But What If We're Wrong? (10 page)

Here's what I mean: Let's say there are infinite universes that exist over the expanse of infinite time (and the key word here is “infinite”). Within infinity, everything that
could
happen
will
happen.
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Everything. Which would mean that—somewhere, in an alternative universe—there is a planet exactly like Earth, which has existed for the exact same amount of time, and where every single event has happened exactly as it has on the Earth that we know as our own . . . except that on Christmas Eve of 1962, John F. Kennedy dropped a pen. And there is still another alternative universe with a planet exactly like Earth, surrounded by an exact replica of our moon, with all the same cities and all the same people, except that—in this reality—you read this sentence yesterday instead of today. And there is still another alternative universe where everything is the same, except you are slightly taller. And there is still another alternative universe beyond that one where everything is the same, except you don't exist. And there is still another alternative reality beyond that where a version of Earth exists, but it's ruled by robotic wolves with a hunger for liquid cobalt. And so on and so on and so on. In an infinite multiverse, everything we have the potential to imagine—as well as everything we
can't
imagine—would exist autonomously. It would require a total recalibration of every spiritual and secular belief that ever was. Which is why it's not surprising that many people don't dig a transformative hypothesis that even its proponents concede is impossible to verify.

“There really are some highly decorated physicists
34
who
have gotten angry with me, and with people like me, who have spoken about the multiverse theory,” Greene says. “They will tell me, ‘You've done some real damage. This is nuts. Stop it.' And I'm a completely rational person. I don't speak in hyperbole to get attention. My true feeling is that these multiverse ideas could be right. Now, why do I feel that way? I look at the mathematics. The mathematics lead in this direction. I also consider the history of ideas. If you described quantum physics to Newton, he would have thought you were insane. Maybe if you give Newton a quantum textbook and five minutes, he sees it completely. But as an idea, it would seem insane. So I guess my thinking is this: I think it's extraordinarily unlikely that the multiverse theory is correct. I think it's extraordinarily likely that my colleagues who say the multiverse concept is crazy are right. But I'm not willing to say the multiverse idea is
wrong
, because there is no basis for that statement. I understand the discomfort with the idea, but I nevertheless allow it as a real possibility. Because it
is
a real possibility.”

Greene delivered a TED talk about the multiverse in 2012, a twenty-two-minute lecture translated into more than thirty languages and watched by 2.5 million people. It is, for all practical purposes, the best place to start if you want to learn what the multiverse would be like. Greene has his critics, but the concept is taken seriously by most people who understand it (including Tyson, who has said, “We have excellent theoretical and philosophical reasons to think we live in a multiverse”). He is the
recognized expert on this subject. Yet he's still incredulous about his own ideas, as illustrated by the following exchange:

Q:
What is your level of confidence that—in three hundred years—someone will reexamine your TED talk and do a close reading of the information, and conclude you were almost entirely correct?

A:
Tiny. Less than one percent. And you know, if I was really being careful, I wouldn't have even given that percentage a specific number, because a number requires data. But take that as my loose response. And the reason my loose response is one percent just comes from looking at the history of ideas and recognizing that every age thinks they were making real headway toward the ultimate answer, and every next generation comes along and says, “You were really insightful, but now that we know X, Y, and Z, here is what we actually think.” So, humility drives me to anticipate that we will look like people from the age of Aristotle who believed stones fell to earth because stones wanted to be on the ground.

Still, as Greene continues to explain the nature of his skepticism, a concentration of optimism slowly seeps back in.

In the recesses of my mind, where I would not want to be out in public—even though I realize you're recording this, and this is a public conversation—I do hold out
hope that in one hundred or five hundred years, people will look back on our current work and say, “Wow.” But I love to be conservative in my estimates. Still, I sometimes think I'm being too conservative, and that makes me excited. Because look at quantum mechanics. In quantum mechanics, you can do a calculation and predict esoteric properties of electrons. And you can do the calculation—and people have done these calculations, heroically, over the span of decades—and compare [those calculations] to actual experiments, and the numbers agree. They agree up to the tenth digit beyond the decimal point. That is unprecedented—that we can have a theory that agrees with observation to that degree. That makes you feel like “This is different.” It makes you feel like you're closing in on truth.

So here is the hinge point where skepticism starts to reverse itself. Are we the first society to conclude that
this time
we're finally right about how the universe works? No—and every previous society who thought they were correct ended up hopelessly mistaken. That, however, doesn't mean that the goal is innately hopeless. Yes, we are not the first society to conclude that our version of reality is objectively true. But we could be the first society to express that belief and is never contradicted, because we might be the first society to really get there. We might be the
last
society, because—now—we translate absolutely everything into math. And math is an obdurate bitch.

[
3
]
The “history of ideas,” as Greene notes, is a pattern of error, with each new generation reframing and correcting the mistakes of the one that came before. But “not in physics, and not since 1600,” insists Tyson. In the ancient world, science was fundamentally connected to philosophy. Since the age of Newton, it's become fundamentally connected to math. And in any situation where the math zeroes out, the possibility of overturning the idea becomes borderline impossible. We don't know—and we
can't
know—if the laws of physics are the same everywhere in the universe, because we can't access most of the universe. But there are compelling reasons to believe this is indeed the case, and those reasons can't be marginalized as egocentric constructions that will wax and wane with the attitudes of man. Tyson uses an example from 1846, during a period when the laws of Newton had seemed to reach their breaking point. For reasons no one could comprehend, Newtonian principles were failing to describe the orbit of Uranus. The natural conclusion was that the laws of physics must work only within the inner solar system (and since Uranus represented the known edge of that system, it must be operating under a different set of rules).

“But then,” Tyson explains, “someone said: ‘Maybe Newton's laws still work. Maybe there's an unseen force of gravity operating on this planet that we have not accounted for in our equations.' So let's assume Newton's law is correct and ask, ‘If there is a hidden force of gravity, where would that force be coming from? Maybe it's coming from a planet we have yet to discover.' This is a very difficult math problem, because it's one thing to say, ‘Here's a
planetary mass and here's the value of its gravity.' Now we're saying we have the value of gravity, so let's infer the existence of a mass. In math, this is called an inversion problem, which is way harder than starting with the object and calculating its gravitational field. But great mathematicians engaged in this, and they said, ‘We predict, based on Newton's laws that work on the inner solar system, that if Newton's laws are just as accurate on Uranus as they are anywhere else, there ought to be a planet right
here
—go look for it.' And the very night they put a telescope in that part of the sky, they discovered the planet Neptune.”

The reason this anecdote is so significant is the sequence. It's easy to discover a new planet and then work up the math proving that it's there; it's quite another to mathematically insist a massive undiscovered planet should be precisely where it ends up being. This is a different level of correctness. It's not interpretative, because numbers have no agenda, no sense of history, and no sense of humor. The Pythagorean theorem doesn't need the existence of Mr. Pythagoras in order to work exactly as it does.

I have a friend who's a data scientist, currently working on the economics of mobile gaming environments. He knows a great deal about probability theory,
35
so I asked him if our contemporary
understanding of probability is still evolving and if the way people understood probability three hundred years ago has any relationship to how we will gauge probability three hundred years from today. His response: “What we think about probability in 2016 is what we thought in 1716, for sure . . . probably in 1616, for the most part . . . and probably what [Renaissance mathematician and degenerate gambler Gerolamo] Cardano thought in 1564. I know this sounds arrogant, but what we've believed about probability since 1785 is still what we'll believe about probability in 2516.”

If we base any line of reasoning around consistent numeric values, there is no way to be wrong, unless we are (somehow) wrong about the very nature of the numbers themselves. And that possibility is a non-math conversation. I mean, can 6
literally
turn out to be 9? Jimi Hendrix imagined such a scenario, but only because he was an electric philosopher (as opposed to a pocket calculator).

“In physics, when we say we know something, it's very simple,” Tyson reiterates. “Can we predict the outcome? If we can predict the outcome, we're good to go, and we're on to the next problem. There are philosophers who care about the understanding of
why
that was the outcome. Isaac Newton [essentially] said, ‘I have an equation that says why the moon is in orbit. I have no fucking idea how the Earth talks to the moon. It's empty space—there's no hand reaching out.' He was uncomfortable about this idea of action at a distance. And he was criticized for having such ideas, because it was preposterous that one physical object could talk to another physical object. Now, you can certainly have that conversation [about why it happens]. But an equation properly predicts what it does. That other conversation is for people having a beer. It's a beer conversation. So go ahead—have that conversation. ‘What is the nature of
the interaction between the moon and the Earth?' Well, my equations get it right every time. So you can say that gremlins do it—it doesn't matter to my equation . . . Philosophers like arguing about [semantics]. In physics, we're way more practical than philosophers. Way more practical. If something works, we're on to the next problem. We're not arguing
why
. Philosophers argue
why
. It doesn't mean we don't like to argue. We're just not derailed by
why
, provided the equation gives you an accurate account of reality.”

In terms of speculating on the likelihood of our collective wrongness, Tyson's distinction is huge. If you remove the deepest question—the question of why—the risk of major error falls through the floor. And this is because the problem of
why
is a problem that's impossible to detach from the foibles of human nature. Take, for example, the childhood question of why the sky is blue. This was another problem tackled by Aristotle. In his systematic essay “On Colors,” Aristotle came up with an explanation for why the sky is blue: He argued that all air is
very slightly
blue, but that this blueness isn't perceptible to the human eye unless there are many, many layers of air placed on top of each other (similar, according to his logic, to the way a teaspoon of water looks clear but a deep well of water looks black). Based on nothing beyond his own powers of deduction, it was a genius conclusion. It explains why the sky is blue. But the assumption was totally wrong. The sky is blue because of the way sunlight is refracted. And unlike Aristotle, the person who realized this truth didn't care why it was true, which allowed him to be right forever. There will never be a new explanation for why the sky is blue.

Unless, of course, we end up with a new explanation for
everything
.

[
4
]
A few pages back, I positioned two scientists—Tyson and Greene—on opposite ends of a continuum of confidence, constructed inside my own mind. But even in the context of this fabricated binary, they agree on things far more than they differ. Since the dawn of civilization, people have argued about (and continually increased) the age of the known universe; when I asked both men if there was any chance the current age of our universe will be recalculated again, they both had the same answer. “It will not happen,” says Tyson. “That number [13.79 billion years, plus or minus 0.2] is actually quite stable,” reiterates Greene. Even on points of conflict, they generally force themselves into alignment: When I told Tyson that Greene was open to the possibility that our understanding of gravity might drastically change, Tyson implied that I may have phrased the question incorrectly.

“He's pointing forward to a time when our understanding of gravity includes our understanding of dark matter,” said Tyson. “That there will be some other understanding of gravity, but it will still enclose Newton's laws of gravity and Einstein's general relativity. So he may have presumed your question meant, ‘Is there anything
left
to be discovered about gravity?' And that question is not clear to someone who researches gravity.”