Galileo Galilei (1564-1642) was an Italian mathematician, physicist and astronomer. He made many contributions to physics and astronomy but is primarily known for improving the telescope and for using it to observe that the earth is not the center of the universe; he empirically verified Copernicus hypothesis that the solar system is composed of one sun and many planets, and that the earth is one of the many planets; and that there are many stars in the Milky Way Galaxy, our galaxy; and that some of these stars have planets orbiting around them.
Our sun, a medium star, has a group of planets orbiting around it. The planets orbit around the sun and not the sun around them. In other words, the sun is the center of our solar system and not the other way around.
This finding directly refuted the then Christian belief in geocentricism, the idea that the earth is the center of the universe. Copernicus and Galileo posited heliocentrism, the notion that the sun is the center of our solar system.
Galileo, in effect, invalidated the teachings of the Roman Catholic Church, the belief that the earth, hence man, is the center of the universe, and is the center of God’s creation. In practical terms, Galileo said that God did not create man to be the center of his creation.
As would be expected, Galileo’s position did not sit well with the leaders of the Catholic Church, for it means that their authority over the masses was based on false premises. Perhaps, to protect their authority and continue exercising control over the Christian masses the leaders of the Catholic Church were not about to permit Galileo to continue teaching that he has empirical proof for Copernicus hypothesis that the sun is the center of the solar system. They invited Galileo to Rome to explain himself and offered him an opportunity to recant what he said.
Galileo was forced to recant or else the Holy Terror, the Holy Inquisition would have condemned him to death and he would have been burned at the stakes and to death. Apparently, desiring to live Galileo recanted and endorsed the teaching of the Church. But his caving in was not good enough for the Church, for it sentenced him to house arrest. He died while in this prison.
It should be noted that it was actually the Polish astronomer, Nicolas Copernicus, who first posited the hypothesis that the earth orbits around the sun, not Galileo. What Galileo did was use his telescope to verify the hypothesis. He lent empirical proof to a theoretical hypothesis of another astronomer. In that sense he was an empirical scientist, a person who verifies conclusions before accepting them. He is therefore one of the founders of modern physics and astronomy, and modern science in as much as science is empirical and inductive rather than mere Aristotelian speculation about things.
Galileo helped establish what is now called the scientific method, a methodological approach to phenomena that accepts as true only those observations that can be demonstrated as true, as existent. Galileo’s book: Dialogue Concerning the Two Chief World Systems, can be seen as the first scientific text book. In that book he elucidated how he got his results, experimentation, a corner stone of the scientific method. He was not just speculating about things but showing that they, in fact, exist.
Galileo made other contributions to science, such as improving Kepler’s telescope. His improvement was able to magnify what it looked at so that Galileo was able to see the stars and planets more clearly than the Kepler telescope engendered. With his telescope he was able to ascertain the nature of the surface of the moon, as not smooth but rough with mountains and valleys etc. Furthermore, with his telescope he corrected the contention by Kepler that the moon caused ocean tides. Instead, Galileo contended that ocean tides are caused as the earth rotated around the sun; tides are caused as the earth rotated on its axis around the sun, he posited.
Galileo also made contributions to what we would now call applied science (technology) as opposed to pure science (epistemology). He improved the Geometric and military compass and in so doing aided surveyors and gunners. He also improved the thermometer.
In physics and astronomy, Galileo made seminal contributions. His views on gravitation though rudimentary set Isaac Newton on the path to discovering the correct nature of gravitation.
It is said that Galileo had dropped two different objects, objects with different masses, down from the leaning Tower of Pisa, and that they hit the ground at the same time. In doing so he proved that mass (weight) does not affect the rate and speed at which objects dropped to the ground. Instead, there was a force, gravitation that pulled objects to the ground and did so uniformly despite the weight of the objects.
Common sense, especially as explicated by Aristotelian thinking, had predicted that heavier objects would reach the ground before lighter ones. In effect, Galileo discovered the law of uniform acceleration.
Galileo also established that a body moving on a level surface will continue in the same direction at a constant speed unless disturbed (Newton made this his first law of motion).
Galileo made contributions to sound frequency and, indeed, had a rudimentary understanding of what became a key component of Einstein’s special relativity. He posited that the laws of physics are the same everywhere in the universe; that any system that is moving at a constant speed in a straight line, regardless of its speed, is influenced by the same laws of physics.
Galileo made other contributions to science. However, he is noted for his empirical verification of Copernicus heliocentric hypothesis and in doing so established the experimental and empirical method in science. This is not a small contribution to science; and for it he was imprisoned by the Roman Catholic Church, the holy terror of his time. Galileo is a giant of science, and modern science owes a lot to his scientific discoveries.
It is fitting that we begin our survey of seminal scientists with Galileo rather than others, such as Greek atomists and Aristotle, for though Aristotle catalogued empirical phenomena non-of his conclusions are actually scientific in the sense that they can be tested and verified and or falsified. Galileo’s observations regarding the solar system can be verified and or falsified. In as much as science is predicated on verifiability and falsifiability of hypotheses, and Galileo met those criteria, he was the father of modern science.
Galileo Galilei. The Assayer. (1623)
Galileo Galilei. Dialogue Concerning the Two Chief World Systems. (1632)
Galileo Galilei. Two New Sciences. (1638)