The Fine Structure Constant

There are a lot of mysteries in our universe. Two that are especially puzzling are the nature of time and the origin and nature of human consciousness, but there are others, of course. One such is something physicists call the fine structure constant.

Astrophysicist Paul Sutter explains that this constant is "a measure of the strength of the interaction between charged particles and the electromagnetic force. The current estimate of the fine-structure constant is 0.007 297 352 5693, with an uncertainty of 11 on the last two digits. The number is easier to remember by its inverse, approximately 1/137."

There are several peculiarities about this number.

First of all, no one knows why it has the value it does or where it comes from. It's value seems awkward and ungainly and is completely unexplained. No current theory predicts it.

Sutter states that,

We have no explanation for the origins of this constant. Indeed, we have no theoretical explanation for its existence at all. We simply measure it in experiments and then plug the measured value into our equations to make other predictions.

Second, unlike other constants in nature this one has no units. It's not measured in any dimensions or units like meters/second or miles/hour.

Third, it has to have the precise value it has for the universe to be able to sustain life. As Sutter explains,

If it had any other value, life as we know it would be impossible. And yet we have no idea where it comes from....Change that number, change the universe. If the fine-structure constant had a different value, then atoms would have different sizes, chemistry would completely change and nuclear reactions would be altered.

Life as we know it would be outright impossible if the fine-structure constant had even a slightly different value.

It's truly remarkable that such a finely-tuned parameter would exist, and indeed there are dozens, if not hundreds of similarly fine-tuned values to the forces and constants in the universe. This chart shows the exactitude with which two such forces, the strong nuclear force and the strength of electromagnetism (i.e. the fine-structure constant), must be calibrated in order for a life sustaining universe like ours to exist:

Note that the axes on the above chart are logarithmic, every increment represents an increase by a power of ten. To plot these parameters on a standard scale the chart would have to be enormous.

It also compares just two of the hundreds of parameters that must be set with exquisite precision in order for the universe to be the kind of place in which life could exist.

Such precision could just be a lucky accident, of course, or it could be the consequence of intentional engineering. If we were to be guided by experience and nothing else, I think it safe to say that we'd dismiss the first alternative as quite literally incredible.

Sutter has more on this at the link or if you prefer you can watch him discuss the fine-structure constant on this 16 minute YouTube video: