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The Basics of Relativity

Lesson 1: Relativity - What is it?

  1. Fermilab's Time Dilation Challenge.
  2. The Basics of Relativity (6 seconds)
  3. The Relativity Game - Challenge what you know!

Note: For Fermilab's Time Dilation Challenge and The Relativity Game, you need Shockwave. You may painlessly Download Shockwave here if you do not have it.

Lesson 2: Time Dilation

  1. The equation.
  2. Where does that come from?
  3. I still don't get it! Give me the basketball analogy.
  4. So what? There's an equation. How do I use the equation in the game?
  5. Practice Problems.
  6. Examples to aid your practice.

Lesson 3 : Relativistic Mass

  1. The equation.
  2. Where does that come from?
  3. I still don't get it! Give me the space pool analogy.
  4. So what? There's an equation. How do I use the equation in the game?
  5. Practice Problems.
  6. Examples to aid your practice.

Lesson 4 : Length Contraction

  1. The equation.
  2. Where does that come from?
  3. I still don't get it! Give me the pole and the barn analogy.
  4. So what? There's an equation. How do I use the equation in the game?
  5. Practice Problems.
  6. Examples to aid your practice.

Einstein's Second Postulate of Special Relativity

This second statement by Einstein is more wierd than it may seem. What he essentially says is that light behaves in a different way than r experience predicts.

Show me the wierdness!

Mr. Wegley's little brother is a Junior at SIU Carbondale. He is 6'4" and 220 lbs. and can hurl a fast ball with a speed of around 90 miles an hour.

That means that I would measure the speed of his throw to be 90 miles per hour if I stood at rest.

If I had my choice, I'd rather have my brother throw his 90 mile per hour fast ball at me when I'm moving directly away from him with a speed of 90 miles per hour.

In this case, his ball would not catch me.

Question:

In my reference frame, I would measure it's speed to be ___ miles per hour:

A stupid case scenario would be if I were to move at him at 90 miles per hour as he threw at me at 90 miles per hour.

Question:

Now I'd measure the ball's speed to be ___ miles per hour:

So what's the big deal with Einstein's statement that the speed of light is constant from all reference frames?

The weirdness of Einstein's statement is that if Jimmy threw light at me (pointed a flashlight toward me and turned on the light) I would see it move at precisely 300,000,000 m/s (186,000 miles per hour) regardless of my speed.

If I were at rest, I'd measure the speed of light to be 300,000,000 m/s. If I ran away from him at 200,000 m/s (warm up well before trying this) I would measure the speed of light to be 300,000,000 m/s -> no more and no less!

If I ran at him at 200,000 m/s, I would still measure the speed of light to be 300,000,000 m/s. A famous physicst named Michelson showed how true this statement is! You can read more about Michelson if you go back to the basics of relativity link in these pages.

 

 


© Brian Wegley, 1998
Comments and suggestions can be sent by e-mail to
Brian Wegley of Glenbrook South High School..
This page last updated on 7/23/98.