One possible cause of gamma-ray bursts is collisions between comets in the oort cloud. imagine that two comets collide head-on. each is a spherical ball of ice, of radius 1km and density 1000 kg/m3 , travelling at 100 m/s. if the collision happens at a distance of 1000 au from the earth, and 1% of the collision energy is released as radiation, what fluence would you measure at the earth?