If you could watch a time-lapse movie of the interstellar medium over hundreds of millions of years, what would you see?
A) Gas that changes only in very slow and steady ways, so that the movie would in fact be quite boring.
B) The entire disk of the Milky Way would pulsate in and out as it contracts to form stars and then blows out in supernovae and then contracts to form stars again and so on.
C) The movie would alternate back and forth between being very bright when there is a lot of gas and very dark when there is very little gas.
D) Gas that is often moving at high speed, particularly after one or more supernovae, and constantly changing form between molecular clouds, atomic hydrogen, and hot, ionized bubbles and superbubbles.
D
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In South Africa, it's usually quite warm around the time of the Northern Hemisphere winter solstice and quite cool around the time of the summer solstice
Indicate whether the statement is true or false
Which of these problems arise partly from coal-fired power plants but not from nuclear power plants?
A) global warming B) acid rain C) Both of the above. D) nuclear weapons proliferation E) All of the above.
Which of the following ions is isoelectronic with a neon atom?
a. N3- b. Li+ c. Cl- d. F2-
The greenhouse effect is occurring because
a. the ozone layer is being depleted b. the amount of carbon dioxide in the atmosphere is increasing c. the ionosphere reflects low frequency radiation d. more ultraviolet radiation is penetrating the atmosphere e. none of the above