently, time can only pass if there is a change in energy - either through expenditure or a gain.

To illustrate this, consider two bodies falling freely through space and in close proximity. Both will experience the passage of time at the same rate. If we then apply a force to one of the bodies, we expend energy to do so and we set that body off on an altered trajectory and the distance between the bodies increases. We can see distance therefore as a proxy for time: you cannot have a difference in time without there being some expenditure of energy - ie you trade one for the other.

So, in the visible universe, we have a huge amount of energy, that under the laws of entropy, is moving towards a net uniform state ultimately across the entire universe - the cold dark hypothesis. This process can only happen through the mechanism of time and in fact ‘drives’ time which is manifest as distance between objects hence we see it as an expanding universe.
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Are there observable examples of entropy at it's conclusion?
 
#2,051
Discopete said:
... the contention is that the BB happened "everywhere" all at once, not from a singularity. This is what I have been questioning.
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The confusion arises because the observable portion of the universe was once packed into an incredibly tiny volume. All of space was filled with energy at the Big Bang, but the volume of space that could be observed was tiny. The volume of observable space then expanded, but there was no centre to the expansion.
 
#2,056
Discopete said:
can the mass of matter before the BB be calculated as to how large it was?
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We have no accepted theory for that, although there is speculation. Such a mass could be extremely small,
or even just a random quantum fluctuation. The only well accepted theory begins after inflation is over,
and can't accurately model the universe before that point.

One interesting approach is to consider deep time, and the identity of the far future and the far past, both being
a universal vacuum. There may be a very smooth (and very slow) transition from the future to the past, which
would then form a new universe, without any special initial conditions, or big bang, needed.
 
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#2,059
Discopete said:
So what adjustments were made to accommodate inflation? Or was inflation needed to accommodate expansion?
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A single theory could not be devised without needing inflation at a certain point. Inflation was invented
as a "patch" between theories of pre-inflation and theories of post-inflation. Many theorists are not happy
with this situation, though it works if you accept that inflation actually happened. There have been several
versions of inflation (to correct early problems with it), such as getting inflation to stop at some point.
 
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#2,060
TNT said:
... vague definition of; universe, space, observeable space..
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Since it was the observable universe to which I was referring, let me supply this definition in the hope that it may help. 🙂

The observable universe is a spherical volume centered on the observer, regardless of the shape of the universe as a whole. Every place in the universe has its own observable universe, which may or may not overlap with the one centered on Earth.
Click to expand...
 
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