THE THEORY OF GENERAL RELATIVITY states that the gravitation is due to the fact that the heavenly bodies create a sort of dent in the spacetime fabric. Now, WHAT IS THE REASON THAT THE HEAVENLY BODIES CREATE SUCH KIND OF A DENT? Let us for example take an elastic sheet and place metal ball on it. The ball will make a depression in the elastic sheet. But, the ball creates that dent because something (i.e. the gravity of the earth) is pulling it and forcing it to create such kind of dent. So, I repeat my question- What is the reason that the heavenly bodies (like stars, planets, etc) create such kind of a dent in the spacetime fabric?