It’s a wintertime question that you may have had as you struggled down a frozen sidewalk, or strapped on some ice skates: Just why is ice slippery, anyway? It turns out the answer is somewhat complicated.Mechanical engineer Robert Carpick studies tribology, the science of surface interactions, from friction to wear to lubrication. He joins Host Ira Flatow to wrangle some new ideas about the slippery science of ice.Guest: Dr. Robert Carpick is the John Henry Towne Professor in the department of mechanical engineering and applied mechanics at the University of Pennsylvania in Philadelphia.The transcript for this episode is available at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.