Briefly explain why astronomers think that dark matter must be composed of Weakly Interacting Massive Particles (WIMPs) rather than difficult to see normal objects like planets, brown dwarfs, and the faintest low mass main sequence stars
What will be an ideal response?
Measurements of deuterium abundance indicate that the total amount of normal matter (which would include planets, brown dwarfs, and stars) cannot account for the total mass observed in galaxies. Observations of the mass distribution in colliding clusters shows that the dark matter passes right through the collision, while the normal matter gets caught up in the middle.
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If one-third of the members of a symphony orchestra are absent because of head colds, thus reducing the overall intensity of sound by 33%, what will be the reduction in the decibel level?
a. 15 dB b. 17 dB c. 11 dB d. 1.8 dB e. 4.1 dB
The figure shows two point sources of light, A and B. B emits light waves that are +? radians out of phase with the waves from A. A is 3? from P. B is 5? from P. (? is the wavelength.) The phase difference between waves arriving at P from A and B is
A. 0 rad. B. ? rad. C. 2? rad. D. 3? rad. E. 4? rad.
Plate tectonics differs from continental drift because it
A) provides a credible driving force. B) did not explain the fit between South America and Africa. C) showed that ancient ice sheets did not exist. D) showed that Pangaea broke up much later than predicted.
When using 529-nm light, how far is the adjustable mirror of a Michelson interferometer moved when 600 fringe shifts are counted? A fringe shift occurs when the intensity goes from bright to dark or when it goes from dark to bright
a. 1.58 × 10^-4 m c. 9.90 × 10^-6 m b. 7.94 × 10^-5 m d. 3.97 × 10^-5 m