In 2015, Wired told us that physicists were desperate to be wrong about the Higgs boson. They yearned to push the Standard (Big Bang) Model of the universe “in new directions.” But the unmindful particle “acted just like the model said it would act, obeyed every theorized rule.”
In the silence that followed, asking for evidence for these physicists’ proposed infinity of universes (the multiverse) felt like assaulting a victim’s feelings. At the Guardian, Stuart Clark later informed us that “Brexit and Trump are nothing compared to the alternate universes some astronomers are contemplating.” Really? Regional political upsets vie with a multiverse?
Astronomers, Clark tells us, pin their hopes on the Cold Spot, a cool patch of space from the early universe: “We can’t entirely rule out that the Spot is caused by an unlikely fluctuation explained by the standard theory. But if that isn’t the answer, then there are more exotic explanations.” Indeed. There are more exotic explanations for almost anything.
Eugene Lim insisted at The Conversation in 2015 that parallel universes are science: “Whether we will ever be able to prove their existence is hard to predict. But given the massive implications of such a finding it should definitely be worth the search.” Very well, but some people research ghosts on the same basis. What makes the multiverse quest “science” but the ghost hunt “anti-science,” once evidence no longer matters as much as it used to?
Cosmologists sense the problem and strive to rescue their multiverse from the nagging demands for evidence. Pop science media offer a window into major trends.
One is cosmic Darwinism. Lee Smolin has advocated a cosmic version of Darwinian natural selection in which the most common universes will be those most suitable for producing black holes, as our universe does. Is Darwinism the cause? In “The Logic and Beauty of Cosmological Natural Selection” (Scientific American, 2014), Lawrence Rifkin admitted that the main problem with the hypothesis is lack of direct evidence:
But keep in mind that from a direct evidence perspective, cosmological natural selection is no worse off at this point than proposed scientific alternatives. There is no direct evidence that universes are created by quantum fluctuations in a quantum vacuum, that we live in a multiverse, that there is a theory of everything, or that string theory, cyclic universes or- brane cosmology even exist.
Then why should we not set all such speculations aside? There is no obvious need for hurry.
Darwinism, as in natural selection acting on random mutations, is a theory developed by Darwin and his followers to account for complex, specified information in life forms on this planet. Whether it is correct or not when used as intended, if it is applied to an undetected multiverse, it becomes philosophy (metaphysics).
An anecdote suffices. As Michael Egnor has observed here, philosopher Joseph P. Carter told us in the New York Times that the universe does not care about purpose. Evolutionary psychologist Michael E. Price disputes that view at Psychology Today, insisting that in a multiverse natural selection can create purpose. His position is denied by most of natural selection’s advocates in biology. But, riffing on Smolin, Price explains that “life is more likely than black holes (or anything else) to be a mechanism of universe replication.” If this kind of ungrounded assertion is the best naturalism can do for us now, why do we encourage it?
Physicist Ethan Siegel counsels at Forbes that we must not “doubt the Multiverse’s existence without considering the very good, scientific reasons that motivate it.” But “very good scientific reasons” are precisely what we lack, unless the term “scientific reasons” now includes immunity to “experimental and observational tests.” Similarly, physicist Brian Cox told us in 2016 that the “idea of multiverses is not too big a leap” from cosmic inflation. But he is dealing with leaps of the imagination, not of physics discoveries.
Earlier this year, skeptical mathematician Peter Woit fretted with science writer John Horgan at Scientific American, “The problem with such things as string-theory multiverse theories is that ‘the multiverse did it’ is not just untestable, but an excuse for failure.” Commenting elsewhere on Zeeya Merali’s A Big Bang in a Little Room (2017), he noted that she contemplates “the possibility that “string theory and inflation may be conspiring against us in such a way that we may never find evidence for them, and just have to trust in them as an act of faith.” He would describe it as “a scientifically worthless idea.”
With a clash of world views, where to begin? Woit and Horgan assume that post-modern science is a quest to understand reality, just as traditional science has been. It is not.
For many people today, post-modern science is more of a quest to express an identity as believer in science, irrespective of evidence. Cosmologist Paul Steinhardt got a sense of this in 2014, when he reported that some proponents of early rapid cosmic inflation “already insist that the theory is equally valid whether or not gravitational waves are detected.” It fulfilled their needs. In 2017, cosmologist George Ellis, long a foe of post-modern cosmology, summed it up: “Scientific theories have since the seventeenth century been held tight by an experimental leash. In the last twenty years or so, both string theory and theories of the multiverse have slipped the leash.”
We have so much more data now. But it provides no evidence for a multiverse. That’s nothing unusual historically (think phlogiston and ether for great ideas that did not work). We used to just adjust. But today, increasing numbers of science-minded people demand a post-modern science that adapts to their needs. After all, we evolved to survive and pass on our genes, not to understand reality.
As a result, many cosmologists and science writers speak as if the multiverse merely awaits routine administrative clearance to morph into textbook science, absent evidence. Characteristically, they see themselves as fighting a conservative (fuddy-duddy) establishment which clings to a role for mere evidence.
Fine tuning of our planet and our universe for life sets limits on mere belief by challenging us to calculate probabilities. The multiverse is deeply attractive by comparison because it dissipates evidence. It conjures unimaginably infinite, unproven, and incalculable probabilities. As New Scientist puts it, “We merely inhabit one out of the infinite selection.” That feels so right just now.
The multiverse has only ever existed, so far as we know, in the mind of man. Its most promising research programs, string theory and early rapid cosmic inflation theory, have bounced along on enthusiasm alone, prompting ever more arcane speculations for which there may never be any possibility of evidence.
But like so many other empty ideas, the multiverse has consequences. If we accept it, we abandon the view that science deals with the observed facts of nature. We adopt the view that it tells us what we want to believe about ourselves. In other words, the multiverse is science’s assisted suicide.