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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. Ptolemy proposed an Earth-centred Universe. Ptolemy: 90 – 168 AD. Nicolaus Copernicus (1473 – 1543).

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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. Ptolemy proposed an Earth-centred Universe Ptolemy: 90 – 168 AD

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

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

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

  8. The Observations of Galileo Earlier observed phases of Venus

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

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

  11. The Observations of Galileo Phases of Venus impossible to explain in an Earth-centred model Clear evidence that the Earth went round the Sun, and not the other way round

  12. 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

  13. 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?…

  14. Johannes Kepler predicted a transit of Mercury on 29th May 1607 Instead, he ‘discovered’ sunspots

  15. Johannes Kepler predicted a transit of Mercury on 29th May 1607 Instead, he ‘discovered’ sunspots

  16. May 7th 2003: Transit of Mercury

  17. Pierre Gassendi (1592 – 1655) Observed a transit of Mercury on 7th November 1631 Predicted by Kepler in 1629, although he didn’t live to see it

  18. November 24th 1639 Jeremiah Horrocks (c1619 – 1641) “The Founder of English Astronomy” (Eyre Crowe, Walker Art Gallery) William Crabtree (1610 - 1644) “Crabtree watching the transit of Venus” (Ford Madox Brown, Manchester Town Hall)

  19. Halley travelled to St Helena in 1677, to map the Southern Skies He observed a transit of Mercury on November 7th Transit observations could measure the astronomical unit! Edmond Halley (1656 - 1742)

  20. Halley travelled to St Helena in 1677, to map the Southern Skies He observed a transit of Mercury on November 7th Transit observations could measure the astronomical unit! Edmond Halley (1656 - 1742)

  21. Method relied on an accurate estimate for the radius of the Earth In 1669 Jean Picard (1620 – 1682) measured (0.2% error)

  22. In 1716 Edmond Halley appealed to astronomers to observe the Venus transits of 1761 and 1769 Edmond Halley (1656 - 1742)

  23. In 1716 Edmond Halley appealed to astronomers to observe the Venus transits of 1761 and 1769 He predicted the astronomical unit could be measured to an accuracy of 1 part in 500 Edmond Halley (1656 - 1742)

  24. “I am afraid we must wait till the next transit, in 1769…before astronomers will be able to do justice to Dr Halley’s noble proposal” Neville Maskelyne (1732 - 1811)

  25. The 3rd June 1769 Venus Transit Captain James Cook set sail for Tahiti in August 1768, onboard the Endeavour with astronomer Charles Green Captain James Cook

  26. The 3rd June 1769 Venus Transit Endeavour arrived in Tahiti on 13th April 1769 – constructed a fort, and an observatory, at Point Venus Captain James Cook

  27. The 3rd June 1769 Venus Transit Endeavour arrived in Tahiti on 13th April 1769 – constructed a fort, and an observatory, at Point Venus Transit observed by Cook, Green and Solander Captain James Cook

  28. The 3rd June 1769 Venus Transit: Tahiti Captain James Cook

  29. The 3rd June 1769 Venus Transit Father Maxmilian Hell (1720-1792) observed the transit from Lapland

  30. The 3rd June 1769 Venus Transit After years of analysis, the results of the 1769 observations were published. e.g. Thomas Hornsby (1771):- Cassini de Thury 1 A.U. = 93,726,900 miles (between 90 and 94 million miles) Captain James Cook “Happy is our Century, to which has been reserved the glory of being witness to an event which will render it memorable in the annals of the Sciences!”

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