Why does a spinning top weigh more than one at rest?

It does? Well, actually, yes it does. But the difference is going to be so very very tiny, nobody could measure it. It weights more because the energy of spinning has some weight. But I would wonder if it's even as much as the weight of one atom.

The top would need to be spinning at a million rounds per second, or weight many many tons to start with, before the extra weight could be measured.

It has to do with the torque the spinning top is exerting.

Have you ever carried a sleeping child? We are heavier while we sleep too.. I don't know how this is similar but it must be :)

sorry if it didn't help! Lol