Did you know that helium is the second most abundant element in the universe?

It’s true! Even though we apparently are running out of it here on Earth…

Helium was first discovered on the sun by a French astronomer named Pierre-Jules-Cesar Janssen in 1868 as a yellow line in the sun’s spectrum while he was observing a solar eclipse from India.

Around the same time, an English astronomer named Sir Norman Lockyer noted the line at a wavelength of 587.49 nanometers. He knew it couldn’t be produced by an element that was known at the time. Lockyer named the new element helium after the Greek sun god, Helios.

Italian physicist Luigi Palmieri saw the same line, at 587.49 nanometers, in gasses coming from an eruption of Mount Vesuvius. In 1895, Swedish chemists Per Teodor Cleve and Nils Langer finally confirmed helium on Earth in the mineral cleveite.

About 0.0005 percent of the earth’s atmosphere is made up of helium, but it’s not bound to the earth by gravity and is constantly escaping into space. The decay of radioactive elements in the earth’s crust replenishes the helium in the atmosphere.

Alpha decay creates alpha particles. Once these particles capture two electrons each, they turn into helium atoms and travel to the atmosphere through cracks in the crust.

Helium is commercially extracted for all kinds of uses: inflating party balloons, scientific balloons, and blimps are the most obvious ones.

It’s also used in arc welding, for pressurization of fuel tanks of liquid-fueled rockets, and in supersonic wind tunnels. Deep sea divers use it in their tanks to avoid nitrogen narcosis. Liquid nitrogen is important in superconductor study and for superconductor magnets.

I wonder if Pierre-Jules-Cesar Janssen knew how useful helium would be this far into the future…