- #71
juanrga
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zeffur7 said:How do we know space is not infinite?
In science we can't know beyond what is observed/measured. The observable universe has a finite radius. You only can speculate beyond that.
zeffur7 said:How do we know space is not infinite?
Oldfart said:IF our universe is infinite, would that rule out the possibility that other universes exist?
Oldfart said:... it's not like we're going to use up all the room.
phinds said:That's my story and I'm sticking with it !
Oldfart said:IF our universe is infinite, would that rule out the possibility that other universes exist?
Justaman said:It is. There is no beginning, and no end, only transition. Same with time.
Oldfart said:Well, it just seemed to me that if space was already infinite, it would be meaningless to consider that it was becoming infiniter. Anyway, thanks -- I read about Hilbert's Hotel, no joy. I evidently have a personel conceptual problem with infinity, possibly stemming from incorrectly thinking that if something increases, it increases from a defined point in space and time. and the amount of increase would be measured from that point.
phinds said:Personal theories are not allowed on this forum. You should read the rules. This is a physics forum, not a theology forum.
maggiemaeu said:... the word is in my opinion and possibly in fact a paradox, so saying anything about measuring infinity or infinity getting bigger is just contradictory. QUOTE]
ANOTHER Personal theory and this one DEFINITELY contrary to the facts.
phinds said:Personal theories are not allowed on this forum. You should read the rules. This is a physics forum, not a theology forum.
Constantin said:The Observable Universe is finite.
It has a center, any observer being at the very center of his own Observable Universe. And it has an edge, the furthest away it is possible to see. That edge is moving away and the Universe is expanding, but it's still finite.
Thanks, I well understand this, and how it serves to assert that the entire universe (consisting of everything beyond our OU) is indeed infinite. Since the OU that exists at the edge of my OU is twice as far away from me...and so on.
Same thing with time. It has a beginning, the Big Bang. And an edge, the "current moment". The "current moment" is continuously moving, same as the edge of the Observable Universe. So the time spent since the Big Bang keeps increasing, but it's still finite..
Justaman said:Quite simply, I don't think time ever began or will end, and that space continues for an infinite distance in all directions.
With infinite time comes infinite possiblities, so it seems unlikely to me that all matter sat in singularity eternally until 13B yrs ago.
Rather, I think (there I go again) the expansion/contraction cycle is a continuous and infinite process- the contraction cycle including material collisions of increasing frequency with decreased proximity, arriving at and passing a "central gravitational point" (thus entering expansion phase) at inconsistent intervals around the central (and dynamic) point.
This would then mean that expansion/contraction exists with or without a "big bang" event, and that all matter only occasionally (though repeatedly) forms an instantaneous singularity that, once again, "bangs".
Not even light could escape the gravitational pull at singularity, so the OU would be quite small. Would this mean that space-devoid of matter even 2 feet away- would be finite? I personally would not consider it so, making it infinite in all directions correct?
Assuming infinity of space and time, it seems likely that an infinite number of expansion/contraction/big bang cycles would be occurring at all times, of course located well beyond our OU, but part of a larger "universe".
As with cells in our body, it seems these universes must occasionally interact with/effect each other in some way, just as cells in our own body do.
Associated by proximity, would this then make our universe part of a finite "organism" which, on a universal scale taken to infinity, co-mingles with an infinite population of similar "organisms"? And so on, and so on...
Constantin said:A very good argument against the repeated "expansion/contraction/big bang cycles":
Evidence shows the Universe is expanding at an accelerated rate, so it will never contract again.
Justaman said:Begs the question: What's out there, pulling it? I mean this in a purely scientific way. But obviously a topic for a different board. Sorry for the intrusion...
Thanks all, very interesting (and at times entertaining) thoughts.
phinds said:maggiemaeu said:... the word is in my opinion and possibly in fact a paradox, so saying anything about measuring infinity or infinity getting bigger is just contradictory. QUOTE]
ANOTHER Personal theory and this one DEFINITELY contrary to the facts.
sorry, didn't mean it as an opinion, just presenting a problem in the arguement. honestly, there are many definitions of the word that are contradictory. the fact being that infinity is an argueable word, you have to narrow it down a little more. how could this be contrary to the facts? it is a fact that the word has different meanings and which ones you use is your business, not mine. all I'm saying is that specifics are needed in discussing infinity to avoid confusion.
i do admit i should have been more careful about how i conveyed that.
Constantin said:A very good argument against the repeated "expansion/contraction/big bang cycles":
Evidence shows the Universe is expanding at an accelerated rate, so it will never contract again.
maggiemaeu said:phinds said:sorry, didn't mean it as an opinion, just presenting a problem in the arguement. honestly, there are many definitions of the word that are contradictory. the fact being that infinity is an argueable word, you have to narrow it down a little more. how could this be contrary to the facts? it is a fact that the word has different meanings and which ones you use is your business, not mine. all I'm saying is that specifics are needed in discussing infinity to avoid confusion.
i do admit i should have been more careful about how i conveyed that.
There is nothing contradictory about infinity being able to get bigger. It can and does. This is a standard part of any reasonable definition of infinity and if you think otherwise, you might find it interesting to study up on the subject.
Constantin said:Mathematically infinity can get bigger, smaller, and you can joggle with it in different ways.
But can you give any example in physics of something that was proven to be infinite ? Because I don't believe there is such an example.
khemist said:A simple way to think of infinity.
Consider all the real numbers -> 1, 2, 3, 4, etc...
One would certainly consider that an infinite set (give me any number, and I can get another number by simply adding 1). Now, take all the real even numbers -> 2, 4, 6, etc...
That is certainly an infinite set as well, but it has half the values as the original set!
phinds said:No, it's the same number. It SEEMS like half as much but that's that thing about infinity ... you can't treat it in normal mathematical operations as though it were like other numbers. Half of infinity is still infinity, as is twice infinity. Very UNintuitive.
khemist said:That is what I am saying... Although the even set has half the numbers, it is still infinity. Read what I wrote a bit more closely :)
phinds said:maggiemaeu said:There is nothing contradictory about infinity being able to get bigger. It can and does. This is a standard part of any reasonable definition of infinity and if you think otherwise, you might find it interesting to study up on the subject.
i grudgingly admit you're right here. anything you recommend reading?
maggiemaeu said:phinds said:i grudgingly admit you're right here. anything you recommend reading?
I've been away from formal study to long to have any idea what's a good text these days. Others here can undoubtedly give you some good advice. If you don't get anything in this thread, start another specifically asking for advice on math books discussing infinities (there is a heiarchy of them, named "aleph null" (the "normal" infinity) "aleph 1" and so forth.
khemist said:A simple way to think of infinity.
Consider all the real numbers -> 1, 2, 3, 4, etc...
One would certainly consider that an infinite set (give me any number, and I can get another number by simply adding 1). Now, take all the real even numbers -> 2, 4, 6, etc...
That is certainly an infinite set as well, but it has half the values as the original set!
zeffur7 said:1. Infinity = the state or quality of being infinite.
2. Infinite = not finite, boundless, unlimited, indefinite, immeasurably/exceedlingly great.
e.g.: the dimensions of the universe/multiverse.