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 then we can only 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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Which contracts more when the temperature is decreased? Equal volumes of
A) iron. B) wood. C) water. D) helium. E) all contract the same
A wave barrier is produced in water when the speed of an object
A) matches the speed of waves in water. B) exceeds the speed of waves in water. C) is less than the speed of waves in water. D) none of the above
The speed of electromagnetic waves in air is 3.0 × 108 m/s. What is the wavelength of FM radio waves having a frequency of 3.0 × 108 Hz?
A. 3.0 m B. 0.333 m C. 10 m D. 1.0 m E. 6.0 m
Which of the patterns shown below would appear on a screen when monochromatic light first passes through a narrow slit for which a = ? and then strikes the screen? Note that the darkest area in each illustration represents the brightest area on the screen.
A.
B.
C.
D.
E.
