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Galileo Galilei lived from 1564 to 1642. Galileo, is considered to be the father of modern science, and a paramount figure in bringing about the scientific revolution.
Galileo was an Italian and a central figure to the development of modern science. This was the transition from natural philosophy to modern science.
Galileo was also a controversial figure at the time for his proposals of Copernican heliocentrism.
Galileo made many contributions to physics:
Speed: Galileo is considered to be the first to seriously study speed. To Galileo, speed was the relationship between the distance traveled and the time it took. This was the distance traveled per unit of time. He was also one of the first to understand sound frequency. Galileo, in 1638, attempted to devise an experiment to measure the speed of light. The idea was that one could measure the delay of an uncovered lantern with how it was perceived some distance away. Galileo deduced that if light were not instantaneous, then it was very rapid. However, the result of Galileo's velocity experiments for light were inconclusive. The experiment was tried again in 1667, in Florence, with lanterns separated by about a mile, however, the results were inconclusive again. The speed of light (186,000 miles per second) is of course too small to be measure by these Earthly experiments.
Velocity and inertia: Galileo proposed that moving objects retain or continue to have their velocity, as long as their are no impediments to their motion acting on them. Bodies moving on a level surface would keep moving, if they remained undisturbed. This was the notion of classical inertia that preceded Newton's first law. This was also a major contradiction to the Aristotle's view that bodies required a mover to continue to act on it.
Gravitation and free fall: Modern study of gravitation, indeed, began with Galileo. Galileo had two famous experiments: dropping balls off of the Leaning Tower of Pisa (this one is perhaps apocryphal) and rolling balls down an incline. Galileo's insight is going to be that gravitational acceleration is the same for all objects. He put forth that the only reason it appeared that more massive objects have a stronger gravitational pull acting on them, is due to air resistance. This set the stage for Isaac Newton develop his theory of gravitation.
Galilean relativity or invariance: The idea of relativity, did begin with Galileo in 1632, where he proposed that the laws of motion are the same in all inertial frames. In other words, the laws of physics are the same in a system moving at a constant speed and in a straight line.
Projectile motion: A projectile, is a moving object, where, the only force acting on it is gravitation. Air resistance is ignored. Galileo proposed that projectiles will follow a kind of parabolic path, that could be calculated.
I want to talk about Galileo’s contributions to observational astronomy.
The accepted models of the solar system, at the time of Galileo, were either the geocentric model of Ptolemy, or the model of Tycho Brahe, a model that incorporated both heliocentric and geocentric principles. Geocentrism, portrays the solar system, with the Earth at the center, with the Sun, and other planets, revolving around the Earth. This was also the Aristotelian view. Thus, the Heliocentrism, that is going to be proposed by Galileo and Nicolas Copernicus, will be controversial. Heliocentrism, places the Sun, at the center of the solar system, with the other planets, revolving around the Sun. Galileo is going to support heliocentrism, based on his telescope observations, and will publish them in 1610, in his “Starry Messenger”.
Starry Messenger, was published on March 13, 1610. It was the first scientific publication made, based on telescopic observations. He observed our own Moon, and proposed that the darker areas were flat, while the lighter areas were of higher elevation, such as craters and mountains. Galileo was also able to see about ten times more stars with his telescope, than were visible with the naked eye at the time.
The design for the Galilean telescope was first used in 1609. Images could be magnified up to 30 times. However, due to design flaws, the images were typically distorted and blurred. Nonetheless, it was sufficient for Galileo’s investigations of the sky. The telescope was able to see the phases of Venus, the craters of the Moon and four natural satellites of Jupiter.
Galileo was able to observe the full set of Venus' phases.
It also should be noted, that in a geocentric model of the Solar System, this kind of observation would not be possible.
Galileo proposed that the darker areas were flat, while the lighter areas were of higher elevation.
The Moon, had been observed prior to Galileo. However, the cause of it's spottiness, was not known. Galileo knew, that these shaded and lighter areas were indicative of some kind of topographical features. These were craters and lunar mountains. Galileo was also able to estimate the height of these lunar mountains.
Indeed, Galileo will observe four moons of Jupiter. These are the four largest of Jupiter’s moons: Io, Europa, Ganymede and Callisto. Galileo is going to observe them in January of 1610. Galileo confirmed that these were, indeed, natural satellites of Jupiter, in March, of that same year. This was the first time, an object was observed to be orbiting another planet.
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