Changes

A [[planet]]'s or [[star]]'s '''Roche limit''' is the smallest distance a satellite (which is held together only by gravitational forces) can approach it without being desintegrated disintegrated by tidal forces. Generally, there are two forms of the Roche limit: one for a solid satellite, an other, bigger one for a fluid satellite. According to the [[NASA]]/[[IPAC]] extragalactic database, ''for a satellite of negligible mass, zero tensile strength, and the same mean density as its primary, in a circular orbit around its primary, this critical distance is 2.44 times the radius of the primary. (For the Moon, whose density is lower than that of Earth, the Roche limit would be 2.9 Earth radii.)''<ref>[http://nedwww.ipac.caltech.edu/level5/Glossary/Glossary_R.html Caltech Astronomical Glossary]</ref> Thus the [[Moon]] couldn't circle the [[Earth]] in a distance less than 18,500km (11,500 miles).