When considering the number of technologically advanced civilizations in our Galaxy, it is useful to consider
a. the average life span of an alien.
b. the average life span of the civilization.
c. the distance to the civilization's planet.
d. the type of advanced communication they use.
B
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Which of the following features of a telescope determines its light-gathering power?
A) The magnifying power of the objective B) The diameter of the primary mirror C) The focal length of the eyepiece D) The length of the telescope tube
Each of the following is a prediction of the theory of relativity. Which one is crucial to understanding how the Sun provides light and heat to Earth?
A) If you observe someone moving by you, you'll see their time running slowly. B) Gravity is curvature of spacetime. C) E = mc2 D) Time runs slower on the surface of the Sun than on Earth. E) Space is different for different observers. Time is different for different observers. Spacetime is the same for everyone.
The standard unit of time in the mks system is the
a. meter b. kilogram c. second d. minute e. microsecond
A resistor is made out of a long wire having a length L. Each end of the wire is attached to a terminal of a battery providing a constant voltage V0. A current I flows through the wire
If the wire were cut in half, making two wires of length L/2, and both wires were attached to the battery (the end of both wires attached to one terminal, and the other ends attached to the other terminal), what would be the total current flowing through the two wires? A) 4I B) 2I C) I D) I/2 E) I/4