The field of thermodynamics studies the behavior of energy flow in natural systems. From this study, several physical laws have been established. The laws of thermodynamics describe some of the fundamental truths of thermodynamics observed in our Universe. Understanding these laws is essential to students of earth and environmental science because many of the processes studied involve the flow of energy.

First Law of Thermodynamics

            The first law of thermodynamics is often called the Law of Conservation of Energy. This law suggests that energy can be transferred between systems in many forms. Also, it cannot be created or destroyed. Thus, the total amount of energy available in the Universe is constant. Einstein's famous equation (written below) describes the relationship between energy and matter.

E = mc²

In this equation, energy (E) is equal to matter (m) times the square of a constant (c). Einstein suggested that energy and matter are interchangeable. His equation also suggests that the quantity of energy and matter in the Universe is fixed.

Second Law of Thermodynamics

            Heat cannot be transferred from a colder to a hotter body. As a result, natural processes involving energy transfer must be one-way, and all natural processes are irreversible. This law also predicts that the entropy of an isolated system always increases with time.Entropyis the measure of the disorder or randomness of energy and matter in a system. Because of the second law of thermodynamics, energy and matter in the Universe are becoming less useful as time goes on. Perfect order in the Universe occurred the instant after the Big Bang when energy, matter, and all the forces of the Universe were unified.

Third Law of Thermodynamics

            The third law of thermodynamics states that if all the thermal motion of atoms (kinetic energy) within a material substance could be removed, a state called absolute zero would occur. Absolute zero results in a temperature of 0 K (Kelvin) (-273.15°C or -459.67°F). The Universe will attain absolute zero when all energy and matter are randomly distributed across space. Scientists estimate that the temperature of the Universe (and space) one minute after the Big Bang was about 100 million K. After 100 years, the ambient temperature of the Universe had dropped to 100,000 K because of the expansion of space and the more widely distributed matter and energy. The current temperature of the now immense voids of space is about 2.7 K (-270.5°C or -454.8°F).