In this video from It's Okay to Be Smart, learn the difference between heat and temperature, why wind makes us feel colder, and what it's like to live as a mass of jiggling atoms. This is the physics of cold. You've felt cold before. Sometimes it's cold outside. But what if I told you that "cold" isn't real? There's no substance or quantity called "cold" in science. We can't measure the amount of "cold" in something. Instead, it's about what is NOT there.