The astronomical unit (AU) is defined to be equal to the
A) average distance between the Earth and Sun
B) average distance between the Sun and the planet Pluto
C) distance between the Sun and the nearest star
D) diameter of the Earth
Question 2
Which of the following best explains why a solar day is longer than a sidereal day?
A) Because Earth orbits the Sun at the same time it rotates, Earth must make slightly more than one full rotation between noon one day and noon the next.
B) The precession of Earth's axis gradually changes the length of the solar day while leaving the length of the sidereal day alone.
C) The fact that Earth's orbit is not a perfect circle causes the length of the solar day to vary during the year, so that it the solar day is sometimes longer and sometimes shorter than a sidereal day.
D) The Sun rotates much as the Earth does, but more slowly, so that a solar day is longer than a sidereal day.
Major moons of Uranus in order of increasing distance (left to right), at their proper relative size
A Piece of Mars on Earth
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Earth’s orientation
Precession: Earth’s axis rotates, or “wobbles”
Planet Earth compared to all its water and air!