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05/18/2005
Mixed-up Dinos and Electrons
Initially, I intended last week’s column to be primarily about a
mixed-up dinosaur. However, on posting day, I rewrote the
column completely and the dino was replaced by a two-headed
turtle and split brains. This week, the dino gets top billing.
Paleontologists of the Utah Geological survey and the Utah
Museum of Natural History at the University of Utah reported
the discovery of fossils of this new dinosaur species in the May 5
issue of Nature. The scientists didn’t just find a single fossil;
they found a mass graveyard of these strange feathered dinos in
an area near the town of Green River, Utah. The dino was
named Falcarius utahensis; Falcarius means sickle-maker, a term
appropriate to later members of its family of dinos known as
therizinosaurs. The later therizinosaurs were strictly plant-eaters
and had 3-foot claws shaped like sickles.
Falcarius u. lived 125 million years ago and probably didn’t
realize at the time how mixed up it was. Dinosaurs had been
voracious meat-eaters early on but later, some of the biggest
dinos were strictly plant-eaters. Falcarius utahensis seems to
have been caught in the act of evolving from a carnivore to a
vegetarian. To me, the artist’s rendering of the dino on the Utah
Geological Survey Web site looks like a big bird but instead of
wings it had legs with 4-inch claws. The resemblance to a bird
may not be coincidental since birds apparently evolved from a
branch of the therizinosaur family. When I saw the claws, I
thought that they were obviously suited for catching and tearing
apart other animals. On the other hand, maybe they were the
beginnings of those later 3-foot claws mentioned above. I
imagine the 3-footers helped the plant-eater to pull down
branches or ferns to nibble on.
Falcarius’ teeth were not the sharp serrated teeth of a meat-eater
but were more suited for grinding up plant food. Furthermore, it
was developing a potbelly big enough to handle fermenting
plants and sturdier legs to carry the additional weight. The adult
Falcarius was about 13 feet long and stood just 4 and a half feet
tall. It also had a long neck that would help it to reach the plants
to nibble on. You may recall reports of feathered dinosaur
fossils found in China some years ago. Back 125 million years
ago, the continents weren’t all split up as they are today and the
speculation is that there could have been a migration of dinos
over land either from what is now North America to China or
vice versa.
I’ve read of creationists citing a lack of “missing links” as a
weakness in Darwin’s theory of evolution. Falcarius utahensis
sure looks like a missing link to me. But let’s turn now to what
might be another missing link that, if real, could possibly resolve
an obviously ridiculous, yet widely accepted situation in the nano
world of physics and quantum mechanics. The June issue of
Discover has an article on this disturbing problem that has
haunted the physics world for the better part of a century. The
article’s title sums up the problem: “If an Electron Can Be In 2
Places at Once, Why Can’t You?”. The article, by Tim Folger, is
about one of the superstars of theoretical physics, Sir Roger
Penrose. Penrose, like any sane person, is skeptical that anything
can be in two places at the same time.
However, in the weird world of electrons, atoms and other tiny
particles, it’s been proved time and again that these particles can
be in two places at once. Prove it, you say? Take the famous
“double-slit” experiment. You shine light through two slits with
a screen sensitive to light on the other side of the slits. What do
you see on the screen? There are light and dark areas where the
light waves passing through the slits interfere or reinforce each
other. It’s like the crests of two ocean waves coming together to
form a wave twice as high, but if the crest of one wave meets the
trough of the other, they cancel and there’s no wave. What’s
that, you say? Aren’t we celebrating the fact that 100 years ago
Einstein showed that light is actually photons, little packets of
energy? Light is particle and wave simultaneously – hard
enough to accept.
OK, let’s try the same double-slit experiment but just let one
photon through at a time. What do you know? As the number of
photons builds up, the same wavelike interference pattern
develops. How can that be? The photon must be interfering with
itself; it’s passing through the two slits at the same time! But
notice in the double-slit experiment that we didn’t try to measure
whether the photon went through one slit or the other. Suppose
we close off one of the slits. Now we know which slit it went
through - the interference pattern disappears. You can do this
same experiment with electrons and atoms, even with buckyballs
(those soccer ball-like molecule with 60 or more carbon atoms),
and get the same results. But try shooting bullets through the
slits and you don’t get those wave-like interference patterns. It’s
back to the title of the article – if electrons can do it, why can’t I?
Why can’t bullets?
Notice that a key point in the double-slit experiment is that you
do not try to see which slit a photon goes through. Once you try
to determine the location of the photon, all bets are off. It’s not
in two places; it’s where you find it. It’s like Schrodinger’s cat,
which I’ve probably mentioned previously. Schrodinger, whose
wave equation is a rock of quantum mechanics, proposed an
experiment to show how silly quantum mechanics can be if
applied to the world around us. Schrodinger said let’s put a cat
in a box with a radioactive material that has a 50-50 chance of
emitting a particle in the next hour. Also put in the box a
detector that, if it detects a particle, triggers a hammer that breaks
a container of prussic acid, hydrogen cyanide. The cyanide kills
the cat. If you’re a cat lover, substitute an animal of choice.
OK, close the box. For the next hour, you don’t know if the cat
is alive or dead. Quantum mechanics would say that these are
two states, alive and dead. Since we can’t measure the state of
the cat and the chances are 50-50 that a particle has been emitted,
the cat is half dead and half alive. It’s in two states at once! Yet,
you know darn well that if you open that box, you’ll find the cat
is either alive or dead, no in between state.
Being in two places at once bothered Einstein and still bothers
Penrose, he of the famed Penrose tiles, which you may have
encountered when looking to tile your kitchen floor. Einstein
spent most of his life trying to figure out how to combine his
theories of space, time and gravity with the weird world of
quantum mechanics. So have many other brilliant theoretical
physicists. None has as yet succeeded.
Penrose thinks he may have the answer, the missing link. His
idea? Gravity, which he thinks the theorists have ignored in the
nano world, the assumption being that any effects would be too
small to make any difference. Penrose has an experiment he
thinks will show that gravity cannot be neglected. Furthermore,
he thinks it will show that being in two places at once is
impossible. The experiment involves mirrors – tiny ones.
Initially, Penrose envisioned sending X-ray laser beams
thousands of miles to tiny mirrors in outer space. If the mirror is
tiny enough, quantum mechanics says it can be in two positions
at once. Penrose says that gravity will force the mirror into one
or the other position. The outer space experiment would be
extremely difficult, not to mention very expensive. However, a
former postdoc of Penrose’s, Dirk Bouwmeester, came up with a
way to shrink the experiment down to a tabletop. The
experiment involves splitting a beam of light and sending it back
and forth in an arrangement of two more or less normal mirrors,
a detector and a really tiny mirror. Bouwmeester and his
colleagues at the University of California, Santa Barbara, will
start small and work their way up to a mirror diameter of about a
tenth the width of a human hair, the size of a speck of dust!
The successful accomplishment of this experiment will require
the utmost skill in eliminating any outside factors that could
affect the results. Think of trying to control a speck of dust and
you only begin to appreciate the challenge. My impression from
their Web site is that the UCSB workers have been at it for a
couple of years already. I find it intriguing that very large
mirrors in telescopes are revealing the secrets of Einstein’s
universe (did you see the recent photo of a planet orbiting a
distant star?) while a speck of a mirror may unite that universe
with the world of tiny particles that make it up.
Allen F. Bortrum
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