That is an interesting question that a couple of us have tackled before. I feel that it isn't necessarily as cut and dry as you may think though.
It raises an extremely fundamental question that I doubt anyone can answer.
What is the actual 'true' nature of the universe?
Yes, we know bits and pieces, but can we say or prove exactly how it all works, what the 'true' nature of it all is? You may as well ask the same fundamental questions about God..
We don't understand the nature of time (quantifiable universal property or just our perception?) and neither do we understand the true nature of space.
Are we sure that we can rely on our system of spatial co-ordinates?
We perceive the universe as an expanding entity. Galaxies, stars etc are all moving apart. We suppose that these observable elements of the universe are all there is. Thus their positions can only be determined in relation to each other.
What if we are missing something? Here's a question that may be related.
What is dark matter? Isn't it invisible(undetectable) and isn't it supposed to account for about 99% of the volume of the universe? (I'm not completely sure of that figure, so don't hold me to it..)
I guess it thus came about because we can only account for 1% of the universe's mass, rather than through any observation of dark matter itself. Anyway...
What if this is the missing part of the puzzle? What if this is the underlying foundation, the basic fabric of the universe that everything that we know exists within? This could throw a very different light altogether on 'space' as we know it.
Here's an exotic theory that I remember from somewhere or other..
Imagine that space is like the surface of a balloon. 'Embedded' within this surface (anchored/fixed if you like) are the planets, stars, galaxies - everything that we can observe. (I'll assign dark matter as the surface at this point). We obviously can't detect this surface, yet it is the medium in which everything exists. (I supose that you have to try to imagine this surface existing in 3 dimensions rather than 2...but 'surface' is the nearest metaphor, so you get the picture)
Imagine the expansion of the universe in terms of steadily blowing air into the balloon. In relation to each other, the galaxies are moving apart(our system of spatial co-ords comes into play).
What about the position of the galaxies etc in relation to the undetectable 'surface' (dark matter) though?
The answer is that in relation to the medium in which they exist, they haven't moved at all. It's a matter of perspective. If you had a system of 'true' universal co-ordinates (taking the dark matter/underlying medium/surface of the balloon/ether into account) everything is always in the same place. This is because you are 'riding' the 'surface' of the universe (existing within it) along with everything else.
This all obviously depends on galaxies etc being fixed points on the 'surface' of course. Imagine everything as a point 'drawn' on the surface of the balloon.
It appears that we would have a seemingly paradoxical situation. Everything is moving apart, at the same time as not moving at all. However, once again it depends on your perspective.
What rammifications would this have on our perception of time? On time travelling and arriving at a different point in space to the one that you left?
I think that it's difficult to accurately predict these kind of effects of such an excursion, when we truly don't understand the 'real' nature of either space or time.
I hope that the intent of this message isn't misunderstood.
If it causes anybody out there to question the wisdom of putting too much stock in our present relatively limited understanding of the universe, epecially when dealing with the kind of matters that we do hear, then it has fulfilled it's purpose.
Just think of this as a mental catalyst, or maybe a mental laxative
))
