Solved cryptogram
A clock in motion keeps time more slowly, and flying atomic clocks around the world showed it.
Physics Facts, sourced to HyperPhysics, Georgia State University.
Solve it yourself
This fact is a cryptogram here: 76 letters over 20 different ones, graded hard.
Or go to the puzzle’s own page first.
What it means
This is not an illusion or an instrument error; the moving clock genuinely logs less elapsed time. At everyday speeds the difference is far too small to notice, which is why the idea feels absurd. In 1971 Hafele and Keating carried cesium clocks aboard commercial airliners in both directions around the planet and compared them with clocks left at home. The readings differed by the predicted fractions of a microsecond.
The claim comes from HyperPhysics, Georgia State University.
- SourceHyperPhysics, Georgia State University
- CollectionPhysics Facts
- Difficultyhard
- Length76 letters, 20 of them different
Nearby in the collection
The facts either side of this one.
- HyperPhysics, Georgia State Universitymedium, 67 letters
- HyperPhysics, Georgia State Universitymedium, 69 letters
- HyperPhysics, Georgia State Universitymedium, 72 letters
- HyperPhysics, Georgia State Universitymedium, 76 letters
About as hard as this one
Scored closest to it by the model behind our guide to solving cryptograms.
- HyperPhysics, Georgia State Universityhard, 68 letters
- NISThard, 74 letters
- NISThard, 73 letters
- U.S. Department of Energymedium, 76 letters