How is the "Fermi Paradox" normally stated?
A) Why are we here?
B) Who are we?
C) Where are we?
D) Where is everybody?
D
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The decay of a sample of radioactive atoms is studied by observers moving in different ways. One moves at 0.8c, another at 0.5c, another at 0.25c, and one at speed zero with respect to the sample. The one with a speed of ________ will measure the shortest half-life.
Fill in the blank(s) with the appropriate word(s).
The universe first became transparent to most light, coinciding with the origin of the cosmic background radiation, when the universe cooled enough to allow the formation of
A) atomic nuclei. B) stars and galaxies. C) neutral atoms. D) protons and neutrons. A) 8.7 keV B) 7.8 keV C) 7.8 MeV D) 3.7 MeV E) 8.7 MeV
Two masses m1 and m2, with m1 = 3 m2, undergo a head-on elastic collision. If the particles were approaching with speed v before the collision, with what speed are they moving apart after collision?
a. 3 v b. v/3 c. 3v/4 d. v
Imagine for a moment that despite all the evidence, Earth actually is not rotating and orbiting the Sun. Which of these hypothetical observations (none of them are real) would be inconsistent with our Sun-centered view of the solar system?
A) We find that we are unable to measure any parallax for a distant galaxy. B) We discover an Earth-sized planet orbiting the Sun beyond the orbit of Pluto. C) We discover that the universe is actually contracting, not expanding. D) We discover a small planet beyond Saturn that rises in the west and sets in the east each day.