- #91
RuroumiKenshin
What about that SCIAM article about parallel universes I described a post or two ago??
The Infinity Experience: Can we truly comprehend infinity?
Click For Summary
Infinity is a concept that describes something that goes on forever, and it is not a number. The discussion explores the paradox of whether an infinite universe can expand, with some arguing that spatial expansion does not contradict the idea of infinity. Brane theory is mentioned, with the assertion that branes are not sub-universes but rather mathematical constructs. The conversation highlights the distinction between mathematical and physical infinities, emphasizing that while mathematics allows for the manipulation of infinite sets, the physical universe operates under different constraints. Ultimately, the thread raises fundamental questions about the nature of infinity and its implications for understanding the universe.
- #92
Mentat
- 3,935
- 3
While I don't think it's funny, the point is that if his wooden leg is named "Smith", what's the name of his other leg (while originally you would have thought they meant "there's a man, named "Smith", with a wooden leg").
- #93
drag
Science Advisor
- 1,097
- 1
Majin, had he said it to me I'd personally
be deeply offended...
- #94
sage
- 110
- 0
greetings , physicists
"This is what drag, and others, keep saying, but I disagree. If someone speaks of the spatial dimensions themselves as expanding, then it doesn't follow that just some things could be getting farther apart, but all things should be getting farther apart. And if all things are getting farther apart, then this has to be happening throughout the entirety of space. Of course, there is not "entirety of space" in an infinite universe, which is why I don't think that everything can get farther away from everything else, in an infinite universe. Thus, the spatial dimensions cannot expand, in an infinite universe, IMCO (in my current opinion)".
__________________
spatial dimensions are expanding only in the region of the universe which have began from big bang singularity.this is the only region we know of till date and it is here that our laws of physics hold.
beyond this our concept of spatial dimensions may not hold even!it is only that the expanding entity which we call our universe interacts in some unknown way with whatever that lies outside to create
what we call spatial dimension.same goes for our temporal dimension,physical laws,forces,matter-energy etc.so you see though the universe may be infinite "our universe" is not and so it can certainly
expand.
"and has since expanded. It is also possible that God said "Let there be light." We can never know at, least in this life, because as the universe has expanded faster than the speed of light, at least in the inflationary phase the origin, and Big Bang is outside our light cone, beyond the limit of our sight".
this is something that i have not understood about inflationary theory.if the universe expanded faster than light does that not mean it went back in time?well what does THAT MEAN?
majinvegeta,if you think big bang theory is correct then how could our universe be infinite?i know that some geometries of space time allow an infinite universe.but how can such a model be comatible with the idea that our universe began from a singularity a finite time ago?can someone illuminate me on that point.anyway parallel universes if true only strengthens my point that the universe we speak about is only a part of the whole, of which perhaps we will never know anything.
i like jokes.just let it not drown the main subject.no offence meant of course! NOTE:THE WORDS UNDER THE SIGN " " ARE QUOTES.I HAVE MERELY REPLIED TO THESE.i should have put the quotation marks before.SORRY !
"This is what drag, and others, keep saying, but I disagree. If someone speaks of the spatial dimensions themselves as expanding, then it doesn't follow that just some things could be getting farther apart, but all things should be getting farther apart. And if all things are getting farther apart, then this has to be happening throughout the entirety of space. Of course, there is not "entirety of space" in an infinite universe, which is why I don't think that everything can get farther away from everything else, in an infinite universe. Thus, the spatial dimensions cannot expand, in an infinite universe, IMCO (in my current opinion)".
__________________
spatial dimensions are expanding only in the region of the universe which have began from big bang singularity.this is the only region we know of till date and it is here that our laws of physics hold.
beyond this our concept of spatial dimensions may not hold even!it is only that the expanding entity which we call our universe interacts in some unknown way with whatever that lies outside to create
what we call spatial dimension.same goes for our temporal dimension,physical laws,forces,matter-energy etc.so you see though the universe may be infinite "our universe" is not and so it can certainly
expand.
"and has since expanded. It is also possible that God said "Let there be light." We can never know at, least in this life, because as the universe has expanded faster than the speed of light, at least in the inflationary phase the origin, and Big Bang is outside our light cone, beyond the limit of our sight".
this is something that i have not understood about inflationary theory.if the universe expanded faster than light does that not mean it went back in time?well what does THAT MEAN?
majinvegeta,if you think big bang theory is correct then how could our universe be infinite?i know that some geometries of space time allow an infinite universe.but how can such a model be comatible with the idea that our universe began from a singularity a finite time ago?can someone illuminate me on that point.anyway parallel universes if true only strengthens my point that the universe we speak about is only a part of the whole, of which perhaps we will never know anything.
i like jokes.just let it not drown the main subject.no offence meant of course! NOTE:THE WORDS UNDER THE SIGN " " ARE QUOTES.I HAVE MERELY REPLIED TO THESE.i should have put the quotation marks before.SORRY !
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- #95
drag
Science Advisor
- 1,097
- 1
This objection has been expressed and answered
before in this thread, we meant - ALL things(if the
expansion occurs throughout the infinity discussed).
Anyway, what's your likely argument for this being
impossible for all objects ? (In addition to the more
traditional difficulties with infinity.)
Live long and prosper.
- #96
sage
- 110
- 0
DEAR DRAG i have edited my post somewhat.please see it again.sorry for the inconvinience!
- #97
drag
Science Advisor
- 1,097
- 1
You got it ! THE ANSWER ! God's last message
to his creation !
Well, some people seem to think, which is
also why such a thread was posted that the
Universe may be infinite (I mean "normal"
space-time). Anyway the issue of this
being correct or incorrect is far above me
so I'll prefer not to comment on this,
not to mention that there is seemingly no
conclusive probabalistic proof on either
side so far.
We're discussing the expansion part here
because it was proposed as one of the
main aspects in this theoretical paradox
of infinity.
Live long and prosper.
- #98
Mentat
- 3,935
- 3
Everyone, listen to my new good buddy, sage!
Sage, I agree entirely with you here. In fact, I have been trying to make the same point for some time now.
The universe is not "expanding faster than light", so to speak. What is actually happening is the space between all objects is increasing.
There's the ever-famous "balloon analogy" that is often used to describe this, and it goes kind of like this: Let's say that there is a balloon with spots on it. None of the spots can move away from each other at a speed greater than 1cm/second. However, the rule doesn't apply to what happens when the balloon itself expands, because the spots are not really moving at all.
Does that help at all?
- #99
RuroumiKenshin
But how do you explain the Doppler effect? It's used as evidence to prove the universe is expanding.
On the other hand, studies show that models of an infinite universe make more sense (not logical, apperently) than finite models.
On the other hand, studies show that models of an infinite universe make more sense (not logical, apperently) than finite models.
- #100
drag
Science Advisor
- 1,097
- 1
That's NOT a doppler effect, Majin. As space-time
expands the EM waves also expand.
- #101
Mentat
- 3,935
- 3
I believe that the Universe is expanding. My previous post just refines ones view of what it means to "expand", according to Relativity.
- #102
sage
- 110
- 0
clearing misunderstandings
"This is what drag, and others, keep saying, but I disagree. If someone speaks of the spatial dimensions themselves as expanding, then it doesn't follow that just some things could be getting farther apart, but all things should be getting farther apart. And if all things are getting farther apart, then this has to be happening throughout the entirety of space. Of course, there is not "entirety of space" in an infinite universe, which is why I don't think that everything can get farther away from everything else, in an infinite universe. Thus, the spatial dimensions cannot expand, in an infinite universe, IMCO (in my current opinion)".
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"Everyone, listen to my new good buddy, sage!
Sage, I agree entirely with you here. In fact, I have been trying to make the same point for some time now".- MENTAT.
no wonder you agree with me mentat.they were originally posted by you!they are quotes!thanks for calling me buddy,and THANK YOU for explaining to me how the universe could indeed have expanded faster than light during inflationary phase.you are my buddy too you know!
let me state clearly what my views are:
1) mentat asked how could our universe expand as it is infinite
2) drag said a infinite universe can indeed expand.
3) i said the universe we study is NOT infinite.it CANNOT BE as it began at a big bang a finite time ago(10 billion?18 billion?estimates vary)but if an entity began expanding from a point a finite time ago at no later stage can it be infinite.it's common sense.
4) since universe we know is finite it can expand.CASE CLOSED.
majin vegeta you said models of an infinite universe made more sense.can you tell us briefly what these models are?thanks
"This is what drag, and others, keep saying, but I disagree. If someone speaks of the spatial dimensions themselves as expanding, then it doesn't follow that just some things could be getting farther apart, but all things should be getting farther apart. And if all things are getting farther apart, then this has to be happening throughout the entirety of space. Of course, there is not "entirety of space" in an infinite universe, which is why I don't think that everything can get farther away from everything else, in an infinite universe. Thus, the spatial dimensions cannot expand, in an infinite universe, IMCO (in my current opinion)".
--------------------------------------------------------------------------------
"Everyone, listen to my new good buddy, sage!
Sage, I agree entirely with you here. In fact, I have been trying to make the same point for some time now".- MENTAT.
no wonder you agree with me mentat.they were originally posted by you!they are quotes!thanks for calling me buddy,and THANK YOU for explaining to me how the universe could indeed have expanded faster than light during inflationary phase.you are my buddy too you know!
let me state clearly what my views are:1) mentat asked how could our universe expand as it is infinite
2) drag said a infinite universe can indeed expand.
3) i said the universe we study is NOT infinite.it CANNOT BE as it began at a big bang a finite time ago(10 billion?18 billion?estimates vary)but if an entity began expanding from a point a finite time ago at no later stage can it be infinite.it's common sense.
4) since universe we know is finite it can expand.CASE CLOSED.
majin vegeta you said models of an infinite universe made more sense.can you tell us briefly what these models are?thanks
- #103
drag
Science Advisor
- 1,097
- 1
Greetings !
Correction.
drag said that the point of the Universe
being finite/infinite is irrelevant here as
the thread deals with the possible paradox
of an expanding given infinite Universe.
Had I been a sadistic human being I'd ask
you to precisely formalize the connection.
And even if you succeeded in this task I would
then ask you to prove that the type of "common
sense" you used is indeed absolute and
must "make sense".
I guess you should be glad I'm not a sadistic
human being...
Peace and long life.
- #104
Mentat
- 3,935
- 3
What do you mean, sage made it pretty obvious: If something starts out finite, it will never reach infinity. This just has to do with the basic definition of infinity, which means "going on forever".
On the off chance that you still don't understand it, think of how long it would take a finite entity to reach infinity. Answer: forever. Since forever hasn't passed yet (and never will), the universe would never reach infinity.
I'd say that it's not just "common" sense, it's definitive, and strikes at the very meaning of the words being used ("finite"; "infinite"; "expansion"; etc...).
- #105
Mentat
- 3,935
- 3
It sounded like my style, when I first read them. I just assumed you had come really close.
thanks for calling me buddy,and THANK YOU for explaining to me how the universe could indeed have expanded faster than light during inflationary phase.you are my buddy too you know!
Well, good. And you're welcome.
- #106
drag
Science Advisor
- 1,097
- 1
Maybe it just became infinite - like an on/off
switch - no expansion (a word that discribes
the derivative of the ratio between the volume
and the time) involved.
- #107
HazZy
- 100
- 0
- #108
Mentat
- 3,935
- 3
No, because that means that there was a time when it was not infinite. If there was a time when it wasn't infinite, it can never become infinite.
- #109
drag
Science Advisor
- 1,097
- 1
Why ?
(I was trying to avoid being sadistic, but
it just didn't work out that way... )
- #110
Mentat
- 3,935
- 3
I've seen this before, and it is a perfectly acceptable cosmological model, but doesn't answer the question of how the spatial dimensions themselves can expand, if the universe is already infinite. You see what I mean? While the model proposed in your link could be true, I wasn't questioning it, I was questioning the model of a universe (by which I mean the whole universe) that was small and became infinite.
- #111
Mentat
- 3,935
- 3
'
I don't like repeating myself...
- #112
drag
Science Advisor
- 1,097
- 1
Can't say I like it either, so I won't...
I'll let you do all the work - go 7 messages
back (including this one).
- #113
Mentat
- 3,935
- 3
Originally posted by drag
Can't say I like it either, so I won't...
I'll let you do all the work - go 7 messages
back (including this one).
Nothing is instantaneous, according to Relativity, so your on/off example is flawed from the start. Then you have the matter of the Universe's having been finite at some point in time. This also does not allow the Universe to (at any point, short of forever) reach infinite size.
- #114
drag
Science Advisor
- 1,097
- 1
The BB itself doesn't make sense according to
Relativity, so ?
Like I said, this thread was dealing with the
hypothetical case of an infinite Universe and
the related possible paradox, not with the
scientific indication or possibility of the
Universe's nature.
Live long and prosper.
- #115
sage
- 110
- 0
look at the third question that majin asked.so drag let us leave the decision of what this thread is dealing with to him.not that i am saying that the universe could not be infinite.read on.
but before that let's clarify whether a finite quantity can expand to become an infinite one.consider the set of all positive integers.it's infinite.now consider the set{1}.it is a finite subset of the above infinite set with no. of elements being one.now say add other positive integers serially one after another in ascending order such that the set increases by n integers per second with n being finite.so when will the set become infinite?NEVER.or not until infinite time has elapsed.i can give more examples but the fact is iff the universe was finite at the time of the big bang it cannot be infinite today.this applies well to our observable universe which was just a point at the time of the bang.indeed hazzy's site gives it's actual radius.so what's the point?
now let us talk about the total universe.that's a red herring.you can't see it, observe it and there is no hope of observing it in future.what's the use thinking of something we can't even verify.but i must say the approach of physicists is rather pragmatic.they feel we live in an unbiased sample of the universe and whatever is true for the part we can see is true in general.research shows that our part is most probably flat.a flat surface extends to infinity.so they conclude the entire universe is a flat surface extending to infinity.if so by our previous conclusions it follows the universe as a whole must be infinite at the beggining of the big bang.since it has been expanding since(vide the idea that anything that holds here holds everywhere). so we come to the original question-can a infinite entity get bigger?
seen a thin rubber sheet?strech it-it elongates does it not?now assume a rubber sheet of the same material extending to infinity say along its length.mark 2 points on it by a sketch pen.now strech holding the sheet at these two points.surely the sheet will elongate(i.e. the dist. between the points increase)otherwise we will have to conclude that rubber has suddenly become as rigid as stone just because it extends to infinity.absurd is'nt it.verdict-infinite entities can expand and there is no logical fallacy in assuming that the universe, infinite at the time of the bang is expanding ever since.
i must say that any assumptions about the entire universe is purely hypothetical and will change constantly as more advanced theories come into being to explain newer facts about the observable universe which we are only beggining to probe in detail.anyway drag what does a switch has to do with the universe.enlighten me will you?
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- #116
drag
Science Advisor
- 1,097
- 1
Greetings !
To her...
Did you also remember to tell the Universe
it must follow mathematical logic ?
I was just giving an example to Mentat how one
state can change into another (a light switch is
a good example - light/no light).
Live long and prosper.
- #117
LogicalAtheist
Drag - You're a female? How old are you?
- #118
drag
Science Advisor
- 1,097
- 1
NO ! NO ! NO !
Oh, sorry ! I meant - no, I'm not.
MajinVegeta is, and I believe she said she's 13.
Live long and prosper.
- #119
LogicalAtheist
Oh ok, I thought you were corrected someone calling YOU male.
Majin, hmm 13, hmmm. Darn.
Majin, hmm 13, hmmm. Darn.
- #120
heusdens
- 1,736
- 0
Philosophy of Nature. Time and Space
Here is a contribution to this issue of infinity.
http://csf.colorado.edu/psn/marx/Archive/1877-AD/p1.htm#c5"
Here is a contribution to this issue of infinity.
http://csf.colorado.edu/psn/marx/Archive/1877-AD/p1.htm#c5"
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