Equation 6 · Part 5 · Radioactive Clocks: How Nuclear Physics Gave Evolution Its Time

Symbol N_235

\frac{N_{206}}{N_{238}} = e^{\lambda_{238} t} - 1, \qquad \frac{N_{207}}{N_{235}} = e^{\lambda_{235} t} - 1,

N_{235}

What this part means

the surviving parent uranium atoms.

Its job in the formula

$N_2$ 35 occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.

Full expressionSymbol N_235Article meaning

Where the article explains it

where $N_{206}$ and $N_{207}$ are the radiogenic lead atoms accumulated from each chain and $N_{238}$ , $N_{235}$ are the surviving parent uranium atoms.

The passage around this formula

…a single zircon crystal reports two ages that must agree if nothing has disturbed the system since: $\frac{N_{206}}{N_{238}} = e^{\lambda_{238} t} - 1, \qquad \frac{N_{207}}{N_{235}} = e^{\lambda_{235} t} - 1$ . where $N_{206}$ and $N_{207}$ are the radiogenic lead atoms accumulated from each chain and $N_{238}$ , $N_{235}$ are the surviving parent uranium atoms. Plotting these two ratios against each other traces a curve, the concordia, on which a grain that has behaved as a closed system since crystallization must fall; a grain that has lost lead at some later date instead falls off the curve along a…

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A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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