Hot and Cold Coils
exhibit consists of copper coils in three sections. One outer coil
is cool to the touch and the other is warm. The center section is
made up of alternate rings of cool and warm tubing. A hand placed
on the center section feels painfully hot, but it's not. This illusion,
called a thermal grill illusion, was first demonstrated in 1896.
Scientist still can't explain the prickly, burning sensation it