Developed the universal law of gravitation.

Sir Issac Newton developed the Universal law of Gravitation.

Explanation :

With the interesting quest for the answer why does the apply fall from a tree on the Earth, one of the wisest scientists Sir Issac Newton started investigating the action and thus developed the Universal law of Gravitation by estimating what caused the motionless apply to accelerate towards the Earth.  

According to his second law of motions, an objects which are at rest (apply attached to the twig of the tree) could get in motion (fall towards the Earth) only through an external force exerted on him by the Earth. He called this force has “Gravity” or the “Gravitational Force”.

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.