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cid
2005-Feb-04, 03:31 PM
These have been nagging me for some time now, and so far, i couldn't get an answer that i considered satisfying and so, why not try in here...
So, if the universe is limited, what could exist behind it's border ?
And if the universe is unlimited, wouldn't that in theory mean, that in this moment, infinite cids are just typing this message ? Or are there just unlimited possibilities ?

It's only theory, i know, but it would be nice to hear your thoughts.

ToSeek
2005-Feb-04, 04:03 PM
If the universe is limited (which the current belief is that it isn't), then it's limited like the surface of a sphere: there's no border, but if you keep going far enough you end up back where you started.

If the universe is unlimited, then it's spatially unlimited, not materially unlimited. My understanding is that there was a finite amount of matter in the Big Bang, so if you go far enough you will run out of galaxies.

Evan
2005-Feb-04, 04:03 PM
Imagine a universe where you can travel in a "straight" line for a very long time, in any direction you choose. Then imagine that if you do so you eventually end up where you started, approaching your starting location from behind. It is a limited universe but where could a border be? This doesn't necessesarily describe our universe but it is one possiblity of a finite universe with no border.

skrap1r0n
2005-Feb-04, 04:34 PM
I have thought of the "Infinite Universe" thing quite a bit. I consider myself a person of faith so I have asked the question that if there are infinite possibilities, then wouldn't the odds of there being a "God" be the same as the odds of biogenesis.

I have also wondered how Occam's Razor applies to the evolution/creationism argument.

Back to your argument, the universe is expanding at the speed of light. I'm not sure if there is a barrier that light cannot travel past. light will radiate away in all directions and it has to go SOMEWHERE within our universe, otherwise the universe would be losing matter/energy.

Evan
2005-Feb-04, 04:58 PM
then wouldn't the odds of there being a "God" be the same as the odds of biogenesis.

Hmm. One is a matter of belief, the other is a matter of knowledge. Not the same thing. I don't see how probability enters into it.

JohnW
2005-Feb-04, 05:07 PM
I have thought of the "Infinite Universe" thing quite a bit. I consider myself a person of faith so I have asked the question that if there are infinite possibilities, then wouldn't the odds of there being a "God" be the same as the odds of biogenesis.
If the Universe is truly infinite, then anything which does not break the laws of physics can happen, and is happening, infinitely many times. This meand there are infinitely many Earths out there, and infinitely many Earths identical in every way except one. For example (this is a fun game!)
- Genghis Khan spoke Dutch;
- Cricket is the most popular sport in the US;
- I am better-looking.
Plus, and this is where it gets tricky for the theologians, infinitely many Earths in which Hitler is revered as a saint, or the Bible says Moses drowned in the Red Sea.
And people say they are uncomfortable with the concept of the Big Bang...

skrap1r0n
2005-Feb-04, 05:23 PM
then wouldn't the odds of there being a "God" be the same as the odds of biogenesis.

Hmm. One is a matter of belief, the other is a matter of knowledge. Not the same thing. I don't see how probability enters into it.

Well I am not coming from this from a faith angle. I mean in an infinite universe, the odds of there being an intelligent being that can be everywhere/everywhen at once is the same as the odds of evolution of cynobacteria.

I know I am toeing the faith/science line here, and I am not really wanting this to go towards a debate on faith. I am just saying, in an infinite universe, ANYTHING is as possible as anything else. If referring to an infinite universe, for someone to say This happened, but that didn't is a false statement, the best we can speculate is to say, this happened but that couldn't.

joema
2005-Feb-04, 05:28 PM
...If the Universe is truly infinite, then anything which does not break the laws of physics can happen, and is happening, infinitely many times. This means there are infinitely many Earths out there...
Infinite simply means infinite physical size, not infinite mass or infinite planets, or infinite dimensions.

Evan
2005-Feb-04, 05:29 PM
ANYTHING is as possible as anything else

I disagree. Even in an infinite universe if we allow that the "rules" as we know them apply throughout the universe, which does seem to be the case, then what is possible is constrained by those rules, everywhere.

Normandy6644
2005-Feb-04, 05:32 PM
I have thought of the "Infinite Universe" thing quite a bit. I consider myself a person of faith so I have asked the question that if there are infinite possibilities, then wouldn't the odds of there being a "God" be the same as the odds of biogenesis.
If the Universe is truly infinite, then anything which does not break the laws of physics can happen, and is happening, infinitely many times. This meand there are infinitely many Earths out there, and infinitely many Earths identical in every way except one. For example (this is a fun game!)
- Genghis Khan spoke Dutch;
- Cricket is the most popular sport in the US;
- I am better-looking.
Plus, and this is where it gets tricky for the theologians, infinitely many Earths in which Hitler is revered as a saint, or the Bible says Moses drowned in the Red Sea.
And people say they are uncomfortable with the concept of the Big Bang...

This very same concept can be applied to parallel universe theory, where basically (if there are an infinite number of parallel universes) everything that can be imagined is happening. Some changes would only be on the scale of the position of a single atom, but others would be completely different universes unrecognizable to us (in this universe) but completely real and ordinary to their inhabitants, i.e., this board is run by someone named Dave ( :wink: ) and Phil Plait is simply a member. :D

Squink
2005-Feb-04, 05:38 PM
My understanding is that there was a finite amount of matter in the Big Bang, so if you go far enough you will run out of galaxies. I think that's wrong. Doesn't the matter in the universe derive from the collapse of the false vacuum into spacetime? IIRC Guth suggested that the initial singularity could have generated as few as a couple hundred kilograms of matter, and the rest we see came about as the product of inflation. If inflation is still going on, somewhere beyond the observable universe, it'll continue to produce more new matter.

skrap1r0n
2005-Feb-04, 05:40 PM
ANYTHING is as possible as anything else

I disagree. Even in an infinite universe if we allow that the "rules" as we know them apply throughout the universe, which does seem to be the case, then what is possible is constrained by those rules, everywhere.

I qualified that with


for someone to say This happened, but that didn't is a false statement, the best we can speculate is to say, this happened but that couldn't.

Kaptain K
2005-Feb-04, 06:51 PM
Good job cid! Just look what you started! :o

Evan
2005-Feb-04, 07:03 PM
for someone to say This happened, but that didn't is a false statement, the best we can speculate is to say, this happened but that couldn't.

If it is accepted that "it couldn't" doesn't that imply it didn't?

skrap1r0n
2005-Feb-04, 07:20 PM
for someone to say This happened, but that didn't is a false statement, the best we can speculate is to say, this happened but that couldn't.

If it is accepted that "it couldn't" doesn't that imply it didn't?

No, things COULD be possible but not happen. If something ISN'T possible, it can't happen.

Ow I think I just gave myself an anurism with that comment...

Normandy6644
2005-Feb-04, 09:13 PM
My understanding is that there was a finite amount of matter in the Big Bang, so if you go far enough you will run out of galaxies. I think that's wrong. Doesn't the matter in the universe derive from the collapse of the false vacuum into spacetime? IIRC Guth suggested that the initial singularity could have generated as few as a couple hundred kilograms of matter, and the rest we see came about as the product of inflation. If inflation is still going on, somewhere beyond the observable universe, it'll continue to produce more new matter.

Well, there is also the theory of spontaneous inflation, that is to say that the observable (to us) universe is only a fraction of the total universe, and that inflation-esque events happen in other parts of the total universe that are spacelike separated from us so that the two "sections" of the total universe could exist entirely independent of each other and neither would be any the wiser.

Taibak
2005-Feb-04, 09:20 PM
My understanding is that there was a finite amount of matter in the Big Bang, so if you go far enough you will run out of galaxies. I think that's wrong. Doesn't the matter in the universe derive from the collapse of the false vacuum into spacetime? IIRC Guth suggested that the initial singularity could have generated as few as a couple hundred kilograms of matter, and the rest we see came about as the product of inflation. If inflation is still going on, somewhere beyond the observable universe, it'll continue to produce more new matter.

I agree with Squink, but for another reason. If you go far enough to run out of galaxies, you've found yourself an anisotropic, non-homogenous universe. To the best of my knowledge, there's no evidence of that.

cid
2005-Feb-04, 10:17 PM
Kaptain, yes and i love it
:D

Some thoughts make my brain want to drop out of my nose and do a moonwalk around my chair, but nonetheless i love it and thank you guys for taking your time. I'll think twice about posting my questions on quantum theories, though.

Got some minor problem with the thought a limited universe, so, even if it is a kind of sphere, there has to be some kind of outside, has it ? If, just in theory, you had the possibility to leave that universe, where or what would you be ?
And infinity....well, i can live with it in mathematics, but as a real thing, it makes me kinda uncomfortable, considering JohnW thoughts.

Jorge
2005-Feb-04, 10:30 PM
Kaptain, yes and i love it
:D

Some thoughts make my brain want to drop out of my nose and do a moonwalk around my chair, but nonetheless i love it and thank you guys for taking your time. I'll think twice about posting my questions on quantum theories, though.

Got some minor problem with the thought a limited universe, so, even if it is a kind of sphere, there has to be some kind of outside, has it ? If, just in theory, you had the possibility to leave that universe, where or what would you be ?
And infinity....well, i can live with it in mathematics, but as a real thing, it makes me kinda uncomfortable, considering JohnW thoughts.

whell if its a sphere, if we would go up(or down(we need to fidn them first thouhg)) woun't we leave the sphere(up) or hit something we can pass true(down)?

skrap1r0n
2005-Feb-04, 11:30 PM
Kaptain, yes and i love it
:D

Some thoughts make my brain want to drop out of my nose and do a moonwalk around my chair, but nonetheless i love it and thank you guys for taking your time. I'll think twice about posting my questions on quantum theories, though.

Got some minor problem with the thought a limited universe, so, even if it is a kind of sphere, there has to be some kind of outside, has it ? If, just in theory, you had the possibility to leave that universe, where or what would you be ?
And infinity....well, i can live with it in mathematics, but as a real thing, it makes me kinda uncomfortable, considering JohnW thoughts.

I think the problem your having is that your imagining the univers with a 3D brain.

joema
2005-Feb-05, 12:07 AM
Already been stated, but I wanted to repeat: there's a difference between an open (unbounded) universe and one of infinite size. Our globe is unbounded but of finite size.

Also an infinite sized universe doesn't necessarily mean infinite number of planets, in the "Sliders" sense. Rather it's just infinitely big. In fact matter could be finite in an infinite universe.

Infinite is a powerful notation. It doesn't mean big -- it means infinite size in the mathematic sense.

Interplanetary vacuum is about 1 atom per cubic centimeter. Intergalactic vacuum is maybe 1 atom per cubic meter.

Even if extragalactic vacuum was 1 proton per trillion quintillion cubic parsecs, in an infinite size universe, mass will still be infinite. Given infinite volume, you can conjure up whatever mass you want -- unless vacuum becomes truly absolute at some point.

As previously stated, another possibility is an inflationary faster than light expansion occurred at some point, placing some matter beyond our current perception -- gravity moves at the speed of light so there could be infinite (or at least large) amounts of mass the influence of which hasn't reached our region.

It was much more comfortable thinking of the universe as a finite size :)