If we say that a galaxy has a lookback time of 1 billion years, we mean that
A) its light traveled through space for 1 billion years to reach us.
B) is now 1 billion light-years away.
C) it was 1 billion light-years away when the light left the galaxy.
D) it is 400 million years old.
A
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A significant step in "unifying" the forces of nature was the discovery that two of the so-called fundamental forces were two parts of a single force. The two forces that were so unified were
A) the electromagnetic force and the weak force. B) the weak force and the strong nuclear force. C) the electromagnetic force and the strong nuclear force. D) the electromagnetic force and the gravity force.
A truck has four times the mass of a car and is moving with twice the speed of the car. If Kt and Kc refer to the kinetic energies of truck and car respectively, it is correct to say that
A) Kt = 16Kc. B) Kt = 4Kc. C) Kt = 2Kc. D) Kt = Kc. E) Kt = Kc.
For total internal reflection, light is ______________ and none is ______________
a. reflected, refracted b. refracted; transmitted c. transmitted, refracted d. transmitted; reflected
The process of making an uninhabitable planet like Mars habitable and suitable for humans is referred to as
A) bioforming B) bioadaptation C) terra-restructuring D) terraforming