On a dark summer night in the northern hemisphere, we can see the Milky Way, but we can't see the center of the Milky Way. Why not?
A) Interstellar dust and gas absorb and scatter visible light.
B) We are in the center of the Milky Way.
C) There are no stars in the center of the Milky Way, just a supermassive black hole.
D) The center of the Milky Way does not emit enough visible light.
A
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The dust in the interstellar medium can make distant stars look redder than they really are
Indicate whether the statement is true or false
Selena states that 
proves that entropy has a definite value at the beginning and end of an adiabatic free expansion. Ron says 
, where W is the number of microstates of a given macrostate. Which one, if either, is correct?
A.
B.
C.
in an adiabatic free expansion.D.
E.
Might a region of intergalactic [between the galaxies] space, containing no material particles, contain energy?
A) No, because only material particles can possess energy. B) No, because physically nothing exists except particles and empty space. C) No, for both of the above reasons. D) Yes, it might contain the thermal energy of intergalactic gases. E) Yes, in the form of electromagnetic fields and other force fields.
Length Contraction: Observer A sees a ruler moving by in a relativistic rocket and measures its length to be LA. Observer B moves along with the rocket and measures the length of the ruler to be LB. What is true about these two length measurements?
A. LA > LB B. LA = LB C. LA < LB D. LA could be greater or smaller than LB depending on the direction of the motion.