Archimedes of Alexandria was a Greek mathematician and philosopher active in the 3rd century BC. He lived mostly in Syracuse, Sicily. He made contributions to engineering, especially in making military machines such as catapults. He designed a screw pump to pump water, but is best known for Archimedes Principle - an object is immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object - which could be used to determine the volume of objects by placing them in water if the object sinks, the volume of the object is equal to the volume of water displaced. This solved a problem presented to him by the King of Syracuse , who asked him to find if his crown was made of pure gold. By weighing the crown and finding its volume, the density of the crown could be found.
In 1906 a lost work was discovered, "Archimedes Palimpsest" was discovered. This illustrated a method to find the approximate are of a circle, the formulae for the volumes and surface area of a sphere and cylinder, the area under a quadratic curve (parabola) by splitting them into smaller units. This method is called 'Archimedesâ€™ method of exhaustion'. From this also an estimate of the value of pi was found. Among other things, he worked on irrational numbers, the concept of infinity, an estimate of the number of grains of sand required to fill the Universe, the lever principle (supposedly he said 'Give me a place to stand on and I will move the Earth@).