Tom is going to your left at 90% of the speed of light and Joan is going to your right at 90% of the speed of light. What will Tom say about you and Joan?
A) You are moving away from him at 90% the speed of light. Joan is moving away from him at 180% of the speed of light.
B) You are moving away from him at 90% the speed of light. Joan is moving away from him at as speed that is faster than 90% of the speed of light, but slower than the whole speed of light.
C) You are moving away from him at 90% the speed of light. Joan is moving away from him at as speed of light.
D) You and Joan are both moving away from him at 90% the speed of light.
B
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One of the most fundamental discoveries about the universe has been that it is expanding. "The universe is expanding" means
A) the cosmological horizon is growing with time. B) galaxies are growing with time. C) distances between most galaxies are getting larger. D) our estimate for the size of the universe has increased over the last century.
Nineteenth-century scientists thought the "ether" to be
A) the cause of the gravitational force. B) the medium for the propagation of light waves. C) the medium for the propagation of sound waves. D) All of the above. E) None of the above.
Most of Earth's seismic activity, volcanism, and mountain building occur along
A) convergent boundaries. B) divergent boundaries. C) plate boundaries. D) transform fault boundaries.
What species absorbs photons in a protostar's outer layers?
A) H B) H2 C) H+ D) H- E) dust