Knocking on Heaven's Door (4 page)

IT’S IMPOSSIBLE

People too often confuse evolving scientific knowledge with no knowledge at all and mistake a situation in which we are discovering new physical laws with a total absence of reliable rules. A conversation with the screenwriter Scott Derrickson during a recent visit to California helped me to crystallize the origin of some of these misunderstandings. At the time, Scott was working on a couple of movie scripts that proposed potential connections between science and phenomena that he suspected scientists would probably dismiss as supernatural. Eager to avoid major solecisms, Scott wanted to do scientific justice to his imaginative story ideas by having them scrutinized by a physicist—namely me. So we met for lunch at an outdoor café in order to share our thoughts along with the pleasures of a sunny Los Angeles afternoon.

Knowing that screenwriters often misrepresent science, Scott wanted his particular ghost and time-travel stories to be written with a reasonable amount of scientific credibility. The particular challenge that he as a screenwriter faced was his need to present his audience not just with interesting new phenomena, but also with ones that would translate effectively to a movie screen. Although not trained in science, Scott was quick and receptive to new ideas. So I explained to him why, despite the ingenuity and entertainment value of some of his story lines, the constraints of physics made them scientifically untenable.

Scott responded that scientists have often thought certain phenomena impossible that later turned out to be true. “Didn’t scientists formerly disbelieve what relativity now tells us?” “Who would have thought randomness played any role in fundamental physical laws?” Despite his great respect for science, Scott still wondered if—given its evolving nature—scientists aren’t sometimes wrong about the implications and limitations of their discoveries.

Some critics go even further, asserting that although scientists can predict a great deal, the reliability of those predictions is invariably suspect. Skeptics insist, notwithstanding scientific evidence, that there could always be a catch or a loophole. Perhaps people could come back from the dead or at the very least enter a portal into the Middle Ages or into Middle-earth. These doubters simply don’t trust the claims of science that a thing is definitively impossible.

However, despite the wisdom of keeping an open mind and recognizing that new discoveries await, a deep fallacy is buried in this logic. The problem becomes clear when we dissect the meaning of such statements as those above and, in particular, apply the notion of scale. These questions ignore the fact that although there will always exist unexplored distance or energy ranges where the laws of physics might change, we know the laws of physics on human scales extremely well. We have had ample opportunity to test these laws over the centuries.

When I met the choreographer Elizabeth Streb at the Whitney Museum, where we both spoke on a panel on the topic of creativity, she too underestimated the robustness of scientific knowledge on human scales. Elizabeth posed a similar question to those Scott had asked: “Could the tiny dimensions proposed by physicists and curled up to an unimaginably small size nonetheless affect the motion of our bodies?”

Her work is wonderful, and her inquiries into the basic assumptions about dance and movement are fascinating. But the reason we cannot determine whether new dimensions exist, or what their role would be even if they did, is that they are too small or too warped for us to be able to detect. By that I mean that we haven’t yet identified their influence on any quantity that we have so far observed, even with extremely detailed measurements. Only if the consequences of extra dimensions for physical phenomena were vastly bigger could they discernibly influence anyone’s motion. And if they did have such a significant impact, we would already have observed their effects. We therefore know that the fundamentals of choreography won’t change even when our understanding of quantum gravity improves. Its effects are far too suppressed relative to anything perceptible on a human scale.

When scientists have turned out to be wrong in the past, it was often because they hadn’t yet explored very tiny or very large distances or extremely high energies or speeds. That didn’t mean that, like Luddites, they had closed their minds to the possibility of progress. It meant only that they trusted their most up-to-date mathematical descriptions of the world and their successful predictions of then-observable objects and behaviors. Phenomena they thought were impossible could and sometimes did occur at distances or speeds these scientists had never before experienced—or tested. But of course they couldn’t yet have known about new ideas and theories that would ultimately prevail in the regimes of those tiny distances or enormous energies with which they were not yet familiar.

When scientists say we know something, we mean only that we have certain ideas and theories whose predictions have been well tested
over a certain range of distances or energies
. These ideas and theories are not necessarily the eternal laws for the ages or the most fundamental of physical laws. They are rules that apply as well as any experiment could possibly test, over the range of parameters available to current technology. This doesn’t mean that these laws will never be overtaken by new ones. Newton’s laws are instrumental and correct, but they cease to apply at or near the speed of light where Einstein’s theory applies. Newton’s laws are at the same time both correct and incomplete. They apply over a limited domain.

The more advanced knowledge that we gain through better measurements really is an improvement that illuminates new and different underlying concepts. We now know about many phenomena that the ancients could not have derived or discovered with their more limited observational techniques. So Scott was right that sometimes scientists have been wrong—thinking phenomena impossible that in the end turned out to be perfectly true. But this doesn’t mean there are no rules. Ghosts and time-travelers won’t appear in our houses, and alien creatures won’t suddenly emerge from our walls. Extra dimensions of space might exist, but they would have to be tiny or warped or otherwise currently hidden from view in order for us to explain why they have not yet yielded any noticeable evidence of their existence.

Exotic phenomena might indeed occur. But such phenomena will happen only at difficult-to-observe scales that are increasingly far from our intuitive understanding and our usual perceptions. If they will always remain inaccessible, they are not so interesting to scientists. And they are less interesting to fiction writers too if they won’t have any observable impact on our daily lives.

Weird things are possible, but the ones non-physicists are understandably most interested in are the ones we can observe. As Steven Spielberg pointed out in a discussion about a science fiction movie he was considering, a strange world that can’t be presented on a movie screen—and which the characters in a film would never experience—is not so interesting to a viewer. (Figure 1 shows amusing evidence.) Only a new world that we can access and be aware of could be. Even though both require imagination, abstract ideas and fiction are different and have different goals. Scientific ideas might apply to regimes that are too remote to be of interest to a film, or to our daily observations, but they are nonetheless essential to our description of the physical world.

[
FIGURE 1
]
An XKCD comic that captures the hidden nature of tiny rolled-up dimensions.

WRONG TURNS

Despite this neat separation by distances, people too often take shortcuts when trying to understand difficult science and the world. And that can easily lead to an overzealous application of theories. Such misapplication of science is not a new phenomenon. In the eighteenth century, when scientists were busy studying magnetism in laboratories, others conjured up the notion of “animal magnetism”—a hypothesized magnetic “vital fluid” in animate beings. It took a French royal commission set up by Louis XVI in 1784, which included Benjamin Franklin among others, to formally debunk the hypothesis.

Today such misguided extrapolations are more likely to be made about quantum mechanics—as people try to apply it on macroscopic scales where its consequences usually average away and leave no measurable signatures.
⁵
It’s disturbing how many people trust ideas such as those in Rhonda Byrne’s bestselling book
The Secret,
about how positive thoughts attract wealth, health, and happiness. Equally disquieting is Byrne’s claim that “I never studied science or physics at school, and yet when I read complex books on quantum physics I understood them perfectly because I wanted to understand them. The study of quantum physics helped me to have a deeper understanding of
The Secret
, on an energetic level.”

As even the Nobel Prize—winning pioneer of quantum mechanics Niels Bohr noted, “If you are not completely confused by quantum mechanics, you do not understand it.” Here’s another secret (at least as well protected as those in a bestselling book): quantum mechanics is notoriously misunderstood. Our language and intuition derive from
classical reasoning
, which doesn’t take quantum mechanics into account. But this doesn’t mean that any bizarre phenomenon is possible with quantum logic. Even without a more fundamental, deeper understanding, we know how to use quantum mechanics to make predictions. Quantum mechanics will certainly never account for Byrne’s “secret” about the so-called principle of attraction between people and distant things or phenomena. At those large distances, quantum mechanics doesn’t play this kind of role. Quantum mechanics has nothing to do with many of the tantalizing ideas people often attribute to it. I cannot affect an experiment by staring at it, quantum mechanics does not mean there are no reliable predictions, and most measurements are constrained by practical limitations and not by the uncertainty principle.

Such fallacies were the chief topic in a surprising conversation I had with Mark Vicente, the director of the movie
What the Bleep Do We Know!?
—a ?lm that is the bane of scientists—in which people claim that human influence matters for experiments. I wasn’t sure where this conversation would lead, but I had time to spare since I was sitting on the tarmac at the Dallas/Fort Worth airport for several hours waiting for mechanics to repair a dent in the wing (which first was described as too small to matter—but then was “measured by technology” before the plane could depart, as one crewmember helpfully informed us).

Even with the delay, I realized if I was going to talk to Mark at any length, I had to know where he stood on his film—which I was familiar with from the numerous people at my lectures who asked me off-the-wall questions based on what they had seen in it. Mark’s answer caught me by surprise. He had made a rather striking about-face. He confided that he had initially approached science with preconceived notions that he didn’t sufficiently question, but that he now viewed his previous thinking as more religious in nature. Mark ultimately concluded that what he had presented in his film was not science. Placing quantum mechanical phenomena at a human level was perhaps superficially satisfying to many of his film’s viewers, but that didn’t make it right.

Even if new theories require radically different assumptions—as was certainly the case with quantum mechanics—valid scientific arguments and experiments ultimately determined that they were true. It wasn’t magic. The scientific method, along with data and searches for economy and consistency, had told scientists how to extend their knowledge beyond what is intuitive at immediately accessible scales to very different ideas that apply to phenomena that are not.

The next section tells more about how the notion of scale systematically bridges different theoretical concepts and allows us to incorporate them into a coherent whole.

EFFECTIVE THEORIES

Our size happens to fall pretty much randomly close to the middle in terms of powers of ten when placed on a scale between the smallest imaginable length and the enormity of the universe.
⁶
We are very big compared to the internal structure of matter and its minuscule components, while we are extremely tiny compared to stars, galaxies, and the universe’s expanse. The sizes that we most readily comprehend are simply the ones that are most accessible to us—through our five senses and through the most rudimentary measuring tools. We understand more distant scales through observations combined with logical deductions. The range of sizes might seem to involve increasingly abstract and hard-to-keep-track-of quantities as we move further from directly visible and accessible scales. But technology combined with theory allows us to establish the nature of matter over a vast stretch of lengths.

Known scientific theories apply over this huge range—spanning distances as small as the tiny objects explored by the Large Hadron Collider (LHC) up to the enormous length scales of galaxies and the cosmos. And for each possible size of objects or distance between them, different aspects of the laws of physics can become relevant. Physicists have to cope with the abundance of information that applies over this enormous span. Although the most basic laws of physics that apply to tiny lengths are ultimately responsible for those that are relevant to larger scales, they are not necessarily the most efficient means of making a calculation. When the extra substructure or underpinnings are irrelevant to a sufficiently precise answer, we want a more practical way to calculate and efficiently apply simpler rules.