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Class Information for PHYS/ASTR 1080 can be found at: www.physics.utah.edu Click on courses Click on Does ET Exist?

Class Information for PHYS/ASTR 1080 can be found at: www.physics.utah.edu Click on courses Click on Does ET Exist? ( George Cassiday …that’s me) Everything about the class HW, Exams, Syllabus, etc can be found by following the appropriate links . Does ET Exist?.

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Class Information for PHYS/ASTR 1080 can be found at: www.physics.utah.edu Click on courses Click on Does ET Exist?

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  1. Class Information for PHYS/ASTR 1080 can be found at: • www.physics.utah.edu • Click on courses • Click on Does ET Exist? (George Cassiday…that’s me) • Everything about the class HW, Exams, Syllabus, etccan be found by following the appropriate links.

  2. Does ET Exist? The Copernican Revolution

  3. The Celestial Sphere — A crystalline sphere in which all the stars are embedded surrounds the Earth and rotates CW once every ~24 hr!

  4. An Early Model 8 Nested Crystalline Spheres — one each for the Moon, Sun, all of the planets (up to Saturn) and the stars.

  5. Aristotle’s Cosmos — The Eight Heavenly Spheres The third book of the “Divine Comedy” concerns Dante’s spiritual ascent through the heavenly spheres. The first book … the ‘Inferno‘ … concerns Dante’s descent into hell. A modified version of Aristotle’s model was adopted as the ‘scientific’ underpinning of the basic tenets of medieval Catholicism. By the 1600’s, a challenge of Aristotle was viewed as an attack on Catholicism.

  6. Botticelli’s Map of Hell What awaits in the 9th circle … if you don’t do your homework! The 9th Circle…

  7. Observation of Mars (2007-2008) Castor & Pollux (Gemini) East West May 3, 2008 There appears to be a problem here … Aug 19, 2007 Aldebaran (Taurus) Betelgeuse (Orion)

  8. Planet moves eastward (prograde motion) when here But — How to Explain Retrograde Motion? Planet moves westward (retrograde motion) when here • Planetary motions as a combination of circles: • Planet moves along ‘epicycle’ • Center of epicycle moves along ‘deferent’ • Motion along epicycle is faster than motion along deferent

  9. Ptolemy’s Geocentric Model 90-168 C.E. eccentric

  10. Question An epicycle is A mechanical contraption that is easier to ride than a bicycle. A mathematical construct designed to explain the retrograde motion of planets. A wild frenzy that afflicted ancient Greeks who drank too much retsina. A small fraction of the cyclic orbit of the planet Mars.

  11. Question Geocentric means … Earth centered Sun centered Wobbly orbit Circular orbit

  12. Nicolaus Copernicus (1473 – 1543) Heliocentric Model — why? Esthetics Neoplatonist who wanted to get rid of Ptolemy’s equant and resulting non-uniform circular motion. Correct 10-day discrepancy between occurrence and prediction of a conjunction of Jupiter and Saturn.

  13. Mercury & Venus …Just Before Sunrise maximum elongation 460 — Venus Elongation Angle 280 — Mercury

  14. Planetary Distances Inferior Planets θ = 460 D = 1 AU dVenus / 1 AU = sin 460 dVenus = 0.72

  15. Retrograde Motion in Heliocentric System

  16. Question Copernicus demonstrated that the observed retrograde motion of the planets could be understood in terms of a model in which the planets orbited Venus. as an effect due to the relative motion of planets as they orbited the Sun. as an effect caused by the sudden reversal of their motion due to an applied force. in terms of a model in which the Sun orbited the Earth.

  17. Tycho Brahe (1546-1601) or, as he liked to call himself Tycho — The Great Uraniborg — Tycho’s Observatory Tycho realized that progress in astronomy required systematic, rigorous observation, night after night, using the most accurate instruments obtainable. He was, perhaps, the world’s greatest observational astronomer.

  18. Tycho’s Quadrant Observations accurate to +/- 1 arcmin … 30 times better than any before!

  19. Stellar Parallax If stars confined to thin celestial sphere, then angle between any two of them should change as Earth orbits Sun … the angle does not change!

  20. Question Tycho developed a model of the solar system that was essentially the same as the Copernican model if you looked at things from the point of view of an immobile Earth. He developed this model because Tycho thought Copernicus was a heretic whose work contradicted Church dogma. he was jealous of Galileo who claimed that the Earth was in motion he was a great admirer of Copernicus and did not want to completely discredit his work he could detect no parallax for the stars

  21. Johannes Kepler (1571 – 1630) Using Tycho’s data, Kepler discovered 3 laws of planetary motion — a watershed in the history of science!

  22. Kepler’s 1st Law Planets travel in elliptical orbits around theSun — with the Sunlocated at one of the foci.

  23. Kepler’s 2nd Law A planet covers equal areas in equal times. If T(A→B) = T(C→D), areas (painted in tan) are equal.

  24. Kepler’s 3rd Law

  25. Question Kepler’s 3rd Law of Planetary Motion states that ____ The further a planet is from the Sun, the faster it moves. T2 = R3 where T is the period of the planet’s orbit in years and R is in AU. An imaginary line joining the Sun and the planet sweeps out equal areas in equal times. The orbit of the Sun around the Earth is elliptical

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