Subject: A BLACK HOLE IS BORN

On many television documentaries about black holes, they show the space-time continuum as a flat gridded sheet, and show how gravity bends that sheet. This is really just an analogy, making our three dimensional space two dimensional. So you could try that yourself, maybe taking a sheet and putting it in a frame of wood. A linen sheet won't bend much, so maybe a piece of thin rubber might do, like, ah, well, a rubber sheet. They can be found in kid's stores, I bet.

You could roll a heavy ball and show how it distorts the sheet more than a light ball, just like a massive object distorts space more than a less massive object. You can also roll something light, like a ping pong ball, across the distortion made by a massive ball. That shows how the gravity of an object can change the trajectory of a moving object. To make a black hole, use something very small and dense to make a big dip in the sheet, then pinch it with your fingers and pull it down. When the walls of the hole are nearly vertical, you have yourself a black hole. You could even cut a hole out of the bottom if you'd like, but that will make a second demo tougher! ;-)

[Moderator's note: you could try to demonstrate the birth of a black hole by demonstrating some kind of implosion. I've seen this done by having the air pumped out of a sealed steel drum- the outside air pressure then crushes the drum. This demo is not the easiest thing to arrange; maybe your teacher can help you with other ideas.]