Nature is a whore. It likes to spread itself all around until it’s been everywhere. Most everything in nature seeks a balance, a point where it is evenly distributed. The greater the disequilibrium, the more it tries to even the score.
The water on the Earth is constantly seeking a common level. This causes the formation of rivers and streams to channel the water from high to low. The more water there is upstream, the more the rivers will flow. Electrons seek a common level as well. Whenever there is a pool of electrons, you can be sure that they are trying to disperse themselves and when they do, you get an electric current. The more electrons you have in one spot, the greater the electric current will be when they disperse. Heat is the same way, constantly trying to even itself out. The greater the source of heat, the quicker the heat will transfer itself to somewhere colder.
But that is only half the story. It is true that the greater the disequilibrium, the greater the drive for nature to equalize it. And it is true that this greater drive causes quicker action. But, there is another factor in the speed at which nature equalizes itself: resistance.
Some materials conduct electricity better than others, just as some conduct heat better than others. Metals happen to be good conductors of both heat and electricity. Other materials like rubber are poor conductors of both heat and electricity. We call those types of materials insulators.
Your body is in a constant state of thermal disequilibrium with its environment. Our bodies are happiest at a temperature of 98.6 degrees Fahrenheit, but we prefer to live in an environment of about 72 degrees (which we refer to as room temperature). Everything around your house that is at room temperature is actually cold compared to you. That is why we mammals are said to be warm-blooded. It seems strange, but we actual prefer to live in a cold environment.
The heat in your body is constantly escaping, constantly trying to reach a balance with its environment just like the rest of nature. This turns out to be a good thing because your body also makes a ton of heat, most of it from muscular expenditure. Have you ever heard of burning calories? Calories are a measure of the energy content of food. One of the ways to measure calories is to set the food on fire and measure the amount of heat it generates. In fact, calories are a measure of heat. One calorie is the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. As your body uses food for energy, heat is released as a by-product. If this heat did not dissipate into the environment, you would boil yourself to death, and no one wants that.
The human body tries very hard to maintain its internal temperature of 98.6 degrees F. If you run around and generate too much heat, you sweat. Your body opens up holes (pores) in the skin to allow some of its water to evaporate, carrying heat along with it. If your internal temperature starts to drop below 98.6, you shiver. This burns calories to generate more heat. But you won’t shiver for long because your body will send a signal to your brain as well. This signal conveys a simple message: COLD! When your brain gets this signal it will probably respond by putting on a blanket or more clothes (insulation) or by turning the heat up in the house. Both of these actions achieve the same goal of slowing down the transfer of heat from your body to the environment, but they achieve it in different ways. The blanket works by physically slowing down the transfer of heat because the cotton, wool, or plastic that the blanket is made from is not a good conductor of heat. On the flip side, turning the heat up in the house works because it lessens the temperature difference between your body and its environment and therefore lessens nature’s desire to equalize that difference.
When your body is dissipating heat at the same rate in which it is generating it, then it feels comfortable. When it is generating more heat than it is dissipating, then it feels hot. When it is dissipating more heat than it is generating, then it feels cold. This means that when you touch an object, it feels hot or cold not solely based on its temperature but also on how fast or slow it conducts heat away from your body. If you pick up a pillow at room temperature, it will feel normal because it conducts heat from your body at about the same rate as the air does, but if you pick up a metal pan at room temperature it will feel downright chilly because it is conducting the heat from your body much faster than air, triggering your body’s COLD! signal. And that, my friends, is why metal feels cold to us – because heat is a whore that really likes metal. Or something like that.