
Tests of General Relativity - skolos
https://arxiv.org/abs/1811.00364
======
Ono-Sendai
Should be renamed to 'Tests of General Relativity with GW170817', it sounds
like a survey article.

~~~
LolWolf
Yes, please. The current title is quite misleading: I thought it was a
“methods and history of GR tests” survey article when I clicked on it.

------
skolos
The test confirmed GR. In particular the test results contradict theories with
massive graviton and theories with "gravitational leakage" into the large
extra dimensions of higher-dimensional theories of gravity.

~~~
Filligree
Annoyingly yes. We _know_ the theory can't be exactly true, just like we
_know_ quantum mechanics can't be, but this always happens when we test them.

As much as it'd be great to make a theory of everything, we need something to
work off. Right now the physicists are honestly just spinning their wheels.

~~~
pavel_lishin
> _just like we know quantum mechanics can 't be_

Wait, how do we know this?

~~~
nwallin
Because we exist.

Quantum field theory (QFT) does a great job describing the electromagnetic,
strong and weak nuclear force, and has done a spectacular job describing
reality in ways too numerous to count. But it has two principal failings.

The first is that every time someone tries to incorporate a quantum field
theory of gravity, the inevitable conclusion is "the first time a graviton
interacts with a particle, the entire thing collapses into a black hole".
Because we haven't collapsed into a black hole, we know our theory is
incomplete.

The second is the vacuum catastrophe. QFT predicts a value of the zero point
vacuum energy (very closely related to dark energy, aka the cosmological
constant) of roughly 10^112 ergs per cubic centimeter. With a bit of a hack,
we can get this to cancel out to precisely 0. However, the observed value of
the zero point vacuum energy is roughly 10^-8 ergs per cubic centimeter. Which
isn't even close to 10^112, but more importantly, it is also not zero, so our
hack to cancel it out doesn't work.

------
chairmanwow
The pdf is 15 pages, but really only 6 pages of it is actual content. Is it
common for there to be 3 full pages of authors on a paper like this? Seems a
little bizarre to my untrained eye.

~~~
chikei
Yes, it's common for large scale collaboration experiment like this. Papers
from ATLAS/CMS have about 15 pages for authors (for example
[https://arxiv.org/pdf/1806.00425.pdf](https://arxiv.org/pdf/1806.00425.pdf)
[https://arxiv.org/pdf/1804.02610.pdf](https://arxiv.org/pdf/1804.02610.pdf)).

------
m0skit0
So GR is right again, what a surprise...

~~~
isostatic
It is, but it's really annoying.

What could be better than finding a situation where GR doesn't apply?

~~~
m0skit0
Oh yeah, it would be great, like the news about the particle whose speed
exceeded c. Unfortunately I don't think it is going to happen after all these
years and all these advanced experiments that only confirm it over and over.

~~~
sseth
Newton's theory of Gravitation stood for almost 230 years before being
superseded by GR. During this time it was proven right over and over. And in
fact in many ways what happens with great theories is not that they are proven
wrong, but rather that they are extreme conditions where there predictions
deviate slightly from reality. In the case of gravity I believe one of the
very few deviations from Newton's gravity known was the precession of the
perihelion of Mercury - there was not that much known that was wrong about it.

I think it is fair to at least hope to find deviations from GR which would
have to be at much more extreme conditions given the greater precision of
today's measurements.

