[Marxism] Something Faster Than Light? What Is It?

Louis Proyect lnp3 at panix.com
Mon Oct 24 08:13:12 MDT 2016


NY Review of Books
Something Faster Than Light? What Is It?
Jim Holt NOVEMBER 10, 2016 ISSUE

Spooky Action at a Distance: The Phenomenon That Reimagines Space and 
Time—and What It Means for Black Holes, the Big Bang, and Theories of 
Everything
by George Musser
Scientific American/Farrar, Straus and Giroux, 286 pp., $27.00; $16.00 
(paper)

The Irish physicist John Stewart Bell, who in 1964 proposed a way to 
observe ‘spooky action’ of particles experimentally, at the Large 
Electron-Positron Collider at CERN, near Geneva, Switzerland, 1989
In physics, as in politics, there is a time-honored notion that all 
action is ultimately local. Aptly enough, physicists call this the 
“principle of locality.” What the principle of locality says, in 
essence, is that the world consists of separately existing physical 
objects, and that these objects can directly affect one another only if 
they come into contact.

It follows from the principle of locality that remote things can affect 
each other only indirectly, through causal intermediaries that bridge 
the distance between them. I can affect you, for instance, by extending 
my arm and giving you a pat on the cheek, or by calling you on your cell 
phone (electromagnetic radiation), or even—very, very slightly—by 
wiggling my little figure (gravitational waves). But I can’t affect you 
in a way that jumps instantly across the expanse of space that separates 
us, without anything traveling from me to you—by sticking a pin in a 
voodoo doll, say. That would be a “nonlocal” influence.

The idea of locality emerged early in the history of science. For the 
Greek atomists, it was what distinguished naturalistic explanations from 
magical ones. Whereas the gods were believed to be capable of acting 
nonlocally, by simply willing remote events to occur, genuine causality 
for the atomists was always local, a matter of hard little atoms bumping 
into one another. Aristotle adhered to the principle of locality; so did 
Descartes. Newton (to his own distress) seemed to depart from it, since 
gravity in his theory was an attractive force that somehow reached 
across empty space, perhaps instantaneously. But in the nineteenth 
century Michael Faraday restored locality by introducing the concept of 
a “field” as an all-pervading, energy-carrying medium through which 
forces like gravity and electromagnetism are transmitted from one object 
to another—not instantaneously, as would be the case with nonlocal 
action, but at a fixed and finite speed: the speed of light.

The principle of locality promises to render the workings of nature 
rational and transparent, allowing complex phenomena to be “reduced” to 
local interactions. Nonlocality, by contrast, has always been the refuge 
of the occult and the hermetic, of believers in “sympathies” and 
“synchronicity” and “holism.”

Albert Einstein had a deep philosophical faith in the principle of 
locality. He couldn’t imagine how science could proceed without it. 
“Unless one makes this kind of assumption,” Einstein said, “physical 
thinking in the familiar sense would not be possible.” He dismissed the 
possibility of voodoo-like, space-defying, nonlocal influences as 
“spooky action at a distance” (spukhafte Fernwirkung).

But in the 1920s Einstein, alone among his contemporaries, noticed 
something disturbing: the new science of quantum mechanics looked to be 
at odds with the principle of locality. It seemed to entail “spooky 
action at a distance.” He took this to mean that there must be something 
seriously amiss with the quantum theory, which he himself had helped 
create. (Einstein’s 1921 Nobel Prize was for his work on the 
photoelectric effect, a quantum phenomenon, not for his discovery of 
relativity.) He came up with clever thought-experiments to make the 
problem he saw vivid. Defenders of the quantum consensus, chief among 
them Niels Bohr, endeavored to rebut Einstein, yet they failed to 
appreciate the true force of his logic. Meanwhile, quantum theory’s 
growing record of success in explaining chemical bonding and predicting 
new particles made Einstein’s qualms look merely “philosophical”—which 
can be a term of abuse in physics.

And so the matter stood until 1964, a little under a decade after 
Einstein’s death. That was when an Irish physicist named John Stewart 
Bell did what no one had imagined was possible: he showed that 
Einstein’s philosophical objection could be put to an experimental test. 
If quantum mechanics was right, Bell proved, “spooky action” could 
actually be observed in the lab. And when the experiment Bell described 
was carried out—imperfectly in Berkeley in the 1970s, more decisively in 
Paris in 1982, and near authoritatively in Delft late last year—the 
“spooky” predictions of quantum mechanics were vindicated.

Yet the reaction to this news—from physicists with an interest in 
philosophy, from philosophers with an interest in physics—has been 
strangely equivocal. Some have declared the revelation that nature 
flouts the principle of locality to be “mind-boggling” (the physicist 
Brian Greene) and “the single most astonishing discovery of 
twentieth-century physics” (the philosopher Tim Maudlin). Others think 
that nonlocality, though perhaps a little spooky on the face of it, is 
nothing to get metaphysically exercised over, since it “still follows 
the ordinary laws of cause and effect” (the physicist Lawrence Krauss). 
Still others—notwithstanding Bell and the subsequent experiments—deny 
that the world genuinely contains nonlocal connections. Prominent among 
them is the Nobel laureate Murray Gell-Mann, who insists that all the 
talk of “action at a distance” amounts to a “flurry of flapdoodle.”

This ongoing debate and its historical background are engagingly 
described by George Musser in Spooky Action at a Distance. Musser writes 
that the disagreement over nonlocality is “intellectually pure.” There 
is nothing financial or personal about it. And if it seems stubbornly 
unresolvable, that may be because it goes to a deeper issue: Just what 
should we expect from physics—a recipe for making predictions, or a 
unified picture of reality?

That was the issue that divided Einstein and Bohr in the early days of 
quantum mechanics. Einstein was, metaphysically speaking, a “realist”: 
he believed in an objective physical world, one that existed 
independently of our observations. And he thought the job of physics was 
to give a complete and intelligible account of that world. “Reality is 
the real business of physics” was how he put it.

Bohr, by contrast, was notoriously slippery in his metaphysical 
commitments. At times he sounded like an “idealist” (in the 
philosophical sense), arguing that physical properties become definite 
only when they are measured, and hence that reality is, to some extent, 
created by the very act of observation. At other times he sounded like 
an “instrumentalist,” arguing that quantum mechanics was meant to be an 
instrument for predicting our observations, not a true representation of 
a world lurking behind those observations. “There is no quantum world,” 
Bohr provocatively declared.

Bohr was happy with the quantum theory; Einstein was not. Popular 
accounts often claim that Einstein objected to quantum mechanics because 
it made randomness a fundamental ingredient of reality. “God does not 
play dice,” he famously said. But it was not randomness per se that 
bothered Einstein. Rather, it was his suspicion that the appearance of 
randomness in quantum mechanics was a sign that the new theory didn’t 
tell the whole story of what was going on in the physical world. And the 
principle of locality had an important part in this suspicion.

Here is the simplest of the thought-experiments designed to illustrate 
this, which has become known as “Einstein’s Boxes.” Start with a box 
that contains a single particle—say, an electron. According to quantum 
mechanics, an electron confined to a box does not have a definite 
location until we look inside to see just where it is. Prior to that act 
of observation, the electron is in a mixture of potential locations 
spread throughout the box. This mixture is mathematically represented by 
a “wave function,” which expresses the different probabilities of 
detecting the electron at the various locations inside the box if you do 
an experiment. (In French, the wave function is evocatively called 
densité de présence.) Only when the observation is made does 
potentiality turn into actuality. Then the wave function “collapses” (as 
physicists say) to a single point, and the electron’s location becomes 
definite.

Now suppose that, before any such observational experiment is carried 
out, we put a partition through the middle of the box containing the 
electron. If this is done in the appropriate way, the wave function of 
the electron inside will be split in two: loosely speaking, half of the 
wave function will be to the left of the partition, half to the right. 
This is a complete quantum description of the physical situation: there 
is no deeper fact about which side of the partition the electron is 
“really” on. The wave function does not represent our ignorance of where 
the particle is; it represents genuine indeterminacy in the world.

Next, we separate the two partitioned halves of the box. We put the left 
half-box on a plane for Paris, and the right half-box on a plane for 
Tokyo. Once the boxes have arrived at their respective destinations, a 
physicist in Tokyo does an experiment to see whether there is an 
electron in the right half-box. Quantum mechanics says the result of 
this experiment will be purely random, like flipping a coin. Since the 
wave function is equally split between the two half-boxes, there is a 
50–50 chance that the Tokyo physicist will detect the presence of an 
electron.

Well, suppose she does. With that, the wave function collapses. The act 
of detecting an electron in the Tokyo box causes the part of the wave 
function associated with the Paris box to vanish instantaneously. It’s 
as though the Paris box telepathically knows the (supposedly random) 
outcome of the Tokyo experiment and reacts accordingly. Now if a 
physicist in Paris looks in the right half-box, he is certain not to 
find an electron. (Of course, the “collapse” could have gone the other 
way, and the Paris physicist could have found the electron.)

That is the orthodox quantum story, as developed by Bohr, Werner 
Heisenberg, and other founders of the theory. It is called the 
“Copenhagen interpretation” of quantum mechanics, since Bohr was the 
head of the physics institute at the University of Copenhagen. According 
to the Copenhagen interpretation, the very act of observation causes the 
spread-out probability wave to collapse into a sharply located particle. 
Hence what has been called the best explanation of quantum mechanics in 
five words or less: Don’t look: waves. Look: particles.

To Einstein, this was absurd. How could merely looking inside a box 
cause spread-out potentiality to snap into sharp actuality? And how 
could looking inside a box in Tokyo instantly change the physical state 
of a box on the other side of the world in Paris? That would be “spooky 
action at a distance”—a clear contravention of the principle of locality.

Einstein’s intuition was just what common sense would suggest: the 
particle must have been in one box or the other all along. Therefore, 
Einstein concluded, quantum mechanics must be incomplete. It offers a 
blurry picture of a sharp reality rather than (as its defenders 
insisted) a sharp picture of a blurry reality.

Bohr never confronted the simple logic of Einstein’s Boxes. Instead, he 
focused his polemical attention on a later and more elaborate 
thought-experiment, one that Einstein came up with in the 1930s after he 
had left Germany and relocated to the Institute for Advanced Study in 
Princeton. It is referred to by the initials “EPR,” after Einstein and 
his two junior collaborators, Boris Podolsky (from Russia) and Nathan 
Rosen (from Brooklyn).

The EPR thought-experiment involves a pair of particles that get created 
together and then go their separate ways. Einstein saw that, according 
to quantum mechanics, such particles would be “entangled”: they would 
stay correlated regardless of how far apart they moved. As an example, 
consider what happens when an “excited” atom—an atom whose energy level 
has been artificially boosted—sheds its excess energy by emitting a pair 
of photons (particles that are components of light). These two photons 
will fly off in contrary directions; eventually they will travel to 
opposite sides of the galaxy and beyond. Yet quantum mechanics says 
that, no matter how vast the separation between them, the two photons 
will remain entangled as a single quantum system. When subjected to the 
same experiment, each will respond exactly as its partner does. If, for 
example, you see the near photon successfully make its way through a 
polarizing filter (like the kind in sunglasses), you automatically know 
that its distant partner would do so as well, provided the near and 
distant filters are set at the same angle.

You might think that such entangled particles are no more mysterious 
than a pair of identical twins who have moved to different cities; if 
you see that twin A in New York has red hair, you automatically know 
that twin B in Sydney is a redhead too. But unlike hair color, quantum 
properties do not become definite until they are subjected to a 
measurement. When particle A is measured, it snaps out of a mixture of 
possibilities into a definite state, and this supposedly forces its 
entangled partner B to snap out of its own mixture of possibilities into 
an exactly correlated state.

If quantum mechanics is right, the entangled particles are not like a 
pair of identical twins; rather, they are like the magical coins that 
are sometimes imagined in thought experiments: although they are not 
altered or weighted in any manner, they know to always land the same way 
when flipped. It is as though there were a telepathic link between the 
entangled particles, one that enables them to coordinate their behavior 
instantaneously across vast distances—even though all known methods of 
communication are, in accord with relativity, limited by the speed of light.

Einstein’s conclusion in the EPR thought-experiment was the same as in 
Einstein’s Boxes: such a link would be “spooky action at a distance.” 
Quantum entanglement can’t be real. The tightly choreographed behavior 
of the widely separated particles must be pre-programmed from the start 
(as with identical twins), not a matter of correlated randomness (as 
with magic coins). And since quantum theory doesn’t account for such 
pre-programming—referred to by physicists as “hidden variables”—it gives 
an incomplete description of the world.

The EPR reasoning is clear enough up to this point. But the paper that 
Einstein, Podolsky, and Rosen published in 1935 went further, attempting 
to discredit the Heisenberg uncertainty principle, which states that 
certain pairs of physical properties of a particle—such as the 
particle’s position and its momentum—cannot both be definite at the same 
time. (Einstein later blamed this overreach on the younger Podolsky, who 
wrote the last section of the EPR paper.) That muddied matters 
sufficiently to give Bohr the opening he needed for his rebuttal—which 
proved to be a masterpiece of obscurity. A decade after he produced it, 
Bohr confessed that he himself had difficulty making sense of what he 
had written. Yet as Musser observes, “most physicists just wanted the 
Bohr-Einstein debate to be over, so they could get on with applying 
quantum mechanics to practical problems. Because Bohr promised closure, 
they rallied around him and wrote off Einstein as a has-been.”

One later physicist who stood apart from this consensus was John Stewart 
Bell (1928–1990). The son of a Belfast horse-trader, Bell made his 
career in applied physics, helping to design the first particle 
accelerator at CERN (the European physics center near Geneva). But he 
also looked on the conceptual foundations of physics with a 
philosopher’s eye. In the clarity and rigor of his thought, Bell rivaled 
Einstein. And like Einstein, he had misgivings about quantum mechanics. 
“I hesitated to think it might be wrong, but I knew that it was rotten,” 
he said.1

Reflecting on the EPR thought-experiment, Bell ingeniously saw a way to 
tweak it so that it could be made into a real experiment, one that would 
force the issue between quantum mechanics and locality. His proof that 
this was possible, now famous as “Bell’s theorem,” was published in 
1964. Amazingly, it required just a couple of pages of high school algebra.

The gist of Bell’s idea was to get entangled particles to reveal their 
nonlocal connection—if indeed there was one—by interrogating them more 
subtly. This could be done, he saw, by measuring the spin of the 
particles along different angles. Because of the peculiarities of 
quantum spin, each measurement would be like asking the particle a 
“yes”/“no” question. If two separated but entangled particles are asked 
the same question—that is, if their spins are measured along the same 
angle—they are guaranteed to give the same answer: either both “yes” or 
both “no.” There’s nothing necessarily magical about such agreement: it 
could have been programmed into the pair of entangled particles when 
they were created together.

But if entangled particles are asked different questions—that is, if 
their respective spins are measured along different angles—quantum 
mechanics then predicts a precise statistical pattern of matches and 
mismatches in their “yes”/“no” answers. And with the right combination 
of questions, Bell proved, this pattern would be unambiguously nonlocal. 
No amount of pre-programming, no “hidden variables” of the kind 
envisaged by Einstein, could explain it. Such a tight correlation, Bell 
proved, could only mean that the separated particles were coordinating 
their behavior in some way not yet understood—that each “knew” not only 
which question its distant twin was being asked, but also how the twin 
answered.

All that remained to settle Einstein’s quarrel with quantum mechanics 
was to do the experiment Bell outlined and see whether or not this 
statistical pattern emerged. It took technology a little while to catch 
up, but by the early 1970s physicists had begun to test Bell’s idea in 
the lab. In experiments measuring properties of pairs of entangled 
photons, the pattern of statistical correlation Bell identified has 
invariably been observed. The verdict: spooky action is real.

So was Einstein wrong? It would be fairer (if a bit melodramatic) to say 
that he was betrayed by nature—which, by violating the principle of 
locality, turned out to be less reasonable than he imagined. Yet 
Einstein had seen more deeply into quantum mechanics than Bohr and the 
other defenders of quantum orthodoxy. (Einstein once remarked that he 
had given a hundred times as much thought to quantum mechanics as he had 
to his own theory of relativity.) He realized that nonlocality was a 
genuine and disturbing feature of the new theory and not, as Bohr and 
his circle seemed to regard it, a mere mathematical fiction.

Let’s pause here to note just how strange the quantum connection between 
entangled particles really is. First, it is undiluted by distance—unlike 
gravity, which falls off in strength. Second, it is discriminating: an 
experiment done on one photon in an entangled pair affects only its 
partner, wherever that partner may be, leaving all other photons, near 
and far, untouched. The discriminating nature of entanglement again 
stands in contrast to gravity, where a disturbance created by the 
jostling of one atom will ripple out to affect every atom in the 
universe. And third, the quantum connection is instantaneous: a change 
in the state of one entangled particle makes itself felt on its partner 
without delay, no matter how vast the gulf that separates them—yet again 
in contrast to gravity, whose influence travels at the speed of light.

It is the third of these features of quantum nonlocality, its 
instantaneousness, that is the most worrisome. As Einstein realized 
early on, it would mean that the entangled particles were communicating 
faster than the speed of light, which is generally forbidden by the 
theory of relativity. If, for example, particle A is near the earth and 
its entangled twin B is near Alpha Centauri (the nearest star system to 
the sun), a measurement performed on A will alter the state of B 
instantly, even though it would take 4.3 years for light to get from A to B.

Many physicists tend to brush off this apparent conflict between 
relativity theory and quantum mechanics. They point out that even though 
quantum entanglement does seem to entail “superluminal” (faster than 
light) influences, those influences can’t be used for communication—to 
send messages, say, or music. There is no possibility of a “Bell 
telephone” (as in “John,” not “Alexander Graham”). And the reason is 
quantum randomness: although entangled particles do exchange information 
between themselves, a would-be human signaler can’t control their random 
behavior and encode a message in it. Since it can’t be used for 
communication, quantum entanglement doesn’t give rise to the sort of 
causal anomalies Einstein warned about—like being able to send a message 
backward in time. So quantum theory and relativity, though conceptually 
at odds with each other, can “peacefully coexist.”

For John Bell, that wasn’t good enough. “We have an apparent 
incompatibility, at the deepest level, between the two fundamental 
pillars of contemporary theory,” he observed in a 1984 lecture. If our 
picture of physical reality is to be coherent, Bell believed, the 
tension between relativity theory and quantum mechanics must be confronted.

In 2006, an impressive breakthrough along these lines was made by 
Roderich Tumulka, a German-born mathematician at Rutgers. Building on 
the insights of Bell and other philosophically-minded physicists, 
Tumulka succeeded in creating a model of nonlocal entanglement that 
fully abides by Einsteinian relativity. Contrary to what is widely 
believed, relativity does not completely rule out influences that are 
faster than light. (Indeed, physicists sometimes talk about hypothetical 
particles called “tachyons” that move faster than the speed of light.) 
What relativity does rule out is absolute time: a universal “now” that 
is valid for all observers. Entangled particles would seem to require 
such a universal clock if they are to synchronize their behavior across 
vast distances. But Tumulka found a way around this. He showed how a 
certain speculative extension of quantum mechanics—known, for 
complicated reasons, as “flashy GRW”—could allow entangled particles to 
act in synchrony without violating relativity’s ban on absolute 
simultaneity. Although the mechanism behind this nonlocal “spooky 
action” remains obscure, Tumulka at least proved that it is logically 
consistent with relativity after all—a result that might well have 
surprised Einstein.2

Strangely, Tumulka’s feat of reconciling nonlocality with relativity 
goes unmentioned by Musser. This is a grave omission in an otherwise 
enlightening (and highly entertaining) book, one that takes us beyond 
earlier popular treatments into the speculative thickets of contemporary 
physics: cosmic “wormholes,” “branes,” “twistors,” and so forth. Far 
from being a quietist about nonlocality, Musser ends up embracing its 
most extreme implications: “Nonlocality does mean we live in a holistic 
universe, one that isn’t reducible to its spatial parts.”

In a holistic universe, things that seem to be far apart may, at a 
deeper level of reality, not be truly separate at all. The space of our 
everyday experience might be an illusion, a mere projection of some more 
basic causal system. A nice metaphor for this (proposed by the 
philosopher Jenann Ismail) is the kaleidoscope. Don’t think of entangled 
particles as “magical coins” somehow exchanging messages across space. 
Rather, think of them as being like the multiple images of a glass bead 
tumbling about in a kaleidoscope—different mirror reflections of the 
same underlying particle.

Despite such radical implications, the physics profession has (for the 
most part) taken the demonstration of nonlocality in stride. Younger 
physicists who have grown up with nonlocality don’t find it all that 
spooky. “The kids here say, that’s just the way it is,” one senior 
physicist tells Musser. Among the elder generation, there seems to be a 
widespread impression that the weirdness of nonlocality can be evaded by 
taking a “non-realist” view of quantum mechanics—by looking upon it the 
way Niels Bohr did, as a mathematical device for making predictions, not 
a picture of reality. One contemporary representative of this way of 
thinking is Stephen Hawking, who has said, “I don’t demand that a theory 
correspond to reality because I don’t know what it is…. All I’m 
concerned with is that the theory should predict the results of 
measurements.”

Yet a deeper understanding of entanglement and nonlocality is also 
crucial to resolving the perennial argument over how to “interpret” 
quantum mechanics—how to give a realistic account of what happens when a 
measurement is made and the wave function mysteriously and randomly 
“collapses.” This is the very problem that vexed Einstein, and it is one 
that still vexes a small and contentious community of physicists (like 
Sir Roger Penrose, Sheldon Goldstein, and Sean Carroll) and philosophers 
of physics (like David Z. Albert, Tim Maudlin, and David Wallace) who 
continue to demand from physics the same thing that Einstein did: a 
unified and intelligible account of how the world really is. For them, 
the conceptual foundations of quantum mechanics, and the role of “spooky 
action” in those foundations, remain very much a work in progress.

1
Bell made this remark in an interview with Jeremy Bernstein, who 
produced a superb memoir of Bell in his 1991 book Quantum Profiles 
(Princeton University Press). ↩
2
Anyone looking for a deeper account of these issues should consult Tim 
Maudlin’s brilliant and indispensable Quantum Non-Locality and 
Relativity (third edition, Wiley-Blackwell, 2011). ↩
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