Ice is wonderful because its properties are difficult to understand even though it is so omnipresent in our world. Back in the 1800s, a scientist called Michael Faraday thought that there's something coating ice that allows it to stick together. He realized that there was somehow an intrinsic layer of liquid water that always sits atop the surface of ice. The answer goes back to another weirdo property of ice that has less to do with why it's slippery and more to do why in certain circumstances it's sticky.