Phage

Not exactly. What many people call "space" is anything outside the atmosphere of the Earth, but in the terms of the universe it is an area in which things can exist. This space can be occupied by matter or other forms of energy, or it can be completely empty. Our universe is all the matter and energy that exist, and also all the empty space in which matter and energy can exist. We do not know if space is infinite or not because we have not found an edge, but it does seem to be getting larger. (I will talk about time later down.)

This is a good way to think of it in a general sense, but it is much more complex. Lets just say that the rate at which time passes is variable and relative to the observer.

Try to imagine a point rather than a 3 dimensional object. A point has no length, width, or depth at all. Think of a map grid; point (32,57) is infinitely small.

Negative on the last half of number 4; space itself was a single point. Length, width, and depth were meaningless because everything including the capacity to exist was all in the same place (all places were one). I cannot really comment about if atomic activity was stopped or not because pretty much all of our understanding of the universe today make no sense in that context.

Matter and energy did extend out, but space extended as well. Suddenly things could exist apart from each other. This can also be considered to be the start of time.

Scientists are talking about not only the matter and energy but also the capacity to exist that makes up our universe. There might be other universes "outside" our own but it would be a peculiar concept indeed.

I would like to make a simple analogy to better explain the concept of "space", as you seem to be thinking of it as merely a vacuum. Remember that a vacuum is "A space empty of matter".

Lets imagine a piece of paper, which for our example will be completely 2 dimensional (no thickness). On this paper we will draw a stick figure and let him explore the area. Soon enough he will come to an edge of the paper. Beyond the edge of the paper the capacity for drawn things to exist ceases. You are probably thinking of this piece of paper floating in the air somewhere or sitting on a table; you are still stuck thinking in a 3 dimensional context. Remember in our example I only defined the sheet of paper and outside the sheet of paper is truly nothing.

If you can begin to think in the terms of 2 dimensions then you can understand how hard it would be to add an unknown type of dimension to our 3D view. Scientists cannot disprove the possibility of other universes but they would be separated from us by an indescribable void and located in a manner which hurts my brain to think about.

mtb_chris

It seems to me that is space was infinite, and we trace it back to the big bang, then it must have been infinite then, just incredibly dense. You can't shrink infinity into a point, or expand a point into infinity.

If space was at one time a singularity, it must now be finite. I guess.

Phage

Keep in mind that just because we cannot find an edge does not indicate that something is infinite, therefore any declarations of space being infinite in size are only speculation. With space "stretching" it is quite possible that if there is an edge it would be impossible to observe or reach because space is being created faster than the speed of light.

Then again, the current workings of the universe may not conform to current logic and we need to reorder our ways of thinking to understand it.

Yakk

Phage, there is no need for the "finite sized universe" hypothesis.

All experiments attempting to find the width of the universe have failed.

If this was true, space was never a point.

On the other hand, there are models that seem to indicate a phenomina like our visible universe could inflate out of a 20-lb concentration of a particular strange field in a hot medium. If this was the case, then the visible universe would just be an inflated bubble within something else, much much larger than our cosmic horizon. We would be like underwater animals, living at a hot spring on the bottom of the ocean. A seemingly infinite universe to them is just some small corner of the 'real' universe.

Secondly, below Plank-distance and Plank-time, modern physics is silent. In the early parts of the big bang, the equations of physics keep spewing out infinities and nonsense: cosmologists have pushed back the model of the universe to fractions of a second after "time 0", but the last little bit is not understood.

The fact is, alot of these things are still up in the air. So making definite statements about things like this isn't honest.

There are many models which explain why the visible universe seems like it is. One of the strongest involves a 'space inflation field' in a very hot early universe -- that model explains everything from the baseline universal ratio of helium to hydrogen to the clustering of galaxies to the tempurature and tempurature variation of interstellar space, to redshift from far galaxies and stars. The "hot inflation" model of the universe is called "the big bang". But even in that one model, there are many details that are not ironed out, and there are competing theories that explain what we can see but make different predictions about things we can't yet detect. (Example: gravity wave predictions differ between the "big bang" model and the "brane collision" model)

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Last edited by JHVH : 10-29-4004 BC at 09:00 PM. Reason: Time for a rest.

Phage

My point was that it is not possible to prove that the universe is infinite in size, you can only prove it is finite. Your statement at the top about space never being a point needs clarification; if we view space-time as being created in the Big Bang then space could certainly have been a point. With the observed expansion of space-time there is no indication that it is expanding "into" anything at all.

Too true, and as our understanding of the universe increases we may come across truths which defy our current logic.

Yakk

Suppose you had a theory that indicates that space is infinite, and has other corroborating things it also indicates. That is pretty strong evidence.

Remember, science 'facts' are statements that are disprovable and have proven hard to disprove. No statement in science (unless you include mathematics in science) are "proved" in the strict sense. Trial by fire is the rule: if the statement survives tough challenges, you gain confidence in it.

Eventually, you end up with as much confidence in a statement as you should have when using Newton's laws to work out the path of a baseball.

Why could it not have come into being infinite in 4 dimensions (space x 3 and time x 1)? If the current extent of space is indeed infinite, then no amount of inflation could have inflated a point to infinite space.

Alot of current theories claim that space-time is infinite in at least one dimension (time), it doesn't seem that much of a stretch to assume that it is infinite in 4, especially with the current knowledge that the universe is not folded up within the observable radius.

My point is simply that saying "space started as a point that defined all that is" is overly strong. That is one of the theories.

Others include spacetime being an inflation of a relatively small area (from plank-area to something as huge as an atom or even more), the brane-collision model, just something that happens within blackholes, or many other quite decent theories.

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Last edited by JHVH : 10-29-4004 BC at 09:00 PM. Reason: Time for a rest.

Phage

I can understand why some theories would say that time is infinite in the dimension of time, but what corroborates that? We already know that there was a start, and just because we have not come to an end does not mean that there will not be one. Sure, we cannot come up with a good reason for it to end (but then we don't really have a good reason for it to start anyway).

I take issue with your statement that nothing except mathematics in science is proven. For instance, anyone can go out and determine the boiling point of water at standard pressure. This is an observable phenomenon. Stating that the universe is infinite in size is not an observable phenomenon and cannot be proved correct, only disproved.

As you said, if theories are hard to disprove then your confidence in them becomes greater. However this only applies if it is reasonable that tests can be performed that would disprove the theory if it was wrong. An example of this in action: I propose that the center of the star Alpha Centauri A suddenly formed little green men last Tuesday. It is very difficult (impossible we presume) to disprove such a theory but it does not make any sense for us to gain confidence in it because of that.

Now look at the theory "Space is infinite in size." Is it within our capacity to disprove this theory? No, but it is also unreasonable to assume that it is within our capability at this time to disprove it were it false.

In any case, your point is well taken. Our discussion is based on current theories and views of the structure of the universe and are very likely to change as we progress. One day we may be looked back at in the same way we look back at those who believed that the world was flat.