From 3.5 billion Reddit comments

1 point

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7th May 2018

A summary?

Gravity is what we call the fact that massive objects (and energy, by extension) tend to follow geodesics in curved spacetime.

From a GR perspective, it's not a "thing" in the same way as electromagnitism, or the strong force, or the weak force. It's simply the tendency for massive objects to move in a straight line.

This is an analogy. It's designed to give intuition, but it's not at all rigorous. Again, if you want the rock solid explanation, you have to deal with differential geometry and tensor calculus and those field equations linked above.

It's not a perfect analogy. You would (rightfully) ask: "what about things that aren't already moving? why would something like gravity 'pulling' on them cause them to move, that's not them continuing to move in a straight line.", and you'd be right. But that's because the best I can do with out getting absurdly mathy is give you a mediocre analogy. If you want to know the real deal, you have to crack a book.

Also: I "referenced" that book because it's one of a few introductory General Relativity books that people who are in grad school for physics use. That means most professors who are actively involved in research use it. So your claim that "no one of any authority" would use it is absurd.

Here it is incase you're being sincere, something tells me you're not though:

14 points

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14th Apr 2018

1 point

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16th May 2022

This is enough background to try Hartle's book: https://www.amazon.com/Gravity-Introduction-Einsteins-General-Relativity/dp/0805386629

1 point

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7th Jan 2015

Pretty introductory, not a ton of math but enough to satisfy most undergrads. Includes a section on introductory Tensor Calculus.

Probably the best intermediate book, does GR at an intermediate level. Includes several chapters on the math needed.

Covers GR at a fairly advanced level. More rigorous books exist, but are not appropriate for a first course.

< $50

$100 - $200

< $50