Of the many great scientific mind of the past, Galileo has to be counted among the greatest. He is called the "Father of Modern Science", the "Father of Modern Physics", and the "Father of Modern Astronomy".
Single-handedly, Galileo moved the world of science in his day from the basis of logic to the basis of mathematics. He developed the modern scientific method by insisting that all scientific experiments use mathematics to analyze results. This innovation changed all methods of experimentation to date, making them open to verification by replication. Today any experiment must be done in such a manner that anyone else can perform the same experiment and get virtually the same results. This verifies the accuracy of the experiment.
Through his statistical based experiments on motion, light waves, sound frequency and material strengths, he was able to develop many theories that later led to more complex discoveries and theories. For instance, he was able to postulate a basic theory of relativity that provided the foundation for Newton's laws of motion and Einstein's modern theory of relativity.
By combining his mechanical interests with his applied mathematical science he invented many items that, in turn, led to more sophisticated items. Some of these initial forays include the pump, the pendulum, the thermometer, advancements in the telescope, the sector (compass for ships) and, believe it or not, the ball point pen.
His title of Father of Modern Astronomy came from his work on the telescope and his interest in astronomy. He was the major influence in the paradigm shift from thinking everything revolved around the earth, to the fact that the earth and other planets revolved around the sun. He was the first to recognize the Milky Way as a collection of stars and the first to proclaim the craters and mountains on the moon. He observed and recorded sun spots.
Without his work, we would be much delayed in our modern space explorations and understanding of the universe.
His work in physics laid the foundation for much of modern physics. He did many experiments that led to more understanding of motion, of how light waves work and the variations in sound frequencies. He observed tides and movement of water. His work with pendulums enhanced the recording of time. His theories about longitudes led to the development of better ways of navigation and mapping. He was even able to enhance a very fuzzy theory of the atom.
His work touched every aspect of modern space exploration, of time and travel, of scientific experiment logy, modern communication and atomic energy and mass. There is virtually nothing we have in the way of modern technology that isn't somehow connected to this man's work.