18 August: Helium Discovery Day

It's Helium Discovery Day. So here are 10 things you didn't know about Helium:

1. On August 18 1868, the French astronomer Jules Janssen detected a Yellow spectral line signature in sunlight during a Solar Eclipse. This was the first evidence that helium existed. The first evidence that it existed on Earth came in 1882, when Italian physicist Luigi Palmieri found its spectral line in the lava of Mount Vesuvius.
2. Most helium in the universe is helium-4, and is believed to have been formed during the Big Bang. Large amounts of new helium are still being created by nuclear fusion of hydrogen in stars. On Earth, it is mostly created through the breakdown of radioactive materials, and can be found trapped within natural gas.
3. Helium is named for the Greek god of the Sun, Helios.
4. The symbol for helium is He.
5. Helium's atomic number is 2. Its atom has two electrons and two protons. It is the second lightest element, the second most abundant element in the observable universe. It is the second least reactive noble gas and also the second least reactive of all elements.
6. Despite being abundant in the universe, helium is relatively rare on Earth. This is partly because, once released into the atmosphere, it will escape into space. In fact, the world's largest helium reserve in Dexter, Kansas, is expected to run out by 2018. More has been discovered in Qatar, but some scientists now criticise the use of it for frivolous things like balloons.
7. Balloons are only a small part of helium's uses. Because it is so inert, it is used in industry as a protective gas for producing silicon and germanium crystals, titanium and zirconium. Because it can diffuse so much faster than air, it is very useful for detecting leaks in high-vacuum equipment (such as cryogenic tanks) and high-pressure containers.
8. The speed of sound in helium is nearly three times the speed of sound in air. That is why, when people inhale a little from a balloon, it makes their voice sound funny.
9. Inhaling large amounts of helium is very dangerous - death by oxygen deprivation can occur. This is relatively rare among people using it to make their voice sound funny, but it has been known. Right-to-die groups have recommended it as a fast and painless method of suicide as there isn't the panic and sense of suffocation as there is with most means of oxygen deprivation. The cause of death is difficult to trace, too, if any canisters of helium are removed from the scene by a killer before reporting the death.
10. Its melting point is 0.95 K (−272.20 °C, −457.96 °F) and its boiling point is 4.222 K (−268.928 °C, −452.070 °F). Unlike any other element, helium will remain liquid down to absolute zero at normal pressures. Helium was first liquefied on July 10, 1908, by the Dutch physicist Heike Kamerlingh Onnes in the Netherlands.