Evidence? Who Needs it?

In order to escape the overwhelming evidence that cosmic fine-tuning offers to those who believe the universe to be intelligently designed, many skeptics have staked their money, or at least their professional reputations, on the concept of a multiverse, for which there's scarcely any evidence at all. The multiverse, however, seems to be suggested by string theory, for which there's also scarcely any evidence, but it remains a popular hypothesis in some circles nonetheless.

One might be forgiven for thinking that this popularity is due to the fact that without it the multiverse would be seen as sheer fantasy, and without the multiverse there's no escaping the conclusion that our universe appears to have been intentionally designed for life by a mathematical supergenius.

Cosmologist Bernard Carr once said that “If there is only one universe you might have to have a fine-tuner. If you don’t want God, you’d better have a multiverse.” Of course, there could be both, but if there is a multiverse it obviates one of the best arguments for the existence of God, i.e. the argument based on cosmic fine-tuning.*

Denyse O'Leary brings us a nice summary of some of what's being said about string theory in an article at Evolution News and Views. She begins with the relationship of string theory to multiverse theory:

[S]tring theory... undergirds the concept of a multiverse: There are more universes than particles in our known universe.

How so? To work at all, string theory requires at least nine spatial dimensions (six of which are curled up out of our sight) plus time. But if our universe (three spatial dimensions plus time) arose randomly among the ten dimensions of possibilities (the “string landscape"), theorists reckon that there should be about 10^500 universes (or more). [If there are that many different worlds then] literally anything can happen, has happened, and will happen over and over again.

The sheer number suffocates the evidence for fine-tuning. Our universe happens to look fine-tuned? But the theoretical others don’t. New Scientist spells it out: “This concept of a ‘multiverse’ could explain a puzzling mystery — why dark energy, the furtive force that is accelerating the expansion of space, appears improbably fine-tuned for life. With a large number of universes, there is bound to be one that has a dark energy value like ours.”

O'Leary goes on to discuss the theory of Supersymmetry, for which there's scarcely any evidence either, and notes the opinion of Peter Higgs, the physicist who predicted the existence of the Higgs Boson:

Curiously, Peter Higgs...is not a believer in either supersymmetry or the multiverse: “It’s hard enough to have a theory for one universe,” he says. As the Economist pointed out in 2016, “Supersymmetry is a beautiful idea. But no evidence supports it.”

The lack of evidence and the inability to test these theories is starting to embarrass some science writers and critics:

Critics, perhaps less imaginative than the theorists, decry string theory’s lack of testability. Science writer Philip Ball complains, “Proposing something as dramatic as seven extra dimensions, without offering the slightest prospect of testing to see if they are there, is a step too far for some physicists.” ....Physicist Ethan Siegel tells us bluntly at Forbes that string theory is not science: It cannot be tested.

Physicist Frank Close is blunt: “[M]any physicists have developed theories of great mathematical elegance, but which are beyond the reach of empirical falsification, even in principle. The uncomfortable question that arises is whether they can still be regarded as science.”

Science writer John Horgan, even blunter, scoffs [at the proliferation of untestable hypotheses in physics] “At its best, physics is the most potent and precise of all scientific fields, and yet it surpasses even psychology in its capacity for bull****.”

Evidence or no, string theory remains popular. Skeptical Columbia mathematician Peter Woit wonders why: “The result of tens of thousands of papers and more than 30 years of work is that all the evidence is that if you can get something this way that looks at all like the Standard Model, you can get anything. Normally when that happens you simply acknowledge the problem and give up, but for some reason that hasn’t happened.”

If science-based reasoning doesn’t explain string theory, cultural history might: A culture might wish a multiverse into existence despite the facts, to satisfy emotional needs such as making naturalism appear to work. As Philip Ball says, “[N]ailing your flag to the mast of string theory has come to be seen as an expression of faith rather than reason, and physics has become polarised into believers and sceptics.”

The string theory/multiverse complex resists being thrown into the dustbin of discarded scientific ideas because for metaphysical naturalists it's really the only game in town. If there's only one universe then, as Bernard Carr said over a decade ago, you pretty much have to accept that it was intelligently designed. The improbability of so many conditions, force values, parameters, etc. being calibrated within tolerances so fine that deviations in some cases of just one part in 10^120 would have prevented the universe from existing at all is so astronomical as to make the notion that our universe is just an accident literally incredible.

* Here are just a few examples of cosmic traits which must be set to the precise values they have or life as we know it would be impossible:

• Stars like the sun produce energy by fusing two hydrogen atoms into a single helium atom. During that reaction, 0.007 percent of the mass of the hydrogen atoms is converted into energy, via Einstein’s famous e = mc2 equation. But if that percentage were, say, 0.006 or 0.008, the universe would be far more hostile to life. The lower number would result in a universe filled only with hydrogen; the higher number would leave a universe with no hydrogen (and therefore no water) and no stars like the sun.
• The early universe was delicately poised between runaway expansion and terminal collapse. Had the universe contained much more matter, additional gravity would have made it implode. If it contained less, the universe would have expanded too quickly for galaxies to form.
• Had matter in the universe been more evenly distributed, it would not have clumped together to form galaxies. Had matter been clumpier, it would have condensed into black holes.
• Atomic nuclei are bound together by the so-called strong force. If that force were slightly more powerful, all the protons in the early universe would have paired off and there would be no hydrogen, which fuels long-lived stars. Water would not exist, nor would any known form of life.