Choose You This Day: Multiverse or I.D.
If Leonard Susskind is right, cosmologists are escaping the conclusion of intelligent design (ID) by backing into a radically speculative idea: a near infinity of universes. Susskind, a theoretical physicist from Stanford, just published a book, Cosmic Landscape: String Theory and the Illusion of Intelligent Design (Little, Brown 2005), that explores current cosmological thinking about the Anthropic Principle – the observation that the constants of physics in our universe appear finely tuned to make stars, planets and life possible. Susskind was interviewed by Amanda Gefter in New Scientist.
Susskind spoke as if he and other cosmologists have been forced into the concept of a multiverse (multitude of universes, of which our entire universe is just one sample) because the fine-tuning problem won’t go away. Try as they might, physicists cannot come up with a theory that explains why the constants are the way they are. All they know is that, were they different, life would be impossible in our universe. Initially, string theory seemed to allow for a million possible vacuum states that would have determined the type of universe that emerged. That was not enough, Susskind thought; getting one life-giving universe out of a million was still too improbable. When two physicists upped the number of vacuum states to 10500, Susskind became a believer. Out of that many universes, surely some would have the anthropic conditions for life. We notice ours does, because we’re in it. Intelligent design could remain just an illusion, therefore, because uncountable numbers of other universes exist with random values for the physical constants.
When Susskind started sharing this idea, “The initial reaction was very hostile, but over the past couple of years people are taking it more seriously,” he said. “They are worried that it might be true.” Cosmologist Stephen Weinberg considers it “one of the great sea changes in fundamental science since Einstein,” a radical change that alters the nature of science itself.
In a way it is very radical but in another way it isn’t. The great ambition of physicists like myself was to explain why the laws of nature are just what they are. Why is the proton just about 1800 times heavier than the electron? Why do neutrinos exist? The great hope was that some deep mathematical principle would determine all the constants of nature, like Newton’s constant. But it seems increasingly likely that the constants of nature are more like the temperature of the Earth – properties of our local environment that vary from place to place. Like the temperature, many of the constants have to be just so if intelligent life is to exist. So we live where life is possible. (Emphasis added in all quotes.)
Susskind remarked that the conclusion of a vast ensemble of universes came as a disappointment to many physicists. He himself finds the idea that reality might be vaster than we ever imagined “exciting.” It doesn’t destroy the hope for a grand unified theory, he claims; now, the challenge is not to explain just our universe, but the entire array of all possible universes. Unfortunately, another disappointment is the realization there appears to be no principle of natural selection among the universes that would favor the life-giving types. There is “no evidence for this view,” he admitted; “Even most of the hard-core adherents to the uniqueness view admit that it looks bad.” Furthermore, Susskind is unconvinced by appeals to exotic forms of life that might exist without worlds; “in my heart of hearts,” he said with resignation, “I just don’t believe that life could exist in the interior of a star, for instance, or in a black hole.”
Susskind denied that belief in a multiverse will bring on the “Popperazzi” – those who follow Karl Popper’s teaching that an idea must be falsifiable to be scientific. His reason? Undetectable universes are no more metaphysical than claiming our universe is homogeneous, including the parts beyond our observational horizon. He even suggested ways to test it, such as looking for evidence of negative curvature that might suggest our universe tunneled from one vacuum state to another.
Last, Gefter asked him if we are “stuck with intelligent design” if we do not accept his landscape hypothesis.
I doubt that physicists will see it that way. If, for some unforeseen reason, the landscape turns out to be inconsistent – maybe for mathematical reasons, or because it disagrees with observation – I am pretty sure that physicists will go on searching for natural explanations of the world. But I have to say that if that happens, as things stand now we will be in a very awkward position. Without any explanation of nature’s fine-tunings we will be hard pressed to answer the ID critics. One might argue that the hope that a mathematically unique solution will emerge is as faith-based as ID.
A blogger named David Heddle on HeLives.com, with “reformed views of a nuclear physicist,” found Susskind’s remarks in this interview profoundly unsatisfying; “To save materialism,” he quipped, “Susskind argues that we must explain this fine-tuning, and his landscape has the best chance of playing the role of a white knight.”
George Ellis (U of Cape Town) also reviewed the book for Nature last week.1 He quipped about how physicists used to deal with real, observable stuff; “Nowadays things have changed,” he said. “A phalanx of heavyweight physicists and cosmologists are claiming to prove the existence of other expanding universe domains even though there is no chance of observing them, nor any possibility of testing their supposed nature except in the most tenuous, indirect way.” Ellis confirms that Susskind argues for the multiverse because of the “anthropic issue: the ‘apparent miracles of physics and cosmology’ that make our existence possible.” The only way out was to posit a large enough set of random combinations of universes such that “the incredibly special conditions for life to exist will inevitably occur somewhere in the multiverse.” It follows, then, that “The apparent design of conditions favourable to life in our own universe domain can therefore be explained in a naturalistic way.”
What does Ellis think about this argument? He is uncomfortable that it is neither testable nor predicted from well-established physics. It is also a vacuous answer: “if all possibilities exist somewhere in the multiverse, as some claim, then it can explain any observations, whatever they are.” Ellis finds the test that Susskind proposes only partially in its favor, but even then, the data are not exactly supportive. He finds this “a symptom of some present-day cosmology, where faith in theory tends to trump evidence.” He also disparages the use of infinities with “gay abandon” and the use of the “many-worlds” hypothesis of quantum mechanics for support, “an unproven and totally profligate viewpoint that many find difficult to take seriously.” Speaking of faith, Ellis waxes philosophical on the subject – even theological – gently chiding Susskind for lack of scientific rigor:
As a philosophical proposal, the multiverse idea is interesting and has considerable merit. The challenge facing cosmologists now is how to put on a sound basis the attempts to push science beyond the boundary where verification is possible – and what label to attach to the resultant theories. Physicists indulging in this kind of speculation sometimes denigrate philosophers of science, but they themselves do not yet have rigorous criteria to offer for proof of physical existence. This is what is needed to make this area solid science, rather than speculation. Until then, the multiverse situation seems to fit St Paul’s description: “Faith is the substance of things hoped for, the evidence of things not seen.” In this case, it is faith that enormous extrapolations from tested physics are correct; hope that correct hints as to the way things really are have been identified from all the possibilities, and that the present marginal evidence to the contrary will go away. This book gives a great overview of this important terrain, as seen from an enthusiast’s viewpoint.
1George Ellis, “Physics ain’t what it used to be,” Nature 438, 739-740 (8 December 2005) | doi:10.1038/438739a.
Read this as a stunning defeat by the materialists and a victory for intelligent design. In a debate, when your opponent’s only retreat is to espouse an absurd position, you know you are winning. Like bugs scrambling for cover when a rotting log is lifted, the materialists are avoiding the light of intelligent design at all costs. They call to speculative mountains and rocks, saying, “Fall on us, and hide us from the design inference, for the light of fine-tuning has come, and who is able to stand?”
To clarify one mistake in Susskind’s last quote, ID is not faith-based, except in the sense of putting faith in the uniformity of experience. ID makes a design inference when specified complexity is detected. The specification in this case is the precision of the values of physical constants which permit the existence of stars, planets and life. Susskind conceded the point that there does not seem to be any way that the correct values were determined; i.e., the constants appear contingent, not necessary. In most universes, random values would make life impossible. A straightforward application of ID reasoning follows. There is a specification, there is low probability – the universe, therefore, was designed.
Susskind cannot escape Popper’s falsification criterion by claiming others violate it, too. That doesn’t work with cops, nor with scientific requirements. The Popperazzi have a warrant to arrest his landscape hypothesis on the grounds it is unfalsifiable.
This entry can also be taken as a resounding endorsement of claims made in the film and book The Privileged Planet. The second part of the film argued that the fine-tuning of the universe implies intelligent design. In the Q&A portion, William Lane Craig emphasized how precise the tuning is, and dealt squarely with the opposition tactic of retreating into a multitude of universes; he said that cosmologists have been “driven beyond physics to metaphysics” to the “extraordinary” position of postulating an infinite ensemble of universes, all in order to rescue the materialistic, chance hypothesis from the evidence. Guillermo Gonzalez followed up by stating the obvious: this idea cannot be scientific, because there is no way to test it. It’s a metaphysical response to the physics we observe. To this we add, Susskind’s proposed test is circular, because it depends on the very materialistic assumptions that are being contested. Materialism is being debated; the observation of fine-tuning is not.
The admissions made by Susskind in this interview provide all the more reason to hand out copies of the Privileged Planet DVD to skeptical friends and invite them to think about it. Now you can print out copies of this New Scientist interview as supportive material, and ask the skeptic if he or she finds the multiverse escape clause as awkward as Susskind describes it, or more “faith-based” than following the evidence to its logical conclusion. “Come to the light” can be an appropriately modern invitation to the cosmological sinner.