Gravitation is a landmark graduate-level textbook that presents Einstein's general theory of relativity and offers a rigorous, full year course on the physics of gravitation. ( )

□^2h'(jk) = -2ϰT(jk) ... solve for h'(jk) and those are gravitational waves moving at the speed of light! The speed of light bit is from the square operator at the front. Translated, the h'(jk) are like a source of energy-momentum, the T(jk) bit, in space-time and then space-time bends because of this in a wavy way. Too bad “there were” no Gravitational Waves back then when this book first came out or these three luminaries would have written about it. The way it works is to express the left hand side of Einstein's tensor in terms of the □^2h'(jk). The □ operator is a four-operator containing -1/c^2 x d^2/dt^2. This means you have a wave equation with speed c for the waves.

The authors also forgot to mention the Fifth Force. There are five fundamental forces in the Universe:

- - The Weak Nuclear Force;

- - The Strong Nuclear Force;

- - The Electromagnetic Force;

- - Gravity, the universal Force;

- - Cristiano Ronaldo (some say Ronaldo is an alien come to Earth to teach humans football on how to win 5 Ballon d'Or. You might get beamed up and told off ...)

The Electromagnetic and the Weak Nuclear forces have already been momentarily combined in the laboratory, the so-called "Electroweak" force. If, as a result of the current research the Electromagnetic and Gravity forces can be reliably combined, we'll finally have real Hoverboards. How much energy will be required for these hoverboards? And I presume you mean that will work over surfaces other than just metal as we have hoverboards that work over metal. Oh, if a hoverboard repelled the surface of the earth would they not also repel any being not made of exotic matter that tried to ride it? The shielding that enables a hoverboard to be ridden will be the real technological breakthrough.

It's amazing, isn't it? If scientists work on something directly and immediately relevant to the whole of the world, like climate change, they area accused of just making stuff up for the money. If they work on basic underlying principles that we will need to make significant advances, they are wasting time and money that should be used to save human lives. If they work on pretty much anything directly to do with human health they are evil vivisectionists. If they work on technological development they are greedy capitalists. If they work on anything to do with conservation they are interfering with nature and upsetting the poor wild animals who should be left in peace. I can't help feeling there's a theme here.

Once when my wife and kids went away for a week and I spent the whole time lazing about and never got around to cleaning the living room as I had promised and she came home to see the room had not been touched I had the same explanation to offer her reaction to the discovery. Gravitation didn’t let me! I was glued to the sofa! Maybe I should have told her, "The house was clean and tidy yesterday. Shame you missed it".

Blah blah blah. Wah wah wah.

I don't actually understand any of this pointy-head shit, so to maintain the illusion that I'm an intellectual, I'll invent the world’s most boring conspiracy theory with lots of words I clearly don't understand but which idiots may think sound clever. This conspiracy theory will makes me the sole member of the human race who is smart enough to see through their egg-headed evil plans. ( )

Great simplified explanation for beginners to understand Riemannian geometry ( )

A friend of mine in college liked to take this book from my shelf and drop it on the floor in a demonstration of gravity. As this is a monstrous tome, it made a fairly satisfying "thwomp" upon impact, edifying all present. This is one of the canonical references on general relativity. Favoring the geometric approach over the "index" approach, it is an important resource for any serious GR researcher. On a physical note, the binding cannot hope to cope with the mass of this puppy; it will break immediately.

UPDATE (2020-11-24): Well, the binding never did give way completely but I ended up purchasing the 2017 hardback version to go alongside my original paperback which is collapsing under it's own weight in some sort of recursive lesson on gravity. Even though I am long out of the field, I felt the need to get a lasting copy of this classic text.

"Gravitation" is a thorough introduction to Einstein's general relativity. Assuming basic calculus and mechanics, it introduces the mathematics, notation, and physics required to understand general relativity. In its discussion of experimental tests and post-GR theories it's a little dated, but as a textbook or reference book it's generally pretty thorough, and very accessible. ( )