Is the Universe infinite?

[Cointelpro_Papers]

I for one say no, It is not infinite, and eventually it will collapse back down on itself, and it will all start again, with new random laws, and rules, and new random elements, and constants.

The notion of the Universe being infinite, would mean that every possible situation would have to happen, which would me that their is an infinite number of people exactly like me, doing the exact same thing as I'm doing righ now, and struggling with the same societal hypocrisies that I am.

The known Universe is 15 billion light years, with a 100 billion known galaxy, with each galaxy having a billion stars, and each star averages 4 planets.

[Prisoner_Number_Six]

1. I'll let you know as soon as I

finish my tour of it. Shouldn't take me more than the highest number of years possible plus one...

[ForrestGump]

34. I'll catch you at the Restaurant at the End of the Universe....

[oneighty]

2. Yes.

Because everthing must be someplace.

Understand?

180

[Cointelpro_Papers]

32. Hmm,

I don't know which is more far fetched, our Universe being infinite, or being finite.

[Systematic Chaos]

3. Actually, there's a new theory...

I can't explain it to you precisely but I do remember reading about it in Time a year or so ago, and I then did some internet research. It sounds both well thought out and plausible.

What they say will happen, because of all the dark matter in the universe, is that the universe will continue to expand. However, stars will form less and less as matter becomes sparser and ultimately, all that will be left is numerous black holes. After roughly 10^90 years (that's a 1 followed by 90 zeroes!!) even the black holes will peter out and all that will be left in a universe many trillions of times larger than it is presently is the occasional sub-atomic particle floating here and there. No light, no life, nothing as we know it now.

But, we still have about 10^30 or 10^40 years left to thrive, provided * doesn't wipe us out first.

[Dudley_DUright]

7. Right scenario

but dark matter would actually slow the expansion. However, dark energy can actually do the opposite (which seems to be happening, see post below). Your time scales are a little long for the universe to be "thriving". Those time scales are more for protons to decay (if they indeed do) but star formation would be long over by then.

[Cointelpro_Papers]

8. Ahh, more momentum then gravitational forces

Not enough matter, or gravity to slow down all the momentum the stars have now, and they will keep going forever, and they will turn into black holes, but sence black holes decay through radiation, nothing will remain. But the universe will still be able to be defined. But I believe this is in spite of the dark matter, they estimate their is much matter we have not discovered yet, so this could change.

[Dudley_DUright]

10. But observational evidence of the increase in the expansion rate

is not based on adding up mass, but looking at recession velocities (via the doppler effect) of far away galaxies using type I supernova as standard candles (to get distance). Not completely nailed down yet, but data seems to indicate that the universe expansion rate is increasing, not decreasing. It seems Einstein might have been right after all (even though he called it his biggest blunder) when he introduced the cosmological constant into General Relativity.

[Cointelpro_Papers]

24. Ha, thanks for the laugh, Ether?

He called it his biggest blunder for a reason, and the doppler effect isn't very practical, because of all the redshifting that gravity does between here and wherever the light source is.

[leftyandproud]

15. yess!!

I read about this theory too...The black holes won't disappear though...They will eventually be the only things left out there...and rather than fizzing out, they will combine with other black holes...that suck in other black holes...that suck in other blak holes...eventually creating ones that are many times the size of our entire galaxy...These giants will just float on forever, and since everything is spread out so much, the chances of anything ever running into anything else is very small...

what the hell did I just say...?
my brain hurts

[Dudley_DUright]

19. But if Steven Hawking is right

(and I suspect he is) even black holes don't live forever, but radiate there mass-energy away in the form of Hawking radiation.

[Salviati]

21. Eventually the black holes evaporate...

it has to do with particle-antiparticle pairs popping out of the vaccuum near the event horizon of the black hole. This happens all the time in normal space, the energy needed to create the pair is "borrowed" for a short time (governed by the Heisenberg Uncertainty Principle) and then repaid when the two recombine and annihilate.

If they are formed near a black hole however, one of the pair can get sucked into the black hole while the other escapes. The black hole is left holding the bag, and ends up paying the energy debt. So it looks as if the black hole is slowly emitting particles, it's called Hawking radiation (as it was theorized by Stephen Hawking), but for truely massive black holes, the time to decay is Economicly large (even bigger than astronomically...)

[kixot]

4. Eh, a little shakey, there

The presupposition of an infinite universe does not necessarily mean that every infinite possibility exists within that infinite reality, there would be whatever constraints are imposed within that system. In other words, that the universe were infinite would not immediately imply that there is a world out there where monkeys regularly fly out of your parallel self's butt. Infinite universe does not imply alternate/parallel universe is all I'm saying here.

[Dudley_DUright]

5. Independent questions

Mass-energy density in the universe controls the ultimate fate. There is more and more observational evidence that the universe will not collapse back on itself, but will expand forever (the "heat death" senerio), in fact there is some evidence that the rate of expansion is in fact increasing (due to the so called "dark energy"). It is also pretty certain that the universe is roughly "flat" on the cosmological scale (i.e. Omega = 1) which means that it could be infinite. However, at this point in cosmic history, as you correctly point out, we can only know what is in our observable universe of about 15 billion light years in radius.

[Cointelpro_Papers]

9. IF it was infinite,

expansion of what we know would be irrelevant, and so would collapsing. This question seems more metaphysical, than physical, what we know now, cannot say one way or another.

[Dudley_DUright]

12. No, not true at all

Space itself can expand. Imagine a infinite loaf of raisin bread (raisins representing the galaxies). If we put some yeast in the dough and let it rise, each raisin (galaxy) would move away from all the others and this would be measurable to an observer sitting on one of the (arbitrary)raisins.

[Cointelpro_Papers]

16. But the nature of inifinity,

would make any expansions or contractions irrelevant, it wouldn't be infinite at one time, and then finite at another. It is either finite or not, and if it is infinite, then the expansion and contractions of what we see would be irrrelevant.

[Dudley_DUright]

18. Unfortunately

I don't have time (infinite or otherwise) to explain futher since it is time for bed. May I suggest some good bedtime reading on the topic. One of my favorites is Tim Ferris "Coming of Age in the Milky Way". Good night. :-)

[Cointelpro_Papers]

22. I'm not exactly sure how you could explain infinity to me more,

I don't think you are understanding what i'm saying

[WillyT]

6. Nope, It's Finite... Except For That Stuff On The Other Side !!!

:shrug:

[Neoplatonist]

11. I believe it is not

No, the universe is not infinite. The past consists of numbers and if any one of those numbers are removed, the present, and future would be annihilated instantly; for the present and future potentials of what actually was and are would be removed.

Plotinus, the greatest of the Neoplatonic philosophers, said this about time, "Time is a mimic of eternity, that seaks to break up in its fragmentary flight (the past, present, and future), the permanence of its exemplar (eternity, or God)."

Saint Augustine explains time this way: "What is time? Who can explain this easily and briefly? Who can comprehend even in thought so as to articulate the answer in words? Yet what do we speak of, in our familiar everyday conversion, more than of time? We surely know what we mean when we speak of it. We also know what is meant when we hear someone else talking about it. What then is time? Provided that no one asks me, I know. If I want to explain it to an inquirer, I do not know. But I confidently affirm myself to know that if nothing passes away, there is no past time, and if nothing arrives, there is no future time, and if nothing existed there would be no present time. Take the two senses, past and future. How can they 'be' when the past is now present and the future is not yet present? Yet if the present were always present, it would not pass into the past: it would not be time but eternity. If then, in order to be time at all, the present is so made that it passes into the past, how can we say this present also 'is'? The cause of its being is that it will cease to be. So indeed we cannot truly say that time exists except in the sense that it tends towards non-existence.

"Nevertheless we speak of 'a long time' and 'a short time,' and it is only of the past or future that we say this. Of the past we speak of 'a long time,' when, for example, it is more than a hundred years ago. 'A long time' in the future may mean a hundred years ahead. By 'a short time ago' we would mean, say, ten days back, and 'a short time ahead' might mean 'in ten days' time.' But how can something be long or short which does not exist? For the past now has no existence and the future is not yet. So we ought not to say the past 'It is long.' but 'it was long.' and of the future 'it will be long.' My Lord, my light, does not your truth mock humanity at this point? This time past which was long, was it long when it was past or when it was still present? It could be long only when it existed to be long. Once past, it no longer was. Therefore it could not be long if it had entirely ceased to exist.

"Therefore let us not say 'The time past was long.' For we cannot discover anything to be long when, after it has become past, it has ceased to be. But let us say 'That time once present was long' because it was long at the time when it was present. For it had not yet passed away into non-existence. It existed so as to be able to be long. But after it had passed away, it simultaneously eased to be long because it ceased to be."

I guess it all depends on whom or what you believe. I choose to believe it is mortal. Everything that has a beginning must have an end--cause and effect.

[Dudley_DUright]

14. Difference between infinite in time and infinite in spacial extent

There is lots of evidence that the big bang happened about 15 billion years ago (so the universe is clearly not infinite in time), but it is an open question (but not very important for the reasons stated above) whether it is infinite in spacial extent.

[leftyandproud]

13. yes

and it will not collapse back on itself...It isn't a rubberband...I think some weird science freaks found a way to prove it a few months ago...

[Dudley_DUright]

17. Who are you calling a weird science freak?

:silly: :-)

[leftyandproud]

20. hey!

howdy weird science freak...I got a question...I watched that show with Meg Ryan and Tim Robbins, where she was Albert Einsteins niece or something--anyway...I remember her saying that thing about the old theory that all motion is impossible...and no two objects can ever touch...because when you close half the distance between to objects, you still need to close half of that distance, then half of that distance, then half of that distance etc etc etc, and it is ultimately impossible to ever reach anything, because their will always be a space that needs to be closed.
2/2 = 1
1/2 = .5
.5/2 = .25

as you close the distance...it will always be impossible to reach 0...to be in contact.

Know what I'm sayin?
How do you explain that?

[Dudley_DUright]

25. Zeno's Paradox(s)

A philosophical conundrum from Greek times. Here is a good explanation.

http://www.jimloy.com/physics/zeno.htm

[leftyandproud]

26. thank you.

my brain still hurts...

now, I have a very important question for you...It goes far deeper than this paradox....

the chicken or the egg?

[Salviati]

27. Well, assuming that your object is moving at a constant speed:

Which seems a pretty reasonable starting point.

Then to cover half the distance between the two objects, it will take you a certain amount of time time, I will call it dt. To cover the next 1/4 the distance it will take you 1/2 the time of the first leg, or dt/2. To cover the next 1/8 of the distance it will take 1/2 the time of the previous leg, or 1/4 the time of the first leg, namely dt/4.

Each leg of the journey takes 1/2 the time of the previous leg, so if we add up all the times for each leg of the journey, we get:

dt+dt/2+dt/4+dt/8+dt/16+... = dt* (1+1/2+1/4+1/8+1/16+...)

and so on, adding up all the infinite legs of the journey.

This however is just a geometric series, and it is known how to add up all the infinite number of bits ( see http://mathworld.wolfram.com/GeometricSeries.html )
and the quantity in the parantheses above is just equal to two. (If you don't believe me, you can sit all day with your calculator and add up numbers, but you won't get anything bigger than 2)

So the time it takes for one object to get to the other is just twice the time it takes to cover half the distance (if it's moving at constant speed),which isn't too surprising...

[leftyandproud]

28. wow

I actually understood what you just told me...holy crap.
I need a math tutor like you.

[Philosophy]

23. This is the kind of question you'll never see a Freeper ask

Everything about the nature of the universe that doesn't involve God, guns, or gasoline is irrelevant.

[Ouabache]

29. Yes,

until you get to the end of it.

[Kamika]

30. It is infinite

And also it is constantly expanding.. sooner or later the universe will be so big nothing can exist when there is a billion billion of lightyears between every atom

[Cointelpro_Papers]

31. That makes no sense

If the Universe was infinte it could neither expand nor contract, that is the nature of infinity. It goes for ever, so if it contracted that would mean it would have boundaries to contract, and it wouldn't be infinte, and if it could expand, for the same reasons.

[classics]

33. Depends on when you ask.

With current technology, yes, we would probably die out as a race long before we ever explored any portion of the known universe signifigant enough to even yield a reliable answer to the question, so its effectively infinite.

I think though, as technology advances we will find it is, though we will have to redefine what we mean by 'infinite'.