Footnote on slippery ice

Here is an interesting footnote to the article “Why Is Ice Slippery?” by Robert Rosenberg (Physics Today, December 2005, page 50 ). A wonderful out-of-print biography of Robert W. Wood, ¹ who is especially famous for his research on physical optics and spectroscopy, relates that as an undergraduate at Harvard University in 1891, he heard of the “pressure-molten” theory of glacier sliding, and “totally disbelieved this.”

Wood had access to a powerful hydraulic press at a blower plant and decided to use it to disprove the theory. Water was frozen inside a cylindrical iron block, with a bullet accurately placed in the center of the ice cylinder. “The mighty ram of the hydraulic press” then pressed so strongly on the ice via a steel cylinder that ice needles “forced [their] way through imperfections in the casting” of the iron walls. And yet, when pressure was released and the ice removed, “the bullet was found at the center where it had originally been placed, thus clearly demonstrating that the ice within the cylinder had at no moment existed as pressure-molten water” (italics in the original). Wood, the inventive undergraduate student, published the results. ² His experimental creativity later became legendary, and that early contribution to the “slippery ice” story looks like a harbinger of his future reputation.