Term

Helium

A light inert gas. It is produced when radium and other radioactive elements decay.

Pragmatism: A New Name for Some Old Ways of Thinking, William James

Explained in

• Pragmatism: A New Name for Some Old Ways of Thinking, William James
• Astrophysics for People in a Hurry, Neil deGrasse Tyson

  The second lightest chemical element, a light gas (the one that fills party balloons). In 1868 its lines were seen in the spectrum of the Sun, and it was found on Earth only in 1895.

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