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Equation 6 · Part 4 · Comparing the Main Approaches to Scientific Instruments and Metrology

superscript

h≈5×10−22h \approx 5 \times 10^{-22}
superscript

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 instruments above resolve structure at short length scales. A different family of instruments — laser interferometers — pushes precision along a single dimension (typically a length or a phase difference) to an extreme that has little to do with spatial resolution in the microscopy sense. Ground-based gravitational-wave interferometers are the sharpest publicly documented example: designed to detect a fractional change in arm length, expressed as strain, as small as roughly h ≈\approx 5 ×\times 10^{-22} — a distortion far smaller than a proton’s diameter integrated over a kilometers-long arm [ 10 ] . Reaching that sensitivity is a story about noise budgeting rather than a single dominant…

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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

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