The period-luminosity relation is critical in finding distances with:
A) RR Lyrae stars.
B) trigonometric parallaxes.
C) spectroscopic parallaxes.
D) Cepheid variables.
E) pulsars.
D
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The scarcity of what isotope is a critical test of the density of the present cosmos?
A) carbon 14 B) deuterium C) helium 3 D) helium 4 E) lithium 5
Consider two different isotopes of the same neutral element. Which statements about these isotopes are true? (There may be more than one correct choice.)
A) Both isotopes contain the same number of orbital electrons. B) The sum of the protons and neutrons is the same for both isotopes. C) Both isotopes contain the same number of protons. D) Both isotopes contain the same number of neutrons. E) Both isotopes contain the same number of nucleons.
Which will cool a drink faster?
A) ice cubes B) crushed ice C) no difference for the same mass of ice
If the composition of the atmosphere changed so that less terrestrial radiation was allowed to escape, the Earth would experience
A) higher average temperatures. B) lower average temperatures. C) greater atmospheric pressure and higher temperatures. D) no change in pressure or temperature.