In the Ptolemaic model, retrograde motion is due to
A) relative motion between the Earth and another planet in its orbit
B) the Earth reversing the direction of its orbit about the Sun
C) a planet moving backwards in its smaller circular circle, the center of which moves in a larger circular orbit around the Earth
D) a planet reversing the direction of its orbit about the Sun
C
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At t = 0, a particle leaves the origin with a velocity of 5.0 m/s in the positive y direction. Its acceleration is given by 
m/s2. At the instant the particle reaches its maximum y coordinate how far is the particle from the origin?
A. 11 m B. 16 m C. 22 m D. 29 m E. 19 m
The more massive a main-sequence star, the more ___________ it is, as found by the M-L relation
Fill in the blank(s) with correct word
How many seconds are in one year? (Calculate this, do not look it up.)
A) about 86 thousand (86,000, or 8.6 × 105 ) B) about 380 million (380,000,000, or 3.8 × 108 ) C) about 30 million (30,000,000, or 3 × 107 ) D) about 3,600 (3.6 × 103 )
If the star Alpha Centauri, 4.3 light years distant from the Earth, were to explode this instant, we would not be aware of this event until 4.3 years from now.
a. true b. false