Archimedes was born in Syracuse (ancient Greece) in 287 B.C. He was a great scientist with brilliant contributions to physics, astronomy, and maths. He discovered the concept of density and formulated the principle of buoyancy, which explains why some objects float but some others sink. He stated the laws of the lever and pulleys.
He was also a great inventor. He invented the so-called Archimedean screw, other machines to be used in astronomy observations and calculations, and many war machines that allowed defending his city against the Romans.
But above all, Archimedes was a giant mathematician. He estimated the value of the number π=3.14... starting with the perimeters of inscribed and circumscribed regular polygons. He also made important discoveries about the volume and the surface of spheres and cylinders.
He was a clear example of an absent-minded mathematician. One time, Archimedes was working on a problem he had drawn on the sand of the floor. His city, Syracuse, was in war against the Romans, and it had been taken just when he was thinking about the problem. Then a Roman soldier showed up and shouted at him:
“I order you to come with me to see the General”
But Archimedes answered impatiently:
“Can't you see I am working? I must finish my problem firstly. And stand off my diagram, you are spoiling it”
The soldier got angry, drew his sword and killed Archimedes.