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Tycho Brahe – The Data Taker

Key question: Where are things? Catalogued positions of planets in Uraniborg and Prague Working without telescope Data ten times as accurate as before Died at banquet binge drinking. Tycho Brahe – The Data Taker. Tycho Brahe (1546–1601).

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Tycho Brahe – The Data Taker

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  1. Key question:Where are things? Catalogued positions of planets in Uraniborg and Prague Working without telescope Data ten times as accurate as before Died at banquet binge drinking Tycho Brahe – The Data Taker Tycho Brahe (1546–1601)

  2. collects detailed and accurate (1-2’ accuracy) observations of stellar and planetary positions over a period of 20 years His research costed 5-10% of Danish GNP shows that comets and novas are extralunar contrary to Aristotle Shows that stars can change (Supernova of 1572) Proves that comets are superlunar Tycho Brahe Tycho Brahe observing

  3. Measuring distances with the Parallax • The closer an object is, the more relocated it appears with respect to the fixed stars from different points on Earth

  4. Johannes Kepler–The Phenomenologist Key question: How are things happening? Major Works: Harmonices Mundi (1619) Rudolphian Tables (1612) Astronomia Nova Dioptrice Johannes Kepler (1571–1630)

  5. Kepler’s Beginnings Astrologer and Mystic Tried to find “music in the skies” Tried to explain distances of the 5 known planets by spheres resting on the 5 mathematical bodies  pre-scientific

  6. Kepler’s First Law: Orbit Shape The orbits of the planets are ellipses, with the Sun at one focus

  7. Ellipses a = “semimajor axis”; e = “eccentricity”

  8. Conic Sections From Halley’s book (1710)

  9. Kepler’s Second Law: Motion in Time An imaginary line connecting the Sun to any planet sweeps out equal areas of the ellipse in equal times

  10. Activity: Kepler’s 2nd law • Get out your worksheet books • Form a group of 3-4 people • Work on the questions on the sheet • Fill out the sheet and put your name on top • Hold on to the sheet until we’ve talked about the correct answers • Hand in a sheet with the group member’s names at the end of the lecture • I’ll come around to help out !

  11. Kepler’s Third Law: Relating Orbits The square of a planet’s orbital period is proportional to the cube of its orbital semi-major axis: P 2 a3 Jupiter:53 / 122 = 125/144 ~ 1 a P Planet Semi-Major AxisOrbital Period Eccentricity ____ P2/a3 Mercury 0.387 0.241 0.206 1.002 Venus 0.723 0.615 0.007 1.001 Earth 1.000 1.000 0.017 1.000 Mars 1.524 1.881 0.093 1.000 Jupiter5.203 11.86 0.048 0.999 Saturn 9.539 29.46 0.056 1.000 Uranus 19.19 84.01 0.046 0.999 Neptune 30.06 164.8 0.010 1.000 Pluto 39.53 248.6 0.248 1.001 (A.U.) (Earth years)

  12. One form of Kepler’s 3rd law is P2 /a3 =1. If a planets major axis a is twice as large as Earth’s, what is its period P around the Sun? 1 year A little less than 3 years A little more than 12 years 29 years

  13. Activity: Orbit of Mars • Pick up a worksheet • Form a group of 3-4 people • Work on the questions on the sheet • Fill out the sheet and put your name on top • Hold on to the sheet until we’ve talked about the correct answers • Hand them in at the end of the lecture or during the break • I’ll come around to help out !

  14. Activity: Kepler’s 3rd law • Get out your worksheet books • Form a group of 3-4 people • Work on the questions on the sheet • Fill out the sheet and put your name on top • Hold on to the sheet until we’ve talked about the correct answers • Hand in a sheet with the group member’s names at the end of the lecture • I’ll come around to help out !

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