A、Messenger from the Past
His people said good-bye and watched him walk off toward the mountains. They had little reason to fear for his safety: the man was well dressed in insulated clothing and equipped with tools needed to survive theAlpine climate. However, as weeks passed without his return, they must have grown worried, then anxious, and finally resigneD、After many years everyone who knew him had died, and a note even a memory of the man remaineD、
Then, on an improbably distant day, he came down from the mountain. Things had changed a bit: it wasn’t theBronzeAge anymore, and he was a celebrity.
When a melting glacier released its hold on a 4,000-year-old corpse in September, it was quite rightly called one of the most important archeological finds of the century.Discovered by a German couple hiking at 10,500 feet in the Italian Tyrol near theAustrian border, the partially freeze-dried body still wore remnants of leather garments and boots that had been stuffed with straw for insulation. The hikers alerted scientists from the University of Innsbruck inAustria, whose more complete examination revealed that the man was tattooed on his back and behind his knee.At his side was a bronze ax of a type typical in southern centralEurope around 2000BC、On his expedition perhaps to hunt or to search for metal ore--he had also carried an all-purpose stone knife, a wooden backpack, a bow and a quiver, a small bag containing a flint lighter and kindling, and an arrow repair kit in a leather pouch.
Such everyday gear gives an unprecedented perspective on life in earlyBronzeAgeEurope. "The most exciting thing is that we genuinely appear to be looking at a man who had some kind of accident in the course of a perfectly ordinary trip," says archeologist Ian Kinnes of theBritish Museum. "These are not artifacts placed in a grave, but the fellow’s own possessions. "
Unlike theEgyptians and Mesopotamians of the time, who had more advanced civilizations with cities and central authority, the Ice Man and his countrymen lived in a society built around small, stable villages. He probably spoke in a tongue ancestral to currentEuropean languages. Furthermore, though he was a member of a farming culture, he may well have been hunting when he died, to add meat to his family’s diet. X-rays of the quiver showed that it contained 14 arrows. While his backpack was empty, careful exploration of the trench where he died revealed remnants of animal skin and bones at the same spot where the pack lay. There was also the remainder of a pile of berries.Clearly the man didn’t starve to death.
The trench provided him so with shelter from the elements, and he also had a braided mat of grass to keep him warm.
If injury or illness caused the Ice Man’s death, an autopsy on the 4,000-year-old victim could turn up some clues.
The circumstances of his death may have preserved such evidence, as well as other details of his life.

Freeze-dried by the frigid climate, his inner organs and other soft tissues are much better preserved than those of dried-upEgyptian mummies or the waterlogged Scandinavian "Bog Men" found in recent years.
One concern, voiced by archeologistColin Renfrew ofCambridge University, is that the hot TV lights that greeted the hunter’s return to civilization may have damaged these fragile tissues, jeopardizing a chance to recover additional precious genetic information from his chromosomes. If not, Renfrew says, "it may be possible to get very longDNA、sequences out of this material. This is far and away the most exciting aspec

Aspects of the Sun
Since the beginning of time, human beings have been fascinated by the dramas unfolding in the firmament above--the shifting arch of the sun, the changing faces of the moon, the regular patterns of stars turning as the seasons change. The study of these subtle patterns and relationships in the cosmos evolved intoAstronomy (or "law of the stars"), one of the oldest of the sciences. While different cultures, religions, and scientific theories all offer contrasting explanations for cosmic phenomena, there is one point on which they all agree: there would be no life onEarth if not for the sun.
Modern science has now proven that the sun, whose reliable path across the sky gives us the contours of our days and the duration of our nights, is the focal point of our solar system. The sun is, in fact, a star that is nearly 110 times the size ofEarth and comprises more than 99% of the solar system’s mass, which creates enough gravitational pull to extend to the outer reaches of our solar system and keep all manner of matter (planets, asteroids, meteors and even dust) in orbit. Like other stars, the sun is made up of various gases, the most prevalent being hydrogen at around 74%, and helium at around 25%.Because the sun’s gravitational force inward is equal to that of its thermal pressure outward, it is in a state of hydrostatic equilibrium, which causes the sun to compress into a sphere.
While the sun is a near perfect sphere and appears to the naked eye as a precise and sharply defined yellow circle against the sky (hence its ancient astronomical symbol of a circle with a point at its center), it does not actually have a definite edge or boundary. Instead, the density of its gases decreases exponentially with distance from the core. Like most stars, the sun generates heat and energy via nuclear fusion, which takes place in the core at the center of the sun. This energy must travel through a number of different layers before it reaches the photosphere, the first layer of the sun’s atmosphere, where it escapes into space as sunlight. It is the photosphere that we see when we look at the sun. The layer is about 100 km thick, which is relatively thin compared to other solar layers, and is much cooler than the sun’s outermost atmospheric layer called the coronA、One of the sun’s greatest mysteries is the incredible heat of the coronA、Usually heat decreases with distance from the core; this is true for the sun until you reach the corona, which becomes suddenly hotter by a factor of nearly 200 times that of the photosphere. The exact process of heating and maintaining the corona is still one of the unsolved solar mysteries that continue to fascinate and perplex scientists today.
Another solar mystery is the curious nature of solar flares.Equivalent to millions of 100-megaton hydrogen bombs detonated simultaneously, solar flares are the most intense
and energetic explosions that occur in our solar system. ■
A、These explosions occur on the sun’s photosphere and are difficult to view through the layer’s bright emissions, even with specialized equipment. Solar flares are directly linked to another more easily observable solar phenomenon--sunspots. With the invention of the telescope in 1608, astronomers were finally able to look into the face of the sun and see that it is not a perfect and unchanging yellow disc as they had expected, but that it is often marred by discernibleble mishes or dark spots. ■
B、These dark areas are the coolest regions on the sun’s photosphere and are characterized by intense magnetic activity. The frequency of sunspot occurrences follows an eleven-year solar or sunspot cycle. ■
C、At the minimum end of the cycle, there is very little sunspot activity and at the maximum end, there might be hundreds of visible sunspots.An increased number of sunspots indicates a correlated increase in solar flare activity. ■
D、

您正在结束答题

请确认是否提交试卷？

继续做题确认提交