Galileo's brilliant experiments laid the foundations for the development of Newton's laws of motion. His experimental skill led to the derivation the law of acceleration as well as constructing the best telescopes for terrestrial and astronomical observations. His observations of the satellites of Jupiter provided an analogue for the motions of the planets about the Sun. His advocacy of the Copernican system of the world led to his trial and condemnation for heresy. His great realisation, the foundation of modern scientific enquiry, was that the laws of physics can be expressed in mathematical form.