Solved cryptogram
The typical size of a hydrogen atom is a constant, and it is about a ten billionth of a meter.
Physics Facts, sourced to NIST.
What it means
An atom has no hard edge, so its size is a statement about where the electron is likely to be found rather than a wall. The Bohr radius marks the distance at which the electron in a hydrogen atom spends much of its time. Line up ten billion of them and you have covered a meter, which is roughly the same ratio as a marble to the diameter of the Earth.
The claim comes from NIST, and the page it comes from was read on 2026-08-27 to confirm it still says this.
This is not the kind of claim that goes out of date, which is why it was set as a puzzle rather than a fact with a shelf life.
Solve it yourself
This fact is a cryptogram here: 73 letters over 20 different ones, graded medium.
- SourceNIST
- CollectionPhysics Facts
- Difficultymedium
- Length73 letters, 20 of them different
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The facts either side of this one.
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