Gravitation

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Gravitation

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a natural phenomenon by which all objects with mass attract each other.

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Tides

Back 2

the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans.

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Center of mass

Back 3

a specific point at which, for many purposes, the system's mass behaves as if it were concentrated.

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Gravitational field

Back 4

a vector field pointing directly towards the particle giving the magnitude of the force per unit mass for the array of points in space.

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Orbit

Back 5

the path that an object makes around another object while under the influence of a centripetal force such as gravity.

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Escape Velocity

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the speed where the kinetic energy of an object is equal in magnitude to its potential energy in a gravitational field.

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General relativity

Back 7

the geometrical theory of gravitation published by Albert Einstein in 1915-16 unifying special relativity and Newton's law of universal gravitation.

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Standard gravity

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the nominal acceleration due to gravity at the Earth's surface at sea level.

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Gravitational binding energy

Back 9

the amount of energy required to pull all of the material apart in an object of loose material held together by gravity alone, to infinity.

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Inverse square law

Back 10

any physical law stating that some physical quantity or strength decreases proportional to the square of the distance from the source of that physical quantity.

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Cavendish experiment

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performed in 1797 - 1798, was the first experiment to measure the force of gravity between laboratory masses.

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Orbital period

Back 12

the time it takes a planet (or another object) to make one full orbit.

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Geosynchronous satellite

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a satellite whose orbital track on the Earth repeats regularly over points on the Earth over time.

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Geosynchronous orbit

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an orbit around the Earth with an orbital period matching the Earth's sidereal rotation period.

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Geostationary orbit

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a geosynchronous orbit directly above the Earth's equator, with orbital eccentricity of zero. From the ground, such an object appears motionless in the sky.

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Circular orbit

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an elliptic orbit with the eccentricity equal to zero.

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Ellipse

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the locus of points on a plane where the sum of the distances from any point on the curve to two fixed points is constant.

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Astronomical unit (AU)

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a unit of length nearly equal to the semi-major axis of Earth's orbit around the Sun.

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Perigee

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the point at which an object in orbit around the Earth makes its closest approach to the Earth.

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Aphelion

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point of orbit at the greatest distance from the center

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Perihelion

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closest approach to center in orbit