Galileo di Vincenzo Bonaiuti de' Galilei , Italian: 15 February 1564 – 8 January 1642), commonly referred to as Galileo , was an astronomer , physicist and engineer , sometimes described as a polymath , from pisa , in modern-day Itlay. Galileo has been called the "father of observational astronomy ", the "father of modern physics", the "father of the scientific method ", and the "father of modern science ". Galileo studied speed and velocity , gravity and free fall , the principle and relativity , inertia and projectile motion and also worked in applied science and technology, describing the properties of pendulums and "hydrostatic balances". He invented the thermoscope and various military compasses , and used the telescope for scientific observations of celestial objects. His contributions to observational astro...