Run the Slide Show

1. Run the Slide Show

2. In the style of Einstein, let’s do a “thought experiment”… Imagine two scientists, both with well-operating stopwatches that are synchronized. (meaning they read exactly the same time) Scientist A is standing still on the ground, while scientist B is standing on a skateboard, holding a flashlight in his hand. The skateboard is moving crazy fast: 100 million meters per second.

3. Like this… Draw these two scientists on your graph paper. B When scientist B observes scientist A to be directly beside him, he turns on the flashlight. A pulse of red light leaves the flashlight. 1.0 x 108m/s Draw the light pulse on your paper. A Both scientists start their respective stopwatches the instant the red light pulse exits the flashlight. They are to mark the location of the pulse after 1.0 second has elapsed.

4. Pretty simple experiment, huh? Question: What does scientist B observe to be happening during this experiment? B How fast does he see the light pulse moving? 1.0 x 108m/s 3.0 x 108m/s He sees the flashlight at rest and observes the light pulse to travel away from him at 300 million meters per second (c). A Well, he sees himself at rest (of course), and he sees scientist A traveling at 100 million meters per second away from him.

5. 3.0 x 108m away from him What will he observe as the location of the pulse at 1.0 second? Simple math: distance = (speed)(time) B 3.0 x 108m/s

6. 1.0 x 108 m What does scientist A see? Well, he sees himself at rest (of course), and he sees scientist B traveling at 100 million meters per second away from him. B 1.0 x 108m/s At t = 1.0 second, he observes scientist B to be100 million meters away from him. A Draw the new position of scientist B on your paper, using a scale of 1.0 inch = 50 million meters

7. Where does scientist A observe the light pulse to be at t = 1.0 second? Well, he sees the flashlight moving away from him at 100 million meters per second. What speed does he see the light pulse to travel? (Refer to postulate #2 of Einstein’s theory.) B 1.0 x 108m/s After that, it’s the simple math again: distance = (speed)(time) A When you figure it out, draw the light pulse at that location on your paper, using the same scale. (1.0 inch = 50 million meters) Mark that position with an ‘A’, so you know who made that observation.

8. 1.0 x 108 m Do you remember how far away scientist B measured the light pulse to be at t = 1.0 second? Yep, 300 million meters away from him. (You figured that out a couple slides ago.) B Draw the light pulse at that location on your paper, using the same scale (1.0 inch = 50 million meters) 1.0 x 108m/s A Mark that position with an ‘B’, so you know who made that observation.

9. 1.0 x 108 m So, now you have the position of the light pulse at t = 1.0 second, as observed by these two scientists moving relative to one another. B A Do you see a problem with the results of this experiment? Write down the issue. (Don’t move on until you figure out and describe the problem.)

10. 1.0 x 108 m 3.0 x 108 m 1.0 x 108m/s 3.0 x 108 m This is what your graph paper should look like, and the problem that arises is… B (A) (B) [Don’t worry; scientist A has an idea.] A …how can the two scientists observe the pulse to be in differentlocations at the same instant in time?