Suppose a scientist holds a press conference at which he claims that 10% of the matter in the Milky Way is in the form of dust grains. Does his claim seem reasonable? Why or why not?
A) It is reasonable because we already know that interstellar dust obscures our view through the disk of the galaxy.
B) The 10% figure is too high because there are not enough heavy elements to make that much dust.
C) It seems reasonable as long as we assume that red giant stars—which produce dust grains in their stellar winds—are more common than we thought.
D) The 10% figure is too low because most of the mass of the galaxy is in the form of interstellar dust.
B
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A parachutist jumps out of an airplane and accelerates with gravity to a maximum velocity of 58.8 m/s in 6.00 seconds. She then pulls the parachute cord and after a 4.00-second constant deceleration, descends at 10.0 m/s for 80.0 seconds, reaching the ground. From what height did the parachutist jump?
a. 914 m c. 1520 m b. 1110 m d. 1750 m
Stars of low luminosity will always have large positive absolute magnitude
a. True b. False Indicate whether the statement is true or false
The sedimentary rock known as ______________ consists of rounded pebbles cemented together by silica, calcium carbonate, or iron oxide
a. conglomerate b. breccia c. limestone d. shale
How long, approximately, do geologists estimate it takes for the entire seafloor to be replaced due to plate tectonics?
A) 2 million years B) 20 million years C) 200 million years D) 2 billion years E) longer than the age of the solar system