1889

Length contraction

• Michelson and Morley couldn’t find any direction
• in which luminiferous aether slowed the speed of light.
• George FitzGerald thought he could explain
• their negative result without ruling out aether
• by suggesting that bodies contract
• along the direction of their movement.
• It happens that bodies do contract
• along the direction of their movement
• even though a better explanation
• happens to be that aether doesn’t exist.

Speed of light

• Length contraction would not noticable
• unless the object were moving near the speed of light.
• To measure the length of an object
• we need to communicate with both ends of the object
• simultaneously, but no communication travels
• faster than the speed of light. Ack.
• Not so simple. If you travel with the object,
• it doesn’t change length as it speeds up.
• It changes length only when
• you sees it moving quickly away.
• I thought I understood this,
• but now I’m not so sure.

Happens to be

• You cannot tell
• you cannot smell
• you cannot see it
• but experiment
• and reasoning
• can make it real