21-cm radio waves are emitted by all molecular hydrogen
Indicate whether the statement is true or false
FALSE
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Charge of uniform density (80 nC/m3) is distributed throughout a hollow cylindrical region formed by two coaxial cylindrical surfaces of radii 1.0 mm and 3.0 mm. Determine the magnitude of the electric field at a point which is 2.0 mm from the symmetry axis
a. 7.9 N/C b. 9.0 N/C c. 5.9 N/C d. 6.8 N/C e. 18 N/C
You are in a hot, dense place. You are surrounded by nuclear reactions that are rapidly fusing hydrogen into helium. You notice that your surroundings are cooling and rapidly dropping in density. Within about 5 minutes, the fusion reactions stop
Where are you? A) You are in the center of a massive star near the end of its life. B) You are inside a nuclear power plant on Earth. C) You are in the early universe during the era of nucleosynthesis. D) You are in the center of a star very much like our Sun. E) You are in the center of a star much smaller than the Sun.
Trace fossils are
a. tracks only. b. borings only. c. burrows only. d. all of the above.
What makes white-dwarf supernovae very good standard candles for distance measurements?
A) They are very bright, so they can be used to determine the distances to galaxies billions of light-years away. B) They should all have approximately the same luminosity. C) They occur so frequently that we can use them to measure the distances to virtually all galaxies. D) We have had several occur close to us in the Milky Way, so we have been able to determine their luminosities very accurately. E) both A and B