Lecture Notes: The Blackboard Proof

Chalk forces the pace of understanding.

The best lecture I ever attended contained no slides. Professor R. derived the whole result at a blackboard, and because her hand could only move so fast, our minds could follow. The medium throttled the bandwidth to exactly human speed.

When she erased the second board to make room, she said: if you did not write it down, you have elected to understand it instead.

Key steps, as copied:

1. State what you want to be true.
2. Find what it would cost.
3. Pay in lemmas.

Dust on the sleeve, theorem in the head. Fair trade.

Same energy, different room: on-the-legibility-of-justified-text.