Which of the following is NOT a possible explanation for dark energy?
A: quintessence, a fifth substance to the universe that varies in time.
B: cosmological constant.
C: gravity leaking out to dimensions besides the three spatial dimensions.
D: the speed of light changing dramatically with time.
E: all of the above.
Ans: D: the speed of light changing dramatically with time.
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Why was the Davis experiment only able to detect one-third of the neutrinos originally predicted? a. The number of neutrinos was too great to be held in the tank that Davis designed
b. The neutrinos combined with other particles as they entered Earth's atmosphere. c. The neutrinos distributed evenly among three different flavors while traveling to Earth. d. Most of the neutrinos were absorbed by Earth's atmosphere. e. The other two-thirds of neutrinos dissipated while traveling to Earth.
Magnetic Field of a Long Wire: The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 ?T. What is the magnetic field at a distance of 4 cm from this wire?
A. 2 ?T B. 4 ?T C. 6 ?T D. 8 ?T E. 10 ?T
The pattern of rising hot gas cells all over the photosphere is called:
A) filaments. B) granulation. C) sunspots. D) convective projections. E) prominences.
When a hydrogen electron is in its first excited state, its principal quantum number is
a. zero. b. 2. c. –13.60 eV. d. 1.