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Equation 49 · Part 1 · The Valley of Stability Is a Fitness Landscape

Symbol N

N=184N=184
NN

What this part means

the closed in both.

Its job in the formula

N is part of the quantity the equation computes from the expression on the right.

Where the article explains it

The signature is sharpest in the neutron (or proton) separation energy — the cost of removing one more nucleon from an otherwise identical isotope — which drops abruptly immediately after a magic number is crossed, the nuclear analogue of a fitness cliff rather than a gentle slope; a doubly magic nucleus, closed in both N and Z simultaneously, sits at the intersection of two such cliffs and is correspondingly the most sharply peaked point in its neighborhood on the whole chart.

The passage around this formula

Further out still, past the drip lines entirely in the sense of ordinary particle stability, theoretical models predict a second region of enhanced binding among the superheavy elements — the island of stability — centered on a closed neutron shell now generally predicted near N=184 , well beyond any neutron number reached by nuclei observed to date. As Yuri Oganessian, who led much of the experimental program that produced the heaviest known elements, and Krzysztof Rykaczewski put it in a 2015 review, current experiments reach only as far as N=177 , and “modern theoretical approaches, supported by new experimental data, also point to the existence of long-lived nuclei at and around the…

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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 surrounding passage

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