Which of the following may explain the failure to observe Population III stars?
A. Population III stars had their surfaces contaminated by remnants of massive stars.
B. We do not expect to observe Population III stars, because pure hydrogen and helium stars never formed.
C. The first stars to be formed in the young Milky Way are too far away to be detected.
D. None of these choices is correct.
Answer: A
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An astronaut floating in the International Space Station catches a Frisbee thrown directly toward his or her center of mass. Does the astronaut + Frisbee’s change in thermal energy ?Uth depend on whether the Frisbee is spinning or not, and if so, which case makes it larger?
A. ?Uth is greater if the Frisbee is spinning. B. ?Uth is the same in both cases. C. ?Uth is greater if the Frisbee is not spinning. D. One needs more information to tell.
During a total lunar eclipse, which of the following are true? I. The photosphere of the sun is obscured by the moon. II. The moon is in Earth's umbra. III. The moon is new. IV. The moon is full
a. I, III b. II, IV c. I, II, III d. II, III e. I, II, III, IV
A circular space station (shaped like a big wheel) rotates to produce “artificial gravity”. The apparent weight of an astronaut standing on the inside surface of the outer wall is equal to her weight on earth. The inside surface of the outer wall of the space station is 285m from the axis of rotation. What is the period of rotation of the station?
A. 92 s B. 34 s C. 213 s D. 183 s
One piece of evidence for the waviness of matter is
A) the tiny individual impacts that show up in the double-slit experiment with electrons. B) the random motion of electrons that is observed with powerful microscopes. C) the interference pattern that shows up in the double-slit experiment with light. D) the interference pattern that shows up in the double-slit experiment with electrons. E) the uncertainty that is evident in the outcome of the double-slit experiment with electrons.