Aah, what a great thread this has been. And multiple-universes! Wow, I used to love that idea.
I'm going to carry on here, although not on topic anymore, because I think we're all agreed that some things we have to believe, regardless of whether or not we can prove them, and some things we just can't prove yet.
But what I want to look at hear is this: Xar just mentioned (OK, 4 days ago actually) a near-infinite universe.
What I'm curious about is that near.
Now, personally, I don't think that the universe is infinite, for a reason which I will explain in a subsequent post.
But generally, it's not an idea that people tend to agree with, regardless of how cleverly I explain it. Never asked a scientist about it though, so I'd love to hear what's behind that.
Agreed. What is your view on it Prebe? Is the universe infinite?
For me, the reasoning is simple: The 2nd law of thermodynamics says that entropy always increases. That means that the universe, at some point, will undergo it's ultimate heat death or whatever. If something can die, it can't be infinite, because infinity must include time too.
I can give you my view, but not as a scientist. I can't put any more weight behind my view than anyone else.
Applying laws of thermodynamics to the formation of the universe is perhaps a stretch. (I'm sure physicists do this all the time, shows how much I know)
Thermodynamics work with systems with a boundary (they may be huge, but they still have a boundary). So, in using thermodynamics you presume something about the universe. Presume the very thing you are trying to prove.
Honestly? I don't have a clue. It boggles my mind to think about the universe. I prefer to concentrate on things that I can understand.
"I would have gone to the thesaurus for a more erudite word."
-Hashi Lebwohl
Hmm, OK. The way I think about it is that each star has a finite life, right? Therefore every star must die. At the same time, admittedly, new stars are being born.
And each of them must also die...hmm, actually, you're right...it assumes a finite amount of resources to build new stars from...an assumption that may be unwarranted. Hmm, I'll have to look into this...I thought the eventual heat death of the universe was pretty accepted...where's an astro-physicist when you need one huh?
The eventual heat-death of the universe is still very much disputed, there are several interesting theories regarding the ultimate fate of the universe which do not contemplate the heat-death. For example, the famous Big Crunch theory, in which all the universe collapses back into a singularity and then explodes again into another Big Bang, and goes on and on like this forever; or the Big Rip theory, in which at some point the mysterious force that seems to cause galaxies to accelerate will win over gravity or the nuclear forces, and everything will be torn into sub-atomic particles forever; or many, even weirder theories. Regardless, time is a dimension, so it is intrinsically bound to the universe: when the universe ends, so does time.
All of them contemplate a finite universe though - a universe with a boundary that constantly increases, but which exists nonetheless, and none of them is capable of explaining what is beyond that boundary. Physicists claim that nothing is outside it, not even void.
Weirder theories I've read about recently talk of an infinite multi-universe, for example: they claim that the universe that surrounds us up to a radius of 15 billion light years, more or less, is a Hubble volume, and that beyond it there is no "nothing", but infinite other Hubble volumes. So, according to this theory, travel in a straight line long enough, cross the boundary (which you won't even notice) between this and the next Hubble volume, and you'll find yourself in another area of the multi-universe, with the same physical laws but in which, due to the laws of probability, there is a duplicate of you (or even of Earth), although not necessarily physically identical to you.
Another theory - the theory of inflation, I think - claims that the universe is infinite and floats into an infinite sea of some unknown stuff into which sometimes bubbles form, and each bubble has infinite size and contains a universe, but since the unknown stuff also is infinite and keeps expanding too, these bubbles never touch each other, and you will never be able to travel from one to the other.
Admittedly, physicists have lots of fun with theories about the whole universe...
Of course...forgot about the whole crunch thing, that's plausible too.
And as I said, the whole multiple universe thing, the Graham-Everett-Wheeler model, IIRC, has been one that, implausible as I really find it, has always amused and interested me.
As you point out though, these are models which require a finite universe, even the big crunch, if only along my lines of finite in time.
I like the heat death best though I think. It appeals to my sense of solipsism. Once I die, the universe ends. (For me at least. )
Xar wrote:Well, from a scientific point of view, intelligence IS inevitable... you have a near-infinite universe, billions of years old; I'm not sure it was Fermi who calculated it, but some physicist definitely calculated that the possibility of intelligent life in the universe is significantly higher than 0 - it is, in fact, a near-certainty. With enough time, intelligence becomes inevitable - especially if you have a near-infinite number of worlds where to develop life. At least one of those poor little quivering cells WILL evolve into something intelligent, just according to the laws of statistics!
Are you talking about the line of reasoning that, basically, says:
1) If only 1 in 1,000,000,000 stars has a planet, then there are at least X planets in the universe.
2) If only 1 in 1,000,000,000 planets is capable of supporting life, then there are at least X planets that are capable of supporting life.
3) If only 1 in 1,000,000,000 planets that can support life actually do contain life....
etc
I was going to mention the "near-infinite" also, but for a different reason than Av did. The Silver Surfer used that phrase once, and I didn't like it at all. I don't believe there is such a thing as near-infinite. If something is not infinite, it is infinitely far from being infinite. No? How can anything be nearly to the end of infinite?
All lies and jest
Still a man hears what he wants to hear
And disregards the rest -Paul Simon
And multiple-universes! Wow, I used to love that idea.
