The infinite universe

Yes, if the universe is infinite, (and i presume you mean, continues forever, or infinitely expands), this means the universe will continue to expand without stop.

Infinity is always one more than now. And infinity is larger than any finite real number; so in effect, you can have an infinite amount of infinities.

People say Cantor was smart to know that. I think it's just pure logic, and no genious behind it.

 

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I also fail to see the genius and originality of Cantor since the cardinality of any point on a line is infinite and Euclid and all geometers know this.

And in Book IX Proposition 20 of the Elements, Euclid actually says there are more prime numbers than in any given set of prime numbers.

I believe Cantor's popularity is due to ignorance of the history of mathematics.

 

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I've done pondering behind infinity before, that's obvious, what I asked was whether an infinitely large universe implies a closed system. Thanks for trying I guess..

 

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Imagine we are living in a 1-dimensional universe. All we can tell is that looking one way along the only available dimension, is more or less identical to looking in the opposite direction.

Therefore all we can say is that we appear to be located at the midpoint of a line, with visible boundaries (since distant objects at either "end" are moving away from the "centre" where we appear to be). The boundaries at either end of the line we look along, are assumed to be 'disappearing points", since objects at, or "near" the limit, will eventually move so far away we won't see them any more.

So we can also imagine that this 1-dimensional universe, is infinite in extent - objects have an infinite amount of 'dimension' to move along. Infinity is real, because we really can imagine it, which is because we can never see anything "at" an infinite distance, but we know that real objects can "get" to this imaginary distance from us, by moving along the only dimension we can look (which has 2 directions in it).

 

That is correct. It can be considered a closed system if it is infinitely large.

Two possibilities can be pointed out that explain why that is true.

An infinitely large universe encompasses all energy and so no energy can be gained or lost, i.e. a closed system.

A closed system which is isolated cannot exchange energy outside the system and there is no outside of the universe so no energy can be exchanged outside of it.

It is not customary though to describe the universe as being infinitely large under currently accepted standard cosmology, i.e. Big Bang Theory, so don’t confuse your infinitely large universe with mainstream thinking about the universe.

It is customary to discuss the Big Bang universe in terms of open or closed. If the universe is finite in content and had a beginning as in BBT, it can be either open or closed. It is open if it will expand forever and it is closed if it will someday reverse the expansion and collapse.

In alternative cosmologies, an infinite universe can be proposed. If such a universe is proposed, the energy in it can be finite or infinite. If a cosmology proposes infinite space and infinite energy it is the ultimate open system and yet meets the narrow definition of a closed system of the two possibilities that I pointed out. Clear as mud, right?

 

wouldnt an infinite universe imply an infinite amount of matter/mass, in turn posing serious problems to law of conservation of energy? That's what I think of when people talk about infinite universes.

 

I think energy is conserved in an infinite universe with an infinite amount of matter/mass. The reason I think so is that I don't see how the amount of matter/mass can either cause energy to be created or destroyed.

But then there is the issue of entropy where useful energy gets used up, leaving useless energy. If there is no way to reverse entropy, then useful energy will decline infinitely in a universe whether or not it has an infinite amount of matter.

It all depends of the cosmology that is actually operative

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. BBT with inflation is a complete entropy cosmology. Eternal Inflation is too. The Big Rip cosmology is too. A cyclical universe is too. A de Sitter universe is too. But all of these are finite in matter and energy.

Quantum Wave Cosmology is a set of ideas (as opposed to theory) about an infinite universe with an infinite amount of matter and energy. It is protoscience about the infinite greater universe and infinitesimal quantum realm which defy observation. However, QWC is a cosmology in which entropy is defeated by an arena landscape that features expanding and contracting arenas that mix and merge to renew useful energy from used galactic remnants.

 

I don't know what the term 'customary' has to do with anything. There are currently two possibilities about the size of our universe...

It is either MUCH bigger than our observable universe, or it is very possibly (even likely) infinite.

This is the current 'mainstream thinking about the universe'

 

The universe would not have a 'physical boundary' whether it was infinite or finite. When you imagine a finite universe it is best to imagine a sphere (or balloon) The universe exists on the surface of the sphere. There is no inside or outside of the sphere there is only the surface. Now, with that in mind, where is the boundary (or edge)... there is none. The sphere is a finite size, but without boundary.

The motion of objects within the universe is limited to the speed of light... However, the motion of the universe itself (the expansion of the universe) is not. There are things in the universe, even things that we can still see right now, that are moving away from us at much faster than the speed of light due to the expansion.

Gravity propagates at the speed of light.

 

The CMB is like a mist which can only be seen in the far distance which does not allow us to see what is beyond it. The big bang idea is nonsensical and there are many obvious problems with such an idea. The universe is static in size but of unknown size because of the CMB.

 

An infinitely large universe does not mean that all of it is as the universe we see. Matter might occupy only the smallest portion of it. There may even be pockets of matter and energy scattered throughout it; pocket universes, like ours.

 

So, even though there are dimensions higher than the ones we can observe, we know that if the universe is infinite, it is a closed system? Coolio.

 

We don't have any evidence of physical dimensions beyond three. Mathematicians say there are because they need them, like christians talk of a spiritual world.

Over 99% of the universe may be space without any universes. Whole universes might be like dust motes in an empty vastness.

 

Kaneda, for such a short post you covered a huge swath. Everyone has an opinion and yours is just as good as the next.

But you offer some idle speculation about space and universes that doesn't help focus on what we know and don't know, though I think your point is that "we just don't know". Your post makes me want to add that there are limits to what we can know, and science takes us to those limits and works to extend those limits as its prime objective.

On the macro scale we only see a part of our universe and the best evidence is that the arena that we can see is filled with galaxies that are moving away from each other, i.e. we see an expanding universe. But what we can see is limited to only part of what we think is out there and like you imply, there are many possibilities and "potentially infinite" is a main contender.

On the micro scale, the quantum world, we also only see a part of our universe and the best evidence is that there is more detail to the universe than we have been able to detect to this point. The theory of everything, if it is ever developed, will be based on future discoveries that are revealed at the depths of the quantum realm. And if there is ever a consensus on Grand Unification Theory, that theory of everything will link the quantum world with the potentially infinite greater universe.

Reasonable and responsible speculation must tie to the departure points at the macro and the micro ends of our scientific progress. It should go step by step and fill in the speculated details in a logical progression that takes us beyond science and into protoscience. Any speculation that departs from this logical progression is not protoscience, it is pseudoscience.

 

Id speculate the cosmos in eternal and infinate. Id guess its scale dependant, zoom out and entire an universe would appear like a star or singularity light soarce. The whole cosmos could be dotted with them with vast space of darkness separating them like the night sky. Zoom out even more and universe clusters might merge and appear like a single dot of light again. Of coarse you would need enough time to see the light in the first place.
At these scales, time would be so slow, things would apear to not change for neer eternity.
Who knows?

 

Since when is there a decrease in density as a function of distance?

 

The Universe as we now observe it is technically an open system, as the majority of photons emitted by a light source (such as the Sun) will eventually pass out of the observable universe and be lost for ever (although they may be absorbed and re-emitted a few times on the way).

Another consequence of the fact that we can only observe events within the Hubble Volume is that we don't know if the Universe is infinite in extent or not, or if the rest of the universe (if any) outside the Hubble volume is the same as what we can see.

 

Since the universe.
We know it appears less dense at greater distances from our central observation point - how would you explain this apparent 'density gradient'?

 

Then we're at the center of the universe.
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