Does spacetime have mass?

Blackforest

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?

The Einstein's equations tell us a direct link between the metric tensor (which contains informations concerning the space) and the stress energy tensor. This seems to reveal that yes: the form, the bottle, has an energy, equivalently a mass. (but not the water, the vacuum).

Now, if we change the paradigm and consider the water and the botle as two faces of a Moebius ring... what is inside, what is outside is no more clear. Where does the mass ly?

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

ginga

I believe that the mass is an essential characteristic of the spacetime. You could even say that this is one of the dimensions

ginga

The water can be poured from one bottle to another. And the original bottle will be empty ( without mass of water). But in the space- time it will not go away. Just this mass moves from one point of space- time to another.

cosmik debris

No, I didn't say anything of the sort. The rest of your post is far to jumbled to comment on.

Blackforest

Do you know what?
(a) Personnal attack are forbidden on the forum and
(b) I have no more time to loose with unsympathic remark or people

Do you have any constructive critic concerning my contribution? No ?

Then "Adieu!"

friend

One question that could be asked is if fields in general, like the Higgs field that gives mass to particles, is inherently different than spacetime. Or can a field be a property of spacetime? For example, the curvature of spacetime, R, is a field, right?

atyy

In classical GR, spacetime is a field, as is matter. Matter has localized mass-energy, but spacetime does not.

phinds

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

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.

friend

But matter (particles) are quanta of more distributed fields (of or in) spacetime. I understand that some of the particles come from vector fields, which might come from properties of a scalar fields such as the gradient.

Mark M

Thinking of space-time as a fabric, as phinds pointed out earlier, will lead you down a road of many misconceptions.

The key concept of GR is geometry. When we talk about space-time taking on curvature, we're talking about it in the sense of a curved manifold - it's the metric that is relevant.

In particular, we describe gravitational acceleration of objects with the Ricci tensor. This, along with the other tensors that make up the Einstein tensor, describe how geodesics deviate in the presence of matter.

A very important feature of GR is background-independence. That is, There is no absolute space-time that has an independent existence. There is only the geometric relationships between objects within space-time, as Marcus often says.

Thinking of space as some kind of tangible 'thing' is what is leading you to believe it has mass. You're taking an analogy too far.

Blackforest

Exact.

Blackforest

This is effectively a potential issue for discussion but I interprete the reality in the opposite way.
There exists an immense region called 'the vacuum'; and there is no doubt concerning this point.
In that region, stars are burning and occupy (relative) stable position. This fact gave us the initial idea to construct frames and define 'spaces'.
The same way of thinking applies in my living room although there is a little bit more matter in it than in vacuum.
The manner how I measure the lengths does not influence the existence (or not) of what I am measuring: dont'you think so? The fact is that if I am measuring some thing, then this thing a priori exists. In my living room, this is an evident statement. In 'vacuum' this appears to be more difficult because the thing is suppose to be nothing. The fact is that our laser can reach the next star (or planet) and give us information on the distance with it...

Difficult, isn't it?