Glossary This is a list of important terms found throughout the site and their definitions. You may click on a letter bellow to skip to the first word of that letter. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z acceleration: a measure of how fast an object's velocity is changing (see What is Gravity? Page 6, Small Scale Effects Page 5) black hole: a collapsed star with infinite density which can't be seen by outside observers because light is trapped by a strong gravitational field (see Large Scale Effects Page 9) cavorite: an imaginary substance which can repel or shield against the force of gravity center of mass: the balance point between two masses. For example, on a teeter-totter the center of mass is in the middle (see Large Scale Effects Page 5) centrifugal force: the 'imaginary' force that seems to pull an object outward as it moves in a circle (see Gravity and Us Page 4) Coriolis effect: In a rotating environment, objects move faster the further away they are from the axis of rotations (ie. they move in a bigger circle). When these objects move towards or away from the axis, they will seemingly be pushed to the side due to the difference in speed between it's original position and it's new position. It is a fictitious sideways force (see Gravity and Us Page 5). Einstein's principle of equivalence: states that bodies fall with the same acceleration and that gravity is basically the same as acceleration (see What is Gravity Page 6) energy: the ability to do work (see Small Scale Effect Page 8, Large Scale Effects Page 11) escape velocity: the speed needed to escape the pull of a planet's gravity (see Small Scale Effects Page 9, Large Scale Effects Page 9) event horizon: the region a certain distance from the center of a black hole where any light ray emitted inside it can't escape because of the strength of the gravitational field (see Large Scale Effects Page 9) force: a force is any push or pull exerted on an object (see What is Gravity Page 2, 3) general relativity: a theory put forth by Albert Einstein which deals with the curvature of space-time in order to explain gravity (see What is Gravity Page 5, 6, 7, History Page 7, Small Scale Effects Page 11, Large Scale Effects Page 8, 9, 10) geocentric universe: the early belief that the Earth was the center of the universe, and that the Sun and all the other planets rotated around the Earth (see History Page 3) gravity: a force of attraction between all matter (see What is Gravity? Page 2, the entire web site) gravitational perturbation: the wobble in a heavenly bodies' orbit due to the presence of a massive object exerting a gravitational field (see Large Scale Effects Page 7) gravitational lens: background object which appears as a multiple object due to bending of light in a gravitational field (see Large Scale Effect Page 8) gravity gradient: present when the pull of gravity at one point is different than the pull at another point (see Gravity and Us Page 5) heliocentric universe: the current belief of our universe, in which the Sun is the center of the solar system, and the Earth rotates around the Sun, along with all the other planets (see History Page 5) inversely proportional: Inversely proportional means that something is the direct opposite of another thing. For example, as the distance increases, the force of gravity decreases (see What is Gravity Page 4). Kepler's first law of planetary motion: the orbits of the planets are ellipses, with the Sun at one focus of the ellipse (see History Page 5, Large Scale Effects Page 6) Kepler's second law of planetary motion: in a planet’s orbit, the imaginary line between the planet and the Sun sweeps out equal areas in equal times (see History Page 5, Large Scale Effects Page 6) Kepler's third law of planetary motion: the ratio of the cube of the distance of a planet from the Sun and the square of the orbital period is the same for all of the planets (see History Page 5, Large Scale Effects Page 6) kinetic energy: energy of motion (see Small Scale Effects Page 8) mass: the amount of matter an object contains (see What is Gravity? Page 4, Small Scale Effects Page 3, Large Scale Effects Page 9) matter: anything which has mass and occupies space (any physical substance) (see What is Gravity? Page 2, Large Scale Effects Page 11) micro gravity: when there is very little or no gravity, such as in a spaceship orbiting Earth (see Gravity and Us Page 2) Newton's universal law of gravitation: every object in the universe attracts every other object with a force proportional to the product of their masses and inversely proportional to the square of the distance between the two objects’ centers (see What is Gravity? Page 4, History Page 6, Large Scale Effects Page 3) orbit: the path in space described by a satellite rotating around a larger body, where the motion of the orbiting body is dominated by their mutual gravitational attraction (see Large Scale Effects Page 4, 5, 6, 7) potential energy: stored energy (see Small Scale Effects Page 8) satellite: any object the orbits or revolves around another object (see Large Scale Effects Page 4, 5) tidal effect: the effect experienced when one portion of an object experiences a stronger pull of gravity than another portion (see Small Scale Effects Page 10) weight: a measure of the strength of gravity’s pull on an object (see Small Scale Effects Page 3) A B C D E F G H I J K L M N O P Q R S T U V W X Y Z