Galileo Galilei
The first major figure I will be writing about is a titan in the history of science, Galileo Galilei. Born in Pisa, Galileo was the first modern physical scientist conducting experiments, developing theories, and generally an all-rounder. As Galileo approached the study of astronomy, he was aware of three objections to the Copernican model, rooted in Aristotelian physics. The first was the objection to the Earth being in motion, the second objection was based on the perfection of circles and spheres. The fact that imperfections in the heaven would not be countenance, in the Greek view of the cosmos. The third objection relates to stellar parallax. If the earth is suddenly in motion, then why do the stars known appear to change their brightness and relative positions or angles, as the Earth goes around the sun?
Two thousand years passed before a revolutionary breakthrough was made by a mathematics professor in the ancient maritime republic of Venice. In 1609, Galileo Galilei demonstrated an instrument that would soon be called the telescope. From the tallest build towers, he showed that this device could spot approaching ships hours before their sails were visible to the naked eye. Later, when he aimed his telescope at the night sky, Galileo discovered that the moon was a world with mountains, Jupiter had its own moons, and the Milky Way was a band of countless stars. He conceptualized a situation where someone might be below the deck of a ship sailing on a smooth body of water, and in this sealed environment with no window to the outside, might not be aware that they were in motion. Any experiment they could conduct with falling or dropping objects would look the same as if they were stationary on the surface of the land. That was enough to convince him that the Earth indeed could be moving, and carrying its atmosphere with it at the speed required by its size and rotation. He also recognized that an object in motion might stay in motion, which is against the ideas of Aristotle and also was a precursor to one of Newton’s theories of motion.
In his laboratory, he conducted many experiments with falling or dropping objects, often using inclined planes to slow them down so he could see their motion better, and timing the situation with his pulse. These observations convinced him that the way an object fell had nothing to do with the nature of the object, that so-called light and heavy objects would fall at the same rate of acceleration.
The second objection to the heliocentric model was rooted in the Greek idea that spheres and circles represent perfection, and so should apply to the celestial realm. But Galileo showed with his telescope, that the sun was imperfect, and that it had sunspots. He was also able to show by the differential rotation of the sun, how it could not be a solid object. His telescope also showed the mountains, valleys, and geological features of the moon in extravagant detail, making it clear that the moon was a geological world like the Earth. This observation alone removed the distinction between the Earth as a special world in space. In particular, his series of observations of the four brightest moons of Jupiter, the so-called Galilean moons (although he named them the Medicean moons after his patron the Duke of Medici), are exquisite scientific observations used to show objects going around another object, also confirming Kepler’s laws applying to the moons of the giant planet in the outer solar system.
