Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Isher John Turner on 25/01/2010 13:30:03

Title: How do we define the Universe?
Post by: Isher John Turner on 25/01/2010 13:30:03

Isher John Turner asked the Naked Scientists:
   
A subject that really baffles me is the universe and in particular the size of it. What do we determine as the universe and any ideas as to what's on the other side of it and would this space be considered infinite? if it is considered infinite, then surely it, including us can not be real??

Sorry this question seems a little, out there!

Many thanks

Isher Turner

What do you think?

Title: How do we define the Universe?
Post by: yor_on on 31/01/2010 22:08:55

Those ideas question both space and infinity :)

In math you can prove the idea of a smaller infinity versus an greater. If that is correct then infinity can't be the ultimate infinity any longer:) There can always be one 'bigger'.

And even if the universe is a self-contained 'bubble' of something it won't tell us anything of what might be on the 'outside'. Another thing is the question of what should be seen as a 'outside' if so. A black hole f.ex? Is that 'outside' 'SpaceTime'? Or QM at and under Planck size, would that be 'outside'?

Everything that 'only' follows our arrow of time I, at least, :) believe to be 'inside' SpaceTime . But both atoms electrons and photons have very strange properties, making them very hard to define. So?

Are they 'inside' or 'outside'?

What definitely are 'inside' is, as far as I know, macroscopic objects made out of 'matter'. They are quite easy to see over a period of time and they will be explainable.

But there too we meet what's called 'infinites' saying that we can't get a clearcut solution to a problem which makes them 'unpredictable' too. Like knowing the planets orbits future wise but still finding it impossible to guarantee where exactly the planets will be.

So maybe nothing is what it seems?

And then, what we use to define our universe, like distance, might be more questionable than what we once thought. And where that will end and what it will do to a possible 'outside' I don't know?

Title: How do we define the Universe?
Post by: Soul Surfer on 02/02/2010 00:06:48

This is an interesting question and does not have a single unambiguous answer.  This is because the word "universe" has different meanings to different people (and even the same people)

First let me look at the definition of Universe.

The strict definition is that the universe is absolutely everything that exists.  This results in the answer that the size and shape is undefined and probably unknown and unknowable. It may and probably does contain an indefinite number of individual isolated cells and is sometimes referred to as the multiverse

The most restricted range of definition is that the universe is everything that we can see, be aware, of or could affect us in any way now in the past or in the future.  I tend to call this "the visible universe".

There is a third definition that lies somewhere between the two given above this is the entirety if the cell that contains our visible universe.  That is it includes things that can and will never affect us but out is less than absolutely everything because there are other cells that may or may not be like ours.  I tend to call this definition "our universe"