What is Energy?

When you are running around, people call you energetic. You may have heard about energy. What does it mean to scientists? Who cares about energy?

This video (the song is from Tom Glazer and Dottie Evans from Singing Science Records) provides a good overview of what energy is.

Energy is the ability to do work. It can be used to predict the future! Something called potential energy is stored energy due to the position of things or their arrangement. For example, a ball at the top of a mountain has a lot of potential energy, since it has the potential to move down the hill and lower its energy. When the ball is moving, it has something called kinetic energy. The total energy in a grouping of objects that interacts (including all interactions) is always constant. This is called the Law of Conservation of Energy.

Imagine that you have $10. That $10 can be divided in many different ways among different people. It can also be traded between people. Similarly, the amount of energy in the universe is constant. That energy can be transformed between different forms, such as solar, wind, gravitational potential energy, kinetic energy, nuclear energy, or chemical energy. A field called thermodynamics uses the law of conservation of energy along with a few other laws (such as the fact that disorder, measured by entropy, is always increasing) to predict what will happen to materials under a variety of conditions. A few years ago, I made this song and video with some friends talking about the predictive powers of thermodynamics (unfortunately, I am having difficulty getting it to embed on this site, but it can be seen on YouTube: http://www.youtube.com/watch?v=uqAh5LcCZPA ).
Everyone cares about energy.The food that keeps us alive gives us energy. We use energy to heat our homes and give us light. The computer that you are currently using consumes energy. Energy is hot!