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Transcript
Pluto and Dark Matter Both Star in a Busy Week for Astronomers
25 August 2006
(1) Correction attached
This is IN THE NEWS in VOA Special English.
This week, there were two big developments in astronomical science.
decision to name Pluto a "dwarf planet."
One was a
The other was the announcement earlier in the week that scientists have found direct
evidence for dark matter. But they say they are still not sure what this mysterious
matter is or where it comes from.
Scientists have theorized about dark matter for about seventy years. The idea is that
the matter we see does not have enough gravitational pull to (2) keep galaxies together.
Visible matter has been estimated to represent only about five percent of the universe.
The new findings come from NASA’s Chandra X-ray Observatory and other telescopes.
A team of scientists observed a group of galaxies that formed when two galaxy clusters
smashed into each other. They call it the "(3) bullet cluster." It contains a
bullet-shaped cloud of hot gas from a smaller cluster that passed through the hot gas
from a larger one.
The bullet cluster is more than three thousand million light-years away.
the last one hundred million years.
It formed in
Scientists can observe what they believe to be dark matter only through its gravity.
But the team says the crash was violent enough to break dark matter away from
"normal" matter. Normal matter in galaxy clusters is mostly in the form of hot gas and
stars.
They call it the strongest evidence yet that most of the matter in the universe is dark.
They say the observations cannot be explained by (4) theories of gravity that remove the
need for dark matter. These theories propose that gravity is stronger with huge galaxy
clusters than the theories of Isaac Newton or Albert Einstein would suggest.
The findings will appear in the Astrophysical Journal Letters.
(5) Now on to Pluto. This week the International Astronomical Union met in Prague,
in the Czech Republic, with the goal to officially define a planet.
Scientists voted to set three requirements for a planet: It must orbit the sun.
It must
have enough mass so that its own gravity has formed it into a nearly round shape. And
it must have (6) cleared the area of other objects around its orbit. That is where Pluto
fails: its orbit around the sun crosses paths with Neptune's.
American Clyde Tombaugh discovered Pluto in nineteen thirty. People have long
debated about considering it the ninth planet in our solar system. Now Pluto will be
called a dwarf planet along with at least two others: Xena and Ceres.
(7) The changes divide astronomers. But supporters say (8) recent discoveries of large
objects in the outer solar system require them.
So the new model of our solar system has eight "classical" planets. The smaller, rocky
worlds are Mercury, Venus, Earth and Mars. The four huge gas planets are Jupiter,
Saturn, Uranus and Neptune.
And that's IN THE NEWS in VOA Special English, written by Brianna Blake and
online at voaspecialenglish.com. This is Shep O'Neal.
--Correction: The definition approved by the I.A.U. refers to "planets" and "dwarf
planets" but not to "classical."
Warm-Up Discussion Topics/Questions
1. You have only one month of summer vacation left. What do you want to do before
the fall semester starts?
2. What would you do differently if you could repeat the spring semester of this year?
Discussion Questions/Topics
1.
2.
3.
4.
5.
6.
7.
What does this mean?
What does this mean?
What forms the bullet cluster? When?
Paraphrase.
Paraphrase.
Explain this rather ambiguous statement.
Explain what this means.
8. What do you think this means? Unless you already know the answer, it may not be
easy to understand what this really means.
9. Pluto (冥王星) is now a dwarf planet and not a full-fledged planet any more. Were
you disappointed or were you happy about the decision?
More Discussion Questions/Topics
1. Choose a place you go to often that is important to you and explain why it is
important. Please include specific details in your explanation.
2. Some college students choose to take courses in a variety of subject areas in order
to get a broad education. Others choose to focus on a single subject area in order to
have a deeper understanding of that area. Which approach to course selection do
you think is better for students and why?
TOEFL iBT’s Speaking Section
1. Choose a place you go to often that is important to you and explain why it is
important. Please include specific details in your explanation.
Preparation time: 15 seconds
Response time: 45 seconds
2. Some college students choose to take courses in a variety of subject areas in order
to get a broad education. Others choose to focus on a single subject area in order to
have a deeper understanding of that area. Which approach to course selection do
you think is better for students and why?
Preparation time: 15 seconds
Response time: 45 seconds
Some Timed Readings
Bus Service Elimination Planned (p.231)
(Reading time: 45 seconds)
The university has decided to discontinue its free bus service for students. The reason
given for this decision is that few students ride the buses and the buses are expensive to
operate. Currently, the buses run from the center of campus past university buildings
and through some of the neighborhoods surrounding the campus. The money saved by
eliminating the bus service will be used to expand the overcrowded student parking lots.
The man expresses his opinion of the university’s plan to eliminate the bus service.
State his opinion and explain the reasons he gives for holding that opinion.
Preparation time: 30 seconds
Response time: 60 seconds
Reading Passage for Writing (p.282)
(3 minutes)
Altruism is a type of behavior in which an animal sacrifices its own interest for that
of another animal or group of animals. Altruism is the opposite of selfishness;
individuals performing altruistic acts gain nothing for themselves.
Examples of altruism abound, both among humans and among other mammals.
Unselfish acts among humans range from the sharing of food with strangers to the
donation of body organs to family members, and even to strangers. Such acts are
altruistic in that they benefit another, yet provide little reward to the one performing the
act.
In fact, many species of animals appear willing to sacrifice food, or even their life,
to assist other members of their group. The meerkat, which is a mammal that dwells in
burrows in grassland areas of Africa, is often cited as an example. In groups of meerkats,
an individual acts as a sentinel, standing guard and looking out for predators while the
others hunt for food or eat food they have obtained. If the sentinel meerkat sees a
predator such as a hawk approaching the group, it gives an alrm cry alerting the other
meerkats to run and seek shelter. By standing guard, the sentinel meerkat gains nothing
– it goes without food while the others eat, and it places itself in grave danger. After it
issues an alarm, it has to flee alone, which might make it more at risk to a predator,
since animals in groups are often able to work together to fend off a predator. So the
altruistic sentinel behavior helps ensure the survival of other members of the meerkat’s
group.
In many organizations, perhaps the best way to approach certain new projects (p.250)