Energy

Energy is the capacity to do work. That work can involve moving things or animals or people around in a car, boat, train, or a plane. The same term, "work", could also refer to heating or cooling a building, lifting people in an elevator, powering a computer, and so on. Basically all of our activities, including life itself, require that capacity to do work -- energy.

Some things require a lot of work to get done. Imagine a large, drafty, uninsulated building on a cold night in northern Montana. Imagine heating that building to a temperature at which most people would feel comfortable sitting still, wearing sandals, shorts, and a t-shirt . That would take a lot of work, a lot of energy. Conversely, some actions require very little energy: a baby is strong enough to bat a beach ball and make it move.

These examples are simple and easy to visualize. Obviously, many situations can be much more complex. How do we deal with that complexity? Well, one way to manage complexity is to avoid qualitative statements such "a lot of work" or "very little energy" and instead measure the amount of energy consumed by a particular activity.

So instead of saying, "It takes a lot of energy to heat our house," we ask, "how much energy did we use to heat our house last winter?" and we try to measure that energy. Then we can compare things more quantitatively. We can determine, for example, how much energy was required to heat a particular house to a particular temperature during the waking hours between November 1st of 2008 and February 28th of 2009. Then we can do the same measurements for a different house and compare the measurements to see which house needed more energy.