When the distance between the planet and the satellite is close to a certain extent, the tidal action will disintegrate and disperse the celestial body itself. The distance limit of the disintegrated satellite was first obtained by French astronomer Roach, so it is called Roach limit. When the distance between the celestial body and the second celestial body is roche limit, the gravitational force of the celestial body itself is equal to the tidal force caused by the second celestial body. If their distance is less than that of roche limit, these celestial bodies will tend to split and become rings of the second celestial body. It was named after Edward Roach, the first person to calculate this limit.

According to roche limit's ultimate formula, the real roche limit of the earth and the moon and the calculated roche limit are 265,438+0: 65,438+0, which is 65,438+008,665,438+0728 with formula (3) and 65,438+008,6048 with formula (2).