The Naked Scientists

The Naked Scientists Forum

Author Topic: Momentum of space  (Read 3478 times)

Offline itisus

  • Full Member
  • ***
  • Posts: 56
    • View Profile
Momentum of space
« on: 27/03/2009 06:22:20 »
In GR, space as well as matter has position and momentum.  But space contains only virtual particles.  How does momentum appear?


 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
Momentum of space
« Reply #1 on: 27/03/2009 11:43:13 »
There re two possible areas to which your question could apply so it might be best to state both and wait for clarification.

Firstly the more common concept.  That is of "Momentum space"  This is a conventional way of looking at particle interactions that helps to simplify some of the calculations because the rules of momentum conservation are more clearly visible

Then there is the concept of space having a momentum itself.  This can crop up in some of the inflationary cosmology models and needs to be there to stabilise the equations and stop everything happening at once.  This is a highly theoretical area of science where people are essentially tinkering with equations and concepts to see how things might have developed.

As far as such things being measurable or having any effect on a human or even galactic scale now. this seems very unlikely.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Momentum of space
« Reply #2 on: 27/03/2009 12:13:52 »
What do you mean by saying that space has position and momentum? Space in itself can't have a momentum, as it is defined as being nothing at all. Are you thinking of Fourier transformations maybe? Looking at HUP (Heisenberg's Uncertainty Principle) it seems to define virtual particles momentum as negligible as it doesn't have any existence in measurable time, on the other hand virtual particles do have measurable effects on our world like "the strong nuclear force between quarks - it is the result of interaction of virtual gluons, and the weak nuclear force - it is the result of exchange by virtual W bosons." If that is possible then maybe 'virtual' momentum can exist too? Today everything seems to be ruled by statistics and probability, looking at it that way you might expect that 'if the probability of virtual particles over some 'area' of space will be 'dense' enough over some specific time then it might have a 'constant' effect on spacetime'.
 

lyner

  • Guest
Momentum of space
« Reply #3 on: 27/03/2009 13:10:55 »
Yor-on
Space isn't "nothing". It's space!
You could say there's nothing uotside the Universe by there's no space outside.
 

Ethos

  • Guest
Momentum of space
« Reply #4 on: 27/03/2009 14:06:40 »
Yor-on
Space isn't "nothing". It's space!
You could say there's nothing uotside the Universe by there's no space outside.
Accurate assessment sophie...; I would ask those that continue to insist that space is nothingness, please discribe nothing for me.

The space we call the universe is something, and to define it as nothing is a false concept.

The Big Bang created a place where things could exist, beyond the universe and outside this place, there might be a nothingness. That, unfortunately, is something we may never be able to examine. To travel beyond that boundry is highly unlikely because we are part of this universe and to attempt an exit would only result in an extension of that boundry. We are the universe and the universe is us.........Ethos
 

lyner

  • Guest
Momentum of space
« Reply #5 on: 27/03/2009 14:52:46 »
I thought of the following difference between the two:
Space is anywhere you can go to. You can't go where there is nowhere to go.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Momentum of space
« Reply #6 on: 27/03/2009 19:36:59 »
Ah, but space is nothing.
So, just what is those virtual particles?

huh.
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Momentum of space
« Reply #7 on: 27/03/2009 20:18:57 »
Quote from: Ethos
Accurate assessment sophie...; I would ask those that continue to insist that space is nothingness, please describe nothing for me.
I think one could take either side of this question. Empty space as nothing, would be the absence of any particulate matter. Empty space with properties that allow it to propagate electromagnetic radiation would be something.

I wonder if there is a constant of nature that varies with expanding empty space.

 
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Momentum of space
« Reply #8 on: 27/03/2009 20:25:26 »
Yep Vern, the true complication of space is that it is defined as being composed of nothing, but still having the property of 'distance'. That makes it 'something' to my eyes :)
 

Ethos

  • Guest
Momentum of space
« Reply #9 on: 28/03/2009 02:24:31 »

That makes it 'something' to my eyes :)
Excuse me for asking, but, how can nothingness suddenly become something to your eyes?
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Momentum of space
« Reply #10 on: 28/03/2009 12:39:37 »
Well, one thing is the definition of 'space':) as something existing between two objects. But you're right, I should have written 'vacuum' instead, that would have defined my thought better. But no 'matter' how you see it, matter will freely navigate 'distances' between objects in 'space'. And that's why I'm very sure on that space contain, 'distance'. And as I said, that makes it into 'something' to me. But yeah, I was playing with words here (have to train that English:)

Why I think so? Let's look at the definition of a 'vacuum'.
"A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure.[1] The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty. A perfect vacuum with a gaseous pressure of absolute zero is a philosophical concept that is never observed in practice."

So it's devoid of matter, more or less. The question here is if that is the same as what I see as the idea of 'nothing'. To me the difference is that 'space' or if you like, a vacuum contains 'distance'. A 'true' nothing to me shouldn't contain even that. On the other hand, if one looks at it from the conception of waves and virtual particles then space is filled of 'obstacles' :)

But it isn't, as we prove each time we send something out there, as long as we avoid our own 'debris'. If I think of it that way then 'space' is a matter :) of 'density'. And the way we define that 'density' in QM seems to me to be from a 'probability perspective'. that is, virtual particles or 'wave packets' pops in and out of it the whole time. And if the definition of a 'vacuum' should be so? Then the next question I would have might be, when does those 'pops up' become a reality, like, can one by using 'probability functions' define when a vacuum  becomes 'denser' aka a 'non vacuum', is there a 'threshold' for it?

Vacuum and space is remarkable concepts:)
« Last Edit: 28/03/2009 12:41:18 by yor_on »
 

The Naked Scientists Forum

Momentum of space
« Reply #10 on: 28/03/2009 12:39:37 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums