Why do the constants of nature have the values that they do?
Over the last hundred years, we’ve measured the properties of protons and electrons in great detail. All of those calculations start with how strongly protons and electrons attract each other. The strength of that attraction can be summed up in one number: the fine structure constant. We can measure the fine structure constant to extremely high precision; it’s about 0.0073 (or 1/137).
But nothing in our physical theories explains why the fine structure constant has that particular value. It seems like an arbitrary dial that got set when our universe came into being.
But it turns out that 0.0073 is not just any number. Calculations have shown that if the force of attraction between protons and electrons were stronger or weaker by just a few percent, stars wouldn’t be able to form the complex atoms like carbon that make life possible. Change the fine structure constant by a little more and stars couldn’t exist at all.
Something set the fine structure constant for our universe to this arbitrary-seeming value, and it happens to be exactly the value that we need it to be for complex matter to exist. That seems a bit odd.
When a coincidence gets too , you start to look for an explanation. If your neighbor wins the lottery, you have a lucky neighbor. If your neighbor wins the lottery five times in a row, you start to get suspicious.
Mathematically, the perfectly chosen fine structure constant looks like life and complex matter won quite a few lotteries in a row.
There are a number of other examples of constants like this. Two that are particularly relevant to the early universe are the number of visible dimensions (which determines whether stable orbits are possible) and the density of dark energy (which determined when the universe started to accelerate)—both of which seem to have just the right values they need to have. Make either one a little different and the universe would have no solar systems in it.
- source credit: course guidebook, The Big Bang and the Early Universe, Gary Felder, professor of physics, Smith College