Simultaneit. Pg. 524

Transcription

1 Simultaneit Pg. 524 y

2 Inertial frame of reference: Review 0 At rest or moving with constant speed in a straight line 0 On in which Newton s Cirst law is true Galilean transformation: 0 y = y z = z t = t x = x + vt u = u + v

3 Option A: Relativity A.2 Lorentz transformations Nature of science: Pure science: Einstein based his theory of relativity on two postulates and deduced the rest by mathematical analysis. The Cirst postulate integrates all of the laws of physics including the laws of electromagnetism, not only Newton s laws of mechanics.

4 Einstein s 1 st postulate 0 The laws of Physics are the same in all frames of reference

5 Newton s classical Physics 0 Space and time are absolute. 0 An observer in separate frames of reference must make the same observations.

6 Maxwell This rule breaks down in electromagnetic applications 0 A moving electric charge creates a magnetic Cield 0 A stationary electric charge creates an electric Cield

7 In different frames of reference different explanations are given for the experienced force: 0 The force radiates out from the charge 0 Travels at the speed of light 0 Depends only on medium Conclusion leads to second postulate: 0 The speed of light is independent of the speed of the observer 0 All inertial observers will measure the same value for the free space velocity of light irrespective of their velocity relative to the source

8 Galilean transformation 0. Does not take into account the second postulate 0. Assumes time is an absolute quantity

9 Simultaneous events 0 Simultaneity - Albert Einstein and the Theory of Relativity - YouTube [360p].mp4 0 Stationary observer: events happen simultaneously 0 Observer in moving frame: light in front strikes Cirst Who is correct?

10 Moving observer 0 Light from front turn on Cirst à light travels shorter distance 0 Light from back needs to travel extra distance à takes more time to hit

11 Einstein showed. 0 both observers are correct 0 There is no preferred reference frame Einstein postulated: Different observers will describe the same event with different space time coordinates

12 Option A: Relativity A.2 Lorentz transformations The concept of simultaneity Consider a village clock tower that is just on the verge of striking noon. Consider two observers: A man standing on the village green, and an alien in a rocket skimming the green at high speed, both the same distance from the clock. At the stroke of noon, light from the clock reclects to both the man and the alien: Note that the alien sees noon later than the man!

13 Option A: Relativity A.2 Lorentz transformations The concept of simultaneity Consider a man centered on a moving Clatcar and being observed by another man standing on the ground. At precisely the instant the two observers are opposite each other lightening bolts strike both ends of the Clatcar. Note that the stationary observer saw the bolts simultaneously, but the moving one did not!

14 Option A: Relativity A.2 Lorentz transformations The concept of simultaneity events Since he is midway the light will reach him simultaneously from both matches.

15 Option A: Relativity A.2 Lorentz transformations The concept of simultaneity events She will see light from A before light from B because her reference frame is moving toward A and away from B.

16 Option A: Relativity A.2 Lorentz transformations The concept of simultaneity events Simon will not see simultaneity but will see bird B Cirst since he is approaching its light and receding from bird A s light.