Lesson 1: Relativity  What is it?
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
Lesson 3 : Relativistic Mass
Lesson 4 : Length Contraction

Lesson 1: Relativity  What is it? The Basics of Special Relativity Relativity is a widely used term. It is generally used to describe everything from the comical version of E = mc^{2} to concepts about time travel. Here, we are referring to the theory called the Special Relativity which was first understood by Einstein. In Einstein's Special Theory of Relativity, he laid down two postulates:
These postulates lead Einstein to the conclusion that if you were moving through space with a constant speed and in a constant direction, the rate at which you would travel forward in time changes. Einstein backed up his theory with sound reasoning which showed that indeed, the faster you travel through space, the slower you travel through time. Einstein's theory of relativity also predicted an effect of speed on mass observed by a stationary frame for a moving frame as well as an effect of speed on length measured in the direction of mortion by a stationary frame for a moving frame. The faster you travel through space, the more massive you become and the thinner you become in the direction of motion. When we say time slows down for you, your mass increases, and that your width changes, we mean that an observer would see these effects as that observer observes you. According to you, you are not moving and you measure your time, your mass, and your width as you always did. However, for someone not moving along with you, she would see your clock and heart beat run slow, she would see your mass seem to increase (if she pushed you, you wouldn't accelerate as much as she'd expect), and she would see your width in the direction of your motion as thinner. The consequences of special relativity offer some challenges to conceptualize, but are engaging and intriguing. The effects are often misunderstood as effects that only occur at very high speeds near the speed of light through a vacuum which is 300,000,000 m/s or 186,000,000 miles per second. In fact, all motion, even no motion is under the constraints of special relativity. The amazing thing about relativity is that it is used on a daily basis by people who make things go near the speed of light for a living. These people include high energy physicists! Try your hand at the kind of games they play everyday. Fermilab's Time Dilation Challenge. The Relativity Game  Challenge what you know! 
© Brian Wegley, 1998