Four Forces – Gravity

This week’s videos are all about gravity. However, before embarking on the main videos about the four forces of nature, I decided I needed to make Noether’s Theorem seem plausible. Noether’s theorem tells us that, for every continuous symmetry in nature, there is a conserved quantity. It’s so central to what follows that I think you have to have some confidence in the truth of the theorem. So that’s where I’ll begin.

Now we can examine the first of the four forces: gravity.

There’s a very nice demonstration of how curvature creates forces, and that I reference in the above video. You can see it on YouTube.

Finally, for those who want something a bit more detailed, I’ve put together a 10 minute summary of General Relativity. It took me several years to boil GR down to the absolute essentials so that I could remind myself, on a single sheet of paper, how it all hangs together. so here is the result.

Warning – this one, and the ones that follow, are all maths.

If you would like something a bit more leisurely, then the following video (not by me) does the same thing in about two hours (phew, what a slouch!).

And if you really want to learn GR, then Leonard Susskind’s videos can’t be beaten.

The only book on General Relativity that ever made the slightest bit of sense to me was this one. (And it makes a LOT of sense.)

Cheng: Relativity, Gravitation and Cosmology A Basic Introduction

One thought on “Four Forces – Gravity

  1. Only just got round to watching these two presentations (I haven’t looked at the third one!) I must admit that I hadn’t really thought about forces in terms of conserved quantities leading to local transformations – or, at least, if any of my physics teachers put it that way, I wasn’t paying attention. Looking forward to catching up with the electromagnetism one now!


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