Around 450 BC, the Greek philosopher Empedocles wrote that the world was comprised of four things: earth, air, fire and water. Plato referred to them as the four elements. These were not elements in the modern sense, but rather essences that gave everything their physical properties. The idea that everything was made of these fundamental elements had a deep influence on early Western science. It was a central aspect of alchemy until Robert Boyle demonstrated there were more than four elements in 1661. The four elements also connected to the four humours of the human body, which formed a basis of Western medicine until the 1800s.
Credit: ASU School of Life Sciences
CREDIT: ASU SCHOOL OF LIFE SCIENCES
Over the past two centuries, we have gained…show more content… Part of the reason lies in the fact that they are versatile elements, capable of producing a vast array of chemical compounds, but it also has to do with the fact that they are among the most abundant elements in the universe. To understand why, we have to look to the stars.
The first elements appeared a few minutes after the big bang, through a process known as nucleosynthesis. The elements produced by the big bang consisted of about 75% hydrogen and 25% helium (by mass) with trace amounts of lithium and beryllium. For the next several hundred million years only these four elements existed. Then the first stars appeared. They formed from large clouds of hydrogen and helium, and as they collapsed under their own weight the hydrogen in their cores began to fuse into helium.
The energy produced by this nuclear fusion gives a star the light and heat necessary to counter the force of gravity for a time, but as a star ages the amount of helium in the stellar core increased. As helium become more plentiful in the stars core, some of it fuses into carbon. The carbon interacts with the hydrogen to produce nitrogen and oxygen as well as helium, through a process known as the CNO cycle. As a star ages the CNO cycle becomes the dominant process by which a star creates light and heat. As a result, these elements become fairly plentiful within a
