Ancient metal top year 1987

This one is dated 1987 it is made of metal decorated with pretty childish designs... Dimensions: diameter 20cm x height 16cm. They are a little marked by the time some traces of rust underneath on the red ... Always current and decorative object! If the tops fascinate young and old, it may be because of the mystery of their movement. Why and how do they turn out? When will they stop? Do the shape and material of the tops influence their rotation? So many legitimate questions whose answers are to be sought on the side of science ...