A gravity well is the dip in space around a heavy body that is hard to climb out of. Out of the gravity well, deep in the gravity well, Earth's gravity well.
It explains why launching anything is so expensive, since almost all the fuel goes on climbing out of the well rather than on travelling. The Moon's is shallow, which is why leaving it is easy.
1noungravity wellThe dip in space around a heavy body that is hard to climb out of.
“The probe swung through Jupiter's gravity well to gain speed for its long trip.”
gravity well is a field.
Gravity plus well, from the image of a curved surface dipping around a mass.
From gravity + well,
Etymology from Wiktionary, CC BY-SA
Practised in Science & Space