The energy of the Universe

[exchemist]

10 minutes ago, MigL said:

Then why would you write something so wrong as 'conservation of mechanical energy' ???

Energy ( of all forms, even mass ) is conserved locally; not globally.

 

 

I think the troll has now been banned, but the mods haven't yet dreamt up a suitably humorous post to record it for posterity.

But what a twat, eh?  

[MigL]

4 minutes ago, exchemist said:

But what a twat, eh?  

He'll probably just take his clown show to the next forum, and give them a headache. 

[md65536]

20 hours ago, Markus Hanke said:

Also, it might surprise you to hear that the law of conservation of energy exists only in flat spacetime - in the presence of gravity, things become rather more complicated.

In general and specifically in our universe, a frame of reference in curved spacetime is a strictly local thing, right? There's no global frame of reference that can be used to consider all the energy in the universe. The best we can do is say that for a local frame of reference, what we measure or predict is either consistent or not with the speculation that the total energy of the universe is zero. As far as I know, everything is consistent with it being 0, but there are too many unknowns that we can't measure, to say that it is so.

You can talk about the total energy of the universe, but not in terms of a frame of reference. So if you have a model where say the universe spontaneously comes into existence from nothing, and energy is conserved, and it ends up with curved spacetime and no global frames of reference, there are still ways to describe the energy of that system being 0, but it wouldn't be described using things like a conservation law that applies to frames of reference. There are different descriptions of energy, some frame dependent and some invariant. Is this right?

 

[Markus Hanke]

22 hours ago, Glancer said:

Show me the experiment that supports your incredibly dubious claim.

You’ve got this backwards - it was you who made the claim that spacetime is a mechanical medium, and that energy-momentum is always conserved. Mainstream physics says no such thing. So the onus is on you to show how your claim is right.

2 hours ago, md65536 said:

In general and specifically in our universe, a frame of reference in curved spacetime is a strictly local thing, right?

Indeed.

2 hours ago, md65536 said:

There are different descriptions of energy, some frame dependent and some invariant. Is this right?

Yes, that’s right. The problem is that the gravitational field itself carries energy, but this energy isn’t localisable; if you try to account for it, you generally end up with expressions that are observer-dependent. A further problem is that there is more than one way around this, which is why you get different ways to define the energy content of a region of spacetime, like ADM energy, Komar energy etc etc. It’s not immediately clear how to define it in a general, unambiguous way.

I believe the problem has recently been solved, though I haven’t had time to look into this new development, so I can’t comment yet.

[Kartazion]

18 hours ago, Markus Hanke said:

I believe the problem has recently been solved, though I haven’t had time to look into this new development, so I can’t comment yet.

I'm curious to know what the news is on this. If there is a source it is welcome.

[MigL]

Yeah ! Stop teasing us 🙂 .

[Markus Hanke]

Here’s an article about this paper - it’s actually more about angular momentum (which is just as ambiguous as mass), but the problems are closely related:

https://www.quantamagazine.org/mass-and-angular-momentum-left-ambiguous-by-einstein-get-defined-20220713/

I can’t offer any real details yet, since I haven’t studied the paper itself.

[Kartazion]

5 hours ago, Markus Hanke said:

... - it’s actually more about angular momentum (which is just as ambiguous as mass), but the problems are closely related:

No it's not ambiguous. For example associate the linear displacement of the particle following the rotation of a clock which makes it possible to determine the position of the particle. In this example the direction stay the same and does not depend on the angle. IOW I find it logical and for angular rotation associated with the linear displacement of the particle, namely the speed of the particle according to the angular velocity to be able to determine its mass by mass-energy equivalence. A weak rotation of the angular velocity makes it possible to make move the particle radiatively or linearly in a form of classical interpretation of the mass, whereas a fast rotation determines a flow of it due to the principle of equivalence.

Hence the angular momentum related to that of the mass of a black hole is fully justified.

[MigL]

4 hours ago, Kartazion said:

Hence the angular momentum related to that of the mass of a black hole is fully justified.

Except that mass is also ambiguous.

Some of these problems seem so simple, Markus, such as quasilocal mass, in GR, being indicated by the difference in curvature of a two-dimensional sheet relative to Minkowsky flat. The hard part seems to be finding a method for which mathematical tools are available so as to allow computation.
More of a mathematical problem than a physical one.
Then again, at this level of theory, there's very little difference.

[Kartazion]

Ok. So what does this article brings to the understanding of the energies of the universe?

[MigL]

It doesn't.
But the papers it references might ( I haven't read them ).

Due to gravity's non-linearity, mass cannot simply be weighed , as the gravitational 'field' is also a source of gravity, and the two are difficult to separate. Gravity gravitates, and the 'field' adds to the energy-momentum ( mass ).

The article discusses methods for 'isolating' the mass from non-linear effects.
And methods for using that isolated mass to determine angular momentum.

Maybe you should read it ...
 

[Kartazion]

1 hour ago, MigL said:

Due to gravity's non-linearity, mass cannot simply be weighed , as the gravitational 'field' is also a source of gravity, and the two are difficult to separate. Gravity gravitates, and the 'field' adds to the energy-momentum ( mass ).

The fact that the gravitational waves are spiral indicates in one, that its propagation is asymmetric (outside the binary system), and in two that there is the possibility of being able to interpret the spiral propagation by an interpretation of a linear propagation mechanism (like a kind screw where its position on it is linear). But the more important is the interpretation of gravity as we know it, at the level of the observer, and in its "usual" interaction, acts as a vectorial action, and this attraction due to gravity is therefore perpendicular to the observer and this in relation to the ground i.e. here on Earth. IOW the radius whose source of gravity which is the emitter of it, crosses the gravitational wave by cutting it. I have a clear mechanical interpretation on this subject, but due to the rules of this forum I should open a new thread on it.

[MigL]

Again, you should read the link provided by Markus.

You will find information such as

"Although this way of calculating mass (known after its authors as “ADM mass”) has proved useful, it doesn’t allow physicists to quantify the mass within a finite region. Say, for instance, that they are studying two black holes that are in the process of merging, and they want to determine the mass of each individual black hole prior to the merger, as opposed to that of the system as a whole. The mass enclosed within any individual region — as measured from the surface of that region, where gravity and space-time curvature might be very strong — is called “quasilocal mass.”"

Do you have an aversion to reading ?

[Kartazion]

As you know I like to speak in pictures. Judging by my very first thread [1] on this form, here Figure 1 is how precisely the quasilocal mass is already an excellent visual approach to what I was saying previously. The second interpretation to be made and for the other part not understandable is simply appliclabe to the principle of the mass-energy equivalence.

Figure 1. source: https://www.scirp.org/journal/paperinformation.aspx?paperid=116396 credit: https://orcid.org/0000-0001-7277-1654

 

[1] 

 

 

 

49 minutes ago, MigL said:

Do you have an aversion to reading ?

Yes yes. I understand where the community struggles to understand.

[Markus Hanke]

21 hours ago, Kartazion said:

Hence the angular momentum related to that of the mass of a black hole is fully justified.

I believe you are thinking of specific, symmetric solutions such as the Kerr spacetime. In those special cases the situation is indeed unambiguous - but that’s because these cases assume certain symmetries that remove the extra degrees of freedom.

The problem referred to in the paper pertains to general regions of curved spacetime, where no symmetries or boundary conditions are assumed. Defining the total energy (not just mass) contained in such a region has been an intractable problem - which this paper now solves. I must look at this in detail, but at the moment I’m engaged in other pursuits.

 

[Kartazion]

Hello.

14 hours ago, Markus Hanke said:

I believe you are thinking of specific, symmetric solutions such as the Kerr spacetime. In those special cases the situation is indeed unambiguous - but that’s because these cases assume certain symmetries that remove the extra degrees of freedom.

I indeed have a preference for the interpretation for Kerr–Newman metric which seems to me the one that comes closest to the gravitational singularity, because this metric includes the non-zero mass with a non-zero electric charge and an equally non-zero angular momentum. But I believe that its metric is limited to that of the black hole and does not assume the rest of the space-time to be studied. I will therefore open a new thread to explain if you will the metric which I think could elucidate the interpretation of the gravitational singularity of the big-bang type followed by its metric of expansion of the rest of the space-time of the universe . I don't know if I'm overdoing it but its name is Kartazion Metrics.