Lets talk about nothing..

[DJDD]

Originally Posted by xelasnave

I dont see the difference between space and space time in so far as the space that remains after space time expands is still space...

I know that sounds strange and I see what you are saying... but simple space is surely what we seek to measure with the concept of space time..space is space and space time is a human method of enabling humans to quantify it.

great topic...beats studying for an exam!

are you saying that 'space time' is just a mathematical construct to help understand the universe, whereas 'space' is a an intrinsic property of the universe?

i thought that 'space time' was an intrinsic property, as well, but it was not until the 20th century that we had the mathematics to understand it.

Steven's analogy is what I have read and never fully grasped but that is, i think, because my everyday experience does not lend itself to understanding 'space time'. Unless you know/understand the maths I think that 3D analogies are as good as it gets.

Perhaps if we were some sort of four (or higher)-dimensional beings we could see 'space time' like the three dimensional nose on my face.

[DJDD]

Originally Posted by xelasnave

it comes down to how does space time define the edge of the Universe I guess...

perhaps this is where Hawking's "no-boundary universe" comes into it.


"The geometry of the no-boundary universe would be similar to the geometry of the surface of a sphere, except it would have four dimensions instead of two. You can travel completely around Earth’s surface, for instance, without ever running into an edge."

anyway, that is about where my understanding of this stuff ends.

[Bassnut (Fred)]

You guys should listen to James Valentine on 702 am (ABC radio) fridays at 2pm for a deeper understanding of "nothing", inspirational.

[Glenhuon (Bill)]

Originally Posted by Jen

lol Bill oh do you have that problem at home too do you?

Not a problem, just an observation of a 14year old girl with mobile phone permanently attached to her ear.

Bill

[sjastro]

Originally Posted by xelasnave

Seven you said.........

Hence space-time expands but space doesn't.

I dont see the difference between space and space time in so far as the space that remains after space time expands is still space...

I know that sounds strange and I see what you are saying... but simple space is surely what we seek to measure with the concept of space time..space is space and space time is a human method of enabling humans to quantify it. I may sound as if I make a statement but it is really a question as I still feel I miss something so fundamental it hides the rest.. Like the ballon expanding anology the air expandes and the spots on the ballon remain at relative distance ...let me think about it ..it comes down to how does space time define the edge of the Universe I guess... anyways its great to be thinking albiet some what duller than usual.... I think I am free of her so I can relax...so everything will fall into place.

alex

Space-time is definitely real. Cosmological redshift is a property of space-time. Doppler red shift is a property of space.

Space-time expansion velocity is proportional to distance.
Velocity through space is distance/time.

The inflating balloon is a good analogy by considering the surface to being equivalent to space-time. During expansion of the balloon the dots will move away from each other but not across the surface of the balloon. Spatially they are in the same position hence expansion spatially has not occurred.

Regards

Steven

[ving (David)]

so nothing is just the absence of everything right?

[xelasnave]

Originally Posted by ving

so nothing is just the absence of everything right?

er yes yes indeed... however nothing by its very definition therefore will not be observable due to the absence of all dimenion...

alex