2004-8-16
VOICE ONE:
This is SCIENCE IN THE NEWS, in VOA Special English. I'm Bob
Doughty.
VOICE TWO:
And I'm Sarah Long. When a world famous scientist admits being
wrong about something, people hear about it. But when the subject is
something like quantum theory, they might not understand it.
VOICE ONE:
So we will try our best to explain quantum theory ... coming up
this week on SCIENCE IN THE NEWS.
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VOICE TWO:
Recently, the physicist Stephen
Hawking had an announcement that made news around the world. Mister
Hawking is the Lucasian Professor of Mathematics at the University
of Cambridge in England. He was in Ireland at the Seventeenth
International Conference on General Relativity. This was his
announcement: he has changed his mind about black holes.
Professor Hawking admitted that he had been wrong for thirty
years. He presented a new theory. He says he now accepts that black
holes cannot destroy the information about the objects they swallow.
VOICE ONE:
Black holes are generally the remains of exploded stars -- big
stars. Black holes are extremely dense. The gravity they produce is
great enough to pull in other objects from space. Scientists tell us
this force is so great that not even light can escape.
In nineteen seventy five, Stephen Hawking declared that black
holes destroyed all evidence of whatever they swallowed. He said any
information about matter eaten by a black hole would cease to exist.
VOICE TWO:
Other physicists who study space found that declaration difficult
to swallow. Many argued that the total loss of information would be
impossible; it would violate the laws of quantum theory.
The other astrophysicists argued that there must have been a
mistake in Professor Hawking's math. Over the years, some found a
compromise. They presented mathematical arguments to permit
conflicting theories about information in black holes. But no
scientist was able to discover the problem in the professor's work.
Now Stephen Hawking says he has found the mistakes himself. He
says he redid his work from nineteen seventy five, but in a new way.
He says the new results show that information about what is inside a
black hole is carried back out to the universe by radiation.
Professor Hawking's work in the nineteen seventies had shown that
black holes release radiation. In fact, scientists call this Hawking
Radiation.
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VOICE ONE:
You are listening to SCIENCE IN THE NEWS, in VOA Special English.
Stephen Hawking says his recent work shows something new about
the surface of a black hole. This surface is called the event
horizon. The professor says changes that take place in the event
horizon permit information to leak out of the black hole.
However, he says the information would be changed by the black
hole experience. By this theory, the information would be so changed
that it could not be recognized. Stephen Hawking said he would
publish a complete description of his new work in professional
journals and on the Internet.
The findings could help the scientific efforts to find what is
called a Theory of Everything. Physicists hope to be able to find
the link between the laws that govern the smallest parts of matter
with those that guide larger objects in the universe. These laws
often appear to conflict.
VOICE TWO:
The changes that Professor Hawking describes in the surface of
black holes are quantum changes. Quantum theory describes how energy
and matter act at the level of atoms and particles of atoms. It now
guides most research in physics.
In nineteen hundred, the German physicist Max Planck wrote a
paper that dealt with two forms of energy: heat and light. At the
time, scientists did not understand why increased heat leads to
changes in the color of light. A common example involves what
happens to a piece of metal that is heated. As the temperature
increases, the metal becomes red. As the metal gets hotter and
hotter, it turns yellow and then white. But why?
To explain this, Planck said atoms and molecules must affect
energy in small, separate parts. He called these divisions of energy
"quanta." Material loses light energy as it is heated. The color of
that light is the result of the number of quanta lost. Planck
described an unchanging balance between the energy of each quantum
and the color of the light. This balance is known as Planck's
constant.
Before his paper, scientists thought energy changed in a
continuous flow. But the new work showed that changes in huge
numbers of extremely small parts simply make it appear that way.
VOICE ONE:
Max Planck's finding was the beginning of quantum mechanics. This
describes how matter and radiation operate at the atomic level.
Quantum mechanics describes the structure of the atom and the
movement of its particles. It also explores how atoms take in energy
and release energy as light.
Physicists hope quantum mechanics will help them to understand
actions that conflict with traditional laws of physics. Isaac Newton
developed his theories in England three centuries ago based on
normal human experience. But scientists now know that extremely
small particles and systems do not follow those laws of nature that
Newton observed. Such conflicts must be settled if scientists are to
reach a single theory for everything.
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VOICE TWO:
Several major ideas guide quantum mechanics. One is the idea that
energy is divided into parts. Another is that light energy exists at
the same time both as particles and as a wave. A person sees light
particles. But the particles are spread out in an area that includes
places where they could be but are not. So the probability of where
each particle will be means that light acts like a wave.
Another major part of quantum mechanics is called Schrodinger's
Equation. Erwin Schrodinger, an Austrian, developed this idea in the
middle of the nineteen twenties. It basically says that the act of
measurement changes the nature of that which is being measured. In
everyday life, the effect of this interference is too small to
notice. But, as we said, things are different in the world of atoms
and subatomic particles.
For example, scientists need light to see an electron before they
can measure it. But light is made up of photons. These will affect
the movement of the electron.
VOICE ONE:
Another major part of quantum mechanics is called the Uncertainty
Principle. The German scientist Werner Heisenberg proposed this
idea. The basic explanation is that the exact position of a particle
and its speed and direction can never be known together. In other
words, you can measure either the position or the momentum. But if
you measure one, you sacrifice the other. So it is impossible to
know both at the same time.
But scientists can at least mathematically predict how matter
will act in ways we would think impossible. Again, it is all about
probability.
VOICE TWO:
The study of quantum mechanics has uses in areas like chemistry,
molecular biology and information technology. It has already led to
smaller and more powerful computers.
Quantum theory has also led to a greater understanding of the
universe. The same is true of Albert Einstein's general theory of
relativity. But Einstein's theory deals with larger structures in
the universe; quantum theory deals with the very opposite.
Some scientists are at work to combine these two theories into a
theory of everything. This could help explain the formation of the
universe from the very beginning of time.
VOICE ONE:
One of the scientists involved in this effort is Stephen Hawking.
Many people know about his work from his popular book "A Brief
History of Time."
Professor Hawking is sixty-two years old. That makes him one of
the oldest survivors of A.L.S., or amyotrophic lateral sclerosis.
Americans call this Lou Gherig's disease, after a baseball player
who had it. The disease attacks the nervous system.
Stephen Hawking uses a wheelchair. And he uses a computer to
speak for him. He enters words one letter at a time. Then the
computer serves as his voice.
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VOICE TWO:
SCIENCE IN THE NEWS was written by Caty Weaver and produced by
Cynthia Kirk. This is Bob Doughty.
VOICE ONE:
And this is Sarah Long. If you have a question for our program,
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