CXC CSEC Physics

## Galileo and the method of physics Before Galileo Galilei (1564–1642), most accounts of motion and the heavens rested on the authority of ancient writers, above all Aristotle. Galileo's contribution was a way of working rather than a single discovery: he observed carefully, described what he saw in mathematics, and tested ideas by experiment, accepting the result even when it contradicted received opinion. Several of his studies show the method. Rolling balls down gently sloping planes slowed the motion enough to time it, and showed that the distance covered grows with the square of the time, so that a falling body gains speed steadily. He argued, and tested with bodies of different weight, that in the absence of air resistance heavy and light objects fall together, which contradicted Aristotle's claim that heavier bodies fall faster. He timed the swing of a pendulum and found that the period hardly changes as the swing dies away. With a telescope he saw moons circling Jupiter, the phases of Venus and mountains on the Moon, and by patient daily observation of sunspots he showed that they lie on the surface of the Sun and move with its rotation. Each of these was a measurement that other people could repeat. The steps of the scientific method as Galileo used it, and as physicists still use it, are these. 1. Observe something and ask a definite question about it. 2. Form a hypothesis, a proposed explanation that could turn out to be wrong. 3. Predict what should happen if…