# Warm-Up Exercise 39

## Due 12:15 pm, Wed 28 Nov 2012

Physics 123, Fall 2012

Reading assignment: 39.5

The Lorentz transformation equations relate the space and time coordinates of
"events". What is an "event"? Give some examples.

An "event" is something that happens at a particular place, at a particular time. Examples:
* A teacher slams a book on a table
* My wife opens up our mailbox
* A star goes supernova
* The light from the supernova first reaches an astronomer's eye

The Lorentz transformation equations relate the coordinates of events
occuring in different "frames of reference". What is a "frame of reference"?
Give some examples.

For our purposes, a frame of reference is a viewpoint moving at a constant velocity. Examples:
* Dr Colton in his spaceship
* People on earth watching him leave
* People of Zyzyz, awaiting his arrival

The Lorentz transformation equations are given as Eqn 39.11 and Eqn 39.12
(reverse transformation) (8th edition). Why are the equations for y and z so
trivial?

The equations assume all of the relative motion is in the x-direction.

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