The Love number is a numeric ratio describing the flexibility,
with respect to tidal influences, of a celestial body. Essentially, it
says how solid a planet or moon is.
Love numbers are named after British physicist Augustus Love (1863-1940),
an expert on spherical dynamics.
The Love numbers of some well-known celestial bodies are:
This signifies that the Earth and Venus are considerably less "solid" than the Moon, which is believed to have a "squishy" molten core
under a stiff mantle
. In one month, tidal attraction from the Sun
deform the Moon by about 10 cm (4 inches). By contrast, the Earth moves by as much as 50 cm (20 inches) from the force of the Sun and Moon.