How do we know the expansion of the universe is accelerating?
A) We're really not that sure the expansion is accelerating; it's all just a theory.
B) The rotation curves of galaxies indicate the universe is speeding up.
C) White dwarf supernova in distant galaxies are fainter than they would be if the expansion were not accelerating.
D) Redshifts of distant galaxies are increasing with time, so when we repeat the measurements, the redshifts are larger.
E) We see more of the universe every night, as the observable universe grows in size.
C
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In an isochoric process, the internal energy of a system decreases by 50J. What is the work done?
A. zero B. +50 J C. -50 J D. none of the above
The sound level at 1.0 m from a certain talking person talking is 60 dB. You are surrounded by five such people, all 1.0 m from you and all talking equally loud at the same time
The threshold of hearing is 1.0 × 10-12 W/m2. What sound level are you being exposed to? You can neglect any absorption, reflection, or interference of the sound. The threshold of hearing is 1.0 × 10-12 W/m2. A) 300 dB B) 60 dB C) 74 dB D) 67 dB E) 81 dB
The most striking valley in the solar system is:
A) the Grand Canyon in Arizona. B) Gwenivere on Venus. C) the Discovery Scarp of Mercury. D) Valles Marineris on Mars. E) Valhalla on Callisto.
A sub-surface region that holds and transmits water is called a/an
A) aquifer. B) hydrometer. C) water table. D) aquiclude.