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pick up a phone and suddenly I’m talking to someone thousands of miles
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away. It’s obvious that invisible forces can fly across great distances through
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the power of technology— why not through the power of the mind?
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The human mind is a mysterious thing. It’s not that we know nothing
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about it; wise people have been contemplating the mind’s workings for
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thousands of years, and modern psychology and neuroscience have added
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considerably to our understanding. Still, it’s fair to say that there are more
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looming questions than settled facts. What is consciousness? What
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happens when we dream? How do we make decisions? How do we record
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memories? How do emotions and feelings interact with our rational
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thoughts? Where do experiences of awe and transcendence come from?
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So why not psychic powers? We should be properly skeptical, and try to
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determine through careful testing whether any particular claim actually
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holds up to scrutiny. Wishful thinking is a powerful force, and it makes
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sense to guard against it. But it’s important to be honest about what we
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know and what we don’t. On the face of it, reading minds or bending
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spoons doesn’t seem any crazier than talking over a telephone, and maybe
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less crazy than many of the triumphs of modern technology.
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There is a wide gap between admitting that we don’t know everything
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about how the mind works and remembering that whatever it does, it needs
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to be compatible with the laws of nature. There are things we don’t under-
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stand about, for example, treating the common cold. But there is no reason
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to think that cold viruses are anything other than particular arrangements of
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atoms obeying the rules of particle physics. And that knowledge puts limits
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on what those viruses can possibly do. They cannot teleport from one person’s
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body to another one, nor can they spontaneously turn into antimatter and
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cause explosions. The laws of physics don’t tell us everything we might want
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to know about how viruses work, but they undoubtedly tell us some things.
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Those same laws tell us that you can’t see around corners, or levitate
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through sheer force of will. All of the things you’ve ever seen or experienced
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in your life— objects, plants, animals, people— are made of a small number
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of particles, interacting with one another through a small number of forces.
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By themselves, those particles and forces don’t have the capability of support-
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ing the psychic phenomena that so fascinated my twelve- year- old self. More
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important, we know that there aren’t new particles or forces out there yet to
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be discovered that would support them. Not simply because we haven’t found
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them yet, but because we definitely would have found them if they had the
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right characteristics to give us the requisite powers. We know enough to draw
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very powerful conclusions about the limits of what we can do.
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•
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We never know anything about the empirical world with absolute certainty.
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We must always be open to changing our theories in the face of new infor-
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But we can, in the spirit of the later Wittgenstein, be sufficiently confi-
01
dent in some claims that we treat the matter as effectively settled. It’s pos-
02
sible that at noon tomorrow, the force of gravity will reverse itself, and we’ll
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all be flung away from the Earth and into space. It’s possible— we can’t actu-04
ally prove it won’t happen. And if surprising new data or an unexpected
05
theoretical insight forces us to take the possibility seriously, that’s exactly
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what we should do. But until then, we don’t worry about it.
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Psychic powers are like that. There’s no harm in doing careful laboratory
08
tests to search for people with the ability to read minds or push things
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around through telekinesis. But there’s no real point, since we know such
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abilities aren’t real, just as we know that gravity won’t reverse tomorrow.
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David Hume, writing in An Enquiry Concerning Human Understand-
12
ing, considered the question of how we should treat claims of miraculous
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events, defined as “a violation of the laws of nature.” His answer was Bayes-
14
ian in spirit: we should accept such a claim only if it would be harder to
15
disbelieve it than to believe it. That is, the evidence should be so over-
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whelming that it would strain our credulity more to deny it than to accept
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that the laws we thought governed the world have in fact been violated. The
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same holds for psychic phenomena: as long as the evidence in favor of them
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is weaker than our evidence in favor of the laws of physics (as it surely is),
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our credence in their existence should be extremely low.
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None of which is to say that science is finished, or that there aren’t
22
things we have yet to understand. Every scientific theory we have is one way
23
of talking about the world, one particular story we tell with a certain do-
24
main of applicability. Newtonian mechanics works pretty well for baseballs
25
and rocket ships; for atoms, it breaks down and we need to invoke quantum
26
mechanics. Yet we still use Newtonian mechanics where it works. We teach
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it to our students, and we use it to send spaceships to the moon. It’s “cor-
28
rect,” as long as we understand the domain in which it’s applicable. And no
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future discovery will suddenly make us think that it is incorrect in that
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domain.
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Right now we have a certain theory of particles and forces, the Core
32
Theory, that seems indisputably accurate within a very wide domain of ap-
33
plicability. It includes everything going on within you, and me, and e
very-
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thing you see around you right this minute. And it will continue to be
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accurate. A thousand or a million years from now, whatever amazing
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discoveries science will have made, our descendants are not going to be say-
02
ing “Ha-ha, those silly twenty- first- century scientists, believing in ‘neu-
03
trons’ and ‘electromagnetism.’ ” Hopefully by then we will have better,
04
deeper concepts, but the concepts we’re using now will still be legitimate in
05
the appropriate domain.
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And those concepts— the tenets of the Core Theory, and the framework
07
of quantum field theory on which it is based— are enough to tell us that
08
there are no psychic powers.
09
Many people still believe in psychic phenomena, but they are for the
10
most part dismissed in respectable circles of thought. The same basic story
11
holds for other tendencies we sometimes have to appeal to extraphysical
12
aspects of what it means to be human. The position of Venus in the sky on
13
the day you were born does not affect your future romantic prospects. Con-
14
sciousness emerges from the collective behavior of particles and forces,
15
rather than being an intrinsic feature of the world. And there is no immate-
16
rial soul that could possibly survive the body. When we die, that’s the
17
end of us.
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We are part of the world. Comprehending how the world works, and
19
what constraints that puts on who we are, is an important part of under-
20
standing how we fit into the big picture.
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The Quantum Realm
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t
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he history of science is sometimes told— for dramatic effect, if not
14
always in the interests of accuracy— as a story of revolutions. We
15
had the Copernican revolution in astronomy, and the Darwinian
16
revolution in biology. Physics has witnessed two revolutions that trans-
17
formed the very foundations of the discipline: Newtonian mechanics,
18
which describes the classical world, and quantum mechanics.
19
There’s a story that Chinese premier Zhou Enlai was asked in 1972 about
20
his opinion of the impact of the French Revolution, and he replied, “It’s too
21
early to say.” Sounds too good to be true, and it is. An interpreter later ad-
22
mitted that, given how the question was phrased, it is clear that Zhou was
23
thinking of the student riots of 1968, not the revolution of 1789.
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If they had been talking about the quantum revolution of the 1920s, on
25
the other hand, the quip would have been entirely appropriate. In 1965,
26
physicist Richard Feynman opined, “I think I can safely say that nobody
27
understands quantum mechanics,” and the sentiment is equally applicable
28
today. For a theory that has seen unparalleled empirical success at predict-
29
ing and accounting for the outcomes of high- precision experiments, the
30
embarrassing truth is that physicists cannot claim to have a very good un-
31
derstanding of what the theory actually is. Or at least, if some people know
32
what it is, their views are not widely shared by their colleagues.
33
But we shouldn’t exaggerate the mysteriousness of quantum mechanics
34
just for effect. We understand an enormous amount about the theory—
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otherwise we wouldn’t be able to make those predictions that have been
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checked to amazing precision. Give a well- trained physicist a well- posed
02
question about what quantum mechanics predicts in some specific situa-
03
tion, and they will come up with the uniquely correct answer. But the es-
04
sence of the theory, its final correct formulation and its ultimate ontology,
05
are still very much in dispute.
06
This is unfortunate, because where misunderstanding dwells, misuse
07
will not be far behind. No theory in the history of science has been more
08
misused and abused by cranks and charlatans— and misunderstood by
09
people struggling in good faith with difficult ideas— than quantum me-
10
chanics. We need to get as clear a view as possible of what the theory says
11
and doesn’t say, since it is the deepest and most fundamental picture of the
12
world we now have. Quantum mechanics has direct implications for many
13
issues that confront us as we try to make sense of our human experience of
14
the world: determinism, causality, free will, the origin of the universe itself.
15
•
16
17
Let’s start with the part of quantum mechanics that everyone agrees on:
18
what you will see when you observe a system.
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Consider a hydrogen atom. That’s the simplest kind of atom there is; its
34
nucleus is a single proton, and there is a single electron bound to it. When
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we visualize it in our head, we tend to imagine the electron orbiting around
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the proton much like a planet in the solar system orbits around the sun.
01
This is the “Rutherford model” of the atom.<
br />
02
It’s also wrong, and here’s why. Electrons are electrically charged, which
03
means they interact with electric and magnetic fields. When you shake an
04
electron, it emits electromagnetic waves— that’s the origin of much of the
05
light you actually see in your daily life, whether it’s from the sun or from an
06
incandescent bulb. Some electrons were heated up, started shaking, and lost
07
energy by radiating light. In our hydrogen atom, that orbiting electron car-
08
ries a certain amount of energy, depending on how close it is to the proton—
09
the closer it gets, the less energy it has. So an electron that is far away from
10
the proton, but still bound to it, has a relatively large energy. And it’s being
11
“shaken,” simply by the fact that it’s orbiting around. We therefore expect
12
the electron to give off light and in the process lose energy and spiral closer
13
and closer to the proton. (We expect the same thing for planets moving
14
around the sun, which lose energy by gravitational radiation— but gravity
15
is such a weak force that the net effect is negligible.)
16
When should this process stop? In a Newtonian world, the answer is
17
simple: when the electron is sitting right on top of the proton. Every elec-
18
tron orbiting around every nucleus of every atom should very rapidly spiral
19
to the center, so that every atom in the universe should collapse to the size
20
of a nucleus in less than a billionth of a second. There should be no mole-
21
cules, no chemistry, no tables, no people, no planets.
22
That would be bad. Also, it’s not what happens in the actual world.
23
We can get an idea about what does happen by considering cases when
24
the electron in the hydrogen atom actually does lose energy by giving off an
25
electromagnetic wave. When you collect the emitted light, you notice
26
something funny right off the bat: you only ever see certain discrete wave-
27
lengths. Newtonian mechanics predicts that we should see all sorts of waves
28
with any wavelength you can imagine. What we observe, instead, is only
29
certain allowed wavelengths emitted at each transition.
30
That means the electron in the atom can’t just be in any old orbit.
31
There must only be some special orbits it can be in, with fixed amounts
32
of energy. The reason we observe only certain wavelengths in the emitted
33
light is that the electrons are not gently spiraling inward but spontaneously
The Big Picture Page 27