Solved cryptogram
Helium is light enough to escape Earth's gravity, so the supply in our air keeps leaking away.
Chemistry Facts, sourced to Royal Society of Chemistry.
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What it means
A helium atom at the top of the atmosphere moves fast enough to reach escape velocity, and once it is gone it does not come back. That makes helium the one element on Earth that is genuinely being lost. What we use is dug out of the ground, where it has been accumulating for hundreds of millions of years as heavy elements decay, and it cannot be manufactured at any useful rate.
The claim comes from Royal Society of Chemistry.
- SourceRoyal Society of Chemistry
- CollectionChemistry Facts
- Difficultymedium
- Length75 letters, 19 unique
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