The (In)Finite Universe?

Question

Is the universe infinite or finite? Most scientist accept that an explosion caused our universe, but saying that would also mean that our universe had a measurable size at one point. It grew. Some scientists who support the Big Bang say that our universe is infinite. If this is so, what makes them believe the universe is infinte?

Answer 1

infinite, because the universe is expanding in all directions.

Answer 2

There are a lot of bad answers here, althought he last two are good.

First of all, we don't know if the universe is infinite or not. It is very close to being 'flat', which would mean it is infinite. But if it has a small negative curvature it would be finite but very, very big. We just don't know.

Next, the Big Bang does allow for an infinite universe. If the universe if flat or has positive curvature, it will be infinite and will always have been infinite (at least after the Big Bang itself).

Part of the problem is thinking of the Big Bang as an ordinary explosion. The Big Bang has no center and 'looks' the same everywhere in the universe. Every galaxy sees distant galaxies moving away. This happens even in an infinite universe. Also, the rate of expansion can be more than the speed of light because irt is space itself that is expanding. The limit of the speed of light only applies to movement through space, not the expansion of space itself.

Finally, there is a big difference between the 'observable universe; and the whole universe. THe first is just what we can see and is limited by the speed of light. Since the universe is about 13.7 billion years old, we cannot see anything farther than 13.7 billion light years away. But the universe is almost certainly much larger than this.

Answer 3

It's not so much that they believe that the universe is infinite; they believe that the POTENTIAL size of the universe is infinite.

The truth of the matter is, the size of the universe is so large that no human can even begin to comprehend it, and in reality, there's no way to measure it. The only explanation that some people can fall back on when asked the size of the universe is that it's infinite -- meaning, immeasurable.

The size of the universe is constantly changing because everything is continuing to move outward, and there's no air resistance or gravity in space, so there's nothing to stop the expansion. And one thing we DO know is that the rate of expansion is not slowing down; it's actually speeding up.Therefore, the size of the universe is -- potentially -- infinite.

The $64,000 question is, will the universe ever stop expanding and begin contracting? That is one question that we will never know the question to in our lifetime, which is unfortunate, since it could be a plasuible explanation for how our universe began in the first place. Just before the Big Bang, all the matter in the universe was confined to a single, infinitely small point in space. If this was due to the contraction of the previous universe, then the matter could have potentially "exploded" once more into the universe we currently inhabit now.

Answer 4

It depends on how you define "universe." The space we inhabit is probably finite (albeit very, very large), but there are some credible theories in cosmology where the big bang that created our universe was just one of an infinite number constantly occurring literally all the time. (See the book in the first link below.)

By the way, the big bang was not just an explosion of stuff INTO space, but rather an explosion OF space itself. During the first tiny fraction of a second of our universe's existence, during what's called the inflationary period, our universe expanded at a speed much, MUCH faster than light--so fast that today, the portion of it that we can see may well constitute only a very miniscule fraction of the total space actually out there.

To throw another monkey wrench into the works, some theories of quantum mechanics posit that every time _anything_ in our universe changes--down to the tiniest motion of a single subatomic particle--a new universe is spawned from the previous one. With 10^80 particles in our universe alone each doing something different 10^37 times a second, that's a whole lot of universes....

If you can find it at a local town or university library, I very highly recommend reading the book at the first link below. It gives a good layman's description of inflationary theory, why it's the best theory we have, and some of the pretty radical implications of it.

The second link below is a flash animation. It's a very interesting overview of what it means to live in a multi-dimensional universe with more dimensions than we may be aware of, and thus more universes than we may know of. Click on the "Imagining the Ten Dimensions" link on the left side, and make sure your speakers are on.

Answer 5

The Universe that we can "see" at any one time is finite because our only source of information is photons traveling through space and there are parts of the Universe which are moving away from us faster than light can reach us. (This is NOT in violation of relativity since distant matter is not moving THROUGH space faster than the speed of light, rather it is being carried away from us by expanding space faster than the speed of light. Also, it is not strictly true that photons are our only source of information, it's just most of it. We may also study elemental particles such as neutrinos.) Today the Universe is expanding and accelerating so the size of the Universe that we can see is constantly shrinking as it speeds up. In the distant future we will not be able to see anything beyond the closest groups of galaxies which are gravitationally bound together because everything else will have been pushed away from us by the expansion of space. However, those other parts of the Universe are still there, we just can't see them.

Today we do in fact know that ultimate fate of the Universe. Two groups studying very distant supernovae showed that the supernovae were fainter than would be expected by a decelerating or static Universe meaning that the Universe is actually accelerating in its expansion. It will expand forever under the influence of the mysterious force "dark energy." The two groups were led by Adam Riess and Saul Perlmutter and their work has been published in the Astrophysical Journal as well as documented in the popular press (think Nova).

The question of whether or not the Universe is infinite is tied up in the "shape" of the Universe, that is, is it closed, open, or flat. If the Universe is closed then it is kind of like living on the surface of sphere and not knowing that there is a third dimension: you could walk in a straight line without ever turning and arrive back at our starting point, like sailing around the world. However, you would never have any sense that your path was being curved because it would be curved around an (as yet) undetectable 4th dimension. This Universe is finite but still has no edge. In a flat or open Universe you could travel forever in any direction, making those Universes infinite. The results of the WMAP study, combined with the supernovae result mentioned above suggest that the Universe is basically flat but may be just on the closed side.

Answer 6

you may seem at this countless universe project in terms of dimensions.in accordance to Steven Hawking the universe is like the two-dimensional floor of the earth yet with 2 extra dimensions (3 area and a million time).on the outdoors of the earth a guy can initiate strolling and save strolling continuously without ever encountering a barrier or boundary even nevertheless the earth's floor is finite.He ought to, because of the fact the earth's floor is finite, finally are available the time of a few places persistently.The universe is a 4 dimensional analogy of this and the belief is regular because of the fact the No Boundary theory.The 4-D universe is quite vast and finite yet in 3 dimensions the destiny area customer can stumble on the universe in his spaceship and in no way come to the ingredient. the only countless universe may well be an infinity of finite universes like our own-the biggest multiverse.because of the fact that we can not verify the existence of alternative universes it is appropriate to prepare Occam's razor and not speculate approximately what we would in no way be waiting to confirm and particularly artwork with what all of us comprehend is real or a minimum of testable ie phenomena in our own universe. as a manner to respond to your question the universe is purely very vast and increasing yet to a twenty 5th century astronaut given the job of mapping it it would look countless.

Answer 7

What we mean when we say 'universe' can mean different things. It can mean the visible universe of 13.7 billion light years or the measured diameter of where the farthest galaxies would be right now of 92.94 billion light years or it could include whatever existed before the Big Bang exploded into it and thus whatever exists outside of the Big Bang material. This would use the infinite term.

Answer 8

Finite, but it is expanding. I do not know any scientist who beleives the Big Bang and says the universe is infinite. People who think it is infinite believe in the "Steady State" theory, in which the universe was always this way, and never substantially changed.

Answer 9

The universe is not considered to be infinite. The mere fact that nothing can exceed the speed of light means that the expansion of the universe is finite

Answer 10

The universe is finite and unbound.
Please read Stephen Hawking's books:
A brief history of time.
The universe in a nutshell.