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Dr Martin Hendry Dept of Physics and Astronomy, University of Glasgow

Captain Cook and the Cosmic Yardstick. Dr Martin Hendry Dept of Physics and Astronomy, University of Glasgow. James Cook (1728 – 1779). Retrograde motion of Mars. Early Greek Astronomy. The Greeks inherited ideas from Babylonia and Egypt, but approached astronomy in a scientific way.

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Dr Martin Hendry Dept of Physics and Astronomy, University of Glasgow

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  1. Captain Cook and the Cosmic Yardstick Dr Martin Hendry Dept of Physics and Astronomy, University of Glasgow

  2. James Cook (1728 – 1779)

  3. Retrograde motion of Mars

  4. Early Greek Astronomy The Greeks inherited ideas from Babylonia and Egypt, but approached astronomy in a scientific way Plato (428 – 347 BC): reality a distorted shadow of a Perfect Form. Circle = most perfect form in nature All celestial motions are combinations of circular motions

  5. Early Greek Astronomy The Greeks inherited ideas from Babylonia and Egypt, but approached astronomy in a scientific way Aristotle (384 – 322 BC): Universe divided into two parts: Corrupt, changeable Earth Perfect, immutable heavens

  6. Ptolemy proposed a model which could explain planetary motions – including retrograde loops Ptolemy: 90 – 168 AD

  7. Author of ‘The Sphere’, standard textbook on spherical trigonometry John of Holywood (c. 1200)

  8. The Copernican Revolution Nicolaus Copernicus (1473 – 1543) “In the true centre of everything resides the Sun” De Revolutionibus Orbis (1543)

  9. The Copernican Revolution Simpler explanation why Venus and Mercury appear close to the Sun

  10. Tycho Brahe (1546-1601) Uraniborg observatory Hven, between Denmark and Sweden

  11. Tycho Brahe (1546-1601) Uraniborg observatory Hven, between Denmark and Sweden

  12. Tycho Brahe (1546-1601)

  13. Johannes Kepler (1571-1630) ‘Mysterium Cosmographicum’ published in 1596

  14. ’New Astronomy’ published in 1609 Johannes Kepler (1571-1630)

  15. The Spectacle Vendor by Johannes Stradanus, 1582

  16. Hans Lippershey’s 1608 patent of a device for "seeing faraway things as though nearby." Porta’s sketch of a telescope, August 1609

  17. The Observations of Galileo Galileo Galilei: (1564 – 1642)

  18. The Observations of Galileo • Autumn/Winter 1609, observed: • Craters of the Moon • Moons of Jupiter • Phases of Venus In conflict with Aristotelian / Ptolemaic Universe Galileo Galilei: (1564 – 1642) Published in 1610 ‘Sidereus Nuncius’ (The Starry Messenger)

  19. The Observations of Galileo The Moon is an imperfect world with mountains and valleys, just like the Earth

  20. The Observations of Galileo Moons of Jupiter: supported idea of Earth moving through space, contradicted Aristotelian view of all motions around Earth

  21. The Observations of Galileo Earlier observed phases of Venus

  22. The Observations of Galileo Earlier observed phases of Venus Geocentric model Sun

  23. The Observations of Galileo Earlier observed phases of Venus Geocentric model Heliocentric model Sun Sun

  24. The Observations of Galileo Phases of Venus impossible to explain in geocentric model Clear evidence that the Earth went round the Sun, and not the other way round “Cynthiae figuras aemulatur mater amorum”

  25. Getting the Measure of the Solar System In the Heliocentric model it was easy to determine the relative distances of the planets, using the geometry and trigonometry of the Greeks…

  26. Sun Earth Venus We can use Pythagoras’ theorem!!

  27. Getting the Measure of the Solar System Planet Distance Mercury 0.39 Venus 0.72 Earth 1.00 Mars 1.52 Jupiter 5.20 Saturn 9.54

  28. Getting the Measure of the Solar System Planet Distance Mercury 0.39 Venus 0.72 Earth 1.00 Mars 1.52 Jupiter 5.20 Saturn 9.54 How far is an astronomical unit?…

  29. Eratosthenes: (c 276 – 195 BC)

  30. Eratosthenes: (c 276 – 195 BC) Syene – Alexandria = 5000 stadia Circumference of the Earth = 250000 stadia

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