
Re-Inventing Gravity - dnetesn
http://alliance.nautil.us/article/243/re-inventing-gravity
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elaus
I don't think it's a good idea to publish an article now (August 2017) that
contains information already outdated for more than a year ([no] detection of
gravitational waves) without any kind of notice/cue…

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matt-attack
Why does the article talk about LIGO as if it hasn't already detected gravity
waves? I thought this had already occurred twice if I'm not mistaken.

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harrygallagher4
I was wondering the same thing... Maybe this was written a while ago and
published recently? Not only has it happened twice but the first detection was
over a year ago.

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gaius
I am pleasantly surprised this is about actual gravity and not a new JS
framework just named that.

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hossbeast
"Gravitational waves are the only remaining prediction of general relativity
that has not been observed". False.

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thriftwy
As far as I have read, general relativity is thoroughly battle tested. Any
hand-waving theories of quantum gravity that require amendment of general
relativity thus should be viewed with a grain of salt (instead of dominating
the discussion as some of them seem to do)

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spaceten
I often find myself almost clicking a link to a Nautilus article because of a
compelling headline, then I resist, because too many times the title is the
best part of the article. Takeaway: whoever writes the headlines at Nautilus
is VERY good at their job.

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jpfed
So this is probably a dumb question. But via Noether, the isotropy of space is
equivalent to conservation of momentum and angular momentum, right? So if
space is curved by gravity, doesn't that mean that mean it isn't isotropic
anymore...?

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avz
It does mean that indeed!

Note for example that in a gravity field like the one near the Earth surface
the "down" direction has very different properties than the two horizontal
directions (1).

In particular, an object stationary with respect to the surface released at
altitude will develop linear momentum in the down direction, so in the down
direction momentum is not conserved. OTOH, the linear momentum in any of the
horizontal directions is conserved.

(1) Isotropy means that space has the same properties in all directions.

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bkul
Even if the article is outdated with respect to LIGO, it's mostly still
relevant. Quantum gravity is a major unsolved problem in physics, and one that
we have no idea how to solve.

