Chapter 8: The Alchemy of the Stars

Why do stars shine?

The Ultimate question, in my mind, is, “Why do stars shine?” Obviously, their shine is produced by light energy. Well, where does this light energy come from? The energy to power stars comes from nuclear fusion.

We know that an atom’s nucleus contains two particles: protons and neutrons. Indeed, the particles are held together by the strong force, a very powerful nuclear force, but it has limited range. The effect of the strong force is only felt when protons and neutrons are extremely close at distances less than a millionth of a billionth of a centimetre. The strong force has competition though. Take the helium atom for example. Helium’s nucleus has two protons, which cause an electromagnetic repulsion. However, if the nucleons are close enough, the strong force will overcome the repulsive electromagnetic force.

Nuclear fusion is “the capture by a nucleus of another proton or neutron as a source of energy.” This is called nuclear fusion because it is the fusion of lighter particles leads to the formation of one heavier particle. Consider the case of hydrogen and helium. Four hydrogen nuclei can form a helium nucleus, producing an extremely abundant source of energy. The four hydrogen nuclei have a greater total mass than the final helium nucleus. The excess mass present in the nucleus must be released by the structure. Einstein’s theory of general relativity outlined that energy and mass are interchangeable. If mass decreases, the total amount of energy increases.

Using the Sun as an example, through nuclear fusion, 10 per cent of the Sun’s mass can be converted from hydrogen to helium. If so, this tells us that at this rate, there is enough energy for the Sun to radiate at its current intensity for about 10 billion years. The Sun’s energy production is based on the fusion of hydrogen into helium. These estimates tell us that the Sun, a star, is approximately in the middle of its life cycle.

Quantum Tunneling in Stars

George Gamow defined quantum mechanics as an essential part of nuclear fusion in stars. Later came the “Uncertainty Principle” postulated by German Physicist, Werner Heinzberg. Heinzberg stated that, “We cannot know the exact position and the state of motion of any particle.” For example, if we placed an apple in a bowl, under the classical physics laws, we assume that this apple will not move because it is simply sitting in the bowl. In quantum mechanics, however, we cannot actually be certain of where the apple is, and how or where it is moving. All we know is that the apple is somewhere in the bowl.

We are not used to describing objects in terms of their positions and velocities, but in quantum mechanics, we have to consider that there is an uncertainty. There is only probability that the object is in a certain place or moving at a certain speed. We cannot predict the exact motion of an object or its destination; all we can do is predict the likelihood of various possible outcomes. Like Mr. Barry discussed in grade 12 chemistry, Schrodinger’s equations comes into play. Schrodinger’s equation gives us various possible outcomes and their likelihood at any given moment.

When understanding quantum mechanics, it deals with probability. Even though the apple is resting in the bowl at this specific instant, it is probable that eventually, the apple could be resting outside of the bowl.