Lunar month circular, the speed of Earth's progression around the Sun varies during the year. Thus, the angular rate is faster nearer periapsis and slower near apoapsis. The same is so for the Moon's orbit around the Earth. Because of these variations in angular rate, the actual time between lunations may vary from about 29.18 to about 29.93 days. The long-term average duration is days (29 d 12 h 44 min 2.8016 s). The synodic month is used to calculate eclipse cycles. It is customary to specify positions of celestial bodies with respect to the vernal equinox. Because of Earth's precession of
Thomas Fuller (mental calculator) skill was even used as proof that enslaved Blacks were equal to whites in intelligence, which fueled some pro-abolitionist discussion. When Fuller was about 70 years old, William Hartshorne and Samuel Coates of Pennsylvania were in Alexandria and, having heard of Fuller's powers, sent for him. They asked him two questions which satisfied their curiosity. First, when they asked him how many seconds there were in a year and a half, he answered in about two minutes, 47,304,000. Second, when they asked how many seconds a man has lived who is 70 years, 17 days and 12 hours old, he