The Mystery Of The Fine Structure ConstantThe first fact about electricity is the equal and opposite charge on the proton and electron. We now know that protons consist of three quarks and a lot of binding energy, so protons are not rock bottom reality. Quarks have fractional charges, but isolated quarks are never observed. Meanwhile, ever since the electron was discovered in 1897, we have been unable to find any internal structure to it. So we take the charge of the electron as a fundamental reality. That charge has also been measured in the lab to a very high precision.
In the late 18th century, Coulomb in France conducted experiments that proved that electric attraction and repulsion are governed by an inverse square law having the same form as Newton's inverse square law of gravitation. The statement of that law includes a constant, known as Coulomb's constant, abbreviated q.
Maxwell's theory of electromagnetism, and Einstein's very important extension thereto known as special relativity, point to the speed of light as being a fundamental fact of nature. Electromagnetism is mediated by photon exchange, and photons travel at the speed of light, the universal speed limit for matter and radiation. The meter and second are now defined in such a way that the speed of light is an exact 9 digit number.
Electromagnetism is now grounded in quantum mechanics, and at the heart of quantum mechanics is a universal constant called Planck's constant. Crudely, it measures the smallest amount of radiative energy physics can talk about. The energy of a photon can only be an integer multiple of Planck's constant.
These four constants are all defined in terms of metric system units. For example, the speed of light is stated as so many meters per second. These constants can be combined by multiplication and division in such a way that all units of definition cancel by elementary algebra. What is left is a pure number, called the fine structure constant for historical reasons I won't go into here. The fine structure constant is an empirical quantity that has to be measured in the lab, and it has been measured to at least 10 decimal places. Its first six digits are 137.036. 137 is a prime number, BTW. The value of the fine structure constant is completely independent of any system of measurement, and hence all extraterrestrial civilisations will agree on its value. If there were a radio beacon signaling our existence as a scientifically literate species, that beacon should broadcast the first 21 digits of the fine structure constant in binary. They are:
The fine structure constant is the most important empirical quantity in all of physics. It is the ground zero of electromagnetism, and electromagnetism grounds all of chemistry, biology, geology and so on. Electromagnetism governs all of reality we can talk about using science, except the nucleus (where the weak and strong interaction hold sway) and galaxies and the universe (where general relativity holds sway). Electromagnetism makes electric power possible, and reticulated electricity is probably the single most important detail differentiating our daily lives from those of our ancestors. Electrical technology is probably the most important result of the industrial revolution that began 250 years ago. In particular, the IT technology that makes possible this post and its worldwide diffusion is totally grounded in electromagnetism. You are reading this on a computer screen that translates electric signals into streams of photons reaching the retina of your eye. Is the electron the most valuable domesticated animal lol??
The only rivals of the fine structure constant among pure numbers are the e, pi and i so important to the mathematics of physics.We have no idea why the fine structure constant has the numerical value it has. Even more troubling, if the fine structure constant differed from its actual value by more than 1-2% in either direction, stars would burn too fast or too slow, or not ignite at all. Or chemistry would be impossible. In either way, there would be no biosphere and you and I would simply not exist. The numerical value of the fine structure constant is a spectacular instance of an anthropic coincidence, a just-so fact about physics and the universe that makes it possible for us humans to exist and to talk about the universe.
I owe my awareness of what I write above mainly to the writings of two astrophysicists and cosmologists: John Barrow at Cambridge University and Frank Tipler at Tulane University. Easier introductions to these ideas are two books by Martin Rees: Our Cosmic Habitat and Just Six Numbers.
Richard Feynman used to joke that the fine structure constant made him feel defeated and humbled. About 25 years after I first heard of that constant, I concluded that there is a vast intelligence behind the creation and subsequent evolution of our universe. I accept that Feynman the atheist would decline to follow me here. The fine structure constant does not imply that this vast intelligence values our "worship" or that there is an afterlife. I freely admit that I have grave difficulties with the notion of my having a "soul" that will exist forever. Conversely, I have no difficulty with the prospect that one day my brain will shut down and that will be the end of me.
The value of the fine structure constant is not the only anthropic coincidence bound up with electromagnetism. Gravity runs the show in the large, despite being 39 orders of magnitude weaker than electromagnetism, because all macroscopic ob