Natural Science Forum / Physics / Particle Physics / June 2005

In the June 2005 issue of Discover Science Magazine. Roger
Penrose argued that gravity is the reason why quantum effects
don't occur in the macroscopic world... why we can't exist
in two places at the same time just like in electrons before
measurement. Penrose is just offering an alternative to the
Copenhagen Interpretation where measurement disengage the
quantum states, as well as Everett Many Worlds and etc
interpretations. What follows is the article. Do you have
any killer arguments against it? The url gives the graphic
illustration of the mirror experiment which can prove or
disprove his hypothesis

http://www.pbase.com/image/44715609/original

Excerpt of the experimental details of the article:

"In Einstein's theory, any object that has mass causes a warp in the
structure of space and time around it. This warping produces the effect

we experience as gravity. Penrose points out that tiny objects-dust
specks, atoms, electrons-produce space-time warps as well. Ignoring
these warps is where most physicists go awry, he believes.

If a dust speck is in two locations at the same time, each one should
create its own distortions in space-time, yielding two superposed
gravitational fields. According to Penrose's theory, it takes energy
to sustain these dual fields. The stability of a system depends on the
amount of energy involved: The higher the energy required to sustain a
system, the less stable it is. Over time, an unstable system tends to
settle back to its simplest, lowest-energy state-in this case, one
object in one location producing one gravitational field. If Penrose is

right, gravity yanks objects back into a single location, without any
need to invoke observers or parallel universes.

How long the process takes depends on the degree of instability.
Electrons, atoms, and molecules are so small that their gravity, and
hence the amount of energy needed to keep them in duplicate states, is
negligible. According to Penrose, they can persist that way essentially

forever, as standard quantum theory predicts. Large objects, on the
other hand, create such significant gravitational fields that the
duplicate states vanish almost at once. Penrose calculates that a
person collapses to one location in a trillion-trillionth of a second.
For a dust speck, the process takes nearly a second-long enough that
it might be possible to measure.

Growing excited, he hoists himself to a more upright position on his
sofa. "Here is the scale where you should start to see differences
between what quantum mechanics says and what reality does," he says.
"The superposition that is part of quantum mechanics is unstable for
large objects; an object will assume one or the other position on a
timescale of about a second. Is this true? Well, we have to do an
experiment."

A few years ago, Penrose figured out how to perform that experiment.
Instead of a speck of dust he would use a tiny mirror, which would
allow him to bounce radiation off it to see if it was in one or two
places at the same time. If traditional quantum theory is right, the
doubled state could remain stable for a long time. If Penrose is right,

the mirror would maintain a dual existence for no more than a second
before gravity chains it to a single location.

Penrose initially envisioned putting his theory to the test using an
X-ray laser mounted on a platform in outer space. The laser would shoot

photons toward a tiny target mirror tens of thousands of miles away.
Here is where quantum weirdness comes into play. A half-reflective
mirror, called a beam splitter, would separate each photon into two
states so that it follows two paths (that is, it goes in two directions

at the same time). On one path, the photon strikes the tiny mirror,
moving it slightly; on the other, it is reflected away from the target
mirror, so the mirror does not move.

In the prevailing view of physics, both events occur simultaneously:
The mirror moves and remains in place at the same time because the
mirror-like the photon-can remain in two states at once. On its
return path, the duplicate photon that struck the tiny mirror hits the
same mirror again, returning it to its initial position. The whole
system then returns exactly to its initial state, and there is
fundamentally no way to tell which path the photon took. As a result,
the two versions of the photon interfere with each other and recombine
into a single photon that is always reflected along a path back toward
the laser. No X-ray photons can ever follow the path that leads them to

a detector.

If gravity intervenes, as Penrose expects, it forces the mirror either
to remain at rest or to move-but not both-and the outcome is totally
different. Now the photon cannot follow both paths because gravity
anchors the mirror to a single state. Consequently, each photon will
follow one path only, so it cannot interfere with itself; half the
time that path will lead it to the detector. Thus if an X-ray triggers
the detector, the quartturn duplicate of the mirror must have
disappeared,
and Penrose's view of reality must be correct."

(The following is the start of the article for newbies or people who
want to get perspective of the above.-p6)

"If An Electron Can Be In 2 Places At Once, Why Can't You?
Electrons do it. Photons do it. PHYSICS LEGEND ROGER PENROSE
thinks he finally knows why you and I can't do it too"
by Tim Folger

"Sir Roger Penrose-Knight of the Realm, Emeritus Rouse Ball Professor
of Mathematics at Oxford University, controversial author, and polymath

extraordinaire-is worried that his car might be towed. It is parked
in a temporary space beside Oxford's Mathematical Institute, where
we've arranged to have the first of our meetings. So before settling
down to discuss his solution to one of the greatest mysteries in
physics, he hustles out a couple of times to make sure the car is still

there, displaying impressive bursts of speed for a 73-year-old.
I am sure that he would like to be in two places at once: here in an
otherwise empty conference room with me and outside in the chill autumn

rain, keeping an eye out for the bobbies. That's impossible, of
course, and therein lies the mystery that consumes Penrose.

About 80 years ago, scientists discovered that it is possible to be in
two locations at the same time-at least for an atom or a subatomic
particle, such as an electron. For such tiny objects, the world is
governed by a madhouse set of physical laws known as quantum mechanics.

At that size range, every bit of matter and energy exists in a state of

blurry flux, allowing it to occupy not just two locations but an
infinite number of them simultaneously. The world we see follows a
totally different set of rules, of course: There's just one Oxford
University, just one car, just one Penrose. What nobody can explain is
why the universe seems split into these two separate and irreconcilable

realities. If everything in the universe is made of quantum things, why

don't we see quantum effects in everyday life? Why can't Penrose,
made of quantum particles, materialize here, there, and everywhere he
chooses?

Many physicists find this issue so vexing that they ignore it entirely.

Instead, they focus on what does work about their theories. The
equations of quantum mechanics do a fantastic job describing the
behavior of particles in an atom smasher, the nuclear reactions that
make the sun shine, and the chemical processes that underlie biology.
For Penrose, that is not nearly enough. "Quantum mechanics gives us
wonderful predictions and experimental confirmations for small-scale
scenarios, but it gives us nonsense at ordinary scales," he says,
relaxed now that a receptionist has assured him of his car's safety.
"If you just follow the equations, you get a mess. So you have to
ask: What leads to this world?"

He has an answer, which, if correct, will lead to the first quantum
theory that makes as much sense for people as for particles. Penrose
believes he has identified the secret that keeps the quantum genie
tightly bottled up in the atomic world, a secret that was right in
front of us all along: gravity. In his novel view, the same force that
keeps us pinned to the ground also keeps us locked in a reality in
which everything is tidy, unitary, and-for better and for
worse-rooted in one place only.

Aside from a frustrating inability to manifest in any number of places
simultaneously, Penrose qualifies as something of a quantum phenomenon
himself. There do indeed seem to be many Penroses; they just all happen

to occupy the same body.

There is Sir Roger the physicist, knighted in 1994 for his
contributions to science, among them pioneering efforts to reconcile
Albert Einstein's general theory of relativity with quantum
mechanics. There is Penrose the puzzle master, creator of geometric
illusions that M. C. Escher incorporated into some of his most famous
works. There is Penrose the neuroscientist, who developed a
controversial theory linking consciousness to quantum processes in the
brain. And there is Penrose the author, most recently of a 1,049-page
tome called The Road to Reality, which is modestly subtitled A Complete

Guide to the Laws of the Universe. It's an impressive r,sum, for
someone who was demoted a grade in elementary school because he
couldn't master arithmetic.

On our second meeting, all of those Penroses are slumped on a sofa in
the living room of his spacious home a few miles outside Oxford. A
coffee cup and a plate of cookies rest on his chest, which, since he is

sunk so deeply into the sofa, is almost perfectly horizontal. Tall
windows look out on a lush green yard, damp from the rain. In this
pensive setting, he looks back on the events that convinced him that
quantum theory has serious problems, a view that would be heresy for a
young physicist entering academia today.

Penrose's faith began to waver while he was a graduate student at
Cambridge. The crucial moment came during a lecture by Paul Dirac, one
of the legendary early thinkers in quantum mechanics. "He was talking
about the superposition principle, whereby objects could be in two
places at the same time. To illustrate, he broke a piece of chalk in
two and then tried to explain why you never saw superpositions in real
life. My mind may have wandered briefly, because I never heard his
explanation!" Penrose says, laughing. "But when I think about it,
I'm not sure it did wander, because it's not possible to explain
why you don't see objects in two places at once on the basis of
present-day quantum mechanics. It's a big problem. It's what I've
worried about ever since."

The maddening part of that problem is that the ability of particles to
exist in two places at once is not a mere theoretical abstraction. It
is a very real aspect of how the subatomic world works, and it has been

experimentally confirmed many times over. One of the clearest
demonstrations comes from a classic physics setup called the
double-slit experiment.

In this test, a beam of light is projected through two parallel slits
cut in an opaque barrier and then onto a white screen. When light hits
the screen, it does not produce just two overlapping regions of
brightness. Instead, something strange appears: a series of alternating

light and dark stripes, called an interference pattern. The
19th-century explanation for this was that light is a wave and that
light waves overlap after passing through the slits. The light waves
seem to behave much like water waves on the surface of a pond: Where
two crests meet, the wave gets higher, creating a bright stripe; where
a crest meets a trough, the two cancel out, and the wave vanishes,
yielding a dark zone.

With the development of quantum theory in the early 20th century, the
explanation became far weirder. Physicists realized that light is not a

wave exactly but rather a wavelike particle called a photon. That
discovery suggested a new experiment. In principle, it would be
possible to send light through the slits one photon at a time and
collect them on photographic film. Common sense says there should be no

interference pattern in this case: There is only one photon in the
apparatus at any given moment, so there is nothing for the light to
interfere with.

Then in 1909 a young British physicist named Geoffrey Ingram Taylor
actually ran the experiment and witnessed the bizarre result. As the
photons accumulate on the film, the same old interference pattern of
alternating bright and dark stripes gradually appears, defying common
sense. In this case, there is only one thing each photon can interact
with-itself. The only way this pattern could form is if each photon
passes through both slits at once and then interferes with its
alternate self. It is as if a moviegoer exited a theater and found that

his location on the sidewalk was determined by another version of
himself that had left through a different exit and shoved him on the
way out.

Since then, other researchers have repeated the experiment with
electrons, atoms, even with relatively bulky molecules containing as
many as 70 carbon atoms. The results never vary. Individual atoms and
molecules go through both slits at once. Yet for some reason the laws
of physics take away that ability for large objects like paper clips,
people, and planets. "Something has got to go wrong with quantum
mechanics somewhere," Penrose says. "I regard this as a major
problem that is going to require another revolution. But rather few
people seem to agree with this viewpoint."

When pressed, quantum theorists usually fall back on what is known as
the Copenhagen interpretation. The idea was promoted in the 1920s by
Danish physicist Niels Bohr and his prot,g, German physicist Werner

Heisenberg. In their view, we do not see quantum effects in the
everyday world because the act of observation changes everything,
fixing the many possibilities allowed by quantum mechanics as one. As a

result, when we look, we only see one version of events, with every
object firmly anchored to one position at a time.

The flaw in the Copenhagen interpretation is that it has no basis in
theory-it is more like a story that scientists tell to make sense of
facts that otherwise would seem nonsensical. It also suggests that the
universe does not become fully real until someone observes it. Einstein

found this idea abhorrent. "I like to think that the moon is there
even if I am not looking at it," he fumed in response to Bohr.

Nevertheless, the Copenhagen interpretation was voted the preferred
explanation of quantum weirdness by physicists at a conference in 1997.

The runner-up explanation is an even stranger view of reality. Called
the many worlds interpretation, it was proposed in 1957 by Princeton
University doctoral candidate Hugh Everett III. Its adherents take the
laws of quantum theory at face value: Every possible quantum outcome
really exists-but in worlds parallel to our own. In one universe,
Penrose is talking with me in Oxford; in another, he is watching a
monster-truck rally. From this perspective, people and particles behave

much the same way. We just do not see them in many places at the same
time because each potential location is tucked away in a different
universe

Penrose cannot believe anyone finds either the Copenhagen
interpretation or the many worlds picture satisfactory. "If you take
the equations of quantum mechanics up to the level where you can
actually see things going on, you're driven to an absurd viewpoint.
People are led into views of the world which are pretty fantastical.
And rather than say, 'This is a bit wild, let's try to do something
a bit more commonsense-ish,' they come up with theories that are
completely wild."

After struggling for years to come up with a better explanation, he
finally has a solution.
Turning to gravity for a solution to the quantum mystery is in many
ways a natural strategy, at least from Penrose's perspective. There
are four fundamental forces in the universe: electromagnetism; the
strong force, which binds atomic nuclei together; the weak force, which

is responsible for radioactive decay; and gravity. Gravity is the only
one of the forces that physicists have been unable to explain in
quantum terms. Albert Einstein spent more than 30 years in fruitless
attempts to harmonize his theories of gravity with quantum mechanics,
and his successors are still stumped.

To Penrose, the failures are a clue that physicists are on the wrong
path. Most believe that quantum theory is fundamentally sound but that
our understanding of gravity must change. Penrose says that rather than

seeking to change Einstein's theory of gravity, we should study how
gravity affects an object small enough to exist in the borderland
between the quantum world of atoms and the human world of visible
objects.

An object the size of a speck of dust would provide the perfect test.
At this scale, an object is small enough to be strongly affected by the

rules of quantum mechanics but large enough to observe directly.
Current theory predicts that such an object could exist in more than
one location and could remain in that split state almost indefinitely.
If there were a way to observe the speck without disturbing it, we
would see quantum strangeness laid bare: a macroscopic thing sitting in

two places at the same time, confounding reality as we know it.
Penrose is convinced that conventional quantum theory seems absurd
because it is incomplete. Specifically, it ignores the effects of
gravity. On atomic or subatomic scales, gravity is so weak compared
with the other forces that most physicists see no problem with leaving
it out of the picture. But in Penrose's view, the only way to
understand the quantum world is to consider all the forces that act on
it. To do that, he is combining Einstein's relativity with quantum
physics in a way nobody has considered before.

(The passages that follow is in the first part of this message.
What follow is the continuation of it)

The expense and technical difficulties of aiming X-ray lasers at
targets thousands of miles away in outer space had seemed
insurmountable, but Dirk Bouwmeester, a former postdoc under
Penrose who is a professor of physics at the University of
Califoria at Santa Barbara, saw a way to make it feasible. Along
colleagues with Williarn Marshall and Christoph Simon, he devised
a way to bring Penrose's experiment literally down to Earth - to
a tabletop in Bouwrneester's lab.

The revised experiment relies on a relatively simple
visible-light source rather than an X-ray laser. Still,
everything about Bouwmeester's setup will push the boundaries of
laboratory physics. To give the mirror the same kick a more
energetic X-ray photon would produce, the light photons will have
to reflect back and forth between two mirrors a million times. Un
til now, the largest objects ever studied in a state of quantum
superposition were soccer-ball- shaped carbon molecules called
buckyballs. Bouwmee ster is trying to detect the same effect on a
mirror that is a billion times bigger. If we were able to
observe, that, it would be spectacular, a test of quantum
mechanics in a completely new regime," he says.

The team at Santa Barbara is running the experiment right now,
but with a significantly smaller mirror than needed to test
Penrose's theory. If the current tests succeed, Bouwmeester will
gradually increase the size of the mirror up to the necessary
tenth -of- a-human-hair diameter. He and his colleagues are also
working out ways to shield the experiment from the vibrations,
stray photons, or temperature changes that would ruin the
results. "It is not something that will happen overnight;' he
says. "We need to isolate the quantum world from our world and
see what happens. If everything works well, 1 expect some results
four years from now."

Penrose, who turns 74 in August, is hopeful that he will see the
day when his ideas are vindicated. Not many physicists share this
optimism. Tony Leggett, a Nobel laureate at the University of
Illinois at Urbana Champaign, suspects the experiment will fail
to snow that gravity has any effect on quanturn systems. I take
the quantum paradox as seriously as Penrose does," Leggett says.
"I'm personally convinced that somewhere between the level of the
atom and human consciousness, something has to come in which
changes the structure of quantum mechanics." The problem is that
quantum theory has never yet failed to predict the outcome of any
experiment. Without evidence of some such flaw in the theory,
physicists are lef t groping in the dark for ways to improve it.
I think the odds of them being right are less than 5 percent," he
says.

David Deutsch, a theoretical physicist at Oxford University's
Centre for Quantum Computation, is a leading proponent of the
many worlds theory. He turns the tables on Pentrose, arguing that
his quest is based more on aesthetics than science: If something
is wrong with a theory, or there is some experimental anomaly,
those are rnotivations for changing a theory. When your
motivation comes from a metaphysical reluctance for reality to be
a certain way, then historically that kind of motivation has
never produ ced the right answers."

Penrose responds that he is not changing quantum mechanics; he is
merely putting it to a new, more rigorous test. "You can say we
haven't seen any violation of quantum mechanics, but that's
absolutely what you'd expect, because no experiment has ever been
performed that comes remotely close to the level you'd need to
see any violations. So unless you try to get to this level I'm
aiming for, it's not at all surprising that we haven't been able
to see any deviations," he says.

If Bouwmeester's experiment succeeds, it will show Mat the
fantasy of being in two places at the same time really is
impossible. As a kind of compensation, it will also show that the
number of places science can go is far greater than we have come
to believe. Most physicists today trying to unite Einstein's
theory of gravity with quantum mechanics focus on microscopic
realms beyond the reach of any conceivable experiment. Per. haps
the solution that eluded Einstein is much closet at hand, in the
strange ter ritory where quantum rnechanics just barely emerges
into the human world.

The one Penrose rises from his one chair, preparing to pick up
Max, his 4-year-old son, from school. He has no doubt that Max's
generation will learn physics lessons different from the
confusing, incomplete story that Penrose got from Dirac all those
years ago.

"Is quantum mechanics the last word?" Penrose asks. "There is no
reason to believe that."

End Excerpts.
-------------
back to p6

In deep space, there is no gravity. How come the astronauts don't
become macroscopic quantum objects appearing in different places
at once. What's the arguments why Penrose didn't use this
experiment or argument? Can the body of the spacecraft be a
gravity source of any object inside and vice versa?

p6