Category Archives: Science & Philosophy

Are Many Worlds and the Multiverse the Same Idea?

Sean Carroll 2017.jpg
Sean Carroll is a cosmologist and physicist specializing in dark energy and general relativity. He is a research professor in the Department of Physics at the California Institute of TechnologyA post on his blog recently caught my attention: “Are Many Worlds and the Multiverse the Same Idea?

When talking about “parallel worlds” Carroll distinguishes between: a)the “multiverse” of inflationary cosmology; b) the “many worlds” or “branches of the wave function” of quantum mechanics; and c) “parallel branes” of string theory.” While branes represent a distinct idea, Carroll thinks that the multiverse and many worlds ideas might capture the same basic idea. Here’s how he explains the differences between those two ideas:

When cosmologists talk about “the multiverse,” it’s a slightly poetic term. We really just mean different regions of spacetime, far away so that we can’t observe them, but nevertheless still part of what one might reasonably want to call “the universe.” In inflationary cosmology, however, these different regions can be relatively self-contained — “pocket universes,” as Alan Guth calls them. When you combine this with string theory, the emergent local laws of physics in the different pocket universes can be very different; they can have different particles, different forces, even different numbers of dimensions. So there is a good reason to think about them as separate universes, even if they’re all part of the same underlying spacetime.

The situation in quantum mechanics is superficially entirely different. Think of Schrödinger’s Cat. Quantum mechanics describes reality in terms of wave functions, which assign numbers (amplitudes) to all the various possibilities of what we can see when we make an observation. The cat is neither alive nor dead; it is in a superposition of alive + dead. At least, until we observe it. In the simplistic Copenhagen interpretation, at the moment of observation the wave function “collapses” onto one actual possibility. We see either an alive cat or a dead cat; the other possibility has simply ceased to exist. In the Many Worlds or Everett interpretation, both possibilities continue to exist, but “we” (the macroscopic observers) are split into two, one that observes a live cat and one that observes a dead one. There are now two of us, both equally real, never to come back into contact.

Now clearly these ideas differ. Most notably, in the multiverse, the other universes are far away whereas, in quantum mechanics, they’re right here in different possibility spaces. (technically different parts of Hilbert space.) Still, some physicists have been wondering about the connection between the two ideas. And, after reading the recent literature, Carroll has “gone from a confused skeptic to a tentative believer.”

Carroll has changed his mind because of two ideas that fit together to make this crazy-sounding proposal plausible—quantum vacuum decay and horizon complementarity. Roughly quantum vacuum decay implies that “at any point in space you are in a quantum superposition of different vacuum states.” But horizon complementarity means that “you can talk about what’s inside your cosmological horizon, but not what’s outside.” Carroll concludes:

The result is: multiverse-in-a-box. Or at least, multiverse-in-an-horizon. On the one hand, complementarity says that we shouldn’t think about what’s outside our observable universe; every question that it is sensible to ask can be answered in terms of what’s happening inside a single horizon. On the other, quantum mechanics says that a complete description of what’s actually inside our observable universe includes an amplitude for being in various possible states. So we’ve replaced the cosmological multiverse, where different states are located in widely separated regions of spacetime, with a localized multiverse, where the different states are all right here, just in different branches of the wave function.

Carroll admits not knowing if any of this is true, although he is “inclined to think that it has a good chance of actually being true.” As for the implications for physics and for us, I’m in the dark. I’m simply don’t know what to do with the idea of a multiverse and parallel universes. Try as I may, our mysterious reality confounds me.

Why Earth’s History Appears So Miraculous

A person holds a globe against a background of Earths hit by meteors, crumbling, and colliding with rockets.

Here is a brief recap of Peter Brannen’s recent piece in the Atlantic: “Why Earth’s History Appears So Miraculous: The strange, cosmic reason our evolutionary path will look ever luckier the longer we survive.

Brannen begins by introducing us to the observer selection effect. (An observation selection effect exists when some property of a thing is correlated with the observer existing in the first place. For example, if intelligence hadn’t evolved, we wouldn’t exist, and couldn’t evaluate the probability of intelligence evolving.) The question Brannen asks is whether this bias applies to our planet.

If you consider all the existential threats our planets faced: “It’s something of a miracle that life on our planet has been left to evolve without fatal interruption for billions of years.” Of course, if we had been wiped out we wouldn’t be here to contemplate our existence. Thus, as a result of the selection effect, we probably underestimate the observed frequencies of cataclysmic events. And this means that “our forecasts about the future could be blinded by our necessarily lucky past.”

As Anders Sandberg, a senior research fellow at Oxford’s Future of Humanity Institute says:

Maybe the universe is super dangerous and Earth-like planets are destroyed at a very high rate, but if the universe is big enough, then when observers do show up on some very, very rare planets, they’ll look at the record of meteor impacts and disasters and say, ‘The universe looks pretty safe!’ But the problem is, of course, that their existence depends on them being very, very lucky. They’re actually living in an unsafe universe and next Tuesday they might get a very nasty surprise.

Perhaps this explains the Fermi paradox too. The reason we find no evidence of alien life is because there are no (or few) aliens that have survived and we exist only due to unimaginable good luck.

Consider, for example, that so far we haven’t destroyed ourselves with nuclear weapons. This may lead us to believe that nuclear war is unlikely, but if we take observer selection effects into account we’ll realize that the fact that we’re still here tells us little about our chances for future survival. Nuclear annihilation may be virtually certain but in a big enough universe some civilizations avoid extinction for a long time. We may seem safe but more likely we’ve just been lucky. (In fact, we’ve come close to destroying ourselves with nuclear weapons multiple times. Our planet is just the one where Stanislav Petrov didn’t push the button.)

Extending this insight further, the observer selection effect may explain why the universe hasn’t succumbed to vacuum decay or some other catastrophe. We exist so we think such a scenario is unlikely, but that’s because we’re in a universe that has survived. The situation gets even stranger if you consider the “many worlds” multiverse. As the cosmologist, Anthony Aguirre states:

… suppose the many-worlds interpretation of quantum mechanics is right … So, one of the two versions of us ceases to exist, but do we actually notice that? So one of us keeps going on just as if nothing happened. Arguably, from moment to moment, I can’t rule out that five minutes ago the other version of us died. There’s no way for me to say that. So there’s an interesting, troubling question as to whether these things could be happening all the time and we just don’t even notice it.

All I can say is that the mind boggles at such suggestions. When confronted with possible implications of multiple realities my mind recoils.

Science and the Meaning of Life

The Universe represented as multiple disk-shaped slices across time.

( This article was reprinted in Humanity+ Magazine, Institute for Ethics & Emerging Technologies and Church and State.)

1. Facts and Meaning

All the truths of modern science are at least somewhat relevant to considerations of meaning. But why? What it is about scientific facts that make them especially germane? Consider that the decline of influence the Christian worldview in the 17th century West was the catalyst for the meaning of life question taking on a new significance. And what precipitated that decline? While there were certainly many factors, the rise of modern science was a prominent one. The removal of humans from the physical center of their universe with the rise of heliocentric, and their further demotion as the center of biological creation with the rise of evolutionism undermined much of what had previously given life meaning—specifically, the view that humans were central in the creation and design of reality. In contrast, modern science advances a radically different world-view whose foundation is an unimaginably large body of overwhelming evidence, one which continually grows and deepens the original insights of cosmology, biology and other sciences. One ignorant of such ideas has no chance to construct a realistic worldview.

For our purposes then, we must take into account the truths of modern science. One simply cannot have a coherent picture of what the world is like without knowing something of modern science because science is the only cognitive authority in the world today. Yes, there are an infinite number of things that science has yet to discover, there may be truths that science cannot by its nature uncover, and there may be other means by which to tease truth from reality than the scientific method. Furthermore, science is not dogmatic, and no matter how well confirmed its theories they are always provisional—open to change in light of new evidence. Nonetheless, we insist that the well established truths of science must be a starting point for our inquiry, as theoretical musings and introspection are no substitute for hard-won empirical evidence. Science consists of an immeasurable amount of knowledge—which is daily confirmed by the wonders of the technology it spawns. We simply must begin with the best knowledge of ourselves and our world that we have—the knowledge provided by modern science.[i]

But, as the body of scientific knowledge is vast, which parts of it are most relevant to our inquiry? I think cosmology and biology would be those sciences. Both are precise and both have important things to say about the meaning of life. Cosmology, broadly conceived as referring to the current state of the universe as well as to it origin and fate, is obviously applicable to our concerns. Biology is also most important; it is the science that tells us what human nature is. Given the particular importance to our inquiry of the origin, evolution, and fate of the cosmos, I suggest we focus on what science tells us about these issues to see the importance of scientific knowledge to our inquiry. Surely what we know, and do not know, about these issues is significant to our pursuit.

2. The Origin and Fate of the Universe

Our universe began about 13.81 billion years ago. (That humans have discovered this fact with such great precision is itself a testimony to the power of science. It is truly an astonishing discovery if you stop to think about it, and we are the first living people who have known this.) Cosmology is very speculative as to what happened before then—assuming it even makes sense to talk about a before-–but competing ideas include: 1) the universe emerged from nothingness, space and time were created in the big bang and thus there was no space or time before the big bang; 2) the universe resulted from the movement or collision of membranes (branes), as in string theory; 3) the universe goes through endless self-sustaining cycles where, in some models, the universe expands, contracts, and then bounces back again; and 4) that the universe grew from the death of a previous universe. The last three proposals all argue that the Big Bang was part of a much larger and older universe, or multiverse if you will. Hence such models don’t consider the Big Bang to be the literal beginning.

Although the details of these and other competing models go beyond the scope of our inquiry, suffice it to say that none of them, or any other variants likely to be proposed, have any place in them for supernatural gods nor do they say anything about meaning. The universe is indeed mysterious, but gods apparently will not play a role in explaining it.[ii] Furthermore, scientific cosmogonies have generally replaced the religious cosmogonies that preceded them, at least among the scientifically literate. The main differences between the two types of cosmogonies are first, that the scientific accounts are supported by good reasons and evidence, and second, that there is no obvious place in scientific accounts for meaning, as there was in religious creation myths. It is not surprising then that so many are threatened by a scientific worldview. Even if we are uncertain which if any of the scientific cosmogonies is true, the damage has been done; what we now know of the origin of the universe undermines our previous certainty about meaning.

When we turn to the future of the cosmos the issue is also highly speculative. The most likely scenarios based on present evidence are that the universe will: 1) reverse its expansion and end in a big crunch; 2) expand indefinitely, exhausting all its heat and energy ending in a big freeze; 3) eventually be torn apart in a big rip; 4) oscillate, contract, and then expand again from another big bang, the big bounce; or 5) never end, since there are an infinite number of universes or multiverses. (There are other versions of this basic story.) Needless to say, in none of these scenarios do the gods play a role nor do any of them appear especially conducive to meaning. As was the case with the origin of the universe, the important point is that there are alternative scenarios concerning the fate of the universe that were inconceivable to our ancestors, and these alternatives are not obviously comforting. The mere knowledge of these alternatives undermines our certainty about the meaning of our lives.

However, it should be admitted that science is highly speculative on such matters; these are defeasible scientific claims. Nonetheless, I would not bet against the ability of science to eventually unravel these great secrets, as the march of scientific knowledge is inexorable, and no positing of a “god of the gaps” is likely to help.[iii] Until then, the good news is that views such as the multiverse theory at least give us reason to reject universal death. If universal death was assured, the case against meaning might be overwhelming, but since it is not we may have a window of meaning left open to us. The bad news is that none of the scientific theories look obviously conducive to objective meaning. To be fair, we probably don’t know enough about these highly speculative areas of science to draw strong conclusions about meaning, except to say again that scientific theories about the origin and fate of the cosmos undermine the previous certainty people had regarding these issues.

3. Evolution

In between the beginning and end of the cosmos is its evolution. If you think of this inconceivably long period of time it is easy to understand that things must evolve—they change over time. From 13.81 billion years to today there is a long story of cosmic evolution, the outline of which we know in great detail. The important point for our purposes is that human beings, an incredibly late arrival on the cosmic scene, were forged through genetic mutations and environmental selection. This is beyond any reasonable doubt, and anyone who tells you differently is either scientifically illiterate or deceiving you.[iv] Ernst Mayr, widely considered the twentieth century’s most eminent evolutionary biologist, and sometimes called the Darwin of the twentieth century, put it this way: “Evolution, as such, is no longer a theory for the modern author. It is as much of a fact as that the earth revolves around the sun.” He added: “Every modern discussion of man’s future, the population explosion, the struggle for existence, the purpose of man and the universe, and man’s place in nature rests on Darwin.”

In short, there is simply no way to understand anything about ourselves without understanding evolution—not our bodies, our behaviors, or our beliefs. This is why biology is so crucial to making sense of the human condition; it is the science that makes the study of human nature potentially precise.[v] This does not mean that knowledge of evolution tells us everything about the meaning of life, but that the process of evolution is the indispensable consideration for any serious discussion of the meaning of human life.

In our limited space we cannot discuss all of the implications of evolutionary biology for understanding human life and nature. Suffice it to say that the evolutionary paradigm has been gradually extended by various thinkers since Darwin to apply, not only to our bodies, but to the evolution of minds and behaviors. When we move the application of the evolutionary paradigm from body to mind we find ourselves dealing with the mind-body problem and evolutionary epistemology; when we move the paradigm from mind to behavior, we are in the realm of the fact-value problem and evolutionary ethics. Possibly we will find in the course of our study that we can apply an evolutionary model to meaning as well. Meaning may be something that evolves as the species and ultimately the cosmos evolve.

The importance of evolution for our understanding of meaning extends obviously then from biological to cultural evolution. The future that comes about as a result of cultural evolution may itself be the purpose of life; where we are going, more so than where we came from, may provide meaning. Could it be that the process by which we go from the past to the present is itself an unfolding of meaning?

[i] I would argue that philosophy does not discover truth, science does. Philosophy should concern itself with values and meaning. For more see Jean Piaget’s The Insights and Illusions of Philosophy (New York: Routledge & Kegan Paul, 1977).

[ii] God may be a problem in astrophysics that will stand or fall on the empirical evidence. For more see E.O. Wilson’s “The Biological Basis of Morality” in the Atlantic online April 1998.

[iii] The phrase “god of the gaps” refers to the idea that the gods exist in the gaps of current scientific knowledge. The term is generally derogatory; i.e., critical of the attempt to use gods to explain phenomena that as yet do not have naturalistic explanations.

[iv] This claim is so easy to verify one could construct a separate biography of thousands of works by experts to justify the claim. You could begin simply by consulting the multiple publications and statements at the website of the National Academy of Sciences.

[v] For an introduction to this idea see E.O. Wilson’s On Human Nature (Cambridge: Harvard University Press, 1988), and Consilience: The Unity of Knowledge (New York: Vintage, 1999).

“The Logic and Beauty of Cosmological Natural Selection”

Messier 92 in the Hercules constellation.

I came across a wonderful piece in the June 10, 2014 issue of Scientific American, “The Logic and Beauty of Cosmological Natural Selection” by Lawrence Rifkin MD.  (He writes at or you follow him on Twitter@LSRifkin.)

Rifkin argues that “The hypothesis [of] cosmological natural selection, and its power, beauty and logic provide what may be the best scientific explanation for the existence of complexity and life in the universe.” CNS has been most extensively formulated by the physicist Lee Smolin in his 1992 book The Life of the Cosmos. Here is a basic description:

Throughout the universe, stars that collapse into black holes squeeze down to an unimaginably extreme density. Under those extreme conditions, as a result of quantum phenomenon, the black hole explodes in a big bang and expands into its own new baby universe, separate from the original. The point where time ends inside a black hole is where time begins in the big bang of a new universe. Smolin proposes that the extreme conditions inside a collapsed black hole result in small random variations of the fundamental physical forces and parameters in the baby universe. So each of the new baby universes has slightly different physical forces and parameters from its parent. This introduces variation.

Given these “inherited characteristics, universes with star-friendly parameters will produce more stars and reproduce at a greater rate than those universes with star-unfriendly parameters. So the parameters we see today are the way they are because, after accumulating bit by bit through generations of universes, the inherited parameters are good at producing stars and reproducing.” Of course the existence of stars are crucial because the molecular material contained in stars is a prerequisite of life.

One of the advantages of CNS is that it directly addresses the so-called “fine-tuning problem”–why the laws and parameters of nature are remarkably conducive to life. It answers that the laws of our universe “are the way they are because of non-random naturalistic cumulative inherited change through reproductive success over time.” CNS also explains the complexity and the apparent design of our universe without positing gods, analogous to how natural selection explains the complexity and apparent design of our biology.

Critics might argue that there is no evidence for CNS, but Rifkin points out that there is no direct evidence for other scientific alternatives that would explain the existence of our universe like quantum fluctuations, multiverses, cyclic universes, or brane cosmology. And CNS has the advantage of explaining the fine tuning problem better than the alternatives, which is why Rifkin thinks CNS will eventually be vindicated.

Furthermore CNS has profound implications for the question of life’s meaning. “In a world of branching universes conducive to life, ultimate cosmic doom may be avoided, keeping alive the possibility of eternity – not for us as individuals, or for Homo sapiens, but for the existence of life at large in the cosmos.” So the future of the cosmos is open, still to be determined–surely a more hopeful message that inevitable cosmic death. Yet this does not imply that we were meant to be here, that the universe cares about us, or that any teleology is at work–Rifkin definitely rejects any god of the gaps.

In the end CNS, like any scientific idea, stands or falls on the evidence. “If evidence proves any one of the cosmological alternatives—or an entirely new idea altogether—we will embrace reality, no matter where it leads, and be struck with awe at our ability to discover the grandest of cosmological truths and our place in the universe.”


I am unqualified to adjudicate between various cosmological theories but CNS is a robust theory that is consistent with perhaps the greatest idea of all time–the idea that everything, from the cell to the cosmos, evolves over time. Moreover CNS provides a straightforward solution to the fine-tuning problem. I have no doubt that there is a naturalistic solution to this problem–assuming we can even be sure the cosmos is fine tuned. (Some theorists suggest we don’t know enough to say for sure.) But if our universe is fine tuned, then naturalistic solutions will explain it. Scientific solutions will close this gap in our knowledge like they have previously closed so many others. This is after all one of the main reasons why so few philosophers are non-naturalists.Science works.

Still people will find their gods hiding in the gaps of quantum or cosmological theories, or in dark matter or energy. If you are determined to believe something it is hard to change your mind. But defenders of the gods fight a rearguard action–scientific knowledge is relentless–and these hidden gods are nothing like the traditional ones. Those gods are dead.

And as science closes the gaps in our knowledge the gods will recede further and further into the recesses of infinite space and time until they vanish altogether, slowly blown away, not by cosmic winds, but by ever encroaching thought.

On “The one thing Neil deGrasse Tyson got wrong”

Neil deGrasse Tyson in June 2017 (cropped).jpg

Steve Neumann wrote a provocative piece in the June 7, 2010 issue of Salon magazine entitled: “The one thing Neil deGrasse Tyson got wrong.” Neumann argues that Tyson’s and many other scientists have “come to believe that to distinguish true knowledge from surface appearance and error is still the worthiest goal of human life, with the implication that only because existence is comprehensible is it justified.” Neumann identifies this attitude with scientism which he says “is the conviction that science really is the only worthwhile human endeavor.”This attitude naturally leads to a denigration of other disciplines, as Tyson’s persistent attacks on philosophy reveal.

Neumann argues that Tyson’s attacks on philosophy are misguided and that “the perspectivism and nuance of full-strength philosophy provide the catalyst that can transmute the lead of knowledge into the gold of flourishing.” In other words knowledge is one thing but living well is quite another. We have all known individuals who possess storehouses of knowledge but do not flourish, and we have known simple people who have good lives.  Neumann grants that science contributes mightily to human flourishing but that it can’t solve the problem on its own. 

What we find when we philosophize is that we are by nature ambivalent toward life. We recognize its beauty and joy while at the same time its tragedy and absurdity. But we must resolve this problem aesthetically and philosophically, science plays a subordinate role here. Consider, says Neumann, how we should feel about the vastness of the universe. Should we feel small or large? Now some feel small, some large, and some small and large at the same time. But how we feel is a philosophical response—it’s an aesthetic view of reality that does not derive from the facts alone. The facts alone do not furnish or rescind meaning.

So the human being herself brings to existence her own meaning and her own feeling; the artist in her brings life to existence—and thereby brings existence to life …

… the aesthetic impulse engenders that synthesis of reason and emotion that enables us to muster the will to transcend the reality of those bitter [natural] truths. The individual who wants to resolve her ambivalence toward life must be equal parts scientist, philosopher and poet, cultivating a wholehearted, meditative disposition within herself.

And what is needed in the public sphere is what Nietzsche called an “artistic Socrates,” someone in whom aesthetic feeling combined with the virtues of science “can reshape the disgust at the thought of the horrific or absurd aspects of life into notions with which it is possible to live.” Only this fusion of reason and imagination can reconcile our intellectual and emotional lives, giving us both claritas and gravitas – understanding and profundity.

I think Neumann is right that we begin with the facts as best science can determine them and then philosophize about their meaning. Thus we must be scientist, philosopher, and poet to give meaning to the endless vastness which surrounds us and to the infinite loneliness which penetrates within. We can still affirm life; we can imagine Sisyphus happy; we can release our imprisoned artist. In fact we must if we are to give life meaning. As it turns out, philosophy, poetry and art are still needed.

Still the starting point of our reflections must be the world revealed to us by modern science—as science is the only cognitive authority in the world today. And in the far future, if we augment our intelligence and learn infinitely more about reality, we may even come to know scientifically how to live best and whether meaning in life is possible. By then philosophical reflection may well be an anachronism.2


1. I think this definition of scientism is too strong and makes a straw man of Tyson’s position. A better definition is “scientism is a term used to refer to belief in the universal applicability of the scientific method and approach, and the view that empirical science constitutes the most authoritative worldview or most valuable part of human learning to the exclusion of other viewpoints.” [Sorell, Thomas. Scientism: Philosophy and the Infatuation with Science, (New York: Rutledge, 1994, pp. 1ff.)]

 2. For a contradictory view by a philosopher/scientist see: