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Equation 43 · Part 1 · The Valley of Stability Is a Fitness Landscape

superscript

10−2110^{-21}
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What this part means

A raised number can be a power. When it is a label or bound, it selects a case or the upper limit of a sum; the formula’s structure distinguishes these uses.

Its job in the formula

A raised mark can be a power or an index. Its position and the surrounding notation determine which.

The passage around this formula

The rate of each step varies by a span that is difficult to convey without sounding like hyperbole, and the chart of nuclides is, among other things, a map of that variation. At the fast extreme, some of the lightest particle-unbound configurations decay in a time too short to be meaningfully called a “half-life” in the ordinary sense — lithium-5, unbound against proton emission, has a tabulated half-life of less than 10^{-21} seconds. At the slow extreme, tellurium-128’s double-beta decay to xenon-128 proceeds with a half-life of 7.7(4)×\times10^{24} years according to NUBASE2020’s current tabulation, the longest half-life recorded for any nuclide established to be radioactive [ 2 ] . That…

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Learn the underlying idea

An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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Sources cited in the surrounding passage

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