chapter 1 Flashcards
(27 cards)
retrograde motion
the backward (westward) loops
geocentric
the Earth lay at the center of the universe and all other bodies moved.
epicycle
first step toward this new model, each planet was taken to move uniformly around a small circle.
deferent
center moved uniformly around the earth on a second and larger circle.
ptolemaic model
a series of no fewer than 80 circles.
heliocentric
sun-centered model
retrograde motion
backward, westward loop traced out by a planet with respect to the fixed stars.
copernican revolution
the realization, toward the end of the 6th century, the earth is not at the center of the universe.
laws of planetary motion
three laws derived by Kepler describing the motion of the planets around the sun.
ellipse
geometric figure resembling an elongated circle.
focus
one of two special points within an ellipse, whose separation from each other indicates the eccentricity.
semimajor axis
one-half of the major axis of an ellipse.
eccentricity
a measure of the flatness of an ellipse, equal to the distance between the two foci divided by the length of the major axis.
perihelion
the closet approach to the sun of any object in orbit about it.
aphelion
the point of the elliptical path of an object in orbit about the sun that is most distant from the sun.
period
the time needed for orbiting the body to complete one revolution about another body.
astronomical unit
the average distance of earth from the sun.
radar
acronym for radio detection and ranging.
newtonian mechanics
the basic laws of motion postulated by newton, which are sufficient to explain and quantify virtually all of the complex dynamical behavior found on earth and elsewhere in the universe.
force
action on an object that causes its momentum to change.
inertia
the tendency of an object to continue moving at the same speed and in the same direction, unless acted upon by a force.
mass
a measure of the total amount of matter contained within an object.
accerleration
the rate of change of velocity of a moving object.
gravity
the attractive effect that any massive object has on all other massive objects. The greater the mass of the object, the stronger its gravitational pull.