What is Olbers' paradox, and what is its resolution?
What will be an ideal response?
If the universe were infinite and unchanging, the night sky should be as bright as the Sun because every line of sight should eventually end up looking at the surface of a star somewhere, and the total of all this light would make for a uniformly bright sky. Yet clearly it becomes dark when the Sun sets and that is the paradox. The resolution to this is for the universe to be either finite or changing. In particular, if the universe had a beginning, we would only be able to see a finite number of stars—those that lie within our cosmological horizon—and thus we can have a dark night sky.
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Two metal spheres on insulating stands have the same positive charge Q. If we reduce the distance between the spheres’ centers by a factor of two, the magnitude of the repulsive force between the spheres increases by
A. a bit less than a factor of two. B. exactly a factor of two. C. a bit more than a factor of two. D. a bit less than a factor of four. E. exactly a factor of four. F. a bit more than a factor of four.
The ordering of rocks in sequence by their comparative ages is called
A) faunal succession. B) original horizontality. C) relative dating. D) uniformitarianism.
A proton and electron are separated by 3.5 nm
(a) What is the magnitude of the force on the electron? (b) What is the magnitude of the force on the proton? (c) What is the electric field of the proton at the electron position?
What happens to a given volume of water when heated from 0°C to 4°C?
a. density increases c. density remains constant b. density decreases d. vaporizes