2. Getting the Measure of the Universe Dr. Martin Hendry Glasgow University

4. Ptolemy: 90 – 168 AD

5. Nicolaus Copernicus 1473 – 1543 AD

10. Retrograde motion of Mars

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

20. Solar Eclipses Total Eclipse Zone only about 20km across, but sweeps over many countries as the Earth spins

22. Tycho Brahe: 1546 – 1601 AD

23. Kepler’s laws, published 1609, 1619

24. Galileo Galilei: 1564 – 1642 AD Galilean Moons: 1610

26. Isaac Newton: 1642 – 1727 AD The Principia: 1684 - 1686

27. Nowadays we can use radar: Distance = Speed x Time

28. Nowadays we can use radar: Distance = Speed x Time But what is the speed of light?…

33. Light waves

34. Wavelength Frequency = No of waves produced per second Light waves

35. Wavelength Frequency = 2450 MHz = 2450 Million waves per second Light waves

36. Wavelength Speed = 2450 million wavelength Light waves

37. Light travels 300,000 km every Second…… ……That’s about 10 million, million kilometres every year!!!

38. The stars are VERY far away. The nearest star (after the Sun) is about 40 million million km from the Earth. It takes light more than 4 years to travel this distance. If the distance from the Earth to the Sun were the width of this screen, the next nearest star would be in Rome.

39. Measuring Astronomical Distances: Parallax

40. Even the nearest star shows a parallax shift of only 1/2000 th the width of the full Moon

41. Spectroscopy

42. What can we learn from spectra?

43. Absorption e -

44. Emission e -

46. Wobbly stars: the key to finding extra-solar planets Planets and stars orbit their centre of mass Planets are too faint to see directly - so stars wobble but

47. The Sun’s “wobble”, due to Jupiter, seen from 30 light years away = width of a 10p coin in Madrid

48. Doppler Shift

49. Star Laboratory

50. 51 Peg – the first new planet

51. So we can use spectra to tell what stars are made of….. ……If those stars have planets, we can also use spectra to find them, and tell what gases are in their atmospheres!