Has Polaris always been a good "North Star"? Why or why not?
A) yes, because stars stay fixed on the celestial sphere
B) no, because it is a young star which formed only a few hundred years ago
C) no, because Earth's axis slowly changes the direction it points
D) no, because ancient people did not know how to describe directions on Earth
C) no, because Earth's axis slowly changes the direction it points
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2.36 × 108 is equal to _____
A) 23,600,000 B) 236,000,000 C) 2,360,000,000 D) 23,600,000,000
Radioactive Decay: The half-life of radon-222 is 3.83 d. If a sample of radon initially contains 6.00 × 108 radon atoms, how many of them are left after 10.0 d?
A. 9.82 × 107 B. 7.67 × 107 C. 8.34 × 108 D. 7.29 × 108 E. 8.56 × 108
Compared to the buoyant force of the atmosphere on a 1-kilogram iron block, the buoyant force on a nearby 1-kilogram helium-filled balloon is
A) considerably less. B) considerably more. C) the same.
According to the HST data, very distant (and early) galaxies tend to be:
A) larger and bluer that modern galaxies. B) nothing but quasars. C) smaller, bluer, and more irregular than modern ones. D) redder, due to the recession of the universe. E) very well formed into clusters of nothing but spirals.