Thermodynamics is the branch of physics. It is devoted to the study of heat and energy. While this might sound a little intimidating for a study topic, it isn’t as complicated as it sounds. Survival thermodynamics involves two basic principles, energy conservation and heat transmission. Both of them are extremely important to understand if you are in a true survival situation.
Energy is what allows our bodies to perform work. Without piling chemistry and biology on top of physics, let’s just say we get our energy from the food we eat and leave it at that. Since we don’t live inside a video game, we only obtain a finite amount of energy at each meal, though some foods do give us more energy than others.
The energy conservation aspect of survival thermodynamics simply says to avoid expending more energy performing a task than you’ll earn from completing it. For a moment, think of energy like dollars. If shopping at a store that is two towns away means you’ll save $15 on your grocery bill compared to shopping locally but it will cost you an extra $18 in gas because of the longer distance, have you actually saved any money?
To put a survival focus on this, think about it like this. Let’s say you spend the better part of a day hunting small game. For all of your efforts, you end up with one thin squirrel. You likely expended far more calories than you’ll get from eating the squirrel. On the other hand, if you set up a few snares and then spent a little time foraging some wild edibles, you may end up with more food while expending less energy. You’ll burn fewer calories picking berries and dandelions than you will tramping through a forest, hoping to see something moving.
Remember what Grandpa said? Work smarter, not harder. The same rule that applies to farm chores goes hand in hand with survival.
Hypothermia is a very real risk in the field, even in what we might consider mild temperatures. Cold, like darkness, isn’t really a thing. It is the absence of heat energy. Darkness is the absence of light, of course. We are in trouble when too much heat leaves our bodies and isn’t replenished.
There are four ways our bodies can lose heat. Protect against all of them as best you can in cold weather.
Conduction is loss through direct contact. Sit directly on the ground and you’ll soon notice your backside is getting cooler. The same thing happens if you sit on a large rock. Heat energy tends to want to find a balance so it travels from a warm surface to a cool one. You can help prevent this heat transmission by placing some sort of insulating material between you and the ground, such as a blanket, a foam pad, or piles of grass or pine branches.
Most of our body heat is lost through radiation. We constantly give off heat, some people more than others. This heat will drift away if it isn’t at least somewhat trapped by thick clothing, jackets, and hats.
A thin layer of air around us is warmed as our bodies radiate heat. Water or air can disturb or remove this layer of warmth. We call that heat loss convection. Avoiding wind and staying out of bodies of water will help reduce this loss.
Evaporation is a cooling process. That’s actually why we sweat. The body is trying to cool down by secreting moisture that will evaporate. In cold weather, sweating too much can be deadly. Layer your clothing so you can loosen or remove things to help moderate your temperature as you are working.
Applying Survival Thermodynamics
If you find yourself in the unfortunate position of being lost in the wilderness, employ the principles of survival thermodynamics you just learned to stay warm until help arrives or you can self-rescue. Conserve your energy by sitting down and calmly thinking about the situation. See if you can remember where you zigged when you should have zagged.
When you sit down, make sure you place insulating material between yourself and the ground to help reduce heat loss through conduction. Find a windbreak, if you can, to prevent loss through convection, too. Don’t work up a sweat mindlessly tramping through the forest and thus risk increased heat loss through evaporation.
Having a working knowledge of these basic principles of survival thermodynamics will help keep you warm and safe when you venture outdoors.
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by Mykel Hawke / Aug 27, 2018