Which of the following would NOT cause the gravitational force on an object near Earth's surface to increase?
A. an ore deposit just under the surface
B. a lower elevation
C. an increase in its mass
D. a horizontal velocity
Ans: D. a horizontal velocity
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How does the idea of inflation account for the existence of the "seeds" of density from which galaxies and other large structures formed?
A) Inflation predicts that gravity would have been very strong and thereby would have concentrated mass into seeds. B) Inflation would have caused random, microscopic quantum fluctuations to grow so large in size that they became the seeds of structure. C) Inflation predicts that temperatures and densities should have become nearly equal throughout the universe. D) Inflation tells us that the universe should have a "flat" overall geometry, and this led to the flat disks of galaxies.
Why do O stars exhibit weak hydrogen absorption lines?
A) At these high temperatures, nearly all the hydrogen is ionized, and is therefore unable to interact with light. B) O stars are too cool to excite hydrogen atoms to the first energy level from which they can then absorb visible wavelengths of light. C) O stars contain very little hydrogen.
X-ray bursters are caused by black holes
a. True b. False Indicate whether the statement is true or false
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks to gravitational contraction. What was the major drawback of this idea?
A) It predicted that the Sun could last only about 25 million years, which is far less than the age of Earth. B) It predicted that the Sun would shrink noticeably as we watched it, and the Sun appears to be stable in size. C) It is physically impossible to generate heat simply by making a star shrink in size. D) It predicted that Earth would also shrink, which would make it impossible to have stable geology on our planet. E) It was proposed before Einstein's theory of general relativity and was therefore incorrect.