How do we know that galaxy clusters contain a lot of mass in the form of hot gas that fills spaces between individual galaxies?
A) The hot gas shows up as bright pink in visible-light photos of galaxy clusters.
B) We infer its existence by observing its gravitational effects on the galaxy motions.
C) We detect this gas with X-ray telescopes.
D) We can observe the frictional effects of the hot gas in slowing the speeds of galaxies in the clusters.
C
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The type of EM waves used in radar is __________
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A wave generated in a medium is a longitudinal wave when
a. there is a net transport of matter by the wave. b. the molecules of the medium are unable to exert forces on each other. c. molecular displacements are parallel to the wave velocity. d. molecular displacements are perpendicular to the wave velocity. e. the density of the medium is less than the density of water.
Tables based on a heliocentric model of the universe which used elliptical orbits for the planets were more accurate than ____________________
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A proton with mass 1.67 × 10^-27 kg moves in an accelerator with a speed of 0.600c. What is its total energy? (c = 3.00 × 10^8 m/s)
a. 3.26 × 10^-10 J c. 0.540 × 10^-10 J b. 1.88 × 10^-10 J d. 2.51 × 10^-10 J