攀登英语网 http://www.5pds.com 提供 of the inverse square law for light propagation. I did not have the slightest idea of calculating the distance to the stars. But I could tell that if the stars were suns, they had to be very far away—farther away than 85th Street, farther away than Manhattan, farther away, probably, than New Jersey. The Cosmos was much bigger than I had guessed.
Later I read another astonishing fact. The Earth, which includes Brooklyn, is a planet,
and it goes around the Sun. There are other planets. They also go around the Sun; some are closer to it and some are farther away. But the planets do not shine by their own light, as the Sun does. They merely reflect light from the Sun. If you were a great distance away, you would not see the Earth and the other planets at all? they would be only faint luminous points, lost in the glare of the Sun. Well, then, I thought, it stood to reason that the other stars must have planets too, ones we have not yet detected, and some of those other planets should have life (why not?), a kind of life probably different from life as we know it, life in Brooklyn. So I decided I would be an astronomer, learn about the stars and planets and, if I could, go and visit them.
It has been my immense good fortune to have parents and some teachers who
encouraged this odd ambition and to live in this time, the first moment in human history when we are, in fact, visiting other worlds and engaging in a deep exploration of the Cosmos. If I had been born in a much earlier age, no matter how great my dedication, I would not have known that there were other suns and other worlds. This is one of the great secrets wrested from Nature through a million years of patient observation and courageous thinking by our ancestors. What are stars? Such questions are as natural as an infant 's smile. We have always
asked them. What is different about our time is that at last we know some of the answers. Books and libraries provide a ready means for finding out what those answers are. Stars
A star starts out life from what seems like nothing at all. Stars are born in huge clouds
of gas that are actually far less dense than the space immediately surrounding Earth.
\
that the space shuttle flies through seem as thick as chicken soup,\says Jeff Hester, an astronomer at Arizona State University in Tempe. But because the clouds are so big, they contain a lot of molecules—enough, eventually, to build massive stars.
How big are these clouds that serve as star nurseries? They can be a light-year
across—so enormous it would take light one year to cross one. In contrast, it takes light only one-seventh of a second to travel the nearly 25,000-mile distance that equals the circumference of tiny Earth.
The key to star formation is gravity, says Hester. Gravity causes the multitude of
spread-out molecules to move toward each other and pulls them toward the center of the cloud. \process of star formation. This collapsing process happens relatively quickly (by cosmic standards)—only about 30 million years, or less.
攀登英语网 http://www.5pds.com 提供 Over time the cloud gets smaller and smaller. As the cloud contracts, it also begins to
spin faster. (This is due to a little something called conservation of angular momentum—the same phenomenon that allows a figure skater like Nancy Kerrigan to speed up her spin when she pulls her arms in toward her body. As the mass of gas moves toward the center, the cloud spins faster.) Next, the cloud starts to flatten. \just like when you make a simple pizza,\says Hester. \becomes so strong in the center of the cloud, the center starts to collapse in on itself as it continues to rotate. At this point, you have a disk that's a few times the size of our solar system. (The disk would be about a couple of light-days across, if you 're keeping track of the size of things.) As the disk continues to rotate, matter in the center of the disk starts to move further inward and a big lump forms in the middle of the disk. This lump, says Hester, is a protostar. What happens to the matter that's left over further out in the disk? In our solar system, it
went on to become the planets. (In essence, earth is made up of leftovers.)
Protostars are very hot because so much of the gravitational energy that was once
contained in the loose cloud of interstellar gas has been converted into heat. Protostars are spectacular, glowing with dull red light and infrared light. As a protostar emits this light, it continues to shrink and gets hotter and hotter. Finally, it's hot enough for real star business to begin—nuclear fusion.
At high enough temperatures, atoms slam together at incredibly fast speeds. When this
happens, lighter atoms like hydrogen can fuse together to make heavier atoms like helium. One reaction releases massive amounts of energy; add all the reactions together, and \the energy that makes the stars shine,\star is born.
After a star \on,\he says, its power can cause destruction to the surrounding
environment. A young star expands, tearing apart the cloud that formed it. New stars often break up neighboring stars before they can form. It's hard to overstate what a powerful process star formation is. Even as they are forming, protostars eject huge amounts of material in jets and streams and create violent solar winds.
Unit 5
A Merry Christmas ...
Another Serving?
A Merry Christmas to you all ...
\
large number of British people, then your Christmas will be an alcoholic, rather than a religious, occasion.
攀登英语网 http://www.5pds.com 提供 If you walk down Piccadilly or Oxford Street just before Christmas, you will see an
incredible amount of money being spent on electronic games, bottles of wine, expensive clothes, CDs, cassettes, cameras, and a large number of luxury items. If you walk down the main street of several towns in the Third World just before Christmas, you won't see a large amount of money being spent on presents: in fact, you won't see a large amount of money being spent on anything.
80 % of all disease in the world is caused by bad water supply: for millions of people,
the perfect Christmas present would be a tap in the village square which would give pure, clean, water.
Do we think of these people when we sit down to our Christmas dinner? Of course
not—we 're too busy thinking about the turkey, the roast potatoes, and the presents sitting under the Christmas tree. The whole idea of Christmas now is completely unchristian—I 'm sure that Christ would be furious if he could see what sort of celebrations are being carried out in his name.
So I 'm against Christmas—I agree with Scrooge: \
continue with this wasteful, thoughtless ceremony, then let 's be truthful about it, and call it \—but let 's get rid of the insincere pretence that Christmas is \
Not only for Children?
Recently, a rather sophisticated woman told me shyly that she saves up all her presents
until Christmas morning and then sits up in bed and opens them, just like a child. She thought I would laugh at her and say how silly she was. But in fact I was absolutely delighted to meet someone who treats Christmas as I do.
Many people today have a very different attitude to Christmas. They think it's just a
time when shopkeepers make a lot of money and everyone rushes round buying presents they don't want to give and food they don't want to eat. But have they grown so far away from their own childhood that they can't remember all the good things?
First of all, Christmas takes you out of the ordinary humdrum routine of life. For
children, the fun begins weeks before when the decorations are put up, and excitement gradually mounts as December the 25th approaches.
Everyone seems much friendlier to each other than usual at Christmas-time. You can
lean out of a car window when you 're stopped at the traffic lights and say \and people will smile and respond. You probably wouldn't think of doing that at any other time of the year. Perhaps it's because most people are on holiday or because everyone knows that they are sharing a similar experience. Giving presents can be very satisfying, too, if you plan far enough in advance and really think of the right present for the right person.
Indeed, whatever shopkeepers gain out of Christmas, it is still a \
from which \on non-commercial values.
攀登英语网 http://www.5pds.com 提供 From Your Valentine
Considering the number of ethnic groups that make up the U.S. population, it is not
surprising that Americans have a variety of different holidays. From Thanksgiving to Cinco de Mayo, from Chanukah to the Chinese New Year, they are seldom at a loss for a reason to celebrate. Some of these holidays are rather unusual. Some examples follow.
Groundhog Day, February 2:
The groundhog, a small burrowing animal also known as a woodchuck, is supposed to
come out of his hole to look for his shadow on this day. As the legend goes, if he fails to see his shadow it means spring has come; if he sees it he returns to his hole to sleep, for winter will continue for another six weeks.
April Fool 's Day, April 1:
Don't believe anything you hear on this day of tricks and jokes designed to make you an
\
Halloween, October 31:
After dark, children dressed like ghosts and witches go from house to house shouting,
\children will play tricks on them.
Sadie Hawkins Day, the first Saturday after November 11:
Traditionally, it is the boys who chase the girls, but on Sadie Hawkins Day a girl can
keep any boy she can catch.
On February 14 Americans celebrate another unusual holiday, St. Valentine 's Day, a
special day for lovers. Valentines are cards—usually red and shaped like hearts—with messages of love written on them. Lovers send these cards to each other, often anonymously, on St. Valentine 's Day.
The origins of this holiday are uncertain, but according to one legend, it gets its name
from a Christian priest named Valentine who lived in Rome during the third century after Christ. His job was to perform marriages. for Christian couples. Unfortunately, the Emperor of Rome, Claudius II, did not allow Christian marriages? so they had to be performed in secret. Eventually Valentine was arrested and put into prison. While in prison he fell in love with the daughter of the prison guard.
After one year, the Emperor offered to release Valentine if he would agree to stop
performing these secret marriages. Valentine refused, so the Emperor sentenced him to death. Valentine was executed in 270 A. D. on February 14, the same day the Romans worshiped their goddess of marriage, Juno. Before he was killed, Valentine sent a love letter to the daughter of the prison guard. He signed the letter \ The next valentine was sent in 1415 A.D. Charles, Duke of Orleans sent the valentine
to his wife while he was a prisoner in the Tower of London. His valentine is now on exhibit in the British Museum. The first commercially printed valentines did not appear until 1809. Some of these valentines were not messages of love. Comic valentines, or \
攀登英语网 http://www.5pds.com 提供 were called, were often funny and sometimes insulting. The \in the 1840s when valentine makers started making elaborate and expensive valentines. Jonathan King became famous as a publisher of beautiful and unusual valentines in
Britain in the 1870s. Esther Howland was the first to publish valentines in the United States, in the 1860s. She created handmade designs for valentines, which cost as much as thirty-five dollars.
Today, millions of Americans send and receive valentines on St. Valentine 's Day.
Whether it is an expensive heart-shaped box of chocolates from a secret admirer or a simple handmade card from a child, a valentine is a very special message of love.
Family Rituals
Many American families can boast of certain rituals centered around traditional
occasions, usually holidays. To family members, such small acts seem unremarkable; sometimes, talking about them, they cannot pinpoint when or why the custom began. But social scientists believe that as family life tends to become increasingly fragmented, such repeated ceremonies play a significant role in creating and strengthening our sense of emotional security. Jay Schvaneveldt, a sociologist at Utah State University who has studied hundreds of families, points out that families with the strongest ties have the most rituals. \much for whatever is actually said or done,\—the sense of 'we-ness' that grows out of shared experience. More than anything, the ritual is a symbol of how family members feel about one another.\
There are numerous manifestations of this custom. At Christmas, for example, many
families have special ways of exchanging gifts: \present at a time ... \Or: \children get one package to open on Christmas Eve, and it's always a pair of pajamas.\
Thanksgiving and birthday rituals usually center around food: \wouldn't be
Thanksgiving if Aunt Grace didn't bring her blueberry pie.\privilege of choosing the menu for the entire dinner.\reunions, Sunday prayers, and July Fourth picnics.
But family rituals are just as likely to grow out of spontaneous or chance events. One
woman, without realizing it, started a ritual when she and her husband made a list of their household possessions for a fire-insurance policy. \the job was done I said, 'Well, we know what things we have, but what about intangibles or abstract things?' So we made another list of qualities like love, trust, good health, a sense of humor—what we call our happiness inventory. Now once a year we review it and try to add an item or two to it.\
According to Professor Schvaneveldt, family rituals serve several basic purposes:
Firstly, they reinforce family closeness. A friend of mine prizes the memory of a
childhood event that took place each year on the first warm April Sunday: \out in the yard? breathe in deeply, and say, 'It looks like spring is here at last.' Then I knew that