What contribution did Galileo make to the theory of gravity?

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Galileo Galilei (1564-1642) was a pivotal figure in the development of modern astronomy, both because of his contributions direct to astronomy, and because of his work in physics and its relation to astronomy. He provided the crucial observations that proved the Copernican hypothesis, and besides laid the foundations for a right understanding of how objects moved on the surface of the earth (dynamics) and of gravity.

Newton, who was born the same twelvemonth that Galileo died, would build on Galileo's ideas to demonstrate that the laws of move in the heavens and the laws of move on the earth were one and the same. Thus, Galileo began and Newton completed a synthesis of astronomy and physics in which the former was recognized as but a particular example of the latter, and that would banish the notions of Aristotle almost completely from both.

Ane could, with considerable justification, view Galileo every bit the begetter both of modernistic astronomy and of modernistic physics.

The Telescope

Galileo did not invent the telescope (Dutch spectacle makers receive that credit), but he was the first to use the telescope to study the heavens systematically. His picayune telescope was poorer than even a inexpensive modernistic apprentice telescope, but what he observed in the heavens rocked the very foundations of Aristotle's universe and the theological-philosophical worldview that information technology supported. It is said that what Galileo saw was then disturbing for some officials of the Church building that they refused to even expect through his telescope; they reasoned that the Devil was capable of making anything appear in the telescope, and then it was best not to look through it.

Sunspots

Galileo observed the Sun through his telescope and saw that the Sun had dark patches on it that we now call sunspots (he eventually went blind, peradventure from impairment suffered by looking at the Sun with his telescope). Furthermore, he observed motion of the sunspots indicating that the Sun was rotating on an axis. These "blemishes" on the Sun were reverse to the doctrine of an unchanging perfect substance in the heavens, and the rotation of the Sun fabricated it less foreign that the Earth might rotate on an axis as well, as required in the Copernican model. Both represented new facts that were unknown to Aristotle and Ptolemy.

The Moons of Jupiter

Galileo observed iv points of light that changed their positions with time effectually the planet Jupiter. He concluded that these were objects in orbit effectually Jupiter. Indeed, they were the 4 brightest moons of Jupiter, which are at present normally called the Galilean moons (Galileo himself called them the Medicea Siderea---the ``Medician Stars''). Here is an blitheness based on actual observations of the motion of these moons around Jupiter.

These observations once more showed that there were new things in the heavens that Aristotle and Ptolemy had known nothing almost. Furthermore, they demonstrated that a planet could have moons circling it that would non exist left behind as the planet moved around its orbit. I of the arguments against the Copernican system (and the ORIGINAL heliocentric idea of Aristarchus) had been that if the moon were in orbit around the World and the World in orbit around the Sunday, the World would go out the Moon backside as it moved around its orbit.

The Phases of Venus

Galileo used his telescope to testify that Venus went through a complete ready of phases, just like the Moon. This ascertainment was among the about important in human history, for it provided the first conclusive observational proof that was consistent with the Copernican system but not the Ptolemaic system.

The crucial indicate is the empirical fact that Venus is never very far from the Sunday in our sky. Thus, as the post-obit diagrams indicate, in the Ptolemaic arrangement Venus should always be in crescent phase equally viewed from the Earth because equally information technology moves effectually its epicycle information technology can never exist far from the management of the sun (which lies beyond it), just in the Copernican organisation Venus should exhibit a complete set of phases over time every bit viewed from the Earth because it is illuminated from the center of its orbit.

Phases of Venus in the Ptolemaic and Copernican systems

Information technology is important to note that this was the kickoff empirical evidence (coming almost a century after Copernicus) that immune a definitive exam of the two models. Until that point, both the Ptolemaic and Copernican models described the available information. The primary attraction of the Copernican organisation was that it described the data in a simpler fashion, but here finally was conclusive evidence that not only was the Ptolemaic universe more than complicated, information technology also was wrong.

Myriad Observations Showing Phenomena Unknown to Aristotle

In add-on to the observations noted above, Galileo made many other observations that undermined the authority on which the Ptolemaic universe was built. Some of these included

1. Showing that the planets were disks, not points of calorie-free, as seen through the telescope.
2. Showing that the nifty "deject" called the Milky way (which we now know to be the disk of our spiral milky way) was composed of enormous numbers of stars that had not been seen before.
3. Observing that the planet Saturn had "ears". We now know that Galileo was observing the rings of Saturn, merely his telescope was not good plenty to bear witness them equally more extensions on either side of the planet.
4. Showing that the Moon was not smooth, as had been assumed, but was covered by mountains and craters.

Equally each new wonder was observed, increasing dubiousness was bandage on the prevailing notion that there was nothing new to be observed in the heavens because they were made from a perfect, unchanging substance. Information technology also raised the credibility consequence: could the authority of Aristotle and Ptolemy be trusted concerning the nature of the Universe if there were and so many things in the Universe virtually which they had been completely unaware?

Galileo and the Leaning Tower

Galileo made extensive contributions to our agreement of the laws governing the movement of objects. The famous Leaning Tower of Pisa experiment may be apocryphal. It is likely that Galileo himself did not drib two objects of very different weight from the tower to prove that (contrary to pop expectations) they would hit the footing at the aforementioned time. However, it is certain that Galileo understood the principle involved, and probably did like experiments. The realization that, as we would say in mod terms, the acceleration due to gravity is contained of the weight of an object was important to the formulation of a theory of gravitation by Newton. Here is an animation of experiments with inclined planes that Galileo probably did to confirm these ideas.

Galileo and the Concept of Inertia

Perhaps Galileo's greatest contribution to physics was his formulation of the concept of inertia: an object in a state of movement possesses an ``inertia'' that causes it to remain in that state of move unless an external force acts on it. In order to arrive at this conclusion, which volition class the cornerstone of Newton's laws of movement (indeed, it will become Newton's First Police force of Motility), Galileo had to abstract from what he, and everyone else, saw.

Well-nigh objects in a state of motion do Non remain in that land of motion. For instance, a block of wood pushed at constant speed across a table speedily comes to rest when we stop pushing. Thus, Aristotle held that objects at residual remained at rest unless a forcefulness acted on them, simply that objects in motion did not remain in motion unless a forcefulness acted constantly on them. Galileo, by virtue of a series of experiments (many with objects sliding down inclined planes), realized that the analysis of Aristotle was wrong because it failed to account properly for a subconscious forcefulness: the frictional force between the surface and the object.

Thus, as we push the block of wood across the table, there are two opposing forces that act: the force associated with the button, and a strength that is associated with the friction and that acts in the opposite direction. Galileo realized that as the frictional forces were decreased (for example, by placing oil on the tabular array) the object would move further and further earlier stopping. From this he bathetic a basic course of the law of inertia: if the frictional forces could be reduced to exactly nix (not possible in a realistic experiment, but it can be approximated to loftier precision) an object pushed at abiding speed across a frictionless surface of infinite extent volition keep at that speed forever after we stop pushing, unless a new force acts on it at a later time.

Galileo and the Church

Galileo's challenge of the Church'southward authorisation through his assault on the Aristotelian conception of the Universe eventually got him into deep trouble with the Inquisition. Tardily in his life he was forced to recant publicly his Copernican views and spent his last years essentially under house arrest. His story certainly constitutes one of the sadder examples of the disharmonize between the scientific method and "scientific discipline" based on unquestioned potency. Unfortunately, there nevertheless are many forces in modern social club that would shackle the scientific method of open research in idealogical chains of one kind or another.

Amusingly, In 1992, John Paul proclaimed that the Vatican had erred when information technology condemned Galileo virtually 400 years earlier--this investigation started in 1979.

Supplementary References

cannonexpeoreal.blogspot.com

Source: https://www.pas.rochester.edu/~blackman/ast104/galileo12.html

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