Presentation on theme: "Astronomy enters the modern age"— Presentation transcript:
1Astronomy enters the modern age Galileo GalileiAstronomy enters the modern age
2The State of ThingsAt the time of Copernicus’ death (21 years before Galileo’s birth), the heliocentric model was gaining some limited acceptance among scholars for its simplicity and elegance, but not with the Church.The heliocentric model was no better than the Ptolemaic geocentric model at predicting the positions of the planets.
3A Change in ThinkingWithin 100 years of Copernicus’ death, the heliocentric model would be widely accepted by both scholars and lay people alike.Like many advancements in science, an advancement in technology changed the conventional wisdom.
4Galileo’s Life Born 1564 in Pisa, Italy Galileo goes to Univ. of Pisa, but doesn’t graduate1597 he invents a calculator!
5Galileo’s Life 1589, conducts Leaning Tower of Pisa experiment. 1609, makes his own telescope1642, Galileo dies.
6What did he do for astronomy? Built his own 20 power telescopeObserved the moonSaw that the sun has sunspotsObserved the starsDiscovered 4 largest moons of JupiterObserved that Venus has phases like the moon
12SunspotsMany people think Galileo went blind from looking at the sun. Really it was just old age & disease.Galileo’s sunspot drawings at right.
13How did Galileo find sunspots? He used a camera obscura – just a pinhole in a wall, with the sunlight shining on an opposite wall.You can make one from a piece of cardboard.
14How did that hurt the Greeks? The sun was the second most important heavenly body, after the earth.To find imperfections even on the sun proved that their philosophy was wrong. If that was wrong, what else were they wrong about?
15Galileo observed the stars Before the telescope, a field of stars looked like this.
16Galileo observed the stars But when he viewed the stars through his telescope, the star field looked more like this.There were many more stars!
17ConclusionBecause he could see many more stars with his telescope, Galileo realized that some of them must be too faint to see with the naked eye because they were farther away.The whole idea of the eggshell-thin crystalline sphere of stars was worthless!
18Jupiter has moons!Galileo discovered the 4 largest moons of Jupiter. They’re named after him: the Galilean moons.
19Jupiter has moons!As Galileo watched over several nights, he made drawings of the moons revolving around Jupiter.If you watch at just the right time, you might see the fastest-moving, Io, actually crossing the face of Jupiter.But how does this shoot down the ancient Greeks?
20Io crossing the face of Jupiter photojournal.jpl.nasa.gov
21Next ConclusionThe ancients insisted that everything revolved around the earth, since the earth was the most important celestial body.The Galilean moons proved that revolution could be centered on another celestial body.Earth’s privileged place in the cosmos was gone!
22The Phases of VenusGalileo observed that Venus showed phases, just like the moon.These are his drawings.
23Phases of VenusAristotle’s model predicted crescent phases for Venus, but since Venus never went behind the sun, it couldn’t have a full phase!
24Galileo’s observation of a full phase for Venus proved that Venus revolved around the sun - it wasn’t pinned to a line between the sun & earth.Epicycle of Venus(In the geocentric model, Venus could only show crescent and new phases as seen from the earth. In the heliocentric model, Venus could also show a nearly-full phase.)
25Let’s summarizeThe moon & sun proved that the heavenly bodies weren’t perfect spheres.The stars proved that there weren’t thin crystalline spheres.Jupiter’s moons proved that not all things revolved around the earth.The phases of Venus proved that Venus revolved around the sun, not earth.
26Galileo didn’t stop here Galileo published his findings in a book called The Starry Messenger.Most books at that time were published in Latin – ordinary people couldn’t read them.
27Starry MessengerGalileo was smart enough to publish his book in Italian - everyone could read it!Galileo went into business publishing his book & building telescopes for people. He became fairly wealthy from his business.
28Galileo gets into trouble! Several years later, Galileo published a play called “A Dialogue on the Two Chief World Systems”
29The Pope gets mad!Galileo’s “Dialogue on the 2 Chief World Systems” contrasted the geocentric model with the heliocentric model.Galileo called the character who upheld the geocentric model “Simplicio” or “fool”
30The Pope gets mad!Simplicio used goofy arguments in support of the geocentric model. The character was really an idiot.Problem was, the Pope was very much in favor of the geocentric model. He felt like Galileo was personally making fun of him!If Galileo was making fun of the Pope, he was making fun of the whole Church!
31The Pope ordered Galileo to be tried before the Inquisition.
32Galileo was convicted, labeled a heretic, forced to recant his book, and placed under house arrest until he died 25 years later.The Catholic Church didn’t officially overturn his conviction until 1992!
33What else did Galileo contribute? Galileo also performed a series of experiments where he rolled balls of different masses down inclined planes.
34InertiaGalileo recognized that when the ball reached the bottom of the plane, it continued to move forward on the level surface, even though no force was acting on it.Galileo had recognized that the rolling object possessed inertia.
35Natural Motion Reversed Galileo reasoned that a force of attraction had been applied to the rolling ball to begin its movement. That the ball continued to move on the level surface was a natural or inertial motion.With one experiment, Galileo had reversed the ancient notions of natural and forced motion, and “discovered” inertia!
36InertiaToday, we recognize inertia as the tendency for a mass to continue doing what it is doing:A moving mass will continue moving at the same speed in the same direction (unless an external force changes the mass’s motion.)A stationary mass will remain stationary.