Is the Universe Infinite or Finite? I was having that debate with a friend of mine today. My position was that it is finite because it is expanding. My logic was that the fact that is expanding indicates that it must be finite, because how could something be infinite and getting bigger?

His position was that it was infinite though he couldn't really explain why he thought that. (to give you some context, he also believes his daily horoscope offers him meaningful guidance and that aliens built the pyramids).

You may have guessed by now that neither one of us are physicists, so to settle the argument, I proposed that we contact an expert.

Confident of my correctness, I suggested to my buddy that we should have friend of this here site @seanmcarroll (the brilliant physicist and author of "From Eternity to Here") give us an answer.

I tweeted at Sean the subject line of this thread and he was kind enough to tweet me back in a matter of minutes. He said:

"Nobody knows. Sometimes that's the answer."

He then tweeted

"There may not even be an answer. de Sitter space (e.g.) can be finite or infinite depending on how you slice it."

So not wanting to badger Sean with follow up questions, I ask you: If we know the Universe is continually expanding (which to me suggests that it has a finite size that is increasing), how can it be labeled as anything other than finite?

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That's one of the questions theists love, because they know we don't have the answer, and all they have to say, is, "God did it!" but I suspect that when the answer is known, if it ever is, we will find that the mechanics of a singularity are such that at some point, they can reach critical mass.

They can always say "God did it!" to anything. Which alone tells us that it's meaningless as an explanation. Lack of falsifiability.

Lack of falsifiability certainly prunes completely off the philosophical branch of critical thinking. However, escaping our logical domain, presuming that God created it, is niether here nor there.

No theory will ever be fully established if it's untestable. Tests can take various forms. For example, an astronomical theory isn't subject to verification in a laboratory, but might be verifiable through, for example, telling observations.

You're right, arch; we don't have the answer.

LeMaitre borrowed an answer from Catholicism's catechism and no one asked him for evidence.

What caused the mass to increase to critical?

Don't tell us a mechanically-gifted God did it, even if by doing so you can protect a belief.

RE: "Don't tell us a mechanically-gifted God did it" - PLEASE tell me you know better --

RE: "What caused the mass to increase to critical?" - I wrote a story once about a man who had found the genetic secret to eternal life. H could be killed, of course, but he could not die of natural causes, as his cells renewed. Granted this was set in a recycling universe, which has since been disproven, but he spent billions of years traversing the universe, and once it began to contract, he was excited to watch it begin all over again. He sat in his starship, sufficiently far from the singularity as to not be drawn in, and waited. Millions of years passed, and nothing happened. Finally, he realized that there was a bit of matter missing from the equation, that final little bit that would push the singularity over the edge and allow critical mass to occur - he was the missing matter. He faced an eternity of nothing, as opposed to giving up his desire to live forever so that the Universe could begin again and untold lives would begin as a result of his sacrifice. He aimed his ship for the event horizon, and headed home.


Granted [your story] was set in a recycling universe, which has since been disproven....

Okay, you haven't read Big Bang: A Critical Analysis.

It's authors say the universe recycles and forms more hydrogen.

They also say a BB's heat would have formed an iron-based universe, which long-ago cosmologists accepted.

BTW, the below mention of mechanics is your woo from 19 hours ago.

...we will find that the mechanics of a singularity are such that at some point, they can reach critical mass.

Woo?! You only quoted part of it.

But you win (temporarily), I'll put Big Bang: A Critical Analysis on my reading list, right after I repair my dining table. Strega as my witness!

Like a painting, our thoughts may be canvas bound. Oblivious to what may lay outside the frame. A mega leap in science will be to make a star ship comprise of non-baryonic material untethered by the Higgs Boson. As such oblivious to inertia and gravity. Thus faster than light speed is achievable as the local boundaries of the universe defined by a light cone would not apply. Indeed since elsewhere lies outside a light cone, locally you would disappear to some place else in space and time. However those aboard have inertia, thus science would have to  create a race made of non-baryonic material also. With this thought experiment by  reversing things , It is shown that,  there can be  a non-baryonic vantage point of creation.

Don't forget about quantum fluctuations.

quantum mechanics and classical physics merge across the event horizon of a black hole. The light cone is a local event horizon. photons always map the local event horizon and traveling at the same speed as the time dimension map the light without causality and are thus everywhere at once which is a statement of a quantum mechanical wave form. Escaping the time dimension of the universe will certainly lead to a omnipresence.

Sounds a lot like the scientific equivalent of psychobabble.


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