SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/astro-herschel-infrared

Who discovered infrared light in 1800 by putting a thermometer past the red end of a spectrum?

William Herschel, while measuring the heat of sunlight colors.

Start playing free

  1. Isaac Newton
  2. Galileo Galilei
  3. William Herschel ✔

Why: Herschel spread sunlight into a rainbow and measured each color's heat. A thermometer beyond the red still warmed up, revealing invisible light. It was the first hint of light we cannot see.

Huh, didn't know that: Herschel also discovered the planet Uranus, in 1781.

The dad joke
Infrared is just light that gets cold feet about being seen.
Like this card?
Play the game

References

Answer: William Herschel. Herschel spread sunlight into a rainbow and measured each color's heat. A thermometer beyond the red still warmed up, revealing invisible light. It was the first hint of light we cannot see.

  1. OpenStax Astronomy 2e, 5.2 The Electromagnetic Spectrum openstax.org/books/astronomy-2e/pages/5-2-the-electromagnetic-spectrum
    Astronomer William Herschel first discovered infrared in 1800 while trying to measure the temperatures of different colors of sunlight spread out into a spectrum.
    Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

Astronomy & SpaceWhy is infrared astronomy best done from mountaintops, airplanes or space?Astronomy & SpaceWho built the first successful reflecting telescope, in 1668?Astronomy & SpaceHow big is the largest working refracting telescope, at Yerkes Observatory?

That's stuff everyone should know.