Man, it’s been a looooong time since I put up a new post. That was not intentional. It was part lack of motivation (or inspiration, as the case may be), and part being too busy doing science to sit down and write about it. But, I’ve given myself a New Year’s resolution of sorts to give this blog the love that it deserves, so here it goes…
It’s cold outside. Super cold, actually, thanks to the ridiculous wind that is accompanying our cold front. Walking across campus to my office made me feel like David Attenborough traversing Greenland. Twas good times. (Edit: at least it was when I started writing this LOL)
In the grand scheme of things, however, it’s not even that cold. I mean, it’s not even the coldest it’s been here, let alone truly cold. While pumping liquid helium into the cryostat in our lab, I have experienced true cold; it was basically the exact opposite of the experience of opening your oven and inadvertently burning your face off. You think -10 °F is cold, try -451 °F…
Temperature is an interesting thing, when you really think about it. What exactly is it that we’re talking about when we refer to an object being “hot” or “cold”? It all seems so arbitrary; hot or cold with respect to what?
Further, think about the fact that, unlike most other physical properties, things like mass or length or time, we don’t directly measure temperature. Instead, we are always measuring some other physical quantities response to temperature. In a mercury thermometer, for example, we are measuring the change in the volume of the mercury in response to a change in temperature. In a fancier electric thermometer, like the one you put in your mouth when you’re sick, you’re measuring the change in electrical resistance of some component in response to a change in temperature.
Sometimes, the concept of temperature isn’t even defined. Think about a piece of metal that you are heating with a torch. What temperature is the metal?
Point is, temperature is wacky and we really take the concept for granted. So, let’s think about it for a little bit!
The Concept of Temperature
Imagine two objects, say two cubes of metal, one “warm” and one “cool”. You then bring them together so that they touch and then you observe what happens. There’s all sorts of physical properties that we can observe, as stated above, things like volume and electrical resistance. What you will observe is that after some disruption when they were brought together, eventually, everything stops changing. The volumes, for instance, will change as soon as you touch the two cubes together, but eventually, the volume of each cube become constant. When this happens, we say that the objects have reached equilibrium. More specifically, they have reached what is known as thermal equilibrium. Being in equilibrium doesn’t mean that the values of everything are the same; the cubes won’t necessarily have the same volume. The values of volume will simply not be changing anymore.
The idea of temperature is that physical thing that tells you if you are in thermal equilibrium or not. All systems have some sort of internal energy; consider, for instance, the kinetic energy that each molecule of the air around you has. If you are in thermal equilibrium with your surroundings, life is great. If, however, your surroundings have more internal energy than you do, Nature does what it needs to do to balance everything…by increasing your internal energy and decreasing the surrounds internal energy until you are in thermal equilibrium. Of course, you perceive this as “getting hot”. Realistically, when you heat up, your surroundings cool down, but your surroundings are so vast that you don’t really make a difference; they are like an infinite reservoir of energy. Likewise if your surroundings have less internal energy than you do. In this case, rather than your surroundings giving you energy, they take it away and you fell “cold”.
Back in the day, distinguished gentlemen, such as William Thompson,…
…thought that this transfer was due to the flow of some unseen fluid they called “caloric”. It was later established, much to Kelvin’s (pardon me…Lord Kelvin) credit that this idea was false, which ultimately led to the kinetic theory of gases and the idea that heat was transferred by atomic collisions. He also gave us the important concept of an absolute temperature scale. Of course, the unit of temperature, the Kelvin, one of seven fundamental units in Nature, was named after him. Well played.
Victorian-era science was big on the weird fluids. There was the caloric that transferred heat, the frigoric (seriously) that transferred cold, the phlogiston that was released during combustions, and let’s not forget the fantastic lumiferous æther through which light propagated. But, I digress…
In both cases, you are perceiving a disruption of your body’s “normal state of affairs”, a regulatory process called homeostasis. Needless to say, we are fantastically ordered machines. It takes a lot of energy to create and maintain that order…and Nature doesn’t like it.
There are a lot of laws that are thrown out that Nature must follow. One that truly must be followed, however, is known as the Second Law of Thermodynamics. This law can be stated in many ways, but the one most applicable to this discussion is that “the entropy of the Universe (a closed system) must always increase”. Well, cool…what’s entropy.
Entropy is a deep subject. The popular way to describe it involves the idea of chaos. Think of water. When frozen, the water molecules take on a rigid crystal structure and have a great deal of order to them. As you add energy, these molecules become “agitated” until they finally break their crystalline bonds, thus becoming less ordered. They still weakly interact, however, so they maintain a specific volume. Heat the liquid even more and the molecules overcome this interaction as well and loose volume, becoming even less ordered, as the turn into a gas. In physics, we would say that water vapor has more entropy than liquid water which, in turn, has more entropy than ice. The second law says that this quantity, overall, must increase. Nature does what it needs to do to ensure this happens.
What about a refrigerator? Doesn’t it lower the entropy of the stuff inside? Well, yeah…but it does this using a heat pump, that grill on the back of the device, which exudes heat into the surrounding environment, increasing its entropy. The net effect is that overall entropy is increased.
Back to us and our homeostasis. Based on this idea of order, we have pretty low entropy and, like the refrigerator, we radiate are ridiculous amount of heat back into the environment (some of us more than others…). Our surroundings are constantly adding or subtracting energy from us, and we use the energy we extract from food (calories…at least we kept the word) to maintain order. But the Universe is relentless.
It keeps chipping away until something finally breaks, homeostasis fails, and death occurs. Without that inflow of energy, all of our complexity disintegrates and the second law is maintained. Death is losing the battle against entropy.
Overall, however, we’re sticking it to the Universe. Even though it destroys us, we serve to (minutely) raise it’s entropy over our lifetimes. It turns out that entropy is tied to the amount of energy that can effectively do work. When the entire Universe eventually comes to thermal equilibrium, work will not longer be able to occur. You need “hot” and “cold” for energy to transfer. If everything’s the same temperature, energy can’t flow and nothing interesting can happen. All chemical reactions will cease, everything will become a near-absolute-zero soup and entropy will finally be maximized. The inevitable heat death of the Universe…LOL the joke’s on you, Nature.
A depressing outcome in 100 trillion years…I guess being cold in the winter is the least of my concerns. But at least my face won’t hurt when I go outside.