This video is great. It is Leonard Susskind, physicist, explaining how the basics of special relativity (enough for all the unintuitive stuff, twin paradox and such) can be derived from just two main assumptions:

1. Physics basically works the same regardless of how fast you’re going, as long as you’re not accelerating - the given example is that you’re just as bad at juggling during a perfectly smooth train ride as you are on the ground. Good ol’ Galilean relativity.
2. The speed of light is the same regardless of how fast you’re going (your inertial reference frame). This is rather less intuitive an assumption. Einstein apparently went with it because it’s a consequence of Maxwell’s equations (which are for electrodynamics, not even “regular physics”!), and of course it’s experimentally verifiable.

The explanation, at least to me, makes sense. It makes sense in a way that relativity never has before. You can’t go faster than light because the speed of light is infinity, a consequence of the hyperbolic geometry underlying everything, a sort of asymptote. None of that “it would take infinite energy” crap. Just really basic mathematics - trig! I could explain this to highschoolers. I wish I’d had it explained to me as a highschooler.

I would explain a few things differently, probably because I’m more of a math guy than a physics guy. But this is very advantageous to the explanation - he works through equations more laboriously, uses angles I wouldn’t have thought of, that sort of thing.

Watching this was actually a distraction from what I set out to learn (electrodynamics), but I’m very happy I watched this. It’s nice to see a theory that just… makes sense. I know of course that it’s outmoded now, with closed timelike curves and quantum everything and bla bla bla, but it’s been a while since I’ve had that “click” and it’s pretty nice no matter how unreal the clickee is. If I can come up with a theory as obvious in my lifetime I think I’ll be satisfied (before I go back to trying to build real robots?).

The Strangest Man

Just finished The Strangest Man, a biography of Paul Dirac by Graham Farmelo. Dirac, if you don’t know, was a quantum physicist, most known for the “Dirac equation” describing the behavior of particles like electrons, which also predicted antimatter years before it was observed. But, not being too interested in physics, that’s not why I got it - I only knew of him from the “Dirac sea” technobabble in Evangelion and the Dirac delta equation in engineering anyway. It was actually Amazon’s description that interested me:

[…] he was also pathologically reticent, strangely literal-minded and legendarily unable to communicate or empathize. Through his greatest period of productivity, his postcards home contained only remarks about the weather. […] Farmelo shows a man who, while hopelessly socially inept, could manage to love and sustain close friendship.

I’m single-minded.

Dirac: My work has no practical significance.

Journalist: But might it have?

Dirac: That I do not know. I don’t think so. In any case, I have been working on my theory for eight years and now I have started developing a theory that deals with the positive electrons. I am not interested in literature, I do not go to the theatre, and I do not listen to music. I am occupied only with atomic theories.

Journalist: The scientific world that you have built during the past eight years, does it influence the way you look at everyday occurrences?

Dirac: I am not that mad. Or rather, if it did [have such an influence] then I would go mad. When I rest - that is when I am at sleep of course also when I am taking a walk or when I am travelling - then I make a complete break with my work and my experiments. That is necessary so that there is no explosion here. (Dirac points to his head).

I know Dirac was pretty weird even as physicists go, but I think this just about cements my desire to not go into physics.

Lots of physicists and lots of grins.

Originally hosted here, but it seems to have disappeared from there.

Most physicists found it implausible that nature could be so perverse as to favour a theory that required thirty pages of algebra to explain the simplest atom’s energy levels, rather than Bohr’s theory, which explained them in a few lines.
 — The Strangest Man, a biography of Dirac. Things sure have changed.
Euclid is gone, dethroned,
By dominies disowned,
And modern physicists, Judaeo-Teuton,
Finding strange kinks in space,
Swerves in light’s arrowy race,
Make havoc of the theories of Newton.
 — Poem about relativity in Punch, 20 Jan. 1920
My book came in!

The complete works of Leó Szilárd. I mostly got this for two reasons:

• I happened to read a quote of his I thought was funny.
• It cost me less than I paid for lunch over the last two days, despite that it had to be shipped from another state. The future has its perks.

The (wannabe) scientific mind, ladies and gentlemen and pseudo-Victorian term for anybody else reading this.

Besides that, Szilárd seems like quite an interesting guy; he basically switched out of physics (he was a founder of the Manhattan Project, and was one half of the letter that initiated it) and into biology, though he did continue working with radiation - he wrote “Induction of Mutations in Mammals by Ionizing Radiation” which has got to be the most mad science-y title I’ve seen in real life.

I was going to post a picture of one of the original German papers included (there are translations as well) but I decided my camera is too terrible. Here’s a spoiler - words like “Schwankungserscheinungen” are involved.

Reading a Something Awful thread about physics. Kind of lackluster overall, but it has this nice explanation of the no-communication theorem (says that you can’t transmit information faster than light via quantum entanglement):

Here’s a simplified setup: you have two (hypothetical) quantum “coins” that are entangled, brought far apart, and flipped. If coin A flips heads, B will always flip tails, and vice versa. This is repeated a bunch of times. So Alice takes coins A and Bob takes coins B and they do the experiment. If Alice flips her coin, Bob’s will be then determined to be the other side with 100% probability. If she doesn’t, Bob’s coin is 50/50. But either way, without comparing notes, Bob won’t notice any difference because his coin is 50/50 either way, either “naturally” when Alice doesn’t interfere, or through the entanglement because Alice’s coin is also 50/50. The key point is that any patterns that may arise are not apparent until both experiments communicate with one another at the speed of light or slower. Then Alice and Bob can look at the data and say, “Ah, my flipping of coin A must have caused coin B to behave in this way,” but you can’t actually tell that it did so without some other subluminal communication between Alice and Bob.

So thanks for that, DontMockMySmock.