Gravity is a force which causes many phenomena. It prevents us from flying off the earth as it spins round. It makes the objects that we drop fall to the ground. It dictates the shape of our planet and keeps our earth in its orbit around the sun. The force of gravitation manifests itself as the mutual attraction between masses. Each body in the universe is attracted to every other body. The more massive the bodies and the closer they are to each other, the stronger the force. This programme demonstrates the effects of gravitation on the micro level (how it shapes our own body), through to the macro level (its influence on the past, present and future of the universe).

Our understanding of the force of gravity has come through the efforts of some of the world’s most extraordinary scientists. It was Newton who first formulated the universal law of gravitation. In addition he developed the three standard laws of motion, created calculus and discovered that white light is made up of many colours.

Einstein, who left school with no diploma, went on to revolutionize our ideas about space, time and gravitation. He then devoted the rest of his intellectual life to a quest which most of his peers regretfully believed was destined to failure — the search for a unified field theory which would explain everything from the behaviour of an electron to that of a planet. Max Born, a quantum physicist and friend of Einstein said of Einstein’s refusal to accept the absoluteness of quantum mechanics, 'Many of us regard this as a tragedy, both for him, as he gropes his way in loneliness, and for us, who miss our leader and standard-bearer.'

Edwin Hubble, who discovered that every galaxy appeared to be receding from every other one, first proposed the theory that the universe was expanding. He was an accomplished diver and boxer, who had studied mathematics, science, French, classics and political economics before moving from America to Oxford on a Rhodes Scholarship in Law. He decided he would rather be 'a second-rate astronomer than a first-rate lawyer'. His collaborator, Milton Humason, had a somewhat contrasting background. His formal education ended at 14, nevertheless he progressed from mule-driver at the Mount Wilson Observatory to caretaker, to night assistant, to observer, to staff astronomer and ended up secretary of both the Mount Wilson and Palomar observatories.

The differences in the lives and characters of these four scientists, who contributed so much to our understanding of gravity and the universe, is interesting. Einstein was held in such high esteem by his peers, Newton was in constant conflict with his. Humason dropped out of formal education at 14, whilst Hubble had the benefit of a very broad formal education. Perhaps what they had in a common was their extraordinary ability to observe and then reflect on their observations.