Why is the eclipse year shorter than 365.25 days?
What will be an ideal response?
The Moon's orbit precesses, because of the gravitational pull of the Sun on the Moon, and the precession slowly changes the direction of the line of nodes. The line turns gradually westward, making one complete rotation in 18.61 years. As a result, the eclipse seasons occur about three weeks earlier each year.
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Which of the following statements is true of reflection nebulae?
A) They have a distinctive blue color. B) The gases in reflection nebulae are excited to emit photons. C) The spectrum of a reflection nebula is not the reflected absorption spectrum of starlight. D) They are produced when a hot star excites the gas to produce an emission spectrum.
A current-carrying loop of wire lies flat on a horizontal tabletop. When viewed from above, the current moves around the loop in a counterclockwise sense. For points on the tabletop inside the loop, the magnetic field lines caused by this current
A) circle the loop in a clockwise direction. B) circle the loop in a counterclockwise direction. C) point straight up. D) point straight down.
A right triangle has sides 10 m, 5 m, and 11 m. The smallest angle of this triangle is nearest
a. 32°. b. 27°. c. 22°. d. 63°. e. Not attainable since this is not a right triangle.
In a single-slit diffraction experiment, the width of the slit through which light passes is reduced. What happens to the width of the central bright fringe?
A) It becomes narrower. B) It stays the same. C) Its behavior depends on the wavelength of the light. D) It becomes wider.