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I am certain that there is nothing more important to know than the First Law of Thermodynamics. So, I’m glad you’re here. As a scientific axiom (self-evident truth), this law cannot be mathematically proven because it is the starting point for most proofs, and how would you prove the thing you always start with? Instead, it has only been observed and then described and then never proven wrong. It is at the same time incredibly easy to understand but difficult to see if you aren’t paying close attention.
Behold, the one-and-only First Law of Thermodynamics:
Energy cannot be created or destroyed
To put it in other words, you can’t get something for nothing. What’s great is you already think about the impossibility of creating energy, usually when considering an action or activity that requires fuel. For example, you know as well as anybody else that you need firewood to heat your hot dog, food to keep your heart beating, gas to move your car, a full charge to make your phone glow and electricity to crush the ice in your chia seed and kale smoothie. You can’t do any of these things without first having enough of the right kind of energy. Really, everything we do is just a conversion of energy – taking energy in a certain form and converting it into the form you would like it to be in.
It’s easier to believe (incorrectly) that energy can be destroyed because we appear to witness the destruction of energy all the time. For example, when you hit the brakes on your car it goes from moving to stopped. From the outside, it looks like the kinetic energy of your car simply poofed away to energy heaven. Alas, it lives! Your car was stopped by brake pads pressing against the brake rotors in your wheels. The resulting friction causes the rotors, pads and air around them to heat up. If you measured everything very carefully you would find that the increase in thermal energy was exactly the same as the decrease in kinetic energy. Your refrigerator is also confusing. You put in something warm and it gets cold. Wasn’t thermal energy destroyed? Indeed, it was not. A refrigerator does not “create” cold. Instead a fridge just pumps heat from inside the fridge out into your kitchen. That’s why the air coming out from the bottom or the back of your fridge always feels warm.
These examples illustrate an interesting (and alarming) fact – the conversion of energy is less obvious today because we are separating ourselves from it. One hundred years ago, heating your home meant burning logs that you cut yourself in a furnace right in the middle of your house. You consciously added more fuel to the fire throughout the day and were always aware of the amount of wood left in your stockpile – you were always aware of how much energy you had available. Everyone in the house was drawn to the warmth of the furnace, grateful for the conversion of chemical energy to thermal energy.
Today, the only interaction you have with the heating of your home is turning up the thermostat when your mom/wife/wallet isn’t looking. In the background a seemingly endless supply of energy (as natural gas) is delivered silently to your home, transformed into heat (burned) out of sight in the basement, and moved throughout your home in hidden air ducts. As a result, we spend very little time thinking about the thermodynamic miracle that is fire or the fuel necessary to “create” the warmth. A few dollar signs on a page once a month is the only time we even give thought to our consumption, but we usually picture ourselves burning dollar bills in the furnace, not natural gas.
Electricity makes it even more confusing, probably because you never see it. As a population, we use electricity for basically anything you can think of, which means we use a lot of it. The per capita electricity consumption in the United States is 12,000 kWh every year [1], which is about the same as lighting off 43.5 million matches per person [2]. Or, just imagine everyone you see walking around with 21 lit up 65 Watt light bulbs in their hands turned on every second of every day. Basically, we interact with electricity all the time – probably so much that we don’t even think about it. The TV glows, the oven is warm, the house stays cool… it’s a miracle! But what you need to remember is that energy is not created or destroyed and electricity is energy. Electricity isn’t created from nothing – it is mined from the mountain as coal, transformed into heat in a giant flame, evaporated as steam in the power plant, used to move a generator and then finally enters the power lines as a field created by moving electrons. At that point it arrives at your wall socket and is transformed yet again into whatever form you want; light, heat, sound.
Long story short, when you plug your phone into the wall, you are plugging it into (and taking energy from) a piece of coal, a fast-moving stream, a gust of wind or the sun itself. Electricity just gets that energy from one place to the other.
Even the way we talk about energy is wrong. I think the biggest problem is that the word “energy” means two different things. There is the actual physical concept (see What is Energy?), which I would think is the correct but less known usage, and then there is the idea that energy is fuel, where fuel is energy in a form that mankind has decided is useful (coal, gasoline, electricity, firewood). To quote Wikipedia, the energy industry is “responsible for the production and sale of energy” [3]. Ha, they don’t “produce” energy – they’re just digging stored energy out of the ground. Unfortunately, we have adopted the less accurate definition, as you can see from common phrases like “use energy” or “make electricity.” We must rebel!
Let’s get back to that idea of useful energy. Why do we find some forms of energy useful and other forms less useful? I mean, if energy really isn’t ever destroyed, then how can we have an energy crisis? With our car example, why don’t you take all that thermal energy from your brakes and put it back into your gas tank?
The answer lies in the mysterious, ever present, ultimately fatal Second Law of Thermodynamics.
Joule Thieves 