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View Full Version : Does space have mass/weight?


Adamsavage
2012-Feb-24, 07:57 PM
I was watching a You Tube video, and I wondered if the actual fabric of space has any mass to it ?
Tensor
2012-Feb-24, 09:16 PM
I was watching a You Tube video, and I wondered if the actual fabric of space has any mass to it ?

In General Relativity, no. In Quantum Field Theory, yes.
noncryptic
2012-Feb-24, 09:51 PM
The Lightness of Being: Mass, Ether, and the Unification of Forces: Anticipating a New Golden Age
MIT Libraries
http://mitworld.mit.edu/video/618
transreality
2012-Feb-25, 02:24 AM
dark energy is the missing mass of the universe. It is in all space. space must then have a mass... or at least all the virtual particles popping in and out of existance.
noncryptic
2012-Feb-25, 05:37 PM
dark energy is the missing mass of the universe. It is in all space. space must then have a mass... or at least all the virtual particles popping in and out of existance.

The idea that space has mass is part of the standard model (quantum chromodynamics/vacuum energy (http://en.wikipedia.org/wiki/Vacuum_energy)). It was conceived before the 'discovery' of dark energy and does not depend on dark energy (although dark energy might be the same thing as vacuum energy (http://www.physorg.com/news88256526.html)).
astromark
2012-Feb-25, 07:24 PM
What a silly idea... That space is something.. When we all know its nothing at all.

WRONG. because someone said dark energy and that is the end of empty space.

So sitting here smug in my knowledge.. WRONG. Sigh... one day I will know something more.

Thats not today. Space is full of stuff. Space might be stuff itself. Please continue.
Cougar
2012-Feb-26, 05:07 PM
dark energy... is in all space. space must then have a mass...

Right, especially since observations from WMAP (http://map.gsfc.nasa.gov/universe/uni_matter.html) and Sne Ia lead to the conclusion that 72% of the energy density of the universe is the result of this dark energy permeating all of space. This might be surprising until you realize that the universe is mostly space!
Tensor
2012-Feb-26, 05:48 PM
Right, especially since observations from WMAP (http://map.gsfc.nasa.gov/universe/uni_matter.html) and Sne Ia lead to the conclusion that 72% of the energy density of the universe is the result of this dark energy permeating all of space. This might be surprising until you realize that the universe is mostly space!

Neutrinos permeate all of space also, but that doesn't mean they are space. Dark Energy is just a placeholder until we figure out what it is. We still don't know if it's part of spacetime or just something that produces effects on spacetime, much as normal energy produces warping of spacetime.
Cougar
2012-Feb-26, 07:10 PM
Dark Energy is just a placeholder until we figure out what it is. We still don't know if it's part of spacetime or just something that produces effects on spacetime, much as normal energy produces warping of spacetime.

I quite agree. But at least it is being considered that what was once thought to be the "vacuum of empty space" seems to have turned out to be anything but. It could even be the measurable result of our apparent 3-dimensional-plus-time universe interacting in some way with one or more of the other compactified dimensions that also inhabit our universe. I think you could say that the string-membrane folk have really taken this ball and run with it.
transreality
2012-Feb-26, 10:21 PM
If the Vaccum Energy and Dark Energy are the same thing, then as the universe expands, and has more space then it must also be getting heavier, that is having a greater total mass. This would possibly also mean unless there is a mechanism for turning virtual particles into baryonic particles etc, that the percentage of mass of the universe made up of Dark Energy (or virtual particles, perhaps) is also increasing. Possibly a universe that is getting heavier is in contravention of some laws of conservation; I guess we just don't know that the laws would apply at the greatest scale of all.
Cougar
2012-Feb-28, 01:37 PM
...as the universe expands, and has more space then it must also be getting heavier...

I think your logic is correct.


I guess we just don't know that the laws would apply at the greatest scale of all.

It appears that the conservation law doesn't apply on the scale of the entire universe. Especially if dark energy is confirmed to be accurately described by the cosmological constant.
blueshift
2012-Feb-28, 05:24 PM
Heavier? Heavy refers to weight and the universe has no weight but it does have mass. Anything that expands cools except for gluons locally. Density decreases with expansion so gravity weakens with expansion.

Space does have structure or the 3 dimensions of space and one of time could not maintain themselves here. Space is not just emptiness.
transreality
2012-Feb-29, 10:53 PM
Heavier? Heavy refers to weight and the universe has no weight but it does have mass. Anything that expands cools except for gluons locally. Density decreases with expansion so gravity weakens with expansion.



Sure, for heavier read more massive.

Cooling does that not just apply to the baryonic (and therefore rather small) component of the mass of the universe. Similarly does not gravity relate only to both the Baryonic and Dark matter components, that is, if gravity even contributes to the mass of the universe.

Or is the local density of Dark Energy expected to decrease as the universe expands?