elliptical orbits ..i think is a result of simple geometry..!!!

ellipse..locus of a pt.. wic moves such tht sum of distances from two fixed pts is constant...sun is at one of the focii of tht ellipse.

now why ellipse..??
actually earth experience no torque due to rev. around sun..
thus ang. momentum is conserved..

it follows tht angular velocity * moment of inertia arnd axis is constant..
it now follows tht areal velocity (dA/dt) is constant..

that can only happen wen locus of the earth is an ellipse...
as in an ellipse dA/dt is constant..