[sharpener]

My guess...

In the mathematics of the physics, gravity is a scalar field. We don't really know what gravity is, we just have various descriptions that seem to be useful at various levels of detail. So when folks talk about gravity waves, in the maths it is a pulse traversing a scalar field, and we don't really know what is happening to the space or whatever it is that makes the pulse possible. Is space actually stretchy like elastic? Unknown. But it means that if there is no other potential field that can "bend" a moving gravitational wave's trajectory then gravitational waves will travel in absolutely straight lines.

Light, on the other hand, moves through the potentials generated by the gravity field and is governed by its energy, sort of, to follow geodesics of the gravity field. So in GR light takes the curvy path around objects with gravitational potentials around them. The article doesn't mention if there were any influential masses along the journey.

1.7 secs is about 320,000 miles. Maybe the curves?

[weebull]

Stellar event produces a gravity wave and a light pulse coincidentally at the source. As they travel through space together the gravity wave is compressing and expanding spacetime in the vacinity of the light pulse.

I could very easily believe that interaction by itself would be enough to have measurable effects over interstellar distances.

[abdullahkhalids]

Yes. But our explanation should argue for the direction of difference (whether light arrives first or the gravity wave).

[dTal]

Aha! So the light pulse could be riding a kind of naturally-occuring Alcubierre warp bubble?

[T-A]

> In the mathematics of the physics, gravity is a scalar field.

No, it's a tensor field.

https://en.wikipedia.org/wiki/Riemann_curvature_tensor

[sharpener]

Or only for the things that experience gravity as a curved surface?

Gravity, arguably, does not experience gravity as a curved surface.

[T-A]

How would you go about arguing that?

[westurner]

"Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2015) https://hal.science/hal-01248015/

TLDR; In SQS (Superfluid Quantum Space), Quantum gravity has fluid vortices with Gross-Pitaevskii, Bernoulli's, and IIUC so also Navier-Stokes; so Quantum CFD (Computational Fluid Dynamics).

[T-A]

That article describes a hypothetical microphysical model of gravity. It's an old idea which has been done better by others (see e.g. "The Universe in a Helium Droplet" [1]). Whether right or wrong, it has no bearing on your claim that

> Gravity, arguably, does not experience gravity as a curved surface.

Any valid microphysical model of gravity must be able to reproduce the successes of general relativity in the classical limit, including the ability to match the shape of gravitational waves produced by black hole mergers. So if you want to argue that gravity "does not experience gravity as a curved surface", you have two options:

1) show that the non-linear (i.e. self-interaction) terms of Einstein's equations do not involve curvature or

2) come up with an alternative theory of gravity which does not reduce to general relativity in the classical limit and yet manages to reproduce all its successful predictions.

Which one is it?

[1] https://academic.oup.com/book/11557

[westurner]

[1] (2009) Does not disprove hydrodynamic SQS theories of quantum gravity.

A table of predictive error per experiment,{parameters},model might help us understand.

SQS purports to describe black hole internal topology where others do not. GR does not describe the internal topology of merging black hole vortices. Various theories of Quantum Gravity (QG) attempt to reconcile Dirac's pre-"Dirac sea" antimatter claims.

A unified model must: differ from classical mechanics where observational results don't match classical predictions, describe superfluid 3Helium in a beaker, describe gravity in Bose-Einstein condensate superfluids , describe conductivity in superconductors and dielectrics, not introduce unoobserved "annihilation", explain how helicopters have lift, describe quantum locking, describe paths through fluids and gravity, predict n-body gravity experiments on earth in fluids with Bernoulli's and in space, [...]

What else must a unified model of gravity and other forces predict with low error?

Why do I like Fedi's (2015/2016)? IDK. Maybe it's the abstract, maybe it's that nothing else even tries to do fluids and Bernoulli's. N-body gravity solutions with fluid vortices should predict all existing numerical n-body outcomes?

That so many things in space look fluidic - how many spiral arms are there on a nebula, all existing visual representations of black holes look like fluids, merging neutron stars look like emergent patterns from curl, too

Somehow I doubt anyone has even yet left an evolutionary algorithm online even all night to mutate and crossover the expression tree(s) to minimize predictive error according to existing experimental observations