About what percentage of the original hydrogen and helium of the universe had been converted into heavier elements by the time our solar system was born?
A) 20%
B) 10%
C) 50%
D) 2%
D) 2%
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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.
Less formally defined groupings of stars are called __________________
Fill in the blank(s) with correct word
Electricity and magnetism connect to form
A. mass B. light C. ultra high-frequency sound D. energy
Compared with the spectral lines in the solar spectrum, lines in a supergiant star's spectrum are
a. more narrow. b. broader. c. weaker. d. stronger. e. broader and weaker.