Major achievement: His geocentric (Earth-centred) model of the universe known as the Ptolemaic system.
He produced a number of writings now known as the 'Almagest', completed around 150CE. It contains reports of astronomical observations made over a quarter of a century.
Copernicus was influenced by Ptolemy, Aristotle and Nasir al-Din al-Tusi. He formulated a model that placed the Sun rather the Earth at the centre of the Universe.
Galileo was influenced by Copernicus, Aristotle, Giordano, Bruno and Avicenna.
Major achievements: Galileo built a telescope and was the first person to look at the moon this way. He discovered the moons, Callista, Europa and Ganymede.
Newton was influenced by Galileo, Euclid, Johannes Kepler and Robert Boyle. He was considered the single most influential scientist of the 17th century.
Major achievements: Newton developed the laws of motion and gravity, he developed the concept of infinite series calculus and he was the first to discover white light is made up of a spectrum of colours.
Major achievements: Henrietta Leavitt discovered the relation between the luminosity and the period of Cepheid variable stars, she discovered more than 2,400 variable stars and she developed a standard of photographic measurements accepted by the International Committee on Photographic Magnitudes in 1913, called the Harvard Standard
Hubble was influenced by Allan Sandage. The Hubble Space telescope was named after him. His greatest discovery was the idea that the farther a galaxy is from the Earth, the faster it appeared to move away. His other discoveries were the expanding universe and the fact that some distant faint clouds of light were actually entire galaxies.