If you spend much time on the internet, you will see the same things pop up again and again. For me, it's these “cooling blankets” that people talk about on social media. I mean, it sounds great for summer—just like a blanket that warms you up but in reverse.
Sadly, these products don’t do what they claim. They might be breathable so they don’t make you as hot as an ordinary blanket would, but you’d still be cooler with no blanket at all. However, there is hope. Someone has created a real cooling blanket that's sort of awesome. Of course, there's a bunch of physics here, so let's get to it.
Temperature vs. Energy
Temperature is one of those words everyone uses and no one understands. In chemistry it’s the average kinetic energy, or vibrational motion, of the molecules in a substance. The greater the commotion, the higher the temperature.
But I like this more pragmatic definition: Temperature is the property two objects will have in common when they’re in contact for a long time. So, if you take a hot block of metal and set it against a cold block of metal, eventually they will have the same temperature. Heat flows from the warmer thing to the cooler thing until they equalize. (Note: It doesn’t work the other way around; you can’t transfer “coolness.”)
We also talk about objects having a certain amount of thermal energy, which you’d get by adding up the kinetic energy of all the particles inside it. It depends on three things: the mass of the object, its temperature, and the material it’s made of. So for instance, focusing on mass, big potatoes have more thermal energy than small potatoes at the same temperature.
Now, if you look at the type of material, every substance has a “specific heat capacity,” which is the amount of heat required to raise the temperature of that substance by one degree. Try this at home. Find two objects that have been sitting in your room for a while, so they’re both at room temperature. Here, I have a block of wood and a block of aluminum.