Why Is Gravity Infinite at a Black Hole's Center but Zero at Earth's Center?

[Sasikanth9]

Gravity is zero at the center of the earth. how come the same set of equations predict the gravity to be infinity at the center of a black hole? where does the singularity really come into picture? how is a black holes center different from Earth's center?

 

[Sasikanth9]

http://hubblesite.org/reference_desk/faq/answer.php.id=56&cat=exotic

Should have done more research before posting . Anyways somebody else might find this useful.