The Simulation Situation

There are smart people who think we’re probably living in a simulation. They question whether we’re flesh and blood creatures inhabiting a physical universe. Instead, we’re mental constructs “living” inside an incredibly sophisticated computer program. Our reality is someone else’s virtual reality.

Adam Gopnik of The New Yorker summarizes the logic:

The argument, actually debated at length at the American Museum of Natural History just last year, is that the odds are overwhelming that ours is a simulated universe. The argument is elegant. Since the advance of intelligence seems like the one constant among living things—and since living things are far likelier than not to be spread around the universe—then one of the things that smart living things will do is make simulations of other universes in which to run experiments….

Since there will be only one “real” universe, and countless simulated ones, the odds that we are living in one of the simulations instead of the one actual reality are overwhelming. If intelligent life exists, then we are surely likely to be living in one of its Matrices. As Clara Moskowitz, writing in Scientific American, no less, explains succinctly, “A popular argument for the simulation hypothesis came from University of Oxford philosopher Nick Bostrum in 2003, when he suggested that members of an advanced civilization with enormous computing power might decide to run simulations of their ancestors. They would probably have the ability to run many, many such simulations, to the point where the vast majority of minds would actually be artificial ones within such simulations, rather than the original ancestral minds. So simple statistics suggest it is much more likely that we are among the simulated minds.”

Mr. Gopnik somewhat jokingly suggests that recent events, in particular, an evil buffoon becoming President, a startling turnaround in the Super Bowl, a dumb mistake at the Oscars, are evidence that someone “up there” is messing with us (“Let’s do this crazy thing and see what happens!”). 

In response, Jesse Singal of New York Magazine argues that recent events seem so bizarre because recent history has been relatively calm:

…part of what’s going on here is that over the last few decades, the world has gotten so much less weird — in mostly good ways — that it’s now easier to highlight and harp upon what are, in the grand scheme of things, relatively minor weirdness flare-ups….

We pay more attention to the Patriots coming back from 28–3 in an impossibly short span of time because we’re less distracted by the U.S. trying to napalm its way out of an inconceivably stupid jungle quagmire. We gawk at the Oscar craziness and dwell on it because it stands out in a saner world than many of our parents and grandparents inhabited. Hell, it’s too early to say, but in the long run, barring an unforeseen catastrophe, maybe even [Donald Drump] — God or superintelligent alien simulators willing — will end up getting a mere footnote, rather than a chapter, in the Book of Weirdness humanity continues writing every moment of every day.

I think Mr. Singal is correct, of course. As some have noted, the Oscar thing was bound to happen (it had already happened once before, in 1964 to Sammy Davis Jr.); sports teams occasionally overcome big deficits, especially when the other team helps; and the Electoral College could have done what the Founders intended and elected a normal person (although I have to admit that, as naturally-occurring events in any possible world go, Drump in the White House is hard to accept).

The idea that we are constructs in some kind of vast computer program isn’t the same as what was depicted in the Matrix movies. In the Matrix, we were good, old-fashioned human beings being manipulated into thinking we were somewhere else. In the simulation hypothesis, we’re software that thinks it’s human. But once you start to imagine possibilities like these, it’s hard to conclude we’re one vs. the other. Would it be easier to create virtual beings who think they’re organisms like us or to trick organisms like us into thinking we’re somewhere else? 

That’s one of the problems I have with the idea of the big simulation. It’s the same problem I have with the idea that our minds could be uploaded onto a computer. In theory, a program could execute the same thoughts that you or I have. For example, it could reach the same conclusions we would if presented with the same evidence. But could a program have the same feelings, the same conscious experience, we have when we touch, hear or see? Maybe so, but it’s hard for me to understand how a program could possibly do that. Would the software include components that made the software believe it was conscious when it really wasn’t? Could the evil demon have tricked Descartes into think he was conscious when he really wasn’t?

Of course, there are other problems with the simulation hypothesis besides my personal lack of imagination. Nobody knows how common life is. How often, for example, do chemical components form single-cell organisms? How often does single-cell life make the transition to multi-cellular life? Assuming complex organisms develop, how often do they form stable societies? And how much technological progress do stable societies make before they destroy themselves or hit some other bump in the cosmic road? We know there are lots of stars in the universe, and now it looks like there are lots of planets too, but beyond that it’s all speculation.

It’s also questionable whether advanced civilizations would decide to run such simulations even if they could. Why assume that beings that advanced would care about creating a world like ours? Wouldn’t they have better things to do?

More than a few philosophers and physicists think there are other universes in addition to ours, maybe even an infinite number of them. In one or more of those many universes, every possibility is real. So maybe the universe we experience is a vast simulation. On the other hand, maybe it’s a simulation being run for an audience of one. How do I know that the simulation I’m witnessing is simulating something for anyone else? It would certainly be simpler to simulate a universe for a single “person” (me) as opposed to billions of them (all of you). At any rate, I’m sure I’m here. Are you?

What’s It All About, Woody?

In Woody Allen’s latest movie, Irrational Man, Joaquin Phoenix plays Abe, a moody philosophy professor, while Emma Stone plays Jill, a cheerful undergraduate, who etc. etc. etc.

New York Times critic Manhola Dargis describes Jill as “an eager A student who’s attracted to Abe because that’s how she was written”. That’s very nicely put, but our topic isn’t cinema or gender. Our topic is whether life is meaningless.

From the Times review of Irrational Man:

In Woody Allen’s 1987 drama “September,” a writer and a physicist walk into a room … when the writer asks the physicist, “Is there anything more terrifying than the destruction of the world?” The physicist, sunk deep in gloomy shadow, answers, “Yeah, the knowledge that it doesn’t matter one way or the other — that it’s all random, radiating aimlessly out of nothing and eventually vanishing forever.” The physicist says that he’s not talking about the world. “I’m talking about the universe,” adding, “all space, all time, just a temporary convulsion.”

The exchange is in keeping with Mr. Allen’s oft-repeated insistence, on-screen and off, that life is meaningless, which may be true even if he seems feverishly bent on refuting it with his prodigious cinematic output.

Nobody has ever accused me of always, or even generally, looking on the bright side of things, but I don’t see any connection at all between the end of the universe and the meaning of life. So maybe Woody Allen, who is rather intelligent and can be relatively funny, is having a bit of fun when he suggests that life is meaningless because, meaningless because, in the distant future, the whole shebang will come to nothing.

Apparently not. It was easy to find videos in which Allen, speaking as himself, not through one of his characters, expresses an extremely bleak view of our situation. In one video, for example, when asked to comment on Macbeth’s complaint that life is “full of sound and fury, signifying nothing”, Allen offers this:  

You die and eventually the sun burns out … eventually all the planets and all the stars … the entire universe goes, disappears, and nothing is left at all … and you think to yourself, it is a lot of noise and sound and fury and where is it going? It’s not going anyplace.

He then imagines a cycle in which all of humanity is replaced every 100 years. Each time, people take their lives very seriously, yet “it seems like a big meaningless thing”. Strangely, however, he concludes that “even knowing the worst … it’s still worthwhile …it’s still important to go on”. Further, it’s the artist’s job to help the rest of us understand why this is so.

Not that it makes any difference, but physicists aren’t really sure how the universe will end. Will there be a Big Freeze? Big Rip? Big Crunch? Big Bounce? One reason they’re not sure is that they don’t know enough about dark energy, the strange force that seems to be making the universe expand more quickly. But however it ends, the universe should keep going for billions of years. Its ultimate destination may be nowhere at all, but in the meantime, a whole lot of stuff, including us, will be traveling every which way.

Citing events like the end of the universe or the explosion of the sun as reasons for the meaninglessness of life could be the most ridiculous thing I’ve ever heard a public figure say. It’s like saying that traveling around the world or visiting the Moon is pointless because you’re going to end up back in your own bed and, besides, you’re not going to live forever. 

Life has meaning for anyone who finds it meaningful. None of our experiences, memories, expectations, accomplishments or relationships are inherently meaningful – meaningful in themselves – but they are often meaningful to us and other people. That’s why we say things like “that really meant a lot to me” or (as I heard in a movie this week) “you mean nothing to me”.

To be meaningful in this sense is to be significant. It’s true that we sometimes perceive significance where there really isn’t any, but we don’t always get it wrong. Was it meaningful to you when you finished that task, visited that place, played that song, met that person? Well, no it wasn’t, because billions of years from now, there won’t be anything in the universe except black holes, and they’ll eventually disappear too! Making this supposed connection explicit – “life can only have meaning if the universe lasts forever” – shows what an absurd, lazy idea it is.

To be fair to Woody Allen, however, he might have another idea in mind. When people say life is meaningless, they sometimes mean that life has no ultimate purpose. Our individual purposes (putting food on the table, learning how to surf, becoming a banker) don’t seem important enough in the grand scheme of things. Isn’t there a bigger purpose to all of this?

Perhaps we’re here to propagate the species (until there’s no room on Earth for one more person?). Or help the universe or the Absolute become aware of itself (good one, Hegel). Or to fulfill a divine plan, like glorifying the supreme being forever and ever (the ego!). Or maybe we humans are only here as unwitting contestants in a vast competition run by the rulers of the galaxy to see which planet can produce the best muffins? That’s a possibility.

In addition to the difficulty of identifying which particular cosmic purpose we’re here to serve, there’s another big problem with this idea. Whatever purpose we’re serving, it most likely isn’t ours (especially if we don’t know what it is). Living in order to serve someone or something else’s higher purpose means that we are being treated as a means, not an end. That’s the opposite of what Kant argued is the basis of morality: to treat people as ends in themselves, not as means to achieving something else. Unless we can correctly identify a higher purpose and then adopt it as our own, the desire to serve a higher purpose is the desire to be used. 

In a similar context, Nietzsche criticized what he called “the ascetic ideal”, a way of thinking that helps the less psychologically advanced among us (the “herd”) avoid “suicidal nihilism”. The ascetic ideal, as embodied by Christian morality, requires that:

there is nothing on earth of any power which does not first have to receive a meaning, a right to existence, a value from it, as a tool to its work, as a way and means to its goal [On the Genealogy of Morality, III, 23).

Knowing that we were being used to serve an overriding purpose in the way Nietzsche describes service to the ascetic ideal would certainly add meaning to our lives. That’s true. But whether it would be a desirable meaning is another question.

The world in which we find ourselves should make us wonder what higher purpose would justify or explain what goes on around here. Nature is red in tooth and claw for most living beings. We humans do have Beethoven and Michelangelo, as Woody Allen often says, and surprisingly many people around the world are fairly satisfied with their lives, but consider all the horrendous crap we have to deal with (often at the hands of other humans).

Finding out that all of humanity’s pain and suffering happens for a reason would be adding insult to injury. The world is like this on purpose? It’s more agreeable and understandable that it just worked out this way. If I learned that this whole enterprise was set in motion by some higher-ups (or -up), I’d be very surprised, but also very disappointed. Couldn’t they do a better job? Are we living in a beta version?

They better damn well enjoy our muffins.

Postscript of 7/27/15:

From the 16th century French essayist Michel de Montaigne: “Life should be an aim unto itself; a purpose unto itself” (Essays, III, 12).

Time Flies and Stuff Happens

Jim Holt has written a nice article on that eternally perplexing subject: the nature of time. As expected, it left me properly perplexed.

Consider this passage:

Events judged to be in the past by one observer may still lie in the future of another; therefore, past and present must be equally definite, equally “real.” In place of the fleeting present, we are left with a vast frozen timescape—a four-dimensional “block universe”… Nothing is “flowing” from one event to another. As the mathematician Hermann Weyl memorably put it, “The objective world simply is; it does not happen. Einstein, through his theory of relativity, furnished a scientific justification for a philosophical view of time [called] “eternalism.” Time, according to this view, belongs to the realm of appearance, not reality. The only objective way to see the universe is as God sees it: sub specie aeternitatis [“under the aspect of eternity”].

But wait (if it’s appropriate to use that term). What is the ultimate fate of the universe?

Ever since its birth in the Big Bang, some 13.82 billion years ago, the universe has been expanding. If this expansion continues forever … the stars will burn out; black holes will evaporate; atoms and their subatomic constituents will decay. In the deep future, the remaining particles … will spread out into the void, becoming so distant from one another that they will cease to interact. Space will become empty except for the merest hint of “vacuum energy”. Yet in this future wasteland of near nothingness, time will go on; random events will continue to occur; things will “fluctuate” into existence, thanks to the magic of quantum uncertainty, only to disappear again into the void….But there is another possible cosmic fate. By and by, at some point in the far future, the expansion that the universe is currently undergoing might be arrested—maybe by gravity, maybe by some force that is currently unknown. Then all the hundreds of billions of galaxies will begin to collapse back on themselves, eventually coming together in a fiery all-annihilating implosion.

Well, you might ask, which is it? Does time belong to the realm of appearance, not reality? Or has the universe been expanding for 13.82 billion years?

Is it correct to say the “objective world simply is; it does not happen”? Or should we say that stuff happens all the time?

Holt is probably correct when he says that “most physicists … agree with Einstein that time’s passage is an illusion; they are eternalists.” Here’s how the “Time” article in the Stanford Encyclopedia of Philosophy defines eternalism:

Eternalism says that objects from both the past and the future exist just as much as present objects. According to eternalism, non-present objects like Socrates and future Martian outposts exist…, even though they are not currently present. We may not be able to see them at the moment, on this view, and they may not be in the same space-time vicinity that we find ourselves in …, but they should nevertheless be on the list of all existing things.

The idea here is that the history of the universe may be thought of as a series of events on a continuum that stretches from the past to the future, but which never includes a moment that is “now”. We can say that one event is earlier or later than another (e.g. the Big Bang is about 14 billion years earlier than December 1, 2014), but it’s wrong to think that the moment you or I perceive as “now” has any special significance, so far as the universe is concerned.

It’s as if the timeline of the universe were a long, straight line between points A and B. Between A and B there are many other points, but none of them is more real than any other. Instead, each point on the line and each moment in the history of the universe (and every object that has ever existed or ever will) exists in the very same way.

Nevertheless, as Holt goes on to say, some physicists are “presentists”. So are some philosophers (as well as most “normal” people who have ever thought about the issue). Presentists believe that “now is a special moment that really advances…; this would still be true, they believe, even if there were no observers like us in the universe”. In the words of the Stanford Encyclopedia:

Presentism is the view that only present objects exist. … According to Presentism, if we were to make an accurate list of all the things that exist … there would be not a single non-present object on the list. Thus, you and the Taj Mahal would be on the list, but neither Socrates nor any future Martian outposts would be included.  

I confess that I find presentism much easier to understand than eternalism. In fact, eternalism sounds sufficiently crazy that there must be extremely good reasons for very smart people to believe it.

Is every object and every event in the history of the universe equally real, so that the biggest triceratops who ever lived and the dinner you’re going to have next New Year’s Eve are just as real as the chair you’re sitting on? Holt says Einstein answered that question and the answer is “Yes!”:

What Einstein [showed] was that there is no universal “now.” Whether two events are simultaneous is relative to the observer. And once simultaneity goes by the board, the very division of moments into “past,” “present,” and “future” becomes meaningless. Events judged to be in the past by one observer may still lie in the future of another; therefore, past and present must be equally definite, equally “real.” In place of the fleeting present, we are left with a vast frozen timescape—a four-dimensional “block universe.”

Maybe that’s the conclusion to be drawn from the scientific evidence. On the other hand, quoting the Stanford Encyclopedia again:

Perhaps it can be plausibly argued that while relativity entails that it is physically impossible to observe whether two events are absolutely simultaneous, the theory nevertheless has no bearing on whether there is such a phenomenon as absolute simultaneity.

Thinking about what might be the case beyond our powers of observation may qualify as metaphysics rather than physics, but it seems to me that change is a fundamental feature of the universe, time is the rate of change, and wherever and whenever changes occur, time is passing. My “now” is different from your “now” in the same way that my “here” is different from your “here”. But each “now” marks a real point in time (a point in the overall history of the universe), just like each “here” marks a real point in space (the universe’s overall expanse).

Eternalism, however, treats time as if it’s one more spatial dimension, a dimensioin in which all locations are equally real. I don’t think time is like that at all. Some moments (or temporal locations) were real, some will be real, and when a moment becomes real, it’s now. Not merely from our perspective, but in reality.

Anyway, that’s my opinion. If you and I aren’t more real than Socrates or the 75th President of the United States (whoever she turns out to be) in a very significant sense, meaning that we exist and they sure don’t, well, this isn’t a universe I want to spend time in.

Logic and the World

SelfAwarePatterns is an excellent blog if you’re interested in science, philosophy and similar topics (which covers pretty much everything). Earlier this week, its author, a self-aware pattern named Michael Smith, wrote about the nature of logic. He quoted several brief definitions of logic, including one by Gottlob Frege (1848-1925), one of history’s greatest logicians. According to Frege, logic is “the science of the most general laws of truth”, to which Mike Smith responded:

Gottlob Frege’s definition seems closest to my own current personal intuition about it, namely that logic represents the most fundamental relationships in our universe. These relationships are so fundamental, that we can take them and extrapolate truths using them, and often we’ll be right.

After reading this, I began writing a comment but quickly saw that my comment was turning into a post of my own. And since I need to keep this blog going in order to continue raking in the big money, here it is: 

Whenever I try to understand what logic is and how it relates to the world, I end up thinking about the status of Aristotle’s three fundamental axioms of logic: the Law of Identity (A = A); the Law of Non-Contradiction (it is not the case that A and not A), and the Law of the Excluded Middle (either A or not A), where “A” represents a statement like “Snow is white” or “I’ve never made a single penny writing this blog”.

The Law of Identity seems to reflect how the world is without question, partly because it’s supremely uninformative. As Bishop Butler said: “Everything is what it is, and not another thing”. I’m not sure the Law of Identity states a fundamental relationship, since self-identity isn’t much of a relationship. There is only one party involved. But it seems undeniable that A equals A, whatever A happens to be.

The Law of Non-Contradiction seems to reflect how the world is too. It’s exceedingly hard to imagine how things could be otherwise in our universe or any other universe (e.g., “Vitamin C is ascorbic acid and yet it isn’t.”). Despite this difficulty, some enterprising logicians have accepted dialetheism: the view that the very same proposition can be both true and false. That seems plainly wrong. Can we step into the same river twice? Well, yes, we can (“It’s the mighty Mississippi”) and no, we can’t (“The Mississippi had different water in it yesterday”). But which answer is correct depends on what you mean by “same river”. It’s the same river it was yesterday in one sense, although it’s not the same in another sense.

How about a self-referential statement like “This statement is false”? To be fair, that’s the kind of sentence dialetheist logicians are interested in. If “this statement is false” is true, it’s false. But if it’s false, it’s true. That is certainly weird, but is the sentence in question really both true and false? I don’t think so. It seems to me that it’s a badly-formed sentence. Its apparent meaning contradicts our natural presumption as speakers of a language that speakers don’t undermine their own claims (i.e., give with one hand and take back with the other). In this case, it seems best to follow the doctor’s advice when the patient said “It hurts when I do this”. The doctor, of course, answered: “Don’t do that”. Or in this case, don’t say stuff like “This statement is false”. Just because we can put certain words together doesn’t make it a proper sentence.

Then there’s subatomic physics. Light is a field of waves and also a stream of particles! The evidence indicates that light acts as if it’s a wave in some cases and as if it’s a particle in others, but saying that it acts the same way at the same time makes no sense. To me anyway. It’s better in this case to infer that our everyday concepts of “wave” and “particle” aren’t adequate to describe the nature of light. But that doesn’t mean light is a counterexample to the Law of Non-Contradiction.

So far, so good for classical logic accurately representing the universe. Things get more complicated, however, when we consider the Law of the Excluded Middle. Personally, I don’t buy it at all. The idea is that every proposition is either true or false. Unless we define “proposition” as “a bearer of truth or falsity”, there are lots of propositions that aren’t clearly true or false. There are vague propositions, for example. Has George lost enough hair to be considered bald? What if he lost one more hair, or 500 more, or 50,000 more? Where is the line between being bald and being hairy? And there is the matter of probability. For example, according to the principle of quantum superposition, “a physical system – such as an electron – exists partly in all its particular theoretically possible states simultaneously”. Is an electron here or there? Most physicists think it’s a matter of probability. An electron could be here and it could be there, but it’s not definitely anywhere until it’s measured or otherwise interfered with.

Concerns about vagueness and probability have led to the creation of alternative logics. So-called “many-valued” logics reject the Law of the Excluded Middle. “Fuzzy” logic replaces it with a continuum of values, ranging from true to false and allowing points in between. We might instead reject the Law of Contradiction and accept that some well-formed declarative sentences, like “George is bald”, are both true and false. “Paraconsistent” logics do that. As Mike Smith pointed out in his post, there is even “quantum” logic, which tries to deal with the peculiar laws of quantum physics.

There is good reason, therefore, to believe that Aristotle’s three axioms are somewhat misleading if they’re taken as an attempt to state fundamental features of the world or even relationships between the world and language (or thought). We should agree that the Law of Identity applies to the world (in fact, it applies to every possible world). After that, we’re in a gray area. There is no denying that the world is what it is (as that annoying phrase “it is what it is” seems to call into question – after all, what isn’t what it is?). Furthermore, we learn logic by paying attention to the world and use logic to navigate the world, but logic, I think, is better understood as “the science of the laws of discursive thought” (James McCosh, 1811-1888) than as a general description of how things are.

That God Playing Dice With the Universe Thing Again

Quanta has an article with the intriguing title: “Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?”. Far be it from me to interpret quantum mechanics at all, so I’ll merely quote:

…That nature is inherently probabilistic — that particles have no hard properties, only likelihoods, until they are observed — is directly implied by the standard equations of quantum mechanics. But now a set of surprising experiments with fluids has revived old skepticism about that worldview. The bizarre results are fueling interest in an almost forgotten version of quantum mechanics, one that never gave up the idea of a single, concrete reality.

The experiments involve an oil droplet that bounces along the surface of a liquid. The droplet gently sloshes the liquid with every bounce. At the same time, ripples from past bounces affect its course. The droplet’s interaction with its own ripples, which form what’s known as a pilot wave, causes it to exhibit behaviors previously thought to be peculiar to elementary particles — including behaviors seen as evidence that these particles are spread through space like waves, without any specific location, until they are measured.

Particles at the quantum scale seem to do things that human-scale objects do not do. They can tunnel through barriers, spontaneously arise or annihilate, and occupy discrete energy levels. This new body of research reveals that oil droplets, when guided by pilot waves, also exhibit these quantum-like features.

Assuming that continued experimentation confirms that the probabilistic behavior of these droplets and fluids mirrors the behavior of quantum-level particles, the question would be: Is this similarity a mere coincidence or does it indicate that there is an underlying deterministic basis for apparently spooky, indeterministic quantum events? 

To some researchers, the experiments suggest that quantum objects are as definite as droplets, and that they too are guided by pilot waves — in this case, fluid-like undulations in space and time. These arguments have injected new life into a deterministic (as opposed to probabilistic) theory of the microscopic world first proposed, and rejected, at the birth of quantum mechanics.

“This is a classical system that exhibits behavior that people previously thought was exclusive to the quantum realm, and we can say why,” said John Bush, a professor of applied mathematics at the Massachusetts Institute of Technology who has led several recent bouncing-droplet experiments. “The more things we understand and can provide a physical rationale for, the more difficult it will be to defend the ‘quantum mechanics is magic’ perspective.”

The great French physicist Louis De Broglie first proposed a deterministic pilot-wave theory in the 1920s. David Bohm famously proposed a later version. According to the article, John Stewart Bell, the author of Bell’s Theorem, which supposedly shows that quantum mechanics cannot be deterministically explained by “hidden variables”, was also a proponent:

In 1986, [Bell] wrote that pilot-wave theory “seems to me so natural and simple, to resolve the wave-particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so generally ignored.” 

Of course, many physicists are skeptical, as they should be. Overturning the standard interpretation of quantum mechanics (the indeterministic “Copenhagen” interpretation) would be a very big deal. But doing so would make our universe much less mysterious (no more God playing dice). And it would allow physicists to give up the increasingly popular idea that there are many, many universes (the “multiverse” interpretation of QM). We might then go back to thinking of the universe as a unique, cozy place where everything happens for a reason.

Clearing Up This Multiple Universe Thing (Maybe)

I haven’t been blogging much lately. It’s not that I have anything against blogging – I haven’t been doing much of anything lately, unless breathing and digesting count.

In another universe, however, I’ve been blogging up a storm while hiking through Alabama with Gwyneth Paltrow and Vladimir Putin. That’s what many physicists seem to believe anyway. (In that other universe, Vlad promised Gwyn and me that he’s going to stop interfering with Ukraine.) 

For example, Max Tegmark of M.I.T. has written a book that, according to the New York Times, suggests that he was almost hit by a truck while riding his bike in Stockholm, and the truck hit him, resulting in some slight injuries, and the truck really clobbered him, which meant he didn’t live to write the book he later wrote: 

He endured every possible outcome, happy and unhappy, that can befall a bicyclist who encounters a speeding truck. All of these happened, he argues, because everything that can happen does happen — in at least one of an infinite number of universes.

This extremely large set of parallel universes is called the “multiverse”. Our universe, the particular one that I’m experiencing now, in which I’m not pals with Gwyn and Vlad, is merely one universe among many – no more real than the others. 

Very smart people like Max Tegmark and Stephen Hawking accept the multiverse theory, which is also known as the “many-worlds interpretation of quantum mechanics”. They think this apparently crazy idea best explains the truly crazy stuff that happens at the quantum level of reality, like the double-slit experiment and the situation with Schrödinger’s cat. We’ll probably never know for sure, since verifying the existence of another universe is supposed to be impossible.   

Still, something has been bothering me since I read that article in the Times. When people talk about parallel universes, they usually talk about universes branching off from each other. What supposedly happens is that whenever there’s more than one possibility in a given universe, that universe somehow splits into two or more separate universes. You start out in one universe and get hit by a truck but in another universe you escape injury. In one universe, you order pork chops, in another you have a salad and in a third you go somewhere else to eat. The examples in these discussions are almost always familiar events or decisions, the kind of possibilities we can all relate to.

Physicists, however, don’t usually concern themselves with what people have for dinner. Quantum physics, in particular, concentrates on very small-scale events. Will an atom of carbon-14 decay or not? How frequently do quantum fluctuations (the so-called “appearance and disappearance of virtual particles”) occur? In theory, each of these small-scale, apparently random quantum events marks a divergence in the history of the universe. If an atom decays, the universe goes one way. If it doesn’t decay, the universe goes another way. According to the many-worlds theory, as it’s almost always explained, each event that could have happened differently results in the creation of separate universes.

Of course, since the universe is a very big place, there is room for lots of events to occur, especially the tiny, random ones. Here’s a quote from The Many-Worlds Interpretation of Quantum Mechanics by the physicist Bryce DeWitt: 

This universe is constantly splitting into a stupendous number of branches, all resulting from the measurement-like interactions between its myriads of components. Moreover, every quantum transition taking place on every star, in every galaxy, in every corner of the universe is splitting our local world into myriads of copies of itself [161].

Wow! Is it really possible that equally gigantic, almost exact replicas of the universe, with all its particles, planets, galaxies and so on, are springing into existence zillions of times a second, whenever a sub-atomic particle somewhere in the universe sneezes? And that those replicas immediately start replicating themselves? As that old TV commercial said, that’s one spicy meatball!

The effect seem way, way, way out of proportion to the cause. Where does all the energy come from to create fully-formed copies of previously existing universes? Assuming that these new universes immediately pop into existence, how do they get so big and so detailed so quickly? Or maybe universe creation takes a long “time”, but we don’t notice any breaks in the action because we keep coming into existence with our memories and instrument readings intact, as if nothing weird has happened (remember that you and I have lived through zillions of such universe creations – it’s not as if we’ve always lived in the nice, stable universe and everybody else is off living in copies).

I don’t know enough math or physics to criticize the many-worlds theory for real, but I was pleased to see that one of the things bothering me is a standard objection to the theory. From Wikipedia:

Conservation of energy is grossly violated if at every instant near-infinite amounts of new matter are generated to create the new universes.

To which, proponents of the theory are said to have two responses:

First, the law of conservation of energy says that energy is conserved within each universe. Hence, even if “new matter” were being generated to create new universes, this would not violate conservation of energy. (That doesn’t seem like a very good answer to me, since it amounts to saying, “It’s very strange that there’s an exception to this fundamental law, but that’s what happens”.)

Second, conservation of energy is not violated since the energy of each branch has to be weighted by its probability, according to the standard formula for the conservation of energy in quantum theory. This results in the total energy of the multiverse being conserved. (Which seems to mean that if there’s a 50/50 chance of some atom decaying, each new universe has half as much energy as the last one. Wouldn’t that eventually result in new universes having no energy at all?)

So it was with some relief that I turned to a helpful website called “Ask a Mathematician”. It should really be called “Ask a Mathematician or Physicist”. because it’s apparently a mathematician and a physicist answering questions, most of which have to do with physics (they don’t identify themselves, they just answer questions). A few years ago, they got this question:

According to the Many Worlds Interpretation, every event creates new universes. Where does the energy and matter for the new universes come from?

Here’s some of the physicist’s (rearranged) answer:

If you go online (or read some kind of book or something), you generally find the Many Worlds Interpretation presented as the universe “splitting”. Something along the lines of “everything that can happen will, just in different universes”. Supposedly, every time any kind of quantum event happens that could have one of several results (which is essentially every moment for every thing, which is plenty) the entire freaking universe splits into many universes. But, the universe contains a lot of energy….So, whence does this energy come?

[However,] there is no new energy or matter (or even new universes)…The universe doesn’t split or spawn new universes…. The universe doesn’t branch so much as it meanders and intertwines….If you want a picture to work with, rather than thinking about the universe as an ever-branching tree, think of it as an intertwining (albeit, very complex) rope.

The many (like: many, many) different versions of the universe branch apart, and come together all over the place. That is: one event can certainly lead to several outcomes, but in the same way, several causes can lead to the same event.  Everything that could happen will happen (given the present) and everything that could have happened did happen (given the present)….

A particle comes along with some amount of energy. When it has a choice of two paths it takes both.  The energy of the particle is divided in proportion to the probability of the path taken.  So, for example, a 50% chance of each path means equal division of the energy and matter of the particle.  Before the fork all of the energy is on one path, and afterwards, despite the fact that the particle is behaving as though it’s in two places, the same amount of energy is present, just spread out.

So, while it’s fun to talk about “other quantum realities” and “different universes”, it’s more accurate to say that everything is happening in one universe. One, stunningly complex, weirdly put together, entirely counter-intuitive universe.

Clear? Despite the standard explanation, we’re all living in the same universe, but it’s a universe that has lots of its contents in strange, probabilistic quantum states. Since these various states (like when a photon is 50% likely to be here and 50% likely to be there) are equally real, they can be thought of as parts of different universes, but that’s just a manner of speaking.

Whether or not this way of understanding the multiple universe theory is correct (is it, since Max Tegmark apparently suggests otherwise?), it makes me feel better. For one thing, it’s less mind-boggling. Big branching universes seem both implausible and terribly wasteful. Secondly, I think there’s zero probability that one of me is hiking through Alabama with Gwyneth and Vladimir (while wearing a blue shirt, and a red shirt, and a green shirt, and no shirt, etc. etc.) while also breathing and digesting here in the Garden State.

(Note, however, that if the universe is infinite in time and space and configured a certain way, it’s possible, maybe even a sure thing, that everything that isn’t contradictory happens over and over again. But that’s something to wonder about another day.)

How the Universe Got Big

A team of radio astronomers, working in Antarctica, where the air is clear and dry, have found the first direct evidence for the theory of cosmic inflation. That’s the theory about the origin of the universe first stated by the physicist Alan Guth in 1980.

Here’s some background from an article Guth wrote in 1997 for Beam Line, the magazine of the Stanford Linear Accelerator Center (now the SLAC National Accelerator Laboratory):

Although it is called the “Big Bang theory,” it is not really the theory of a bang at all. It is only the theory of the aftermath of a bang. It elegantly describes how the early Universe expanded and cooled, and how matter clumped to form galaxies and stars. But the theory says nothing about the underlying physics of the primordial explosion. It gives not even a clue about what banged, what caused it to bang, or what happened before it banged. The inflationary universe theory, on the other hand, is a description of the bang itself, and provides plausible answers to these questions and more.

Guth explains that in order for the universe we observe to have begun with a Big Bang, the early universe must have been extremely uniform and have had a precise density. However:

The classical form of the Big Bang theory requires us to postulate, without explanation, that the primordial fireball filled space from the beginning. The temperature was the same everywhere by assumption, not as a consequence of any physical process….

[In addition] the initial values of the [universe’s] mass density and expansion rate are not predicted by the theory, but must be postulated. Unless we postulate that the mass density at one second just happened to have a value between 0.999999999999999 and 1.000000000000001 times the critical density [the boundary value between a universe that will expand forever and one that will eventually collapse], the Big Bang theory will not describe a universe that resembles the one in which we live…

Although the properties of the Big Bang are very special, we now know that the laws of physics provide a mechanism that produces exactly this sort of a bang. The mechanism is known as cosmic inflation.

The National Accelerator Laboratory issued a press release today:

Instead of the universe beginning as a rapidly expanding fireball, Guth theorized that the universe inflated extremely rapidly [faster than the speed of light] from a tiny piece of space and became exponentially larger in a fraction of a second.

For inflation to occur, the universe must have been in a state that allowed a sudden change to release enormous energy, creating an expanding universe almost from nothing. The process was apparently a kind of delayed phase transition, as when water is supercooled below its natural freezing point and then, because of some disturbance, suddenly freezes, generating heat.

However, as Guth immediately realized, certain predictions in his scenario contradicted observational data. In the early 1980s, Russian physicist Andrei Linde modified [the theory so that it] generated predictions that closely matched actual observations of the sky.

The new observations reported today are the first evidence of the existence of gravity waves. These are ripples in spacetime originally predicted by Albert Einstein. The radio astronomers working in Antarctica found traces of these ancient gravity waves by analyzing the cosmic background radiation left over from the Big Bang. Andre Linde reacted to the news: “These results are a smoking gun for inflation, because alternative theories do not predict such a signal. This is something I have been hoping to see for 30 years.”

Future Nobel Prize-winner Alan Guth offered this summary in 1997:

While it may be too early to say that inflation is proved, I claim that the case for inflation is compelling. It is hard to even conceive of an alternative theory that could explain the basic features of the observed Universe. Not only does inflation produce just the kind of special bang that matches the observed Universe, but quantum fluctuations during inflation could have produced non-uniformities which served as the seeds of cosmic structure [in particular, the existence of galaxies].

Physicists doubted whether Guth’s theory would ever be proven. With today’s announcement, cosmic inflation is a big step closer to becoming settled science.