Relativity Question

But the universe is not everything. The number of physicists that believe the universe is everything is almost zero.

Originally posted by doodinthemood
But the universe is not everything. The number of physicists that believe the universe is everything is almost zero.

Do we talk about religion now? Or could we stay on science?

Tell me, what is there besides universe? More than nothing?

Edit:
I found a definition of the word "Universe" at Princeton university: "everything that exists anywhere" (http://wordnet.princeton.edu/perl/webwn?s=universe) I think you exaggerate a little when you say 'almost zero'.
Please state a better definition and its source.

Princeton gives a restrictive definition. The universe is expanding into space.

Originally posted by doodinthemood
Princeton gives a restrictive definition. The universe is expanding into space.

If universe expands into space then there has to be a space before expansion, therfore the space is a part of universe. There was no space before BigBang.

But all this is false. There is no space outside the universe.

We don't come any further in this discussion. You have to accept the concept of universe first.

Originally posted by AThousandYoung
I don't understand the twins paradox either, mostly because I have trouble understanding what exactly is supposed to be happening. How do you decide which twin is the one moving?

The twins paradox is resolved by noting that the spacefaring twin accelerates at the middle of his journey, in order to turn around. Special relativity does not cover accelerating frames of reference, only inertial ones. Thus, when the travelling twin turns around, he enters a new frame of reference and the apparent symmetry of the situation is destroyed.

Originally posted by FabianFnas
If we think of universe as everything, there is no space around the universe. If it were it would be a part of universe and then universe has to expand into itself, which is contradictory.

There is no center in the niverse - or - every point of universe can be considered being the center. 'Center of universe' has thus no meaning, nor 'the edge of universe'.

Space is invariant.

Ok, suppose the two spacecraft are going apart at 0.8C like we just noted. Now they are traveling in opposite directions. Suppose the two craft each have an extremely thin rope with one end spindled on on craft and the other end on craft # 2. Initially they are in close proximity and all the rope is coiled up in a huge spindle on each craft like I said. Light years long rope. So they charge out away from one another, paying out rope. When they reach 0.8C, is the length of the rope increasing faster than the speed of light?

Originally posted by sonhouse
Ok, suppose the two spacecraft are going apart at 0.8C like we just noted. Now they are traveling in opposite directions. Suppose the two craft each have an extremely thin rope with one end spindled on on craft and the other end on craft # 2. Initially they are in close proximity and all the rope is coiled up in a huge spindle on each craft like I said. Lig ...[text shortened]... ope. When they reach 0.8C, is the length of the rope increasing faster than the speed of light?

No.

It doesn't matter if you have a rope and measure its length in each time or if you measure the distance between the spacecrafts at each time. You will get the same answer. How could it be of any difference?

Originally posted by FabianFnas
If universe expands into space then there has to be a space before expansion, therfore the space is a part of universe. There was no space before BigBang.

I would highly recommend "short history of nearly everything" by Bill Bryson.

Originally posted by doodinthemood
I would highly recommend "short history of nearly everything" by Bill Bryson.

And I would highly recommend "Three roads to quantum gravity" by Lee Smolin that clearly demonstrates the concept of space being invariant.

Please, quote me correctly, don't leave out improtant parts. The quotation should be read:

If universe expands into space then there has to be a space before expansion, therfore the space is a part of universe. There was no space before BigBang.

But all this is false. There is no space outside the universe.

I have read that book as a matter of fact. There were few things in it, if any, that I disagreed with. And apologies for the misquoting.

Originally posted by doodinthemood
I have read that book as a matter of fact. There were few things in it, if any, that I disagreed with. And apologies for the misquoting.

Apologies accepted. No harm done.

One interesting thing that I learned from this book was that space and time is discrete. Normally one thinks intuitively that you can half a meter infinitly number of times. In reality there is a shortest distance. The same in time, there is a shortest interval. Totally contraintuitive, but in a larger perspective it makes perfectly sense. This book totally changed my view of the ultimate fabrics of the universe. I recommend it to everyone wanting to read about the front research of universe.

Originally posted by FabianFnas
Apologies accepted. No harm done.

One interesting thing that I learned from this book was that space and time is discrete. Normally one thinks intuitively that you can half a meter infinitly number of times. In reality there is a shortest distance. The same in time, there is a shortest interval. Totally contraintuitive, but in a larger perspective it m ...[text shortened]... f the universe. I recommend it to everyone wanting to read about the front research of universe.

I've always wondered if there's a maximum density in the universe. Any hints in that book?

Originally posted by PBE6
I've always wondered if there's a maximum density in the universe. Any hints in that book?

I don't remember any such statement.
I really recommend this book for all interested in this kind of questions!

I feel better. No one understands it. No one has one answer. No one who thinks they are explaining is really explaining anything. Sounds about right.

Originally posted by coquette
I feel better. No one understands it. No one has one answer. No one who thinks they are explaining is really explaining anything. Sounds about right.

I think i hit it right on the nose. It's not a physics question. 'Tis all aboot Relatives.