Our pal Colin May will argue with anyone — even an astrophysicist. He writes: You can push on a string. Freeze it...

In previous installments, we brought you video of the amazing levitating Slinky, and Peter Barss wondered how the Slinky had been calibrated to work exactly this way. I asked physicists to come forth, and they have—not just physicists, but an astrophysicist. (Who better to explain levitation?) Saint Mary's grad Jonathan Dursi, now a senior research associate with the Canadian Centre for Astrophysics, furnished this detailed by elegant explanation: Sometimes you hear that there's three things taught in first year Engineering (or Physics, or whatever); things fall down; F=Ma; and you can't push on a string.* It's exactly those three things at play...