How should we expect the Milky Way's interstellar medium to be different in 50 billion years than it is today?
A) The total amount of gas will be about the same, but the percentage of elements heavier than hydrogen and helium will have risen from the current 2% to more than 50%.
B) The total amount of gas will be much greater, since many stars will undergo supernovae between now and then.
C) The total amount of gas will be much less than it is today.
D) Thanks to the recycling of the star-gas-star cycle, the interstellar medium should look about the same in 50 billion years as it does today.
C
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The hot spots in a double-lobed radio source
a. appear to coincide with the location of the central galaxy responsible for the jets. b. are where hot excited gas interacts with the intergalactic medium. c. are only found near quasars. d. produce enough visible energy to be imaged at visible wavelengths. e. are always perpendicular to each other.
Large meteoroids are thought to collide with Earth:
A) at least once a decade. B) about once a century. C) a few times in every million-year period. D) once every billion years. E) never; only comets are thought to collide with Earth.
To keep chickens in a chicken coop warm, the kind of lamp to use is
A) fluorescent. B) CFL. C) incandescent. D) LED. E) all about the same
An 800-N woman stands at rest on two bathroom scales so that one scale shows a reading of 500 N. The reading on the other scale is
A) 200 N. B) 300 N. C) 400 N. D) 800 N. E) none of the above