[extropy-chat] FWD (UFO UpDate) Physicist Explains String Theory

Thu Dec 4 03:39:10 UTC 2003

Source: Daily Nexus - UC Santa Barbara's Student Newspaper

< http://www.ucsbdailynexus.com/news/2003/6192.html >

Physicist Explains String Theory to SB
By Ben Krasnow - Staff Writer

Monday, November 24, 2003 

Physicist Brian Greene taught audience members how to see in 10 
dimensions at the Lobero Theatre Sunday night.

A leading string theorist and a member of UCSB's Kavli Institute 
for Theoretical Physics, Greene recounted the highlights of his 
book, The Elegant Universe. After going over the physics 
background necessary to understand string theory, Greene drew 
audible "wows" from the audience when he explained the core 
underpinnings of string theory, and how our understanding of the 
universe could subsequently change.

Greene was introduced by Chris Carter, producer and writer of 
the TV show, 'The X-Files'. Carter recalled reading Greene's 
book and thinking about the implications of these new ideas in 
physics. Sometimes the reality of what theoretical physics 
predicts is hard to grasp, even for a science fiction writer.

"As strange as 'The X-Files' could be, we never got as far out 
as this guy," Carter said.

Theoretical physics describes a branch of science that tries to 
explain physical phenomena by using mathematics and careful 
thought instead of empirical measurements. Greene hailed Albert 
Einstein as the most influential theoretical physicist in 
history.

"He changed the ideas of space and time," Greene said.

Einstein's first major contribution to the modern understanding 
of physics was the introduction of the ultimate speed limit -
 the speed of light, Greene said. Before this maximum speed 
limit was introduced, scientists thought some things could 
happen instantaneously, like gravity. Newton's law of 
gravitation states that the attraction felt between two objects 
is instantaneous. Einstein stated that this is not possible. 
Nothing - no signal, no information, no influence - can travel 
faster than the speed of light.

Light has been measured to travel at 186,000 miles per second. 
The sun is so far away that even at that tremendous speed, it 
takes nearly eight minutes for the its light to reach the Earth. 
If the sun disappeared right now, we could not possibly know 
until eight minutes had passed. Earth's gravitational attraction 
to the sun holds the planet in orbit. If gravity acted 
instantaneously and light did not, the earth would leave its 
orbit before the darkness accompanying the sun's disappearance 
reached it.

"The fact that there is a speed limit is a problem for Newton's 
Law," Greene said.

Greene said that Einstein's second major contribution was his 
theory of general relativity. This theory provides a way to 
understand how gravity works while still obeying the maximum 
speed limit. In fact, Einstein's calculations proved that the 
speed of gravity should be exactly the same as the speed of 
light. Greene said the reason Einstein has been praised so much 
is because his ideas unified two things - the speed of light and 
the speed of gravity. Physical theories that unify separate 
phenomena are always desirable because they approach the idea 
that there is one singular theory that could explain everything 
in the universe, Greene said.

To explain general relativity, Greene used the analogy of a thin 
horizontal rubber sheet. If the sheet was perfectly flat, a 
marble placed on the sheet would have no tendency to roll in any 
direction. If a bowling ball was placed on the sheet, it would 
form a large depression. The marble would roll down into the 
depression, toward the bowling ball. The heavier the bowling 
ball, the bigger the depression, and the faster the marble will 
would roll toward it. If the bowling ball were removed very 
quickly, the rubber sheet would take a short time to return to 
its flat shape. That amount of time is analogous to the speed of 
gravity.

"Gravity is the fabric of space and time," Greene said. 
"Einstein's theory works just a little better than Newton's."

In the case of the sun disappearing, general relativity states 
that the earth would remain in orbit for eight minutes after the 
sun is gone. This is the time it would take for the gravity wave 
to reach earth and release it from the depression in space that 
is currently holding it the sun's orbit.

Besides relativity, there is another area of physics that has 
changed markedly in the last century. This field is called 
quantum theory, and it describes how physics works on a very 
small scale. Greene said that on a macro scale, the warping of 
space is very smooth, like a smooth depression in a rubber 
sheet. On the micro scale, space is not smooth. It is constantly 
churning and moving, like the surface of boiling water. Quantum 
theory describes this rapid and chaotic motion, and has some 
startling physical conclusions.

"If you fire a particle like an electron at a barrier that 
classically it could not penetrate, quantum theory says there is 
a small chance it can," Greene said.

Greene went on to say that there is even a chance that he could 
walk into a solid stone column and come out on the other side. 
The probability is extremely low, but it is not zero according 
to quantum theory.

String theory provides a way to unify the smoothness of macro 
space and the roughness and chaos of micro space, Greene said. 
The basic concept of string theory is that every piece of matter 
in the universe is composed of very small vibrating loops of 
string. The pattern of vibrations, much like the pattern of 
vibrations on the string of a musical instrument, determines the 
properties of the particle it composes, Greene said.

The dilemma is that the mathematics behind string theory require 
the tiny loops of string to vibrate in 10 dimensions. This is a 
problem because no person has ever seen more than three 
dimensions. This conclusion does not daunt string theorists like 
Greene. He explained one way in which the other seven dimensions 
could be hidden to observers by rolling up a sheet of paper. If 
the flat plane of paper represented space, it has two 
dimensions: top to bottom, and left to right. If the paper is 
rolled up into a cylinder, the left to right [[left-to-right]] 
dimension is unchanged, but the top to bottom [[top-to-bottom]] 
dimension is changed into clockwise or counterclockwise. If the 
paper is rolled tighter, the cylinder will be come very thin, 
and from afar it may look like a simple line with no rolled-up 
clockwise dimension. This may be how the seven other dimensions 
of string theory are hidden.

Greene said that string theory could be strengthened by 
observational data from space. When the universe was young, the 
strings that made up all matter were very energetic. As the 
universe cooled down and expanded, the imprint left from the 
energetic strings may have remained. Thus, there could be large, 
string-shaped artifacts in space waiting be found that would 
provide evidence for string theory.

"Nothing to me would be more poetic; no outcome would be more 
graceful ... than for us to confirm our theories of the 
ultramicroscopic makeup of spacetimea and matter by turning our 
giant telescopes skyward and gazing at the stars," Greene said.

-- 
“Only a zit on the wart on the heinie of progress.” Copyright 1992, Frank Rice

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