I was playing around with XNA and wrote a graphical circular motion demo of the Moon orbiting the Earth.
I then decided to replace the circular orbit equation with real gravitational forces: if I simulated the masses, distances and the Moon’s orbital speed (the initial sideways nudge), then the Moon should orbit the Earth.
I forgot to give the Moon the initial sideways nudge, so it fell straight towards the Earth. As they should be orbiting, I omitted their dimensions, only using the distance between them to calculate the gravitational attractive force:
F = G * m1 * m2 / (r * r)
m1 and m2 are the masses of the Earth and Moon. r is the distance between them. So when the Moon hit the Earth, r became zero, because normally planets have dimensions, but mine didn’t: division by zero = infinity. The force became massive and the Moon was flung off the side of the screen at very high velocity.
So, what has mass but no dimension? A singularity. The Earth and Moon had become a micro-black holes and had
collided, resulting in the Moon being flung off to the ends of the Universe. A bit like the tv series Space 1999.🤣 So that’s what happens when black holes collide!