"Most ancient cultures were familiar with the twilight wanderers and guardian of the Sun. Because Mercury is closest planet to the Sun, its hurried orbit takes just 88 Earth days, and switches its appearance from east (morning twilight) to west (evening twilight) in the sky with a slightly variable period of about three months. Mercury also has an orbital plane that is tilted with respect to that of the Earth, so it also bobs up and down in the sky relative to the plane of the Earth and the Sun. Thus, it is sometimes lower than the Sun in declination and at other times it is higher. These two striking orbital peculiarities further contribute to Mercury's elusiveness....By far Mercury has been, most familiar to people living in equatorial and tropical latitudes, especially those with dry climates an clear skies."