The Big Picture
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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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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-
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dent in some claims that we treat the matter as effectively settled. It’s pos-
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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
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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
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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-
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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-
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ian in spirit: we should accept such a claim only if it would be harder to
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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
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things we have yet to understand. Every scientific theory we have is one way
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of talking about the world, one particular story we tell with a certain do-
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main of applicability. Newtonian mechanics works pretty well for baseballs
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and rocket ships; for atoms, it breaks down and we need to invoke quantum
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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-
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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
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Theory, that seems indisputably accurate within a very wide domain of ap-
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plicability. It includes everything going on within you, and me, and e
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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-
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ing “Ha-ha, those silly twenty- first- century scientists, believing in ‘neu-
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trons’ and ‘electromagnetism.’ ” Hopefully by then we will have better,
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deeper concepts, but the concepts we’re using now will still be legitimate in
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the appropriate domain.
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And those concepts— the tenets of the Core Theory, and the framework
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of quantum field theory on which it is based— are enough to tell us that
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there are no psychic powers.
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Many people still believe in psychic phenomena, but they are for the
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most part dismissed in respectable circles of thought. The same basic story
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holds for other tendencies we sometimes have to appeal to extraphysical
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aspects of what it means to be human. The position of Venus in the sky on
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the day you were born does not affect your future romantic prospects. Con-
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sciousness emerges from the collective behavior of particles and forces,
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rather than being an intrinsic feature of the world. And there is no immate-
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rial soul that could possibly survive the body. When we die, that’s the
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end of us.
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We are part of the world. Comprehending how the world works, and
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what constraints that puts on who we are, is an important part of under-
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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
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always in the interests of accuracy— as a story of revolutions. We
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had the Copernican revolution in astronomy, and the Darwinian
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revolution in biology. Physics has witnessed two revolutions that trans-
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formed the very foundations of the discipline: Newtonian mechanics,
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which describes the classical world, and quantum mechanics.
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There’s a story that Chinese premier Zhou Enlai was asked in 1972 about
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his opinion of the impact of the French Revolution, and he replied, “It’s too
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early to say.” Sounds too good to be true, and it is. An interpreter later ad-
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mitted that, given how the question was phrased, it is clear that Zhou was
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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
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the other hand, the quip would have been entirely appropriate. In 1965,
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physicist Richard Feynman opined, “I think I can safely say that nobody
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understands quantum mechanics,” and the sentiment is equally applicable
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today. For a theory that has seen unparalleled empirical success at predict-
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ing and accounting for the outcomes of high- precision experiments, the
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embarrassing truth is that physicists cannot claim to have a very good un-
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derstanding of what the theory actually is. Or at least, if some people know
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what it is, their views are not widely shared by their colleagues.
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But we shouldn’t exaggerate the mysteriousness of quantum mechanics
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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
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question about what quantum mechanics predicts in some specific situa-
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tion, and they will come up with the uniquely correct answer. But the es-
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sence of the theory, its final correct formulation and its ultimate ontology,
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are still very much in dispute.
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This is unfortunate, because where misunderstanding dwells, misuse
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will not be far behind. No theory in the history of science has been more
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misused and abused by cranks and charlatans— and misunderstood by
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people struggling in good faith with difficult ideas— than quantum me-
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chanics. We need to get as clear a view as possible of what the theory says
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and doesn’t say, since it is the deepest and most fundamental picture of the
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world we now have. Quantum mechanics has direct implications for many
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issues that confront us as we try to make sense of our human experience of
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the world: determinism, causality, free will, the origin of the universe itself.
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Let’s start with the part of quantum mechanics that everyone agrees on:
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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
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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.
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This is the “Rutherford model” of the atom.<
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It’s also wrong, and here’s why. Electrons are electrically charged, which
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means they interact with electric and magnetic fields. When you shake an
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electron, it emits electromagnetic waves— that’s the origin of much of the
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light you actually see in your daily life, whether it’s from the sun or from an
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incandescent bulb. Some electrons were heated up, started shaking, and lost
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energy by radiating light. In our hydrogen atom, that orbiting electron car-
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ries a certain amount of energy, depending on how close it is to the proton—
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the closer it gets, the less energy it has. So an electron that is far away from
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the proton, but still bound to it, has a relatively large energy. And it’s being
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“shaken,” simply by the fact that it’s orbiting around. We therefore expect
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the electron to give off light and in the process lose energy and spiral closer
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and closer to the proton. (We expect the same thing for planets moving
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around the sun, which lose energy by gravitational radiation— but gravity
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is such a weak force that the net effect is negligible.)
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When should this process stop? In a Newtonian world, the answer is
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simple: when the electron is sitting right on top of the proton. Every elec-
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tron orbiting around every nucleus of every atom should very rapidly spiral
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to the center, so that every atom in the universe should collapse to the size
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of a nucleus in less than a billionth of a second. There should be no mole-
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cules, no chemistry, no tables, no people, no planets.
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That would be bad. Also, it’s not what happens in the actual world.
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We can get an idea about what does happen by considering cases when
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the electron in the hydrogen atom actually does lose energy by giving off an
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electromagnetic wave. When you collect the emitted light, you notice
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something funny right off the bat: you only ever see certain discrete wave-
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lengths. Newtonian mechanics predicts that we should see all sorts of waves
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with any wavelength you can imagine. What we observe, instead, is only
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certain allowed wavelengths emitted at each transition.
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That means the electron in the atom can’t just be in any old orbit.
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There must only be some special orbits it can be in, with fixed amounts
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of energy. The reason we observe only certain wavelengths in the emitted
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light is that the electrons are not gently spiraling inward but spontaneously