From ancient Greece to the Renaissance, the idea that the different substances that surround us are made up of different combinations of four basic elements (earth, water, fire and air) in different proportions did not seem far-fetched, but this hypothesis was completely overturned. thanks to the development of chemistry. The number of known elements rises to 120 today and, although we were only aware of the existence of about 13 until the seventeenth century, between the eighteenth and nineteenth centuries it had been possible to isolate almost all the elements that appear in considerable quantities and of natural way on land surface (about 90).
But, among all these elements, helium is the only one that was observed for the first time outside the Earth.
In the early 19th century it was discovered that different chemicals tend to absorb different wavelengths (or colors) when light passes through them. This phenomenon was very useful for scientists because they no longer had to chemically separate, purify and concentrate the elements that made up a substance to see what it was made of, a process that could become very long and expensive. Now it was enough to burn them, project their light into a dark chamber and see what colors were missing.
In 1868, the astronomer Norman Lockyer was using this technique to analyze sunlight during an eclipse , precisely to better understand the composition of our star. But, when decomposing the sunlight, he noticed that it was missing a specific shade of yellow that could not be explained by the absorption of any other element known at that time. Lockyer deduced that this color was being absorbed by an unknown element that he named helium , in honor of the word helios with which the Greeks referred to the Sun. And, indeed, in 1895, a chemist named William Ramsay succeeded isolating a gas from a mineral containing uranium that was effectively absorbing the same colors as that element that was leaving its mark in sunlight.
Interestingly, although it is the second most abundant element in the universe after hydrogen , helium is a rare good on Earth because it is in the form of gas under normal conditions and, having such a low density, any trace of helium in the atmosphere rises in the sky and escapes into space.
That is why, on Earth, helium is only found where there are radioactive elements in the Earth’s crust , since its unstable nuclei tend to shed two protons and two neutrons (a helium nucleus). This helium produced by radiation tends to accumulate where it can, such as natural gas deposits, and in this way we can extract it to raise zeppelins in the air, cool our MRI scanners … Or breathe it so that our voice sounds very sharp.
