Bill Davis, age 14, of St. Catharines, Ontario, Canada, for his question:

IS PERPETUAL MOTION POSSIBLE?

A perpetual motion machine would be a device that can continuously produce work with no energy input, or that can continuously convert heat completely into work.

No one has ever succeeded in building a perpetual motion machine. Almost all scientists and engineers believe that no one ever will. They say it isn't possible. A perpetual motion machine could be made to run if it were possible to avoid resistance. However, the moving parts of all machines are subject to friction or some other kind of resistance which slows down the machine.

A second type of perpetual motion machine could be made to run continuously if it were possible to use up all the energy in a large source such as the sea or the atmosphere. No machine yet has been able to do this.