the.com/halflife
a coin atoms flip forever, where half always vanish but never on schedule
means The time it takes for half of a quantity of a radioactive substance to decay, by extension used for anything that loses half its potency or relevance over a fixed period.
from A 20th-century scientific compound stitched from plain English 'half' and 'life,' coined by physicists studying radioactive decay in the early 1900s. 'Half' descends from Old English 'healf'; 'life' from Old English 'lif.' The term spread from nuclear physics into pharmacology (how long a drug lingers in the body) and then into everyday metaphor — the 'half-life' of a meme, a scandal, a battery charge.
- random timing
- no atom knows when its own turn comes
- never zero
- halving infinitely means it technically never fully decays
- wild range
- from nanoseconds to billions of years
- carbon clock
- dead things dated by carbon-14's 5,730-year tick
- bismuth-209
- once thought stable, decays over a billion universes' age
half-life of carbon-14 — 5,730 years, used in radiocarbon dating organic materials
half-life of uranium-238 — 4.468 billion years, basis for dating rocks and earth's age
half-life of technetium-99m — 6 hours, most commonly used isotope in medical imaging