At first, the riddle sounds almost impossible: What can run without legs, fly without wings, bite without teeth, and sometimes become cold? Each clue seems to describe a completely different creature. Something that runs should need feet, something that flies should need wings, and something that bites should surely need teeth. Yet there is one familiar force of nature capable of doing all these things without possessing any of them.

You experience it almost every day, although you can never actually see it. You notice it when leaves race across the sidewalk, when branches begin swaying, when clouds move overhead, or when waves suddenly grow stronger along the shore. Sometimes it arrives as a gentle breeze; other times it becomes powerful enough to change plans, damage property, and transform the weather around us. Still unsure? Think about a freezing winter morning when something invisible touches your face and feels surprisingly sharp. That final clue reveals the answer…