THE BIRTHDAY PARADOX
how many people it takes for two of them to share a birthday — and the same count for codes and fingerprints
THE COLLATZ CONJECTURE
halve the even, triple the odd and add one: the road of 27, the record holders and a problem nobody has solved
THE DOOMSDAY RULE
the weekday of any date in the Gregorian calendar, worked out in the head in three steps
LEAP YEARS
one rule, a cycle of four hundred years and the ninety-seven extra days in it
THE RULE OF 72
the time it takes steady growth to double: the division you can do in your head, how far it misses and why the divisor is what it is
AUDIO CONNECTORS
analog, digital, and speaker wiring · pinouts and balanced signals
AUDIO CARRIERS
seven carriers over a century at one scale, and what each one brought first
BIT DEPTH
how many steps the level is cut into, what a bit adds, and why floating point is not the next row
DECIBEL SCALES
what stands at zero on each of them, and why −10 and +4 are not fourteen apart
DI, REAMP AND PREAMP
three boxes on one ruler of levels — where each one leads from and to
EQUAL TEMPERAMENT
how many cents each interval misses the pure one by, and why exactly that much
TONEWOODS
density, hardness, export · what is measured kept apart from what is taste