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Equation 26 · Part 1 · The Corner of the Equivalence Principle No Experiment Has Touched

superscript

10−910^{-9}
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

Lay all of it out in one table, rows for experiments and columns for the five components, and four columns get real entries: ηcl\eta_{cl} constrained at the 10^{-15} level by MICROSCOPE, η^diag\hat\eta_{diag} constrained by every dual-species and clock test in the list, η^coh\hat\eta_{coh} constrained at the low- 10^{-9} level by Rosi and colleagues’ internal-superposition test, η^sup\hat\eta_{sup} constrained by Overstreet and colleagues’ gravitational Aharonov-Bohm result. The fifth column, η^ent\hat\eta_{ent} , has nothing in it — not a weak bound, not a preliminary number, nothing. The paper’s proposition on this point is not merely that the entangled component happens to be unmeasured; it proves, within its…

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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 article section

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