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17 Cards in this Set

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archaeostronomy
the study of the astronomy of ancient cultures
uniform circular motion
the classical belief that the perfect heavens could move only by the combination of constant motion along circular orbits
geocentric universe
a model universe with Earth at the center, such as the Ptolemaic universe
eccentric
in astronomy, an off-center circular path
heliocentric universe
a model of the universe with the sun at the center, such as the Copernican universe
parallax
the apparent change in the position of an object due to a change in the location of the observer. Astronomical ____ is measured in seconds of arc.
retrograde motion
the apparent backward (westward) motion of planets as seen against the background of stars
epicycle
the small circle followed by a planet in the Ptolemaic theory. The center of the epicycle follows a larger circle (deferent) around Earth
deferent
In the Ptolemaic theory, the large circle around Earth along which the center of the epicycle moved
equant
the point off-center in the deferent from which the center of the epicycle appears to move uniformly
paradigm
a commonly accepted set of scientific ideas and assumptions
ellipse
a closed curve enclosing two points (foci) such that the total distance from one focus to any point on the curve back to the other focus equals a constant
semimajor axis
(a) Half of the longest axis of an ellipse
eccentricity
(e) A measure of the flattening of an ellipse. An ellipse of e=0 is circular. The closer to l e becomes, the more flattened the ellipse
hypothesis
a conjecture, subject to further tests, that accounts for a set of facts
theory
a system of assumptions and principles applicable to a wide range of phenomena that have been repeatedly verified
natural law
A conjecture about how nature works in which scientists have overwhelming confidence