Equation 1 · Part 8 · Radioactive Clocks: How Nuclear Physics Gave Evolution Its Time
fraction
fraction
What this part means
Divide the expression above the line by the one below it.
Its job in the formula
The expression above the fraction bar is divided by the complete expression below it. The denominator must not be zero.
Full expression→fraction→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 fraction a/b means a divided by b. The top number is the numerator; the bottom number is the denominator, and it cannot be zero.
Open the illustrated fractions: division written vertically guide →
Sources cited in the article section
These citations provide research context; check each source for the exact claim it supports.