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Equation 1 · Part 8 · Reactor Phylogenetics: The Family Tree of Fission Power

fraction

P(next adopter=A∣nA,nB)=nA+anA+nB+a+bP(\text{next adopter} = A \mid n_A, n_B) = \frac{n_A + a}{n_A + n_B + a + b}
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.

The passage around this formula

Graded against biological evolution, several parts of this history are exact rather than merely suggestive. Descent is literal: design documents, safety-case arguments, and component specifications pass from Nautilus to Shippingport to the commercial PWR fleet as physical inheritance, not metaphorical resemblance. Variation across national programs — American, French, Soviet, British, Canadian, Chinese — produced genuinely distinct lineages under geographic and institutional isolation, exactly as allopatric speciation produces distinct populations under geographic separation. Selection by markets, regulators, and accidents is observably real and, in the case of TMI, Chernobyl, and Fukushima,…

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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.

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Sources cited in the surrounding passage

These citations provide research context; check each source for the exact claim it supports.