“A significant part of the problem was the weird nature of the Moon’s mass that was not at all what was expected. Instead of a generally constant gravitational field such as the Earth exhibits across its surface, the Moon is an inconsistent, lumpy ball that has huge variations in gravity from region to region.”

“A significant part of the problem was the weird nature of the Moon’s mass that was not at all what was expected. Instead of a generally constant gravitational field such as the Earth exhibits across its surface, the Moon is an inconsistent, lumpy ball that has huge variations in gravity from region to region.”

— Christopher Knight