Rien ne se perd, rien ne se crée, tout se transforme

The Greek Pythagoras is one of the first great mathematicians. Pythagoras and his friends liked to make squares using dots. They studied the number of dots needed to make perfect squares. That's how they started writing numbers in square root form.

2000 years before our era, the Babylonians had already observed that the circumference of a circle is about three times larger than its diameter. Mathematicians do not like approximations.

How can a tiny change in the initial conditions produce a result very different from the one expected? With his board, Galton throws small balls from the top of a studded board. The balls arrive at different places because Galton never throws with exactly the same force and the air never rubs in exactly the same way.

The natural numbers were created to answer concrete and natural needs of numeration: for agriculture, administration and trade, for instance. Other needs appeared quickly, leading to the invention of zero, negative integers and rational numbers.

The British scientist Alexander Fleming cultivated bacteria and enzymes in Petri dishes. On his return from vacation, Fleming noticed the appearance of mould in his containers. A fungus was discovered that led to the production of a medication called penicillin.

At the end of the 19th century, Louis Pasteur succeeded in isolating the rabies virus and producing an attenuated strain. Gradually, vaccines became mandatory, which led to the eradication of more and more diseases.

In ancient times, it was thought that blood was responsible for the emotions and was produced in the liver. When blood circulation was discovered in the 17th century and it was understood that the liver does not produce blood, we wondered what purpose this organ could serve.

In the middle of the 18th century, the American Benjamin Franklin demonstrated that clouds contain electrical charges: he flew a kite on a stormy night and proved that natural electricity exists. It is then understood that electricity is a current between a positive charge and a negative charge.

In 1587, Galileo thought that the heavier an object was, the faster it fell because a hammer fell faster than a feather. Galileo decided to test this by rolling a marble down an inclined plane. He found that whatever their size, they travelled down the incline at the same speed.

In the eighteenth century, Lavoisier will eventually decompose and then recompose the air and find its main composition, which is nitrogen and oxygen. It was later discovered that it also contains rare gases and carbon dioxide.

Born in 1822, the Austrian Gregor Mendel set up a greenhouse where he began experiments on peas. Thus he invented the concept of dominant character and established the first laws of heredity. The very first foundations of genetics were laid.

At the beginning of the 19th century, the German scientist Alfred Wegener studied the geography and geology of mountain ranges. For him, the explanation is very simple: these continents, now separated by oceans, were, at the dawn of humanity, one and the same land.

Since the Antiquity, men have found fossils. It was not until William Buckland and Gideon Mantell, then Richard Owen in the 19th century, that they began to assemble them and deduce that some of them date back to an extinct and still unknown species: the terrible lizards, the dinosaurs.

For a long time, it was thought that plants grew only from the food found in the soil. At the end of the 18th century, the scientist Joseph Priestley and then Jan Ingenhousz conducted experiments on plants to understand how they live and regenerate the air around them. They will find that it is thanks to the sunlight.

At the end of the 18th century, first in England, John Cavendish reconstituted water, then in France, it was Lavoisier's turn. Everyone interpreted it differently, a controversy broke out and it was finally Lavoisier who was credited with the discovery of the composition of water in precise proportions.