Controlling fire is one of thing that makes humans very different from the rest of the animal kingdom. We have harnessed the constructive and destructive powers of fire and used it for thousands of years. We have used it to clear areas to attract game, we have used it to forge weapons and we have used it to warm the spirit on cool winter nights.
What is fire? What is energy? The second question is one I recently asked my freshmen biology class. They began listing many different forms of energy but nobody could really put their finger on what energy really is. Einstein once stated that “Energy cannot be created or destroyed, but can only change in form”. This statement again alludes to the different forms of energy but does not give us a good idea of what it actually is!
Fire in the simplest terms is the light (a form of energy) and heat (another form of energy) release from the combustion of a given material, in this case maple logs. The light and heat is released as the wood is combusted. But where did the energy start?
To figure out where the energy from fire comes from we need to look at what is being combusted. In this case it is wood from recently felled maple trees. Maples are plants and therefore collect all of their energy through the process of photosynthesis. As plants the use light energy from the sun to convert Carbon Dioxide and Water into Glucose (sugar) and Oxygen. The energy is not “used” per say, but merely transferred into the chemical bonds within the Glucose molecule.
The Glucose produced from Photosynthesis is used to create the structures of the plant. Cellulose is a polymer (long chain) of Glucose molecules. Starch, another polymer of Glucose, is used as the plant’s food source (humans also love to eat plant starch!). That simple Glucose molecule itself is broken down releasing energy used to create other complex molecules.
The plant stores all that captured energy within its chemical bonds. Some of the energy is lost through each transfer. The lost energy is returned to the universe. Entropy is a measure of randomness. As the energy leaves the plant at each step of transfer it is said to have higher entropy, or more randomness. This idea of entropy is not easy to think about, but it helps explain how the natural world functions and even how we fit into the ecosystem of Earth.
Next time you sit at a fire and enjoy the heat and light on a cool autumn night take a moment to reflect on how it got there. You are witnessing entropy in action. The energy that originally came from the sun is now being released back into the universe. Its path on this planet is complete. Entropy has the final say.
Up Next: October Frog