A golden ball (actually made of brass) with a cotton thread running through it. Except that you can make the ball descend at will – you can even stop it at any point during the descent.
So far, it could be an example of a simple magic trick, where the thread goes through a curved hole within the ball, so by pulling on the two ends of the thread, you make the ball stop by friction. Except that is not how this works… and this little gadget isn’t finished yet.
Once the ball has reached the bottom of the thread, you can make it go back up again! In fact, you can make the ball do what you want – go up, down, or stop, at will.
Magic? Not really. Inside the ball is a pulley system – two pulleys of different sizes, with the thread wound round both of them. Pulling the two ends of the thread makes the ball go up, releasing the thread lets the ball descend.
