History is full of GREAT DISCOVERIES! But do you know who made them?

A Greek Mathematician named ARCHIMEDES, who lived between 287 BC and 212 BC, made a great discovery which is known as the 'ARCHIMEDES PRINCIPLE'. He was given a problem to solve by King Hieron.

The King had been offered a crown of pure gold, but he thought the crown might contain silver, which is not as valuable. So he asked Archimedes to find out the truth.

It is said that Archimedes realised how he could do this while he was in the bath! The story goes that he noticed the water level was higher when he was in the bath than when he got out. The difference was the size of his body. He ran naked through the streets shouting 'Eureka' as he realised he could now solve the King's problem.

He weighed the crown and put it in a container of water. He got together the same weight in pure gold and put that in water. Although the contents of each container weighed the same, the water levels were different. This meant that the mass of one was bigger than the other, which was proof that the crown must have contained something that was not pure gold.

NICOLAUS COPERNICUS, a Polish Astronomer, managed to prove that THE EARTH TRAVELS AROUND THE SUN and published a book explaining this just before he died in 1543. It was called 'On the Revolutions of the Heavenly Spheres'.

Although a brilliant Ancient Greek called Aristarchus assumed this to be the case thousands of years before, Copernicus added various calculations to back up the theory.

Until Copernicus' book was published, people liked to believe everything travelled around the Earth, with the Earth being at the centre of the Universe. In fact, the new discovery upset the Catholic Church so much that they wanted to keep it a secret and the book was banned for over 200 years!

In 1665, it is said that ISAAC NEWTON saw an apple falling from a tree and first began thinking about a special force that pulled everything towards the Earth. He believed it was the same force that held the Moon in orbit around the Earth - GRAVITY.

Unfortunately, Newton got his sums wrong and decided he must have made a mistake, so he put the gravity theory to the back of his mind. However, many years later, he realised where he'd gone wrong and 'Universal Gravitation' was explained at last!

In 1752, an American scientist called BENJAMIN FRANKLIN proved that LIGHTNING IS ELECTRICITY after creating sparks while flying a kite in a thunder storm.

This was extremely dangerous and other people died copying him - so DON'T try this at home!

Talking of electricity, have you ever heard of 'positive' and 'negative'? These words were introduced to the world of science by Benjamin Franklin.

In 1796, a doctor called EDWARD JENNER discovered a very important SMALLPOX VACCINATION. At that time, many people around the world died of smallpox and those who survived were left with hideous scars.

It was already known that a mild bout of smallpox could prevent a severe bout in the future, but it wasn't possible to guarantee a bout of disease would only be 'mild'. Then Jenner heard that another disease, cowpox, also stopped people catching smallpox. This was a great discovery because cowpox wasn't very dangerous.

In 1796, he tested his theory on an eight year old boy called James Phipps. The boy developed cowpox and then recovered. A while later, he gave the boy an injection which contained smallpox - and must have been very relieved when young James didn't catch the disease!

The word 'Vaccination' comes from a Latin word, Vaccinia, which means cowpox.