Discovering Helium

French astronomer Pierre Jules César Janssen became the first person to observe helium, an element never before seen on Earth, on August 18th, 1868. 

Janssen had been observing a total solar eclipse in Guntur, India when he noticed a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. He initially assumed the line to be sodium, but, upon further investigating his hunch that it might be a new element, concluded he had stumbled upon something hitherto unknown.

In this episode, Arion, Rebecca and Olly try their damndest to explain how Spectroscopy works; reveal which scientist first detected the presence of helium on Earth; and query the French Academy of Sciences’ impartiality when it came to attributing the discovery…

Further Reading:

• ‘How Scientists Discovered Helium, the First Alien Element, 150 Years Ago’ (Smithsonian Magazine, 2018): https://www.smithsonianmag.com/history/how-scientists-discovered-helium-first-alien-element-1868-180970057/

• ‘The High-Flying, Death-Defying Discovery of Helium’ (Science History Institute, 2021): https://sciencehistory.org/stories/magazine/the-high-flying-death-defying-discovery-of-helium/

• ‘Helium 101’ (National Geographic, 2018): https://www.youtube.com/watch?v=hLUcO26Q7wE

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The Retrospectors are Olly Mann, Rebecca Messina & Arion McNicoll, with Matt Hill.

Theme Music: Pass The Peas. Announcer: Bob Ravelli. Graphic Design: Terry Saunders. Edit Producer: Ollie Peart.

Copyright: Rethink Audio / Olly Mann 2026.

This episode originally aired in 2023.

#Science #Discoveries #France #India #1800s

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