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Does The Universe Exist If We're Not Looking?

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    NHNE News List Current Members: 667 Subscribe/unsubscribe/archive info at the bottom of this message. ... DOES THE UNIVERSE EXIST IF WE RE NOT LOOKING? By Tim
    Message 1 of 1 , Aug 14, 2002
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      By Tim Folger
      DISCOVER Vol. 23 No. 6 (June 2002)


      The world seems to be putting itself together piece by piece on this damp
      gray morning along the coast of Maine. First the spruce and white pine trees
      that cover High Island materialize from the fog, then the rocky headland,
      and finally the sea, as if the mere act of watching has drawn them all into
      existence. And that may indeed be the case. While this misty genesis
      unfolds, the island's most eminent resident discusses notions that still
      perplex him after seven decades in physics, including his gut feeling that
      the very universe may be constantly emerging from a haze of possibility,
      that we inhabit a cosmos made real in part by our own observations.

      John Wheeler, scientist and dreamer, colleague of Albert Einstein and Niels
      Bohr, mentor to many of today's leading physicists, and the man who chose
      the name "black hole" to describe the unimaginably dense, light-trapping
      objects now thought to be common throughout the universe, turned 90 last
      July. He is one of the last of the towering figures of 20th-century physics,
      a member of the generation that plumbed the mysteries of quantum mechanics
      and limned the utmost reaches of space and time. After a lifetime of
      fundamental contributions in fields ranging from atomic physics to
      cosmology, Wheeler has concerned himself in his later years with what he
      calls "ideas for ideas."

      "I had a heart attack on January 9, 2001," he says, "I said, 'That's a
      signal. I only have a limited amount of time left, so I'll concentrate on
      one question: How come existence?'"

      Why does the universe exist? Wheeler believes the quest for an answer to
      that question inevitably entails wrestling with the implications of one of
      the strangest aspects of modern physics: According to the rules of quantum
      mechanics, our observations influence the universe at the most fundamental
      levels. The boundary between an objective "world out there" and our own
      subjective consciousness that seemed so clearly defined in physics before
      the eerie discoveries of the 20th century blurs in quantum mechanics. When
      physicists look at the basic constituents of reality‹ atoms and their
      innards, or the particles of light called photons‹ what they see depends on
      how they have set up their experiment. A physicist's observations determine
      whether an atom, say, behaves like a fluid wave or a hard particle, or which
      path it follows in traveling from one point to another. From the quantum
      perspective the universe is an extremely interactive place. Wheeler takes
      the quantum view and runs with it.

      As Wheeler voices his thoughts, he laces his fingers behind his large head,
      leans back onto a sofa, and gazes at the ceiling or perhaps far beyond it.
      He sits with his back to a wide window. Outside, the fog is beginning to
      lift on what promises to be a hot summer day. On an end table near the sofa
      rests a large oval rock, with one half polished black so that its surface
      resembles the Chinese yin-yang symbol. "That rock is about 200 million years
      old," says Wheeler. "One revolution of our galaxy."

      Although Wheeler's face looks careworn and sober, it becomes almost boyish
      when he smiles, as he does when I extend a hand to help him from the couch
      and he says, "Ah, antigravity." Wheeler is short and sturdily built, with
      sparse white hair. He retains an impish fascination with fireworks‹ an
      enthusiasm that cost him part of a finger when he was young‹ and has on
      occasion lit Roman candles in the corridors of Princeton, where he became a
      faculty member in 1938 and where he still keeps an office. At one point a
      loud bang interrupts our interview. Wheeler's son, who lives on a cliff a
      few hundred yards away, has fired a small cannon, a gift from Wheeler.

      Wheeler is gracious to a fault; one colleague describes him as "a gentleman
      hidden inside a gentleman." But that courtly demeanor also hides something
      else: one of the most adventurous minds in physics. Instead of shying away
      from questions about the meaning of it all, Wheeler relishes the profound
      and the paradoxical. He was an early advocate of the anthropic principle,
      the idea that the universe and the laws of physics are fine-tuned to permit
      the existence of life. For the past two decades, though, he has pursued a
      far more provocative idea for an idea, something he calls genesis by
      observership. Our observations, he suggests, might actually contribute to
      the creation of physical reality. To Wheeler we are not simply bystanders on
      a cosmic stage; we are shapers and creators living in a participatory

      Wheeler's hunch is that the universe is built like an enormous feedback
      loop, a loop in which we contribute to the ongoing creation of not just the
      present and the future but the past as well. To illustrate his idea, he
      devised what he calls his "delayed-choice experiment," which adds a
      startling, cosmic variation to a cornerstone of quantum physics: the classic
      two-slit experiment.

      That experiment is exceedingly strange in its own right, even without
      Wheeler's extra kink thrown in. It illustrates a key principle of quantum
      mechanics: Light has a dual nature. Sometimes light behaves like a compact
      particle, a photon; sometimes it seems to behave like a wave spread out in
      space, just like the ripples in a pond. In the experiment, light‹ a stream
      of photons‹ shines through two parallel slits and hits a strip of
      photographic film behind the slits. The experiment can be run two ways: with
      photon detectors right beside each slit that allow physicists to observe the
      photons as they pass, or with detectors removed, which allows the photons to
      travel unobserved. When physicists use the photon detectors, the result is
      unsurprising: Every photon is observed to pass through one slit or the
      other. The photons, in other words, act like particles.

      But when the photon detectors are removed, something weird occurs. One would
      expect to see two distinct clusters of dots on the film, corresponding to
      where individual photons hit after randomly passing through one slit or the
      other. Instead, a pattern of alternating light and dark stripes appears.
      Such a pattern could be produced only if the photons are behaving like
      waves, with each individual photon spreading out and surging against both
      slits at once, like a breaker hitting a jetty. Alternating bright stripes in
      the pattern on the film show where crests from those waves overlap; dark
      stripes indicate that a crest and a trough have canceled each other.

      The outcome of the experiment depends on what the physicists try to measure:
      If they set up detectors beside the slits, the photons act like ordinary
      particles, always traversing one route or the other, not both at the same
      time. In that case the striped pattern doesn't appear on the film. But if
      the physicists remove the detectors, each photon seems to travel both routes
      simultaneously like a tiny wave, producing the striped pattern.

      Wheeler has come up with a cosmic-scale version of this experiment that has
      even weirder implications. Where the classic experiment demonstrates that
      physicists' observations determine the behavior of a photon in the present,
      Wheeler's version shows that our observations in the present can affect how
      a photon behaved in the past.

      To demonstrate, he sketches a diagram on a scrap of paper. Imagine, he says,
      a quasar‹ a very luminous and very remote young galaxy. Now imagine that
      there are two other large galaxies between Earth and the quasar. The gravity
      from massive objects like galaxies can bend light, just as conventional
      glass lenses do. In Wheeler's experiment the two huge galaxies substitute
      for the pair of slits; the quasar is the light source. Just as in the
      two-slit experiment, light‹ photons‹ from the quasar can follow two
      different paths, past one galaxy or the other.

      Suppose that on Earth, some astronomers decide to observe the quasars. In
      this case a telescope plays the role of the photon detector in the two-slit
      experiment. If the astronomers point a telescope in the direction of one of
      the two intervening galaxies, they will see photons from the quasar that
      were deflected by that galaxy; they would get the same result by looking at
      the other galaxy. But the astronomers could also mimic the second part of
      the two-slit experiment. By carefully arranging mirrors, they could make
      photons arriving from the routes around both galaxies strike a piece of
      photographic film simultaneously. Alternating light and dark bands would
      appear on the film, identical to the pattern found when photons passed
      through the two slits.

      Here's the odd part. The quasar could be very distant from Earth, with light
      so faint that its photons hit the piece of film only one at a time. But the
      results of the experiment wouldn't change. The striped pattern would still
      show up, meaning that a lone photon not observed by the telescope traveled
      both paths toward Earth, even if those paths were separated by many
      light-years. And that's not all.

      By the time the astronomers decide which measurement to make‹ whether to pin
      down the photon to one definite route or to have it follow both paths
      simultaneously‹ the photon could have already journeyed for billions of
      years, long before life appeared on Earth. The measurements made now, says
      Wheeler, determine the photon's past. In one case the astronomers create a
      past in which a photon took both possible routes from the quasar to Earth.
      Alternatively, they retroactively force the photon onto one straight trail
      toward their detector, even though the photon began its jaunt long before
      any detectors existed.

      It would be tempting to dismiss Wheeler's thought experiment as a curious
      idea, except for one thing: It has been demonstrated in a laboratory. In
      1984 physicists at the University of Maryland set up a tabletop version of
      the delayed-choice scenario. Using a light source and an arrangement of
      mirrors to provide a number of possible photon routes, the physicists were
      able to show that the paths the photons took were not fixed until the
      physicists made their measurements, even though those measurements were made
      after the photons had already left the light source and begun their circuit
      through the course of mirrors.

      Wheeler conjectures we are part of a universe that is a work in progress; we
      are tiny patches of the universe looking at itself‹ and building itself.
      It's not only the future that is still undetermined but the past as well.
      And by peering back into time, even all the way back to the Big Bang, our
      present observations select one out of many possible quantum histories for
      the universe.

      Does this mean humans are necessary to the existence of the universe? While
      conscious observers certainly partake in the creation of the participatory
      universe envisioned by Wheeler, they are not the only, or even primary, way
      by which quantum potentials become real. Ordinary matter and radiation play
      the dominant roles. Wheeler likes to use the example of a high-energy
      particle released by a radioactive element like radium in Earth's crust. The
      particle, as with the photons in the two-slit experiment, exists in many
      possible states at once, traveling in every possible direction, not quite
      real and solid until it interacts with something, say a piece of mica in
      Earth's crust. When that happens, one of those many different probable
      outcomes becomes real. In this case the mica, not a conscious being, is the
      object that transforms what might happen into what does happen. The trail of
      disrupted atoms left in the mica by the high-energy particle becomes part of
      the real world.

      At every moment, in Wheeler's view, the entire universe is filled with such
      events, where the possible outcomes of countless interactions become real,
      where the infinite variety inherent in quantum mechanics manifests as a
      physical cosmos. And we see only a tiny portion of that cosmos. Wheeler
      suspects that most of the universe consists of huge clouds of uncertainty
      that have not yet interacted either with a conscious observer or even with
      some lump of inanimate matter. He sees the universe as a vast arena
      containing realms where the past is not yet fixed.

      Wheeler is the first to admit that this is a mind-stretching idea. It's not
      even really a theory but more of an intuition about what a final theory of
      everything might be like. It's a tenuous lead, a clue that the mystery of
      creation may lie not in the distant past but in the living present. "This
      point of view is what gives me hope that the question‹ How come existence?‹
      can be answered," he says.

      William Wootters, one of Wheeler's many students and now a professor of
      physics at Williams College in Williamstown, Massachusetts, sees Wheeler as
      an almost oracular figure. "I think asking this question‹ How come
      existence?‹ is a good thing," Wootters says. "Why not see how far you can
      stretch? See where that takes you. It's got to generate at least some good
      ideas, even if the question doesn't get answered. John is interested in the
      significance of quantum measurement, how it creates an actuality of what was
      a mere potentiality. He has come to think of that as the essential building
      block of reality."

      In his concern for the nature of quantum measurements, Wheeler is addressing
      one of the most confounding aspects of modern physics: the relationship
      between the observations and the outcomes of experiments on quantum systems.
      The problem goes back to the earliest days of quantum mechanics and was
      formulated most famously by the Austrian physicist Erwin Schrödinger, who
      imagined a Rube Goldberg-type of quantum experiment with a cat.

      Put a cat in a closed box, along with a vial of poison gas, a piece of
      uranium, and a Geiger counter hooked up to a hammer suspended above the gas
      vial. During the course of the experiment, the radioactive uranium may or
      may not emit a particle. If the particle is released, the Geiger counter
      will detect it and send a signal to a mechanism controlling the hammer,
      which will strike the vial and release the gas, killing the cat. If the
      particle is not released, the cat will live. Schrödinger asked, What could
      be known about the cat before opening the box?

      If there were no such thing as quantum mechanics, the answer would be
      simple: The cat is either alive or dead, depending on whether a particle hit
      the Geiger counter. But in the quantum world, things are not so
      straightforward. The particle and the cat now form a quantum system
      consisting of all possible outcomes of the experiment. One outcome includes
      a dead cat; another, a live one. Neither becomes real until someone opens
      the box and looks inside. With that observation, an entire consistent
      sequence of events‹ the particle jettisoned from the uranium, the release of
      the poison gas, the cat's death‹ at once becomes real, giving the appearance
      of something that has taken weeks to transpire. Stanford University
      physicist Andrei Linde believes this quantum paradox gets to the heart of
      Wheeler's idea about the nature of the universe: The principles of quantum
      mechanics dictate severe limits on the certainty of our knowledge.

      "You may ask whether the universe really existed before you start looking at
      it," he says. "That's the same Schrödinger cat question. And my answer would
      be that the universe looks as if it existed before I started looking at it.
      When you open the cat's box after a week, you're going to find either a live
      cat or a smelly piece of meat. You can say that the cat looks as if it were
      dead or as if it were alive during the whole week. Likewise, when we look at
      the universe, the best we can say is that it looks as if it were there 10
      billion years ago."

      Linde believes that Wheeler's intuition of the participatory nature of
      reality is probably right. But he differs with Wheeler on one crucial point.
      Linde believes that conscious observers are an essential component of the
      universe and cannot be replaced by inanimate objects.

      "The universe and the observer exist as a pair," Linde says. "You can say
      that the universe is there only when there is an observer who can say, Yes,
      I see the universe there. These small words‹ it looks like it was here‹ for
      practical purposes it may not matter much, but for me as a human being, I do
      not know any sense in which I could claim that the universe is here in the
      absence of observers. We are together, the universe and us. The moment you
      say that the universe exists without any observers, I cannot make any sense
      out of that. I cannot imagine a consistent theory of everything that ignores
      consciousness. A recording device cannot play the role of an observer,
      because who will read what is written on this recording device? In order for
      us to see that something happens, and say to one another that something
      happens, you need to have a universe, you need to have a recording device,
      and you need to have us. It's not enough for the information to be stored
      somewhere, completely inaccessible to anybody. It's necessary for somebody
      to look at it. You need an observer who looks at the universe. In the
      absence of observers, our universe is dead."

      The short answer: The cat's fate is undecided until the moment someone
      observes the experiment. Will Wheeler's question‹ How come existence?‹ ever
      be answered? Wootters is skeptical."I don't know if human intelligence is
      capable of answering that question," he says. "We don't expect dogs or ants
      to be able to figure out everything about the universe. And in the sweep of
      evolution, I doubt that we're the last word in intelligence. There might be
      higher levels later. So why should we think we're at the point where we can
      understand everything? At the same time I think it's great to ask the
      question and see how far you can go before you bump into a wall."

      Linde is more optimistic.

      "You know, if you say that we're smart enough to figure everything out, that
      is a very arrogant thought. If you say that we're not smart enough, that is
      a very humiliating thought. I come from Russia, where there is a fairy tale
      about two frogs in a can of sour cream. The frogs were drowning in the
      cream. There was nothing solid there; they could not jump from the can. One
      of the frogs understood there was no hope, and he stopped beating the sour
      cream with his legs. He just died. He drowned in sour cream. The other one
      did not want to give up. There was absolutely no way it could change
      anything, but it just kept kicking and kicking and kicking. And then all of
      a sudden, the sour cream was churned into butter. Then the frog stood on the
      butter and jumped out of the can. So you look at the sour cream and you
      think, 'There is no way I can do anything with that.' But sometimes,
      unexpected things happen.

      "I'm happy that some people who previously thought this question‹ How come
      existence?‹ was meaningless did not stop us from asking it. We all learned
      from people like John Wheeler, who asks strange questions and gives strange
      answers. You may agree or disagree with his answers. But the very fact that
      he asks these questions, and suggests some plausible‹ and implausible‹
      answers, it has shaken these boundaries of what is possible and what is
      impossible to ask."

      And what does the oracle of High Island himself think? Will we ever
      understand why the universe came into being?

      "Or at least how," he says. "Why is a trickier thing." Wheeler points to the
      example of Charles Darwin in the 19th century and how he provided a simple
      explanation‹ evolution through natural selection‹ for what seemed an utterly
      intractable problem: how to explain the origin and diversity of life on
      Earth. Does Wheeler think that physicists might one day have a similarly
      clear understanding of the origin of the universe?

      "Absolutely," he says. "Absolutely."


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