Equation 1 · Part 2 · Radioactive Clocks: How Nuclear Physics Gave Evolution Its Time
Symbol t
What this part means
t is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.
Its job in the formula
t is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.
Full expression→Symbol t→Article meaning
The passage around this formula
The property that makes radioactive decay useful as a clock is not that it happens on a convenient timescale — some isotopes decay in fractions of a second, others over timescales longer than the universe’s age — but that it happens with no memory. An atom of uranium-238 that has existed, undecayed, for four billion years is exactly as likely to decay in the next second as one formed a microsecond ago. There is no wear, no fatigue, no accumulated probability of failure the way there is in a mechanical clock’s escapement or a living organism’s senescence. This absence of memory is what makes decay first-order: the number of decays in a short interval is proportional only to the number of…
Learn the underlying idea
A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.
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Sources cited in the article section
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