1. Do now! Can you continue the gravity questions you started yesterday?

2. Development of models of the Solar system/universe You are here

3. Astronomical observations  The pattern of the stars remains the same from night to night (over the time of a life-time)  These patterns have been labelled constellations Orion’s belt

4. Astronomical observations  The constellations do not appear in the same place  Over the period of one night they appear to rotate around the pole star  Some stars rise above the horizon during the night, and some set behind it.

5. Astronomical Observations  This same movement is continued during the day. The sun rises in the east and sets in the west. Maximum height at midday (in the south in the Northern hemisphere.

6. Constellation position  The constellations have the same relative positions from night to night. ‘ View toward horizon from 59°54'N 11°E, azimuth 0° (N) View toward horizon from 59°54'N 11°E, azimuth 0° (N)

7. Place to place  The constellation you can see also depends on where you are I can’t see the pole star! I’m on top of the world!

8. Constellation position  The location of the pole star varies from night to night as we go through the year, so different constellations may be visible at different times of the year. View toward horizon from 59°54'N 11°E, azimuth 0° (N) View toward horizon from 59°54'N 11°E, azimuth 0° (N)

9. Planets  Some objects that we can see a night behave differently!  Their position DOES change relative to the background of stars.  These objects are called planets (derived from the Greek word for “wanderer”).

10. Planets The planets can sometimes exhibit retrograde motion over the course of several nights.

11. The moon  The moon’s observed motion across the night sky is different again.  It takes part in the nightly rotation around the pole star, but it also wanders.

12. Phases  The moon’s appearance changes over the course of a month. We say it has phases. The Moon's Phases The Moon's Phases

13. Models of the Universe  Aristotle (384-322 BC) Wisdom is the reward you get for a lifetime of listening when you'd rather have been talking.

14. Aristotle’s Universe  Earth at centre (geocentric)  Other objects attached to concentric perfect crystal spheres turning at slightly different speeds  All “fixed” stars were attached to the final sphere

15. Aristotle’s Universe

16. Ptolemy’s (AD 85 – 165) adaption of Aristotle’s ideas  To explain the retrograde motion of some planets, he allowed each planet to move in a small circle (an epicycle)  The centre of the epicycle moved on a bigger circle called a deferent.  Earth is still at the centre (geocentric)

17. Ptolemy’s adaption of Aristotle’s ideas The Universe of Aristotle and Ptolemy The Universe of Aristotle and Ptolemy The Universe of Aristotle and Ptolemy

18. Heliocentric models  Sun-centred (heliocentric)  First proposed by Aristarchus (2 nd century BC), but it has come to be associated with Copernicus (1473-1543)  Orbits are still taken to be circular  Explains retrograde motion of planets

19. Heliocentric models The Copernican Model: A Sun-Centered Solar System The Copernican Model: A Sun-Centered Solar System The Copernican Model: A Sun-Centered Solar System This model also explains why Mercury and Venus always appear close to the sun in the sky To account for slight differences between the model and actual observations, Copernicus was forced to add epicycles too!

20. Galileo "All truths are easy to understand once they are discovered; the point is to discover them."

21. Galileo  His observations with one of the first telescopes added further support to the Copernican view

22. Galileo’s observations  There are mountains on the moon  Venus has phases (like the moon) and appears to change size  Jupiter has objects orbiting it (moons)  There are dark spots on the sun  The sun rotates and the spots on the surface move

23. Galileo in trouble  In 1633 he was tried by the catholic Church and forced to recant his ideas. He remained under house arrest for the rest of his life

24. Kepler  At the same time as Galileo, Johannes Kepler (1571-1642) was adapting Copernicus’s model  His new model gave very good agreement with observations

25. Kepler’s model  Each planet orbits the sun in an ellipse, with the sun at one focus

26. Universal Gravitation If I have ever made any valuable discoveries, it has been owing more to patient attention, than to any other talent. Isaac Newton (1642 – 1727)

27. Universal Gravitation  Newton came up with a physical explanation for Kepler’s model  Newton proposed that every object in the universe attracts every other object with a force that is proportional to the masses of the objects and inversely proportional to the distance between the objects squared

28. Universal Gravitation  This law applies everywhere in the universe  It can explain why an apple falls to earth, but also why the moon stays in orbit around the earth

29. Galaxies  Large collections of stars (100,000,000,000)

30. Edwin Hubble  In 1925 Edwin hubble found that distant galaxies are moving away from us. The further they are away, the faster away they are moving!

31. Big bang Hubble’s discovery implied that in the past the universe must have started from a single point, the big bang! (about 13 billion years ago)

32. Stephen Hawking Mr Porter’s friend Stephen Hawking has been working on the implications of this “Big Bang singularity (black hole)

33. That’s it!

34. Mind map – pages 138 - 139

35. Mind map  Colours  Pictures/drawings  Few words (not complete sentences)

36. Mr Porter likes dislikes familyplaces tea newspapers football Kirsten Dunst teaching red wine dogs banksMr Bean rudeness dogs shopping music 3 kids wife England Norway PNG Peru Tetley Milk, no sugar Guardian Times IndependentNottingham Forest Spiderman trumpet physics Gato negro rock classical Alice George Louis Alison clothes Poo! queuing Blackadder Natwest Poo! Oslo Port Moresby Lima Twice European Champions Wimbledon CD Bristol University cheap Rush Bruckner 12 10 9 21 Marks and Spencer Norway! Lik lik hus

37. Brain map – pages 138 - 139