Question

How has gravitional force occurred in earth? It's towards the earth ....

Answer 1

Gravity is what holds the planets in orbit around the sun and what keeps the moon in orbit around Earth. The gravitational pull of the moon pulls the seas towards it, causing the ocean tides. ... Gravity not only pulls on mass but also on light. Albert Einstein discovered this principle. 
Imagine Earth without Gravity.
We will keep falling down.