Galileo

Galileo Galilei was perhaps the first great experimenter. Unlike most scientists before his time, he asked testable questions and focused on whether details are repeatable. He began a scientific revolution that would change the world forever.

Galileo was born in Pisa Italy in 1564, son to a musician father named Vincenzo Galilei. Little is known about his early years, but he did pick up instruments quickly, learning the lute and organ. It is clear from his writing that his father sparked a critical experimental passion in Galileo. He had 4 other siblings but only 2 survived through childhood. At the age of 8 they moved to Florence. Galileo aspired to becoming a Monk in his youth, but his father convinced him to join medical school at the University of Pisa in 1581.

During his time in medical school it became clear that he was not destined for a career in medicine. He began skipping classes to attend mathematics courses. At the age of 18 he recalls an influential story that took place in the beautiful Cathedral of Pisa. Standing in the Cathedral he observed a large chandelier swinging due to a breeze blowing through the open windows. Using his pulse he timed the swings, realising that it takes the same time to complete a swing each time. He rushed home and repeated the pendulum experiment with different weights/bobs and determined that the weight of the bob didn’t change the time of the swing. It would be over a century before another scientist came along and made the first pendulum to act as a clock.

Eventually Galileo dropped out of medical school and pursued an education in mathematics full time. In 1589 he earned a position as the chair of the mathematics department at the University of Pisa. It was there that he became famous for his observations of falling objects. The story goes that Galileo brought objects(cannonballs and musket balls) of different masses to the top of the Leaning Tower of Pisa, dropped them, and observed them landing at nearly the same time. Although history suggests that this experiment was done elsewhere, its results directly contradicted a belief of Aristotle. Aristotle claimed that “Heavy objects fall faster than light ones.” In his approximation, a 2 pound ball would fall twice as fast as a 1 pound ball… and so on.

Galileo’s published works in Pisa gave him notable fame, and by most accounts he didn’t accept his newfound recognition with humility. He refused to wear the long black gowns of a professor, even writing a biting poem making fun of his colleagues for wearing them. He famously couldn’t “suffer fools,” making enemies and admirers in Pisa. Once his contract ended, the university did not renew it.

Quickly following his departure from the University of Pisa, he moved to eastern Italy to work at the renowned University of Padua in 1562. He taught geometry and astronomy there until 1610. It is in the free-wheeling environment of Venice that Galileo’s work and fame begins its exponential growth. He is such an engaging teacher that flocks of students and locals start attending his lectures. It’s here that he starts pumping out experimental results. Here is a list of some of his discoveries in Padua.

Aristotle’s View: Objects fall at the same acceleration as they approach the ground

Galileo believed that falling objects picked-up speed as they fell. This seemed obvious, because Identical objects dropped at greater heights seem to have larger impacts on the Earth than when dropped from lower heights. He wanted to test his hypothesis, but during his time, there were no devices that could accurately measure the change in speed of a falling object. So he figured he had to slow the speed at which an object falls. He started building long wooden ramps that maintained the same slope. He would release a bronze ball down these ramps, then calculate the amount of time it took to reach the end of the ramp.

Of course in those days there were no stopwatches or mechanical clocks to measure time. Instead he would use a water clock. Basically he had a hanging container of water with a small hole near the bottom he could open and close. He collected the water that came out in another container. He would open the hole at the same time he released the brass ball and close it when it reached the end of the ramp. He would then measure the weight of the water that came out. The water comes out at a uniform rate, so he could accurately measure the speed of a moving object.

His big discovery came in 1604, when he determined that all falling objects accelerate at the same rate, so that when time passes, acceleration increases at the same rate for all objects. That proved Aristotle wrong, showing that objects pick-up speed(accelerate) as they fall. His Law of Uniformly Accelerated Motion allows us to predict how long it would take an object to fall/roll.

For instance, if acceleration is the same as we now know for gravity (9.8 m/s) then we can predict how far an object will have traveled over some period of time. For a 3 second fall an object would travel 44.1 meters, while a 6 second fall would be 176.4 meters. Note that while the rate of acceleration remains the same, the speed of the object does not. If it did, then at 6 seconds the ball should fall double the distance (88.2 m), not ~176. Also note that mass/weight are not factors in the equation at all. Of course this example above makes a lot of assumptions. It assumes that all of the objects are in a vacuum, but its implications are undeniable.

Galileo also started thinking about the path of projectile objects. The followers of Aristotle spoke of objects moving through the air until they “ran out of force” and fell directly downwards. Clearly they weren’t the most observant throwers of stuff, because a thrown object takes the shape of Galileo’s parabola. Galileo noted that the motion of a thrown object was the result of two motions, one horizontal, and the other vertical(gravity). He described the motions as totally separate, so that an object kicked horizontally off a building would land at the same time as an object simply dropped. Gravity was acting on both objects equally. Of course this example ignores things like air resistance, drag, etc. These observations were immediately useful in warfare, deciding on the location and angle of cannons and guns.

Galileo’s most iconic academic discoveries were sparked by a technological breakthrough. In 1608 the first practical telescope was invented in the Netherlands. Galileo got his hands on one, and quickly set about improving its design. The Dutch spyglass was being used primarily as a toy, with only 3x magnification. By 1609 Galileo had improved on the design to get up to 10x magnification. Galileo set up his telescope in St. Mark’s Square in Venice to show off his new invention to local Senators. They could suddenly see ships as far as 55km (35 miles) away.

“I have made a telescope, a thing for every maritime and terrestrial affair and an undertaking of inestimable worth. One is able to discover enemy sails and fleets at a greater distance than customary, so that we can discover him two hours or more before he discovers us.” (Galileo)

The telescope brought Galileo more fame, and earned him a promotion and a raise. With telescope in hand, Galileo started pointing it not towards the sea, but towards the heavens at night. He identified stars, planets, and followed their patterns. At this time the stars were believed by most to be unchanging, in a universe with earth as its center. The moon believed to be a smooth disc, not an earth-like sphere. With the first telescope as his guide, he made a number of discoveries that would confirm Copernicus’ claim that the earth was not the center of the universe, and that the earth was in fact orbiting the sun. In order to prevent this from becoming the longest text in a cache description ever, I have simplified a few of his astronomical discoveries by planet.

THE MOON

With his powerful telescope, Galileo could see the moon wasn’t the “smooth disc” it had been described as. It looked like a sphere with earth-like valleys, mountains, and craters.

“The moon is uneven, full of hollows and perturberances, just like the surface of the Earth itself, which is varied everywhere by lofty mountains and deep valleys.” (Galileo)

JUPITER

Galileo started observing Jupiter, and noticed 4 “little stars” near Jupiter. As time passed, these four little stars seemed to move, even disappearing for periods of time. He determined that these “little stars” were in fact orbiting Jupiter. In fact, he was observing 4 of Jupiter’s 53 moons (crazy, I know). In the early 1600s, the observation that other planets/stars could have their own orbiting moons was dangerous. If moons could orbit Jupiter, and our moon orbit us, then why couldn’t we orbit something else?

THE SUN

Galileo did something dangerous. He looked directly at the sun through his telescope (never ever do this). He noticed that there were spots on the sun that seemed to be moving. He determined that the sun was rotating.

NEPTUNE

He noticed that neptune had different phases, just like our moon. The only explanation for a changing amount of light on venus visible from earth would be that it was orbiting the sun. Copernicus had predicted this observation, but didn’t have the tools to look himself.

He published these findings and many more in a slim book called “The Starry Messenger” on March 13th 1610. His book was an immediate success, and his fame skyrocketed once more. Galileo received a position as “philosopher and chief mathematician” to the Grand Duke of Tuscany. He moved to Florence, was given a pay raise, and the freedom to experiment on whatever he pleased. He started writing in Italian instead of latin, becoming a scientist of the people.

He published another popular mathematics book “The Assayer” in 1623. After meeting with Pope Urban VIII, he was given guidance on including the ideas of Aristotle and Ptolemy in his next book. He does include these philosophers in his controversial Dialogue in 1632. The book was set up as a discussion between three men/ideas. Galileo holds no punches on who (himself) is right about the center of the solar system. The pope was not pleased, and Galileo was summoned to the Inquisition in 1633 under the charge of heresy. His book was banned as well.

Galileo recanted his ideas at nearly 70 years old, agreeing to stop claiming anything other than the church’s Geocentric theory. He may have recanted his work to save his own life, but the damage was already done. The well reasoned explanations for why the earth orbits the sun had already been written and published.

Galileo died on January 8th 1642, having lived to the age of 77. Due to the accusations of heresy and his low standing with the catholic church, Galileo was buried in an underwhelming corner of the Basilica of Santa Croce in Florence. In 1737 his body was moved to a prominent location and a monument erected in his honour. During the move 3 of Galileo’s fingers were removed, and one of them was “pickled” and preserved in the tiny Museo Galileo in Florence.

Fun fact about Dr. Polley: When visiting the museum in 1995 at the age of 13, he badly wanted a picture of the famous pickled finger. There were signs everywhere stating “NO PICTURES.” But with the support of his accomplice mother he snapped a photo and stumbled down the museum stairs as a museum employee came to protest.

You can check your answers for this puzzle on GeoChecker.com.

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