Place the golden metal ball at the top of the ramp and let it go. Does it roll down the ramp in the normal way? No, it rolls down extremely slowly. There doesn't seem to be anything unusual about the golden ball - it weighs about what you might expect. So what is happening? 

A clue - if you make the Snail Ball colder by popping it in the fridge for a while, it rolls down the ramp more slowly. And if you warm it up a bit, it will roll more quickly. 

Inside the Snail Ball, which is hollow, there is a heavy ball bearing, which is smaller than the Snail Ball. There is also a viscous liquid. So the centre of gravity is lower than you might expect, and the heavy internal ball bearing prevents the Snail Ball just rolling quickly down the slope because of the viscous liquid. 

If you don't know the secret it is very puzzling!