Scientists and philosophers continue to reckon with the spreading evidence and implications of fine tuning.

The 18th-century German philosopher Gottfried Leibniz famously argued that the universe as it existed had to be “the best of all possible worlds,” since an omniscient and benevolent Creator would have known what the other possibilities were and selected the best available option. Ever since Voltaire lampooned this answer to the problem of suffering in his novel Candide, Leibniz’s argument has been considered far less useful than his other great feat, the co-discovery of calculus.

And yet Leibniz’s argument is oddly relevant in the early 21st century, as a growing number of scientists and philosophers address what has come to be called “fine tuning”: the puzzle of why our universe is the way it is, and what it could — and couldn’t — have been under different circumstances.

Investigators of fine tuning look, for example, at physical parameters ranging from the weight of a subatomic particle to the cosmological constant that regulates the expansion of the universe, and ask what everything would have been like if those numbers had been any different. In many of these counterfactual universes, slightly altered physical constants yield, when plugged into the mathematical machinery of physics, vastly different results. In many cases, the result is a universe in which no molecules — let alone stars or galaxies — could hold together.

A FIELD GUIDE TO FINE TUNING

David Sloan, a postdoctoral fellow at Oxford University, has watched in recent years as a growing number of subspecialties have began to talk seriously about the notion of fine tuning. “It’s becoming more of a buzzword in the physics literature,” Sloan says. But what fine tuning means can vary by discipline as physicists, chemists, and biologists consider whether the systems they study rely on very precisely calibrated physical constants. With a grant from the John Templeton Foundation, Sloan, his advisor Roger Davies, and a team of other scientists are working to produce the first field guide to fine tuning — an interdisciplinary snapshot of the ways working scientists are currently using the concept. The end result will be a printed book as well as a website where readers can follow forking scenarios to learn about the topic.

“By bringing all these things together to compare and and contrast we are hoping to bring together a sort of nucleus of what is the essence of fine tuning,” Sloan notes. In addition to funding the creation of the field guide and website, the grant supported a June 2017 conference, held in Crete, which drew leaders in the field including dark matter expert Edward “Rocky” Colb of the University of Chicago; the University of Michigan’s Fred Adams, who gave a talk on what stars might be like in other universes; University of Cape Town mathematician George Ellis, who talked about the underlying physics of fine tuning’s effects on biology; and Rutgers philosopher of science Barry Loewer, who examined the philosophical problems provoked by fine tuning. Loewer contrasted Leibniz and his followers’ view that other universes are in some sense possible with the view that there are other actual universes — the so-called “multiverse” scenario.

“The true highlight of the conference for me,” Sloan says, “was seeing all these people come together, discuss and observe how each other refer to these ideas of fine tuning, and the interactions that caused.”

A FORTUNATE UNIVERSE

Another speaker at the Crete conference was the University of Sydney’s Luke Barnes, whose Templeton Foundation-funded work on simulations of galaxy formation has run in parallel with his outreach work, making the latest thought on fine tuning accessible to the interested public. In 2016 Barnes and his advisor Geraint Lewis published A Fortunate Universe: Life in a Finely Tuned Cosmos, a 388-page introduction and overview of the evidence for and potential implications of fine tuning. The book has received favorable reviews both from within the fields of physics and philosophy and in mass-market publications like the Wall Street Journal. In it, Barnes and Lewis meander in Socratic fashion through fine tuning theory, leavening the equations with helpful metaphors and comic asides.

Whether in the book or in his frequent lectures to fellow academics and to members of the broader public, Barnes has noticed that fine tuning spurs a very different type of audience response than the usual scientific presentation. “No matter what the audience, you always get questions,” he says. “When I give talks on other astronomy topics, I sometimes get questions. But when you present fine tuning, people think that either something has to follow from it, or we have to take this fact and insulate it so nobody tries to conclude anything.” Barnes says audience members are sometimes so enthusiastic about the implications of fine tuning theory that as soon as a question is asked, someone else in the audience will shout out a possible answer. “Everyone discovers that they have an opinion,” he says.

TUNED TO BE HEARD?

The very term fine tuning invokes the idea of an entity that is doing the tuning. It’s a metaphoric resonance that accounts for much of the excitement around the concept, even though most scientists emphasize that use of the term should not presuppose conclusions about how the finely tuned scenario came to be. Still, many philosophers and theologians find the apparent unlikelihood of our universe to be a compelling argument that they were fine-tuned with a purpose in mind.

Robin Collins, a philosopher at Messiah College in Pennsylvania and Templeton grant recipient, argues that the laws of physics seem to be dialed in not just to allow a universe in which life can occur, but to give sufficiently intelligent life the ability to learn about it. “Physicists had already noted that the mathematical structure of the laws of nature look unusually good for us discovering what they are,” Collins says. “I’m saying, ‘Let’s see if the actual universe is set up just right so that we humans can discover it.’” According to Collins, the evidence suggests that the universe was not just fine-tuned for galaxies, or life, or even intelligent life, but for scientists.

SCRATCHING THE ITCH

In the final slide of his presentation at the fine tuning conference in Crete, Barry Loewer, who had just outlined some of his philosophical objections to many common interpretations of fine tuning, offered this reflection: “When a physicist sees laws, constants, initial conditions as being fine tuned, it is as if she has an itch. Sometimes scratching it relieves the itch…. Sometimes scratching the itch just causes it to itch more.… And sometimes the itch is just in our minds.”

In funding a variety of approaches to fine tuning, the John Templeton Foundation hopes to help scientists, philosophers, and even the odd theologian come to terms with these different varieties of itchiness. The goal is neither to use fine tuning as an unnecessary crutch for explanations which current science simply has yet to unravel, nor to rule out explanations — whether a deity or a multiverse — not easily examined by the standard tools of science. We may or may not live in the best of all possible worlds, but we certainly seem to live in a world where exploration and discovery, like the fruitful conversations that took place in Crete in 2017, is surprisingly possible.