2. Introducing Relativity Ross Phillips, PLC

3. New Course 2005 Einstein’s Relativity Detailed Study in Unit 3. 2004 many of the pilot schools are preparing to teach relativity. Common sense is the collection of prejudices acquired by age 18 (Einstein)

4. Daunting “Einstein’s contribution has a name for being difficult, but this is quite wrong. Einstein’s contribution is very easy to understand, but unfortunately it rests on the theories of Galileo and Newton which are very difficult to understand!” Renowned relativist and pioneer of the Steady State Theory Hermann Bondi

5. Movement Unit 2: “compare the accounts of the action of forces by Aristotle, Galileo and Newton”. Aristotle: forces cause and maintain motion Galileo: objects will keep moving forever if no other force acted on them Newton: agreed with Galileo but introduced the idea of action at a distance ie. force acts instantaneously between two masses, even if separated by a great distance like the Sun and the Earth.

6. Why did the chicken cross the road? Aristotle: It is the nature of chickens to cross roads. Newton: Chickens at rest tend to stay at rest, chickens in motion tend to cross roads Einstein: Whether the chicken crossed the road or the road moved beneath the chicken depends on your frame of reference.

7. Newton was no Newtonian. God was intervening to keep all the masses in the universe from collapsing into one big mass He believed in absolute space, that was at rest and centred on the centre of mass of the Solar System. He believed in absolute time.

8. Prior to Galileo the Earth was stationary, Aristotle, supported this belief. the Moon is not left behind as it would be if the Earth moves through space. used balls rolling along ramps, and his observations of Jupiter to argue against Aristotle. Galileo

9. Father of Physics you can move without knowing that you are moving! the principle of relativity states that the laws of physics are the same in all inertial reference frames. an idea of the world as an orderly place that could be understood with a set of laws. The Parable of the Ship http://physics.syr.edu/courses/modules/LIG HTCONE/galileo.html

10. Maxwell developed Michael Faraday’s field idea. these fields radiated at the speed of light thus were not instantaneous. Einstein later developed the field theory for gravity in his general relativity.

11. Discussion Topics What familiar examples demonstrate the principle of relativity? In what ways could you state the principle of relativity? How was Aristotle’s relativity different to Galileo’s?

12. Inertial Earth? we are on a body that is hurtling through space but we cannot tell! It was obvious to the person in the street that the Earth was not moving – but it is, (or is it?) due to the principle of relativity, and the nature of the Earth’s movement, that movement is difficult to detect.

13. Can Measure Acceleration, not Velocity How could you measure the speed of the Earth? Stellar aberration and parallax are due to revolving around the Sun Foucault’s Pendulum and weather patterns confirm that the Earth is rotating about its axis

14. Michelson-Morley Expt Attempt to measure the speed of Earth through the aether If successful would violate the principle of relativity as it applied to mechanics http://galileoandeinstein.physics.virginia.ed u/more_stuff\flashlets\mmexpt6.htm

15. Einstein’s Postulates “the laws of electrodynamics and optics will be valid for all frames of reference for which the laws of mechanics hold good”. “light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body”. – Einstein A. (1905) On the electrodynamics of moving bodies.

16. The Challenge You do not really understand something unless you can explain it to your grandmother. (Einstein) I tried to imagine the easiest way God could have done it. (Einstein)

17. What do we mean by “the speed of light”? Einstein defines the time it takes for light to travel from A to B to be equal to the time it takes for light to travel from B to A (clocks stationary to A and B) c is simply twice the distance from A to B divided by the time it takes light to go from A to B and back again.

18. Implications Einstein’s explanation upset the Newtonian concept of time and space as demonstrated by http://casa.colorado.edu/~ajsh/sr/paradox.ht ml#c 2

19. Time Dilation L0L0 t 0 =2L 0 /c vt

20. Were both headings the same length? Yes and no. They are the same length at rest relative to each other

21. Length? The separation of two ends at an instant in time. L0L0 2L 0 =ct 0 L+ vt 1 L+vt 1 =ct 1 L L - vt 2 L-vt 2 =ct 2 t 1 +t 2 =t

22. Sketch the letter L if it is moving near the speed of light: To the rightTo the left Up the pageDiagonally

23. Wisdom? Definition of Theoretical Physics? –If the facts don’t fit the theory, change the facts. (Einstein) Trouble finding questions? –One of Einstein’s students said to him: “The questions in this year’s exam are the same as last year’s!” “True,” Einstein said, “but this year all the answers are different.”

24. Role play In groups, develop a little skit demonstrating what you might look like to observers if you were in a spaceship passing at near the speed of light. Be prepared to discuss the limitations of your skit. Students observing are asked to show where the performance inaccurately depicts relativity.

25. Creative Writing Write a science fiction story about a space ship that travels to another star system at close to light speed. In your story, describe the trip from the point of view of those on board and contrast that with the point of view of those on Earth (a post modern novel!)

26. Argumentative writing topics We can never travel to other stars because it is too far. True or false? Length contraction violates the principle of relativity. Comment on this statement. People travelling fast look fatter because they appear to have more mass. True or false?

27. Spreadsheet task: design a relativity calculator

28. Links http://www.glenbrook.k12.il.us/gbssci/phys /Class/Bboard.html#einstein http://members.tripod.com/conduit9SR Http://www.goshen.edu/~reubendb/relativit y Http://www.pbs.org/deepspace/classroom/a ctivity4.html#objectives a rather challenging activity designed for high schoolsHttp://www.pbs.org/deepspace/classroom/a ctivity4.html#objectives a rather challenging activity designed for high schools

29. Demonstration (Einstein’s inspiration) Electric current induced a magnet moving near a wire Moving a wire through a fixed magnetic field induces a current in the wire Before Einstein these were distinct phenomena http://www.physics.ucla.edu/demoweb/demomanu al/modern_physics/special_relativity/special_relati vity.html

30. Let Einstein Do the Talking http://www.time.com/time/time100/poc/eins tein_audio.html

31. Free Software/ Links http://saintmarys.edu/rtarara/software.html –Great simulations http://www- ed.fnal.gov/data/phy_sci/relativity/student/c halbegin.shtml 2 3 4http://www- ed.fnal.gov/data/phy_sci/relativity/student/c halbegin.shtml 2 3 4 –Great data logging task

32. Books Einstein’s dreams, Alan Lightman (short stories) The Principle of Relativity, Einstein, Lorentz, Weyl, Minkowski (original papers) Special Relativity, A. P. French Relativity and its Roots, Banesh Hoffmann Relativity and Common Sense, Hermann Bondi