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30 Relativity

This page covers the relativity section of the course. 

The key to understanding the Michelson–Morley experiment (Topic 3.1) is realising that turning the apparatus through 90º alters the relationship between the beam paths and the Earth’s motion – no matter which way the Earth is moving. The null result disproves the ether theory.

Inertial frames of reference can be explained as places where the observer is considered to be at rest compared to the measuring equipment they are using. Since the value of the speed of light is always the same, then the observer’s measuring equipment (their ruler or their clock) must adapt to conform with any relative motion. Thus at high relative velocities their ruler would shrink and their clock would slow so as to indicate the correct readings.

Resources

30 Relativity

30 Relativity Book

A2 Relativity Practice Questions

A2 Relativity Timed Assessment

Relative Motion and Inertial Reference Frames

Did you know that everything is moving? Even you, as you're sitting perfectly still, because the earth is moving, and the sun, and the galaxy, and so forth. For this ...reason, it only makes sense to talk about the motion of some object relative to some other object, just as Galileo told us. Watch this and see what I mean!

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