The floating glass

The task here is to balance a glass on a bridge made out of knives. You will need 4 glasses for this (although paper cups or plastic cups will also work).

Fill three of the glasses or cups halfway up with water.
The task is to balance the empty glass on a bridge supported by the other glasses, like in the picture below:

But now we're going to make it much more difficult :-)

Place the three glasses in a triangle with a knife between each of them, like in the picture below:

Now you need to balance the knives on the glasses and the fourth glass on top of the knives. It does work, promise!!! (Scroll down to find the solution.)

Don't you want to try it out for yourself?

Are you sure?

OK, here's the solution:
Place the three knives on the three glasses like this. The knives are crossed in the middle so that each knife is leaning on another one.

And then you can simply place the last glass on top.