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2 Tycho Brahe ( ) (right around Galileo) Born Tyge Ottesen Brahe (I can’t say that correctly) Last of the great astronomers who came before the invention of the telescope

3 What’s the deal with Tycho’s nose?

4 Tycho’s life Born as a twin, but his brother died His uncle took him away from his family when he was two, but his real parents were apparently all right with this.

5 Tycho’s life Observed the total solar eclipse of 1560 So impressed by the fact that it had been predicted that he developed an interest in Astronomy

6 Tycho’s life Became discouraged when he couldn’t find any 2 astronomical charts that agreed with each other Set out to complete his own astronomical chart of the night sky

7 Tycho’s Observatory on the Island of Hven

8 Tycho and the supernova of 1572 A new star appears in the constellation Cassiopeia and temporarily becomes as bright as the planet Venus - why is a new star important?

9 Tycho’s contributions Observed the supernova of 1572 Showed that the comet of 1577 was beyond the earth’s atmosphere Accumulated years of careful observations of the apparent motions of the planets in the sky

10 Tycho’s Contributions Made incredibly detailed catalogues of the sky over a period of 25+ years! Was able to detect stellar parallax! All without the aid of a telescope!!!

11 Tycho’s own model of the solar system was not a success The sun goes around the earth and the other planets go around The sun

12 At one point, he was so famous and rich, he was said to own 1% of the entire wealth of Denmark (in 1580) Held large parties at his castle, and had a dwarf named Jepp sit under the table Tycho = a strange duck

13 Tycho = a strange moose Had a tame moose as a pet The moose died after drinking too much beer at a party and falling down the stairs (the story doesn’t say why the moose was indoors at all, perhaps he knew some good moose jokes)

14 Tycho’s Death “Bladder myth” generally believed to be false Sick for 11 days after the banquet Perhaps………..

15 High levels of Mercury were found in samples of Tycho’s hair recently Tycho himself was an alchemist –He would have known Mercury can kill After Tycho’s death, Kepler took Tycho’s 25 years of observations and used the data to calculate his 3 laws of planetary motion! –Tycho was very secretive with his notes!

16 R.I.P. Rockstar Astronomer

17 But Tycho’s observations paved the way for Johannes Kepler ( , born in Stuttgart, Germany)

18 Kepler: a mystic and a mathematician Uses Tycho’s observations to try to come up with a better model of the motions of the planets Mysterium cosmographicumMysterium cosmographicum (The Sacred Mystery of the Cosmos)

19 Kepler: the man, the myth, the legend Dabbled in the philosophical side of Astronomy and Astrology –At that time, they were one in the same

20 Kepler’s music of the spheres

21 But Kepler was not wacko He came up with 3 laws of planetary motion First Law –Planets move in elliptical orbits with the sun at one focus of the ellipse

22 An ellipse looks like an elongated circle What is an Ellipse?

23 Kepler’s First Law: The orbit of each planet around the Sun is an ellipse with the Sun at one focus. What are Kepler’s three laws of planetary motion?

24 No more uniform circular motion

25 Kepler’s Second Law: As a planet moves around its orbit, it sweeps out equal areas in equal times.  means that a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.

26 Kepler’s third law a is the semi-major axis of the ellipse For a circle a is equal to the radius

27 Kepler’s third law P = period a = semi-major axis (radius for a circle) P 2 = constant X a 3

28 For a planet orbiting the sun Measure P in earth years Measure a in AU (astronomical units, Earth to sun, as we’ll see) –Then P 2 = a 3

29 Examples Earth a =1 gives P = 1 Jupiter a = 5.2 AU P 2 = a 3 = (5.2) 3 = 141 P is the square root of 141, which is about 11.9 So it takes Jupiter about 11.9 years to go once around the sun

30 Kepler By getting rid of uniform motion in circles Kepler got rid of epicycles His laws of planetary motion predicted the motions of the planets more accurately than either Ptolemy or Copernicus

31 R.I.P. F.D.G. Gustavus Adolphus’ (King of Sweden) army destroyed the churchyard where Kepler was buried, so we don’t actually know where his grave is anymore. Sad day.