Learn about energy and how the sun provides the energy needed to sustain life on Earth. Discover energy transfer and how energy is neither created nor destroyed, but moves from one place to another or changes from one form to another.
Energy: The Ability to Do Work
I don’t know about you, but when I don’t have any energy, I find it hard to get anything done.
This idea actually applies to all energy, which scientists define as the ability to do work. Work itself varies, from the sun warming us and providing light on a sunny afternoon to sound traveling across a playground. So, more specifically, energy makes the things around us move or change.
We measure work in joules (J), calculated by multiplying force times distance. One joule of work is equivalent to the force needed to lift an apple the distance of one meter into the air.
The Sun-Powered Universe
Almost all energy comes directly or indirectly from the sun (except nuclear energy, but we’ll get to that later). The sun gives off a specific type of energy, radiant energy, which is sometimes called solar radiation.The sun radiates both the light and the heat that allow life to thrive here on Earth. Plants, for example, take in sunlight directly and use it as an energy source through a process called photosynthesis.
The Earth’s atmosphere is also warmed by the sun, so our planet is the optimal temperature to sustain life. Earth, like the porridge in Goldilocks and the Three Bears, is just right. Any closer to the sun and it would be too hot; any farther away and it would be too cold.One indirect use of the sun’s energy is when humans eat plants and other plant-eating animals to fuel our bodies. Another example is fossil fuels, coal, natural gas, and oil, so named because they are the end product of animal and plant remains stewing deep beneath the Earth’s surface for millions of years. Even the gas we use to run our cars was once plant and animal life powered by the sun.
What is Energy Transfer?
The above examples of how the sun’s energy directly and indirectly sustains life on Earth also show how easily energy passes from one person, place, or thing to the next.
When you eat an apple, you take a product of the sun’s energy, the apple, and use it to fuel your body. Likewise, the energy from a rushing river generates electricity in a hydroelectric plant – and that electricity powers our light bulbs, allowing us to stay up late and do even more work.