The Moon’s distance from Earth changes depending on where it is in its elliptical orbit.
“The commonly cited average distance of 384,400 kilometers is a good approximation,” said Craig Hardgrove, associate professor of Earth and space exploration at Arizona State University and principal investigator of LunaH-Map, a remote mission designed to detect ice deposits on the Moon.
“However, it is elliptical, so its distance from Earth varies,” Hardgrove told Live Science in an email.
“This distance varies from about 356,470 km at its closest point to Earth, called perigee, to 405,600 km at its furthest point, called apogee,” Hardgrove said.
The distance at apogee is so great that the other seven planets in the Solar System could fit between the Earth and the Moon, astronomer Phil Plait wrote for Slate.
The variation of 50 000 km
This thought experiment works if you add up the average diameters of the planets, which are equal to 380,016 km.
“We can thank the Apollo astronauts for the accuracy of these measurements,” Hardgrove said.
Using reflectors left on the lunar surface in the 1960s and 1970s, scientists today can point high-powered lasers at the moon and measure their reflection speed to determine
In fact, the Moon shines 30 percent brighter — and appears 14 percent larger in diameter — during perigee than when it’s apogee, Hardgrove noted.
The distance of the Moon from the Earth varies
“These changes are sometimes called a supermoon when and a micromoon when it’s at its furthest,” he said. Although both the Moon’s distance and its phases follow the same lunar cycle of about 27 days, they are not directly related.
In most cases, the average distance between the Earth and the Moon is accurate enough. However, some cases – such as planning an orbiting or satellite mission – require a more precise measurement, he writes.
Fortunately for researchers on the Moon, these considerations are much less daunting than for missions to Mars, which has a distance variation of 56 million km compared to the Moon’s roughly 50,000 km.
