drnick17 Oct 2006

I will explain both the cause and the cause's cause.

Cause: The rain sliding down the window is caused by a force, particularly gravitational force. The attractive force of gravity between the earth's mass and the rain's mass is allowed to acclerate the droplet because it has a greater magnitude than that of the force of static friction in the opposite direction. The gravitational potential energy the droplet has is now transferring to kenetic and thermal energy. This is why the rain slid down the window.

Cause's Cause: I'm not sure what you mean by "cause's cause" so I'll answer both ways...#1 The gravitational force was caused by both the droplet and the earth having a non-zero mass. Without mass, there is no grav. force. #2 This question is inherantly a theological one as you are assuming there is a reason for gravitational force. For it to have a reason, it would have to benefit from it's action: attracting masses together. As of now, I know not of any benefit to any law of physics for existing. You are trying to place human qualities on something that is not human, not living, not material.

I wouldn't mock a question like that, it was a good question.