dalem

In the model I gave above the universe, the three-dimensional space in which we exist, is represented by the two-dimensional surface of the balloon. As the balloon expands, and assuming infinite elasticity, then the surface - our universe - will also expand.

Now, the model falls apart when you ask "what is it expanding into?" because that is a much more mathematical question requiring a much more mathematical answer (mathematics that are far beyond my meager understanding, as well).

But don't rely on just me - google up or go to a bookstore and buy any book on cosmology or astrophysics by Gribbin, Hawking or Sagan (for starters).

-dale

Praxus

So your saying that the Universe could be expanding into something that does not exist?

For everyone (not Bulg); just because a self-proclaimed authority makes a claim, does not mean that he is right. Just because they are smart, does not mean they are right, either.

Parihaka

This is where the balloon analogy falls down as it is a two dimensional representation of a three dimensional space (or is that 3 of 4?) as there is no outside: or if there is, we have no way of percieving it so effectively it's irrelevant. The universe 'folds' back on itself and creates its space as it expands.

Praxus

There can be NOTHING outside of the Universe. The Universe is ALL that exists, whether we know about it or not.

Parihaka

That was indeed the point I was trying to make

Officer of Engineers

How do you know? The smart guys are saying "we don't know." You, however, are not.

__________________
Chimo

Praxus

No, I mean the definition of the Universe is: the sum of all that exists. So anything and everything that exists, is part of the Universe.

dalem

Are you insane? In addition to the pure math, there is empirical evidence supporting an inflationary universe by the truckload.

If you deny that evidence then you must answer (at least) the following question: What is the explanation for the fact that all distant galaxies are moving away from us at all times in every direction we look?

-dale

Sombra

Praxus are you sure that the universe is everything? Perhaps there are many universes?

It seems that your image of the world is built on flawed axioms like: a feather is lighter then a stone and falls more slowly therefore...

I think Dale gave you already quite a good and easy model to imagine yourself the shape of the universe (balloon) . Going from there you are saying I am living on the balloon and there is nothing outside the balloon.

As Dale pointed out there are many observations to support the theory of an expanding universe. Galaxies moving away from each other, light is bend around big accumulations of masses. ... Everything points to the direction that Einsteins theory is right.

Sombra

If we are already on the topic:

do you believe that the universe is ever expanding or do you believe that someday the expansion stops and contracts again ?

What do you make of some observations that point to the direction of an acceleration of the expansion rate? What would be the driving force behind it?

dalem

One thing I have learned from my days as a student and my lay readings of cosmology and physics since then is that anything is possible in the realm of cosmology. It's not like we have a control experiment going on anywhere to judge the norm.

I don't like the idea of a variable Hubble Constant (or Universal Gravitational Constant, etc.), but barring rigorous mathematics that prove it impossible, I don't doubt that it is possible.

To me the Double Slit experiment demonstrates the need to accept some weirdness.

-dale

Anon

We simply do not know that to be true. Especially if the concept of endless paralell universes is true.

Anon

It is expanding into the unknown abyss at the boundries of the universe. An area of space that is presumably no more than an endless undefined vacuum.

Anon

So it would seem according to ALL available evidence.

Anon

There is simply no evidence whatsoever to back that assumption.

We simply DON'T KNOW what exists beyond the boundries of the universe. Could be an endless vacuum, another universe, or a brick wall.

We just don't know. What we DO know is that the universe is expanding at approx the speed of light, and it always has been since the dawn of time(ie, since the big bang). This is one of the most basic- and most well proven- tenets of modern cosmology.