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SESK: Stuff Everyone Should Know · sesk.info/aero-cavendish-hydrogen

What did English chemist Henry Cavendish discover in 1766 that later lifted balloons?

Hydrogen, which he called flammable air.

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  1. Hydrogen, which he called flammable air ✔
  2. Helium, from the sun
  3. Carbon dioxide, from fires

Why: Cavendish found a gas much lighter than air and called it flammable air. Today we call it hydrogen. Balloon makers later filled balloons with it because it gives a lot of lift.

Huh, didn't know that: Hydrogen is the lightest element in the universe.

The dad joke
Why did the hydrogen atom feel left out? Everyone said it was too light to matter.
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References

Answer: Hydrogen, which he called flammable air. Cavendish found a gas much lighter than air and called it flammable air. Today we call it hydrogen. Balloon makers later filled balloons with it because it gives a lot of lift.

  1. CAP Teacher's Guide for Aerospace: The Journey of Flight (lesson outlines) www.gocivilairpatrol.com/media/cms/2nd_edition_Teachers_Guide_5D3166D76F9B1.pdf
    In 1766, English chemist, Henry Cavendish discovered flammable air (later called hydrogen).
    Checked 2026-10-10.

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