Relativity

Time dilation

A difference of elapsed time between two events as measured by observers either moving relative to each other or differently situated from a gravitational mass.

Frame of reference

A system of geometric axes in relation to which measurements of size, position, or motion can be made. May be thought of as an observer's "point of view"

Mass Energy Equivalence

Described by the famous equation E=mc2, states that matter is equal to concentrated energy.

Speed of light

Equal to 3 x 108 m/s; often called the "speed limit of our Universe".

Universal Gravitation

Newton's Law of Universal Gravitation states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Classical relativity

Originally described by Galileo, refined by Newton, states that the constant motion of an object depends on the inertial frame of reference of the observer.

Joule(J)

SI unit for all types of energy and work

Newton (N)

SI unit for all types of force

Meter (m)

SI unit for length, distance and displacement

Kilogram (kg)

SI unit for mass and inertia

Meters per second (m/s)

SI unit for speed and velocity

Second (s)

SI unit for time

Kinetic energy

The form of mechanical energy possessed by objects in motion.

Length contraction

The physical phenomenon of a decrease in length detected by an observer of objects that travel at any non-zero velocity relative to that observer.

Speed

The rate at which an object moves through 3D space; calculated by dividing distance over time

Force of gravity

The weakest of the fundamental forces of our Universe; commonly called "weight" on the surface of a planet.

Special relativity

Theory of space and time developed by Albert Einstein, states that the speed of light is observed to be the same in all reference frames.

Albert Einstein

physicist, born in Germany, who was possibly the greatest scientist of the 20th century. In 1905 he published his theory of relativity. This led to the equation giving the relationship between mass and energy, E=mc2.

General relativity

the modern theory of gravitation, proposed in 1915, states that all observers, regardless of their state of motion, will see the same laws of physics operating in the universe.