Einsteins Relativity Part 1 Bill Weissbard Albert Einstein

Einstein’s Relativity Part 1 Bill Weissbard

• Albert Einstein as a young man. • As a child he wondered what it would be like to travel with light. Answering this question became the central core to his life’s work.

Einstein’s Postulates • The Speed of Light is Constant for any observer, regardless of the motion of the observer or the motion of the light source. • The laws of physics are always the same in all inertial ( nonaccelerating) frames of reference.

The Luminiferous Ether (? ? ) • For most of the 19 th century, physicists thought that space was permeated by “luminiferous ether” – this was thought to be necessary for light to propagate – sound travels through a medium (air) so light should also travel through a medium • Michelson and Morley performed an experiment to measure earth’s velocity through this substance – first result in 1887 – Michelson was first American to win Nobel Prize in physics • Found that light waves don’t bunch up in direction of earth motion – shocked the physics world: no ether!! – speed of light is not measured relative to fixed medium – unlike sound waves, water waves, etc.

Michelson and Morley measured the speed of light every day and every night for two years They concluded that the speed of light was the same no matter what the earth’s orientation with respect to the sun and the galaxy and that the luminiferous ether did not exist. For this Mickelson won the Nobel prize.