Solved cryptogram
Temperature has no master thermometer. The kelvin is set by fixing the Boltzmann constant.
Physics Facts, sourced to NIST.
What it means
Temperature scales used to be pinned to the behavior of a substance, such as the point where pure water can exist as solid, liquid and gas at once. That works, but it depends on the water being pure and on the pressure being right. Fixing the Boltzmann constant instead makes the kelvin a statement about energy per particle, which is what temperature has always really been, and no sample of anything is involved.
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This is not the kind of claim that goes out of date, which is why it was set as a puzzle rather than a fact with a shelf life.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: 75 letters over 22 different ones, graded hard.
- SourceNIST
- CollectionPhysics Facts
- Difficultyhard
- Length75 letters, 22 of them different
Nearby in the collection
The facts either side of this one.
About as hard as this one
Scored closest to it by the model behind our guide to solving cryptograms.