Nuclear Binding Energy
Stars release energy from nuclear reactions, not chemical reactions. When hydrogen and oxygen burn and become water vapor, chemical energy is released. This is the electromagnetic energy that attracts the negative electrons to the positive nucleus. The energy of weak nuclear reactions is about a million times greater than the energy of chemical reactions. The energy of strong nuclear reactions is about a thousand times greater that the energy of weak nuclear reactions.
When we say that stars burn hydrogen into helium, we are using the word “burn” to describe a nuclear reaction. The two kinds of burning, chemical and nuclear, are alike because both consume fuel and produce heat. They are different because nuclear reactions produce much more energy than chemical reactions. Chemical reactions release the electronic binding energy of molecules. Nuclear reactions release the binding energy of nuclei. Chemical burning can raise the temperature a few thousand degrees. Nuclear burning starts when the temperature is millions of degrees.
Nuclear reactions are much more dangerous for people than chemical reactions, because nuclear reactions emit nuclear radiation. Nuclear radiation consists of fast-moving electrons, helium nuclei, heavier nuclear particles, and gamma rays. These particles and rays can permanently damage the cells of our bodies. Chemical reactions produce thermal radiation or heat. Too much heat can cause burns, but lesser amounts are agreeable when we feel cold. To enjoy the heat of a nuclear fire safely, we need something to stop the nuclear radiation. We bask in the warmth of the Sun, unafraid of nuclear radiation, because the atmosphere of the Earth protects us.
When we say that stars burn hydrogen into helium, we are using the word “burn” to describe a nuclear reaction. The two kinds of burning, chemical and nuclear, are alike because both consume fuel and produce heat. They are different because nuclear reactions produce much more energy than chemical reactions. Chemical reactions release the electronic binding energy of molecules. Nuclear reactions release the binding energy of nuclei. Chemical burning can raise the temperature a few thousand degrees. Nuclear burning starts when the temperature is millions of degrees.
Nuclear reactions are much more dangerous for people than chemical reactions, because nuclear reactions emit nuclear radiation. Nuclear radiation consists of fast-moving electrons, helium nuclei, heavier nuclear particles, and gamma rays. These particles and rays can permanently damage the cells of our bodies. Chemical reactions produce thermal radiation or heat. Too much heat can cause burns, but lesser amounts are agreeable when we feel cold. To enjoy the heat of a nuclear fire safely, we need something to stop the nuclear radiation. We bask in the warmth of the Sun, unafraid of nuclear radiation, because the atmosphere of the Earth protects us.
