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kcrck
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We talk about space time as a fabric. Does it have mass?
kcrck said:We talk about space time as a fabric. Does it have mass?
kcrck said:We talk about space time as a fabric. Does it have mass?
...but I can't imagine how I could ever experience (that is, "see" the distortion of spacetime)...
Does it have mass?
Naty1 said:How about gravitational lensing...and less directly, Shapiro delay..?? or GPS time dilation??
marcus said:That's an interesting question. There is RECENT thought and discussion about that.
The biggest international conference on gravity and spacetime geometry related stuff is the Marcel Grossmann triennial. It's going on this week in Stockholm. There are 1035 participants from all over the world. Here's one talk relevant to this issue:
http://ntsrvg9-5.icra.it/mg13/FMPro...s&talk_accept=yes&-max=50&-recid=41805&-find=
Tony Padilla says NO, vacuum energy does not gravitate. He and have a paper about that. The talk is in session AT2 - Extended Theories of Gravity
Here's the brief summary of the talk:
Padilla, Antonio
Co-authors: Ian Kimpton
Cleaning up the cosmological constant
Abstract: We present a novel idea for screening the vacuum energy contribution to the overall value of the cosmological constant, thereby enabling us to choose the bare value of the vacuum curvature empirically, without any need to worry about the zero-point energy contributions of each particle. The trick is to couple matter to a metric that is really a composite of other fields, with the property that the square-root of its determinant is the integrand of a topological invariant, and/or a total derivative. This ensures that the vacuum energy contribution to the Lagrangian is non-dynamical. We then give an explicit example of a theory with this property that is free from Ostrogradski ghosts, and is consistent with solar system physics and cosmological tests.
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A clean cosmological constant (unrelated to any matter fields, just a constant in the Einstein equation) is the simplest way to get a good fit to the observational data of all sorts---including the observed slight acceleration of distance expansion.
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But there are alternative ideas! Not that space is a substance with INERTIA (the conventional measure of ) but that it is filled with a mysterious "dark energy" which GRAVITATES, so has some aspects associated with mass, and yet paradoxically causes expansion to accelerate. This would replace having a simple constant in the Einstein equation. I think so far this is at the level of FANTASY but people play around with the idea. It gets hyped up.
But anyway there are alternative speculations.
You can probably find some discussion of different "dark energy" if you look thru the program of the Stockholm conference that's happening this week:
http://www.icra.it/mg/mg13/parallel_sessions.htm
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In case anyone is reading thread who's curious about this at a technical level I'll get Padilla Kimpton's paper. Click on "PDF" to get the whole thing.
http://arxiv.org/abs/1203.1040
Cleaning up the cosmological constant
Ian Kimpton, Antonio Padilla
(Submitted on 5 Mar 2012)
Actually I rather incline towards the idea of relational space. That there is substantially no space at all but GEOMETRY instead: a web of relations among events/measurements.audioloop said:very interesting marcus, can you summarize, i mean schematize and systematize.
and what if there is no space, i mean a relational space.
kcrck said:We talk about space time as a fabric. Does it have mass?
atyy said:In classical general relativity, with spacetime conceived as a "fabric", there are two sorts of things - spacetime and matter. Matter is that which has localized mass-energy, while spacetime does not.
All I can see is the EFFECT of the distortion. I can't see the distortion itself.
...with spacetime conceived as a "fabric", there are two sorts of things - spacetime and matter. Matter is that which has localized mass-energy, while spacetime does not.
friend said:As I understand it, the Higgs boson is what gives particles mass, and the Higgs boson is itself a particle. So the question seems to ask if particles (mass) are made of spacetime? This might be an expected question since one might assume that in the beginning when spacetime began to expand, particles came into existence within that spacetime. So it seems there would be nothing else available with which to make particles except the spacetime that must have come first. Maybe the symmetries responsible for particles can be traced back to the symmetries of spacetime. Any thoughts?
Blackforest said:Cosmik debris said : ..."To me there is quite a difference between spacetime and the vacuum. To my way of thinking spacetime is a manifold on which a co-ordinate system is placed".
Ok in fact you say: the water in the bottle is not the bottle in which the water stays. This is the "classical" well admitted actual way of thinking about that item. But with this, the question of the OP would mean: does the bottle have a mass, whatever is in that bottle?
cosmik debris said:No, I didn't say anything of the sort. The rest of your post is far to jumbled to comment on.
Blackforest said:And we come here to the idea pointed out by friend: "to ask if particles (mass) are made of spacetime?" Particles as (topological) deformations of spacetime, allowing to give mass to vacuum when it deforms... Ouah... very speculative... perhaps is it time to go on the beach as suggested by naty1
Blackforest said:... Personnal attack are forbidden on the forum ...
To me there is quite a difference between spacetime and the vacuum. To my way of thinking spacetime is a manifold on which a co-ordinate system is placed.
atyy said:In classical GR, spacetime is a field, as is matter. Matter has localized mass-energy, but spacetime does not.
phinds said:Pointing out, correctly in my estimation, that your post is jumbled is NOT an "attack" it is a simple statement of fact and rewording your post to make sense would have been a more productive response.
Naty1 said:That's a potential issue for discussion, but there is no evidence that spacetime exists in the absence of 'the vacuum'. As soon as there is spacetime, it appears the 'vacuum' and everything it contains, all the jiggly stuff, is also present. Besides, a topoligical manifold is man made construct, a convenience, rather than a physical entity.
Yes, the vacuum does have mass. According to the theory of relativity, even empty space has energy and therefore, mass. This is known as vacuum energy or dark energy.
The concept of mass is not limited to physical objects. In physics, mass is defined as the amount of matter in an object. In the case of the vacuum, it may not have physical substance, but it still has energy, which contributes to its mass.
Yes, the mass of the vacuum can be measured, but it is extremely small. The vacuum energy density is estimated to be around 10^-9 joules per cubic meter, which is equivalent to about 10^-28 grams per cubic meter.
The mass of the vacuum plays a crucial role in the expansion of the universe. It is believed that the vacuum energy, or dark energy, is responsible for the accelerated expansion of the universe. Without it, the universe would not be expanding at the rate it currently is.
The mass of the vacuum is not a fixed value and can change over time. As the universe expands, the amount of vacuum energy also changes, leading to a change in the mass of the vacuum. However, this change is very small and not easily detectable.