Astronomers believe that dark matter exists because
A. the galaxies in clusters move slower than expected on the basis of the material visible in them.
B. it is the only way to explain the black holes in active galaxies.
C. the outer parts of galaxies rotate faster than expected on the basis of the material visible in them.
D. they can detect it with radio telescopes.
E. All of these choices are correct.
Answer: C
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A physics student has to make a choice in the color of paint to put on her geosynchronous communication satellite, MYSAT1. Considering most of its orbit is in sunlight, the decision of a light versus dark color paint will depend on which concept below?
A. A light paint would be better in the sunlight and in Earth's shadow for preventing overheating B. A dark paint would overheat the satellite when it passes through Earth's shadow but not in sunlight C. A light paint would be better for keeping the satellite cool in sunlight D. A dark paint would be better for keeping the satellite cool in sunlight
The observational evidence in favor of the existence of dark energy involves using ________ to calculate ________.
A. the method of standard candles; the distance to distant galaxies B. the method of inflation; the distance to distant galaxies C. Hubble's law; the distance to distant galaxies D. Hubble's law; the age of the Universe
Which of the following are electrically neutral?
A) protons B) neutrons C) electrons D) ions E) none of the above
Suppose you lived on the Moon near the center of the face that we see from Earth. At what phase of the Moon would you see sunrise? What phase of Earth would you see at this time?
What will be an ideal response?