If something in subatomic particles is neutral direction whether if relative or fixed, it acts as centre of gravity so other subatomic(s) point to it (gravitational attraction)... could that be possible?

"Thought experiment approaches have been suggested as a testing tool for quantum gravity theories.[9][10] In the field of quantum gravity there are several open questions – e.g., it is not known how the spin of elementary particles sources gravity, and thought experiments could provide a pathway to explore possible resolutions to these questions,[11] even in the absence of lab experiments or physical observations."

From link: https://en.wikipedia.org/wiki/Quantum_gravity

I think there’s an implied “if” - since we have no working, tested/confirmed theory of quantum gravity, we don’t know if spin has an effect. It might be present in some proposals, but we don’t know if they are correct.

There are no answers at this point, AFAIK

Particle spin is intrinsic angular momentum, and any momentum is a 'source' of Gravity.

Is that what you meant ?

As said, suggested, implied:

Angular momentum has energy.

Energy sources gravity.

Ergo,

Angular momentum sources gravity.

At the moment, we don't know whether the words "quantum gravity" are akin to what people once used to say: "elastic properties of the luminiferous ether".

It could well be the case that these words finally have to be abandoned.

There is also a spin formalism for general relativity. So, in a way, all of GR is about spin. This is because spinors are more basic objects than space-time 4-vectors (for every 4-vector, or event, there are two spinors representing it).

2 hours ago, MigL said:

Particle spin is intrinsic angular momentum, and any momentum is a 'source' of Gravity.

Is that what you meant ?

Yes, I think so.

4 hours ago, joigus said:

Angular momentum has energy.

Energy sources gravity.

Ergo,

Angular momentum sources gravity.

How much, though? ~10^-16 eV-s of angular momentum vs ~1 MeV of mass for an electron.

(The phrasing did not make it clear to me whether it was claiming a source or the source)

6 hours ago, joigus said:

Angular momentum has energy.

Energy sources gravity.

To be honest, I’m not so sure about this. The energy-momentum that forms the source term in the Einstein equations comes from the Noether current associated with spacetime translations, whereas spin comes from Lorentz invariance. These are different things. It is not in fact possible, AFAIK, to define a unique 4-momentum vector for intrinsic spin, so I don’t see how it could - if taken in isolation - act as a source of gravity.

Or am I missing something?

there have been studies into intrinsic spin couplings to gravity example below

https://arxiv.org/pdf/2502.07604

to date as far as I know there are no measured couplings and the article mentions the key violations that would result including those pertaining to freefall differences. There are numerous papers pertaining to this in the Godel Universe for spin gravity couplings which more often that not employ Einstein Cartan spacetimes.

One of the factors against a rotating universe tight bounds is the lack of any measured spin gravity couplings which experimental data places a very tight bound against any universe rotation.

Mashoom has a paper on it pertaining to Godel universe

https://arxiv.org/pdf/2304.08835

Edited 22 minutes ago22 min by Mordred