PHYS: Fractional electrons

From: Eliezer S. Yudkowsky (
Date: Sun Dec 10 2000 - 15:41:18 MST

This is one of the strangest things I've ever heard. Preliminary poking
around on the 'Net seems to confirm that Humphrey Maris is a genuine,
respected physicist, and that the people quoted in the articles are
likewise genuine. Though with news like this I wouldn't be in the least
surprised if someone corrected me and said he had known newts in the
belfry. If it is true, I'm very surprised there's been less flap about

    Can the electron be cut in half?

    AT THE TIME no one even realised it had happened.
    More than thirty years ago, researchers in Minnesota did
    the unthinkable and broke the "indivisible" electron into
    fragments. This, at least, is the contention of British
    physicist Humphrey Maris, and no one has yet been able
    to prove him wrong. "Electron fragments behave to all
    intents and purposes like entirely separate particles," says
    Maris, who is based at Brown University in Rhode Island.
    "I call them electrinos."

    Pause a moment to consider what Maris is saying. The
    electron is the lightest subatomic particle and the one with
    the greatest claim to being absolutely fundamental. In fact,
    in the 103 years since its discovery, there has been no
    other evidence whatsoever that the electron is divisible. It
    is the modern incarnation of Democritus's "uncuttable"

    The claim that electrons are divisible is therefore nothing
    short of a bombshell dropped into the world of physics. "If
    Humphrey is correct, it means a Nobel Prize," says Gary
    Ihas of the University of Florida. Nobel prizewinner Philip
    Anderson of Princeton University thinks Maris must be
    wrong. "But it's not obvious why," he admits.

    Maris does not have definitive proof of his hypothesis. But
    earlier this year he published a paper that put it on a firm
    theoretical basis, and marshalled supporting evidence
    from past experiments. Now he is doing his own
    experiments, trying to break up the electron.

    Whether Maris succeeds or not, he may have found a
    large crack in one of the foundation stones of modern
    physics. "Humphrey has succeeded in exposing a
    fundamental flaw in the framework of quantum theory,"
    says Peter McClintock of the University of Lancaster.

    This astonishing heresy is centred around the electron's
    wave function, the mathematical entity that, according to
    quantum theory, encapsulates everything about the
    electron that it is possible for us to know. Among other
    things, an electron's wave function describes the
    probability of finding it at any particular location. The wave
    function of an electron confined to, say, a spherical cavity
    is the three-dimensional description of how the electron's
    location is "smeared out" over the space.

    In its lowest energy state, the wave function is spherical.
    The next highest energy level gives the wave function a
    dumb-bell shape. "It was while thinking about this state I
    was led to the conclusion that an electron might split in
    two," says Maris. If the dumb-bell could be stretched and
    pinched, he reasoned, might it simply divide?

    Maris is expert in liquid helium, a substance that gives
    physicists the perfect opportunity to test this idea because
    electrons can exist independently and autonomously within
    it. When electrons from a radioactive source are fired into
    a vat of helium, repeated interactions with the electrons of
    the helium atoms slow them down until, finally, they grind to
    a halt. The intruding electrons do not attach themselves to
    helium atoms as a third electron, however. The Pauli
    exclusion principle makes sure of that, because it forbids
    more than two electrons from sharing the same quantum
    state. Faced with helium atoms whose electrons have
    bagged the lowest energy state-the ground state-an
    interloper with no spare energy has no choice but to lodge
    in the space between atoms. There it clears a bubble of
    space around itself-an electron bubble.

    Electron bubbles form only in certain types of liquid-those
    in which the van der Waals force of attraction between
    atoms is weak enough to allow an electron to push them
    apart. In fact only two substances fit the bill: liquid helium
    and liquid hydrogen. At very low temperatures in helium,
    electron bubbles displace more than 700 helium atoms,
    creating a cavity around 38 angstroms (3.8 nanometres)
    across. Inside this cavity quantum mechanics rules,
    ensuring that the electron can occupy only a limited set of
    energy states.

    Light touch
    Maris worked out that an electron in a bubble could be put
    into the dumb-bell-shaped excited state by illuminating the
    helium with light that had a wavelength of about 10
    micrometres, which is easily supplied by a carbon dioxide
    laser. In this state, Maris calculated, the electron imparts
    most of its force to the ends of the dumb-bell; this force is
    enough, he realised, to make the bubble wall wobble
    violently. "I found that the force exerted by the electron was
    enough to elongate the bubble until it formed a thin neck,"
    he says. "If the pressure in the liquid was great enough,
    there was the possibility of it pinching off the neck so that
    the bubble might actually split in two."

    This sounds harmless enough, but the implications are
    staggering. If the bubble split, half of the electron's wave
    function would be trapped in each of the two daughter
    bubbles (see Diagram). As the wave function is the
    essence of an electron, the electron would be split into
    two. The indivisible would have been divided.

    Maris planned to test his idea in the laboratory but first
    decided to search back through the literature to see
    whether anyone had done the kind of experiments he had
    in mind. He soon found what he was looking for. In the late
    1960s, Jan Northby and Mike Sanders at the University of
    Minnesota studied the speed of electron bubbles moving
    in an electric field in liquid helium. They measured the
    electric current that flowed as the bubbles moved, and
    then illuminated the helium with light. The researchers
    expected this to increase the current. They reasoned that
    light would eject some of the electrons from the bubbles,
    and that these would whiz through the helium, boosting the
    current-and that is exactly what they observed.

    But as physicists have since realised, this reasoning was
    flawed. "We now know that knocked-out electrons form
    new electron bubbles," says Maris. "The current should not
    have increased." Inexplicably, however, it did. In 1990 and
    1992, researchers at Bell Labs in New Jersey ran a
    similar experiment, with the same result. No explanation
    has ever been found-until now, perhaps.

    Maris suggests that, instead of ejecting the electrons, the
    light boosted them from the ground state to the
    dumb-bell-shaped excited state, and the electron bubbles
    split. "There were more bubbles, and being smaller they
    were more mobile," says Maris. Although the total charge
    in the system remained the same, the smaller bubbles felt
    less drag in the helium, and thus moved faster.
    "Consequently, the current went up," Maris explains.

    Maris believes he has further evidence to support his
    explanation. Northby and Sanders saw the increased
    current only below 1.7 kelvin, exactly the temperature at
    which Maris's theory says the effect should take hold.
    According to his calculations, electron bubbles should split
    apart only below a critical temperature of 1.7 K. The
    crucial factor is viscosity. If it is too great, says Maris, the
    liquid will behave like treacle, resisting the elongation of
    the bubble and squeezing it back to a sphere. Below
    2.19K liquid helium becomes a superfluid: as you cool it,
    its viscosity starts to disappear. By 1.7 K, Maris
    calculated, the liquid would be so slippery that it couldn't
    stop the bubbles dividing.

    Other experimenters have studied the mobility of electrons
    in a more precise way. They include Gary Ihas and Mike
    Sanders at the University of Michigan in 1971 and Van
    Eden and McClintock of the University of Lancaster in
    1984. These physicists created a short burst of about a
    million bubbles which they carefully timed as they moved
    through liquid helium in an electric field. Since the bubbles
    were created together, they should have crossed the
    finishing line together. To the surprise of the
    experimenters, most of the bubbles arrived in three
    separate clumps.

    Maris's explanation is again simple. Unlike the electrons
    in the Minnesota experiment, these electrons had been
    created in an electrical discharge-a miniature bolt of
    lightning. This produced light, and Maris says that some of
    this light boosted electrons within the bubbles to the
    excited state, causing them to split, and split again. Hence
    the spread of arrival times, with whole, half and quarter
    charges making up most of the current.

    McClintock is not yet convinced by Maris. But he admits
    that nobody else has come up with a plausible
    explanation. "The electrino idea offers a possible way
    out," he concedes.

    Maris has long realised the furore his ideas would cause.
    He spent several years working out the details of electron
    bubble fission and gathering experimental evidence
    without ever telling anyone what he was thinking. "It took
    time to get used to the idea and pluck up the courage to
    announce it," he admits. Finally, in June this year, he
    decided to go public. He presented his work at a
    Minneapolis conference on quantum fluids and solids, and
    then published it in a paper in the Journal of Low
    Temperature Physics (vol 120, p 173).

    The conference organisers thought Maris's work important
    enough to give him an extra two-hour session. At the end,
    more than 100 physicists questioned every aspect of the
    theory. "My first reaction was extreme scepticism, like
    everyone else," McClintock says. Maris, though, had an
    answer for everything. "He'd obviously thought long and
    hard about the whole thing," McClintock concedes.

    Maris was encouraged by the response -or lack of it-from
    his peers. "I was nervous someone would find a hole," he
    admits. "But to my relief nobody dismissed the idea out of

    Experts in quantum theory are not so accommodating,
    though. "The idea of an electron splitting into fractionally
    charged fragments is totally incompatible with quantum
    field theory," says Anthony Leggett of the University of
    Illinois at Urbana-Champaign. He admits that there could
    be something wrong with quantum field theory. "However,
    given its overwhelming success in explaining the world,
    this is highly unlikely," he says.

    According to quantum theory, it is possible to have
    strange "superposition states", where the whole electron
    exists in both bubbles until a measurement forces it to be
    in one or the other. "But we cannot consider states which
    have half an electron on each," Leggett insists. It is
    impossible to solve the equations of quantum mechanics
    with anything other than a whole-charge electron. The
    formulations of quantum electrodynamics, the area of
    physics that deals with the behaviour and properties of
    electrons, don't allow for half electrons, or any other

    "If the electron splits and you can measure a fractional
    charge, this flies in the face of standard quantum
    mechanics as well as high-energy physics," agrees David
    Pritchard of the Massachusetts Institute of Technology.
    "The idea that the electron is a point particle without
    structure is established up to very high energies."

    Half measures
    Like Leggett and Pritchard, most physicists are convinced
    that Maris's claim falls at the first fence, though they cannot
    pinpoint why. Their scepticism is understandable. If Maris
    is right then quantum theory is wrong-and nobody has the
    slightest idea what they would use to replace it.

    Maris being right would have some positive practical
    consequences, however. He speculates about building a
    device which introduces a partition into a cavity to divide
    the wave function of an electron. This could lead to circuits
    which exploit the properties of fractionally charged
    particles, he says. Half-mass, half-charge electrons might
    give electronics a whole new dimension. Then there's the
    possibility of a new kind of chemistry. Maybe you could
    take an electron bubble out of the liquid, attach the
    electron fragment to an atom and do novel chemistry with
    fractional electrons. Could this really happen? Maris says
    he doesn't know.

    The electron fragments, having once been part of the
    same electron, might even be "entangled", sharing a
    strange telepathic link. Quantum physicists have already
    managed to achieve this with photons, and used these
    entangled particles of light to perform astonishing feats
    such as teleportation and elementary quantum computing.
    Fractional charge might add a new string to their bow.

    The most profound consequences of splitting the electron,
    though, would be on theoretical physics. Maris's only
    concrete claim is that an electron's wave function can be
    split and mimic a fractional electron. He has no idea of the
    full consequences of this-and neither has anyone else.
    Maris's hypothesis seems to throw everything we know
    about quantum theory into confusion. At the very least, he
    believes, his work challenges physicists to be specific
    about what they mean by the fuzzy entity that describes
    quantum systems. "People are going to have to hone their
    ideas of the wave function," he says. "Most importantly,
    they are going to have to address the question: what is a
    wave function? Is it a real thing, or just a mathematical

    Physicists have always been content to think of the wave
    function as a mathematical device with observable
    consequences. But Maris believes the time has come for
    the idea to be grounded in reality. For the electron
    bubbles in helium, he says, the size of the bubble is
    determined by how much of the wave function is trapped
    inside the bubble. If there is no part of the wave function
    inside the bubble, the bubble will collapse. "This makes
    the wave function seem to be a tangible object," he

    Maris remains an experimentalist at heart, though. Since
    the theorists have nothing to say about the myriad
    questions he has raised, he believes answers won't be
    found until there is some more evidence to go on-and that
    means doing more experiments. Maris and others, he
    believes, are now looking for that evidence. "Already, the
    results of my experiments are encouraging," he says.

    But Maris also insists that he won't be upset if his idea is
    eventually disproved. Having lobbed in his bombshell, he
    seems to have decided to sit on the sidelines, enjoying
    the ensuing chaos. "What I have come up with is an
    intriguing puzzle," he says. "I want people to think. I would
    be happy if I was completely wrong but made a lot of
    people think."


    New Scientist issue: 14th October 2000


-- -- -- -- --
Eliezer S. Yudkowsky
Research Fellow, Singularity Institute for Artificial Intelligence

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