Retrograde motion
a. is observable for planets located between Earth and the sun.
b. is observable for planets more distant from the Sun than is Earth.
c. is only observable for the moon.
d. is observable for all planets.
e. none of the above
B
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When they were first discovered, quasars appeared to be____
a. small, star-like objects associated with radio emission b. pairs of radio sources c. elliptical galaxies with an X-ray emitting halo d. clouds of gas glowing with green emission lines e. linear jets of matter
The reason the capacitance of a parallel plate capacitor having a dielectric between the plates changes is due to
A. The existence of more dense matter than air or vacuum that forms a barrier for electric field lines and reduces the electric field in the region B. The polarizability of the material, which sets up an electric field opposite to the applied field, thus reducing the electric field strength in the region C. The fact that dielectrics have excess charge that then “shields” the plates from each other, reducing the electric field in the region. D. None of these
Chinese astronomers observed supernovae, and called them _______________ stars
Fill in the blank(s) with correct word
Which of the following does N* represent in the Drake equation, Nc = N* × fp × nHZ × fL × fI × fs?
A) The average number of planets in a solar system B) The fraction of stars that have planets C) The number of stars in our galaxy D) The fraction of suitable planets on which life begins