March equinox equinox. This is most notable at the more extreme latitudes, where the Sun may be seen to travel sideways considerably during the dawn and evening, drawing out the transition from day to night. At the north and south poles, the Sun appears to move steadily around the horizon, and just above the horizon, neither rising nor setting apart from a slight change in declination of about 0.39° per day as the equinox passes. The Babylonian calendar began with the first full moon after the vernal equinox, the day after the Sumerian goddess Inanna's return from the underworld (later known as
Colonization of the Moon serve as a source of construction materials within cis-lunar space. Rockets launched from the Moon would require less locally produced propellant than rockets launched from Earth. Some proposals include using electric acceleration devices (mass drivers) to propel objects off the Moon without building rockets. Others have proposed momentum exchange tethers (see below). Furthermore, the Moon does have some gravity, which experience to date indicates may be vital for fetal development and long-term human health. Whether the Moon's gravity (roughly one sixth of Earth's) is adequate for this purpose, however, is uncertain. In addition, the Moon is the closest large body