Question 1
A sidereal day is defined as ________.
◦ the time between periods when the Sun is at the exact same height in the sky, for example, noon
◦ 24 hours at Greenwich, England
◦ 24 hours in a day
◦ the time for one complete revolution of the earth relative to the celestial reference
Question 2
Axial precession is sometimes called the precession of equinoxes because it results in a gradual shift, relative to the celestial background, of the position where the Sun crosses the celestial equator at the equinox. Astrology is a mythology based on things like your "sign" which refers to the position of the Sun in the celestial zodiac (the 12 constellations along the ecliptic) on your birthday. This system was established almost two thousand years ago. If this mythology were true (and you believe your horoscope) can you use the dates for your "sign" based on this 2000 year old system?
◦ No, although the precession shifts the equinox position, the other zodiac positions do not change because they are fixed to the celestial sphere.
◦ No, because 2000 years is almost 1/12, or one full sign shift, in the zodiac, so the 2000 year old signs are off by almost one full sign.
◦ Yes, the dates are fixed; your sign is your sign.
◦ Yes, any changes are insignificant in 2000 years.
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