THE fundamental constants of physics are the numbers that describe just how strong the forces of nature are. Though every one of their values is derived from experiments, not from some fundamental understanding, they are nevertheless integral to what we call the laws of physics: the constants make the laws work when we use them to describe the processes of nature. And because we assume that the laws of physics are immutable, eternal – we have to assume the constants don’t change either. Which is why astronomer John Webb has got himself into such trouble.
In 1997 Webb’s team at the University of New South Wales in Sydney analysed the light reaching Earth from distant quasars. Something strange had happened to the light during the 12 billion years it took to cross the universe: its spectral composition, the different colours within the light, had changed. The only feasible explanation was that a constant of physics called the fine structure constant, or alpha, had a different value near the time the light started its journey.
Webb’s result has withstood a decade of testing and dispute, and we are getting hints that other constants might change too. The laws of physics might be rather more flexible than we thought. The physical laws and constants have helped us define and tame the natural world. But what if there are no immutable laws? What if the constants aren’t constant? Or, as Webb puts it, a wry smile playing across his lips, “Who decided they were constant, anyway?”