VOA慢速英语 2007 1205b（在线收听）

VOICE ONE:

I'm Steve Ember.

VOICE TWO:

And I'm Shirley Griffith with EXPLORATIONS in VOA Special English.  This week, we tell about a system of planets orbiting a star called Fifty-Five Cancri.  And we hear about a plan to harvest electricity from crowds.  But first, we begin with the latest trip of the space shuttle Discovery to the International Space Station.

(SOUND)

VOICE ONE: 
Shuttle Discovery landing at the Kennedy Space Center

That was the sound of the space shuttle Discovery landing at Kennedy Space Center in the state of Florida last month.  It was the one hundred twentieth shuttle flight and the twenty-third to the International Space Station.

The United States space agency had two main goals for this flight of Discovery.  First, the crew was to move a structure from one side of the space station to the other.  And then they were to add a new room to the space station. But the astronauts faced two unexpected problems during the mission. 

VOICE TWO:

NASA calls the new addition to the space station the Harmony connecting module.  Harmony was built in Torino, Italy as part of an agreement between NASA and the European Space Agency.  It is the first new room added to the space station since two thousand one.  Harmony is about seven meters long and about four meters wide.  It will permit future shuttle missions to attach the European Space Agency's Columbus Research Laboratory. 

It will also permit a Japanese experimental module to be added as well.  Harmony will be a passageway between the laboratories and the rest of the space station.

VOICE ONE:

NASA officials had known there was a problem with a device linked to the solar energy system of the space station.  The part, called a joint, lets one set of solar arrays point toward the sun at all times.  Solar arrays are flat solar energy collectors that gather sunlight and turn it into electricity.  The solar arrays provide power to the space station. 

NASA engineers noted that the joint did not appear to be operating correctly.  It shook as it moved and used too much power.  NASA decided to use the fourth spacewalk of the mission to examine the joint.  Astronaut Daniel Tani went outside the space station to make the examination.  He looked inside the joint and found small pieces of metal. 

NASA officials had hoped that the metal would be aluminum and not steel.  This would have meant that important moving parts were not rubbing together.  However, later examination of the metal showed that it was, in fact, steel.

This meant the joint was damaging itself when it moved.  Supervisors for the space station decided to stop using the joint so that its parts would not rub against one another.  

VOICE TWO:

A second problem developed with one of the space station's solar arrays.  The shuttle astronauts had to move a structure carrying a solar array from one side of the space station to the other.  To do so, they folded the large flat solar panels and moved the structure. 

But a wire caught on one of the solar panels, tearing it in two places when the 
Scott Parazynski repairs the damaged solar array on the International Space Station
astronauts extended it again.  The crew used the space station's robotic arm to carry astronaut Scott Parazynski to the torn area on the solar array.  He was able to repair the array using parts made by the crew on the shuttle.

The repair was very dangerous because the array carries more than one hundred volts of electrical current.  But Scott Parazynski successfully fixed the tear in the solar panel and the space station crew was able to fully extend the array.

The space station is now being prepared for a visit from space shuttle Atlantis.  This mission will attach the Columbus Research Laboratory to the International Space Station.  Launch for Atlantis is planned for December sixth.

(MUSIC)

VOICE ONE:

Science has made it possible to harvest energy from the wind, sun and water.  All these renewable resources are used today to power an energy-hungry world.  But imagine harvesting energy from crowds of people moving to and from work every day.  That is one of the possibilities of piezoelectricity, the science of gaining power from motion.

Some materials create an electrical charge when they are placed under pressure or stretched.  These materials are said to be piezoelectric.  Some crystals, such as quartz, and some ceramic materials are piezoelectric.

VOICE TWO:

James Graham and Thaddeus Jusczyk are two graduate students at the Massachusetts Institute of Technology in Cambridge.  They designed a way to capture the energy of people's footsteps.  They created a design for a special floor covering that moves a little when people step on it.  The movement would create an electrical current that could be captured to provide electrical power. 

Mister Graham and Mister Jusczyk say one footstep could create enough energy to light two sixty-watt lights for one second.  That might not sound like very much energy.  But consider what hundreds of thousands of footsteps might create in an underground train station in a major city.  The two researchers note that it takes about twenty-eight thousand steps to power a train for one second. 

VOICE ONE:

Gathering power from the movements of large groups of people is called "crowd farming."  And interest in crowd farming continues to grow.  Mister Graham and Mister Jusczyk took first prize at an international competition on city design earlier this year.  The Holcim Foundation for Sustainable Construction held the competition. At this point, Mister Graham and Mister Jusczyk only have designs for their large crowd farming project, not a finished product. 

 
Seat designed by James Graham and Thaddeus Jusczyk makes electricity when someone sits
However, they have built a smaller example of piezoelectronics to show how it can work.  They made a seat that creates electricity when someone sits on it.  The action of sitting on the seat turns a wheel that creates an electrical charge.  This then turns on lights attached to the seat. Mister Jusczyk has said that one of the goals of his work is to have people understand the relationship between their movements and the energy produced. 

(MUSIC)

VOICE TWO:

Space scientists have been searching nearby stars for planets with great success.  The United States space agency says that two hundred sixty-four exoplanets have been discovered so far.  But, until now, few of the planetary systems found orbiting other stars have been like our own solar system.  That has all changed with the discovery of a fifth planet orbiting a star called Fifty-Five Cancri in the constellation Cancer. 

Astronomers have known of at least one planet circling Fifty-Five Cancri since nineteen ninety-six.  The star is forty-one light years away from Earth.  It is also very similar to our own sun.

Last month, astronomers announced the discovery of a fifth planet orbiting Fifty-Five Cancri.  What makes the discovery extraordinary is that the new exoplanet orbits in what astronomers call a "habitable zone."  This means temperatures on the planet may be warm enough for liquid water to exist either on its surface or on one of its moons. 

VOICE ONE:

 
An artist's picture of the fifth exoplanet discovered orbiting 55 Cancri, a star similar to our sun
The fifth exoplanet is about the size of the planet Saturn.  Its mass is about forty-five times greater than that of Earth.  Scientists believe it is unlikely to hold life.  But they say that the exoplanet could have one or more large moons like Titan, a large moon of Saturn in our own solar system.  Such a moon could hold water and the conditions for life.  Astronomers add that there may be small planets similar to Earth in this complex planetary system.

Astronomers can find exoplanets by looking for very small movements in nearby stars.  The movements are evidence that the gravity of a massive planet is acting on the star.  By observing a star long enough, astronomers can uncover this evidence.  But currently astronomers do not have the technology to discover Earth-sized planets orbiting even nearby stars.

VOICE TWO:

Scientists made the observations at the Lick Observatory near San Jose, California and the Keck Observatory in Mauna Kea, Hawaii.  More than three hundred twenty separate measurements were needed to identify each of the planets in the system.  Eighteen years of observations were required. The observations started before anyone knew there were planets orbiting other stars.  The United States space agency and the National Science Foundation supported the research.

Other planets in the system orbit the star at distances similar to planets in our own solar system.  The closest orbits at only about five and one half million kilometers from Fifty-Five Cancri.  After our own sun, Fifty-Five Cancri now has the most known planets of any star. 

(MUSIC)

VOICE ONE:

This program was written and produced by Mario Ritter.  I'm Steve Ember.

VOICE TWO:

And I'm Shirley Griffith.  You can find more space and technology news on our Web site, voaspecialenglish.com. Join us again next week for Explorations in VOA Special English.