Random number generator
True randomness is surprisingly hard to achieve. Computer random number generators are actually "pseudorandom" — deterministic algorithms that produce sequences appearing random but reproducible from a seed. For cryptography, lottery systems, and scientific simulations, specialized hardware measures quantum noise or radioactive decay. For picking who does the dishes, pseudorandom is plenty.
Good to know
"Due" numbers are a myth. If you flip heads 10 times in a row, the next flip is still 50/50. Random events don't remember their history. Gamblers who think a number is "due" because it hasn't appeared recently misunderstand independence. Each draw is fresh.
True randomness vs. pseudorandomness. True random numbers come from physical processes (radioactive decay, thermal noise). Pseudorandom numbers come from algorithms — deterministic but unpredictable without the seed. For security applications, cryptographic PRNGs are essential. For simulations, any decent PRNG works.
Randomness doesn't look random. Humans expect random sequences to be evenly spread, but true randomness includes clusters. In a random sequence of 100 coin flips, runs of 6+ heads or tails are expected. A sequence without clusters would actually be suspicious.