S&P 500 Index vs True and Mean Lunar Orbital Velocity | February 2018

The Moon moves around the Earth in 27.32166 days or one sidereal period of revolution. As it does this its position changes, relative to the stars. Since there are 360 degrees in a circle, the Moon moves on the average 360 degrees / 27.32166 days = 13.17636 degrees of geocentric longitude per day to the east and relative to the stars (Mean Orbital Speed = red dotted line in the chart). However, this is the Moon’s theoretical mean orbital speed, met only twice for seconds per lunar month. Since the orbit of the Moon is distinctly elliptical it causes variations in the angular speed (True Orbital Speed) as it moves towards and away from the Earth: when closest to the Earth (perigee), the Moon moves faster (up to 16.72 degrees/day), while when furthest (apogee), slower (down to 10.43 degrees/day).