Conceptual Physics Ch. 34 Special Theory of Relativity

length contraction

Shrinkage of space, and therefore of matter, in a frame of reference moving at relativistic speeds.

simultaneity

Occurring at the same time. In special relativity, two events that are simultaneous in one frame of reference need not be simultaneous in a frame moving relative to the first frame.

rest energy

The "energy of being," given by the equation E-mc^2.

spacetime

Four-dimensional continuum in which all events take place and all things exist: Three dimensions are coordinates of space and the fourth is of time.

postulates of special relativity

First: All laws of nature are the same in all uniformly moving frames of reference.

Second: The speed of light in free space has the same measured value regardless of the motion of the source or the motion of the observer; that is, the speed of light is invariant.

tachyon

Hypothetical particle that can travel faster than light and thus move backward in time.

special theory of relativity

Comprehensive theory of space and time that replaces Newtonian mechanics when velocities are very large; introduced in 1905 by Albert Einstein.

electrodynamics

Study of moving electric charge, as opposed to electrostatics.

interferometer

Device that uses the interference of light waves to measure very small distances with high accuracy. Michelson and Morley used an interferometer in their famous experiments with light.

frame of reference

Vantage point (usually a set of coordinate axes) with respect to which position and motion may be described.

relativistic

Pertaining to the theory of relativity; or approaching the speed of light.

light-year

The distance light travels in a vacuum in one year: 9.46x10^12 km.

time dilation

Slowing down of time for an object moving at relativistic speeds.