Things I learned from Stephen Hawking (tldr of Brief History of Time)

Popular book but they say it’s not widely read. As a teenager I bonked out in the first forty pages too.

Not this…time.

Memorable opener — “it’s turtles all the way down!” (What to say to resist science with an absurd explanation *and* wink at a classic line.)

Relativity is easy. A ping pong ball you bounce on a speeding train — how far did it travel on that bounce? Depends on if you are on the train or platform. Speed varies. Weird fact: light moves at the same speed wherever you see it — platform, train, or speeding meteor. It’s a fact. Measured from all positions. What to do? Idea: You think time moves at a fixed rate. Can’t change the distance-speed, so change the time. It must be that time changes when things are moving fast. Space-time. Now the same light speed varies depending on how fast time was moving and how much distance was covered. On the train more time, on the platform more distance.

The Big Bang and the expanding universe, also easy. Hubble looked out and saw weird colors — all red not blue. The Doppler effect that makes fire engines sound weird as they race by also makes stars look red as they move away (blue if closer). They are moving away from us in nearly every direction — red, no blue. Only possible if the entire universe is expanding. Further: so it must have started at a single point, the Big Bang.

Quantum uncertainty and Schrödinger’s cat. Needlessly confusing! Really small stuff is hard to see because you need light (photons) or something to hit it and bounce off. But if you hit it, you move it. So it’s impossible to see small stuff without messing up the measurement. Simple. (Forget the cat.)

Quantum particles: atoms have parts (neutrons, protons, electrons). They too have parts. Quarks (in flavors), charms, bosons, and these things have antiparticles like anti-electrons (positrons) and they have funny properties like spin (they look different in different situations but are still the same particle) and so forth. Gravitons for Gravity, photons for light. This is zoology in physics. Memorize it and be happy. But nothing to understand except that size, shape, color, mass are not the only things in life. (Also bosons, which sound great.)

Time’s arrow: amazingly there are some properties that only work in one direction of time, not backwards. “Aging” in physics not biology.

Black holes: Hawking had a lot to do with these as did the bad-philosopher/great-mathematician Roger Penrose and the Indian, Chandrasekhar, who did the math en route to Cambridge to prove: a really big star can collapse on itself and become a black hole. Small, dense, high gravity, bends light and everything else so it gets sucked in. (Good news though! Gravity gets weaker with distance so it won’t suck YOU in.)

More on black holes: you can tell Hawking loves these.

That’s it for now!