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Physicist Brian Greene Explains String Theory -
The 'Music of the Universe'
By Robert E. Martin
Brian Greene is a physicist who has been working on the Unified
Theory of 'Superstrings' for more than a decade. Widely recognized for a
number of groundbreaking discoveries in modern physics, Greene is also
known for his ability to clearly explain this cutting-edge research to the
general public. Plus, lest you think him some stuffy white shirt/black tie
type, he has also served as a consultant to the popular television series
Third Rock From the Sun.
After receiving his undergraduate training at Harvard, where he graduated
Summa Cum Laude in 1984, Greene went on to graduate school as a Rhodes
Scholar at Oxford. He joined the faculty at Cornell University as an
assistant professor in 1990 and by 1995 had been promoted to full professor
in both the Physics & Mathematics Department of Columbia University.
Greene's research focuses on the quantum mechanical properties of space &
time. In 1990, Greene and a colleague discovered 'mirror symmetry - a
remarkable property of 'String Theory', which is the hottest development in
physics since Stephen Hawking first peered into a black hole. He also acts
in Pinter plays and has recently written a new book, The Elegant Universe,
which was on the New York Times' Bestsellers List for four consecutive
weeks and was ranked #6.
On Tuesday June 13th, Greene addressed a packed auditorium at the Midland
Grace A Dow Memorial Library, in order to explain how the discoveries of
String Theory may actually be the missing piece in the puzzle of Albert
Einstein's Unified Field Theory. Whereas Einstein proved that the fabric
of space could stretch in time, resulting in our expanding universe, it
does not allow the fabric of space to rip. However, Greene and his
colleagues have shown that in string theory by including quantum mechanics,
the fabric of space can tear, establishing that our universe can evolve in
far more dramatic ways than had been previously envisioned.
"Philosophers, poets, and mathematicians have struggled with the deepest
questions humanity has ever faced," explains Greene, "such as what is
space? What is time? And in order to answer what it means to be a part of
the universe around us, we need to define what those fundamental components
are that make up our universe, and how they influence each other. How do
they drive the evolution of the universe?"
"The greatest era of discovery has happened in the last 100 years,"
continue Greene, "and among the people who contributed to that progress,
the work of Einstein is most pivotal & far-reaching. Even so, one goal that
eluded Einstein was that of finding a 'unified theory' of physics. He
searched for 30 years and came up empty-handed. But now, as enter a new
millennium, string theory may be the unified theory that he was searching
for. "
Background
"In the late 1600s, the first quantitative attempt to understand
gravity was developed by Isaac Newton," begins Greene. "This was a
time
when the Black Death was winning its war against mankind, and Newton
retreated from Cambridge to his family home in England. By the time of the
Great Fire of London, after three days, Newton was ready to return to
Cambridge and describe the motion of planets around the sun and apples
falling from trees to earth with his Universal Law of Gravity. Basically,
what this states is that the reason the earth revolves around the sun is
because the sun, with its incredible mass, essentially keeps the earth in
orbit by taking hold of it. "
"Newton's equation is still used in physics today," notes Greene.
"But then
in the early part of the 20th Century, Albert Einstein realized that
Newton's theory could not be totally correct. Imagine you're outside on a
bright sunny day and the sun suddenly explodes. Light travels at 186,000
miles per second and our sun is 93 millions miles away, so it would take 8
minutes for the light from the sun to reach the earth, alerting us to the
sun's demise 8 minutes later."
"In 1905, Einstein discovered through his Theory of Relativity that
nothing
goes faster than light. There is no information of any kind greater than
the speed of light, so there is absolutely no way to learn about the sun's
demise any sooner. But our motion in space also is affected if the sun
explodes. It changes our orbit in space. So if you were going strictly by
Newton's Law of Gravity, you would know about the sun exploding exactly the
same moment it exploded because gravitational disturbances happen
instantaneously in no time at all, first by feeling it and second by seeing
it. For Einstein, this discovery showed that Newton's law was not the
'whole story', and this is how he disproved it."
"By 1915, the genius of Einstein blazed through with his General Theory of
Relativity," continues Greene. "What distinguishes Einstein's life
the most
from other scientists is that he was willing to ask the simple, seemingly
childlike questions about the universe in a serious way and thing through
their consequences."
"The main question he asked is how does gravity work? What is the
mechanism
by which the sun, so far away, can influence the earth? Ironically,
Newton
wrote that he could not figure out the mechanism of his equations. He said
he could measure the influence of the sun with great precision, but not the
mechanism of how it operates. Instead he wrote that he would 'leave that
question to the consideration of the reader', and many years later it was
Einstein who was up to the challenge."
"Einstein found the medium by which gravity is transmitted in the fabric
of
space & time," states Greene. "And the most radical discovery of
all is
that space and time and light are the medium by which gravity is
transmitted. In order to visualize it, imagine a horizontal rubber sheet
that stretches out and say that is space. If you set a marble going along
it in a straight line it will roll across the sheet. Now, if you take a
bowling ball and plop it in the center of that sheet, it will cause the
sheet to warp & deform. If you send a marble along the sheet now,
with the
bowling ball acting as the sun and the marble as the earth, the marble will
travel along a curved path, rolling along the curved surface of the rubber
membrane. This is the idea you need to apply to the entire universe. The
sun and heavenly bodies by virtue of their mass can warp the fabric of
space around them, and thereby influence the motion of other bodies."
"Thus, the earth is not kept in orbit because the sun is grabbing it, but
because of the distorted spatial environment created by the mass of the sun
that warps & curves the other planets around it, which is a beautiful way
to think of how gravity works."
"But it gets more interesting yet," continues Greene.
"If you now poke that rubber sheet it will cause ripples. In order to
calculate how quickly they spread outwards through this fabric of space,
Einstein discovered they traveled exactly at the speed of light - E=MC2,
and in doing this, he opened a new can of worms."
"Relativity conflicts with quantum mechanics," notes Greene,
"and that is
the deepest conflict physics has faced over 70 years. One set of laws
exists that works with the 'big stuff' such as galaxies in the universe,
only quantum mechanics is a theory of light. It describes 'small things',
and a conflict exists between the two. Between 1900 and 1930, it was
difficult to conduct microscopic experiments. "
"To easily explain it, our knowledge of the microscopic realm is like a
list divided into two columns," relates Greene. "Looking at one
column
limits our ability to understand the second column. If electrons are
elementary particles making up matter, there is a fundamental limitation in
knowing exactly where and how quickly they are moving, which creates a
fundamental limitation on our ability to know what is going on. In essence,
this is the Heisenberg Uncertainty Principle, which tells us that our
universe is inherently jittery and free to roam in all possibilities. In
the microscopic world, laws are random, yet in Einstein's 'macro' universe
the world is a nice gentle curve. Now the issue became how to put this
jittery, stark, frenzied microscopic world into tandem with the large
gentle curve of the macro picture."
"I like to refer to this as the 'Quantum Jitters'," smiles Greene.
"These
microscopic jitters have no influence on the large macro world and in fact,
the macro vision renders it small. But the impact is that the micro world
also renders Einstein's theories insignificant and inaccurate. Some
physicists claim the influence of the micro is so small it isn't worth
worrying about, but others feel it a serious problem."
The Significance of String Theory
According to conventional thinking, while the Universe is
expanding, if one were to run a film of the cosmos in reverse, everything
would be getting closer and more compressed - increasingly smaller in size,
going all the way back to no size at all, which essentially is the modern
scientific answer to the biblical creation articulated in the chapter of
Genesis.
As Greene and other modern physicists view it, however, that isn't true.
"The Big Bang is how the universe evolved from the split second it
occurred
onward, " he notes. "If we attempt to push it back further, the
theories
break down. There is no way to have an understanding of cosmology without
putting relativity and quantum mechanics together."
This is where String Theory enters the picture, because it allows these two
to work together.
2,500 years ago the ancient Greeks asked what is matter made of? What is
the 'fundamental' material of the universe? If we cut it into smaller &
smaller pieces, the smallest thing one discovers is atoms. But they can be
split into even smaller things - the nucleus of the atom, with neutrons &
protons inside of them, and even smaller particles inside of those - such
as quarks.
"Conventional theory says it stops there - with electrons &
quarks," notes
Greene. "But String Theory suggests that there is at least one more layer
of sub-structure - a tiny filament of vibrating energy, that is string
like. This is where the name comes from, because it is just like the string
on a violin or cello that vibrates different musical notes. These small
filaments inside of atoms also vibrate different patterns. You don't hear
them, but you see them. The electron is a 'string' vibrating one way, and
a quark is a string vibrating another way."
"Electrons and quarts are simply vibrating different patterns,"
states
Greene. "In essence, injecting a 'music of the spheres' in a very
microscopic way, which is the basic idea of string theory."
"How it resolves the dilemma of physics is whenever you spread something
out you dilute it. If you take a little drop of ink and drop it into a
pitcher of water, it becomes diluted. Similarly, if we replace these
particle ideas with tiny little loops, we're spreading out the point
particle into a string, diluting the particle. Suddenly that 'violent
jitter' in the space fabric that causes the split in theories doesn't go
away, it simply becomes smaller and less violent - diminished to just the
right degree so that quantum mechanics & relativity are not conflicted, but
exist in harmony - all evened out. In String Theory each of the prior
established theories needs the other for the overall picture to make sense.
Newton, Einstein, and String Theory are all tied together."
More than Three DimensionsS
While conventional thinking leads us to believe there are three
dimensions to the universe - height, width, and depth - string theory
demands that at least six or seven spatial dimensions exist that nobody has
ever seen.
"This gets a tad strange," admits Greene, "but there are more
directions in
which you can walk than the ones you're directly aware of. We've worked
on
it for 15 years, and the reason we don't see these extra dimensions
directly is because they come in two varieties - the obvious ones we see,
and those tiny ones difficult to detect."
"As an analogy, if we take a piece of paper its surface has two dimensions
- left, right, and up & down. But if we fold it or roll it into a tube, it
still has two dimensions on the surface, but the rolling changes the
character of the height & depth into a circular dimension. If we curl it
into a tighter and thinner crossection, we might not be able to see any
dimension at all. Looking a quarter mile away, we lose the visual acuity to
see anything but the dimension of left & right. But if we magnify the
paper, you see you can move left and right crosswise, counterclockwise, and
if you zoom in even further you can tell that an ant could walk inside that
curled paper and you wouldn't even be aware of it."
"These are called the 'conditional dimensions' that String Theory
requires," adds Greene. "We don't have the sufficient magnifying
equipment
to reveal their nature, but we will find new dimensions as we probe the
universe on that microscopic of a level."
Does this mean we'll find tiny little green people there?
"No," laughs Greene. "That is not a prediction of String Theory.
The idea
of having extra dimensions is more rationally motivated than that. Over
about 20 years we've measured 20 numbers to characterize the 'map' of the
universe. By mapping electrons, quarks, electromagnetic strength, and
gravitational force, these numbers are known from precise experiments. But
nobody has an understanding of why those numbers were found."
"What we do know is that if you change any of those 20 numbers by as small
as 2 percent, the universe as we know it disappears," states Greene.
"For
example, if you take a star and change the value of those numbers, the
nuclear properties of the star don't happen - stars don't exist at that
point. Why is it those 20 numbers have just the right values to allow
stars to light up? No theory has answered that question yet."
"String Theory hasn't answered it but it does set up a framework that
allows us to answer these deep questions for the first time. And all of
those 20 numbers - those values - depend upon the vibrational patterns of
the string filaments inside the atom."
"Just like tones running through an oboe, if we knew what the different
dimensions looked like, we might be able to use that information to
determine how strings vibrate, and thus answer the fundamental question of
how and why the universe is the way it is."
"One day," concludes Greene, "we may come to the end of that
line and reach
an understanding so deep it cannot go any deeper. This will represent a
pivotal moment in the history of our species, but it will not be the end of
wonder. I believe that completion of quantum theory will tell us the
substructure of the universe, but like the fundamentals of language, we
will be able to read it all over and better understand our lace in the
cosmos. There are many mysteries yet to be sorted out. But the search for
the fundamental laws of nature are intensely human - ripe with humility,
bittersweet, and showing our existence is a mere moment of conception,
ingenuity, and bravery."
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