题目内容
Life on Other Planets
In 1961, scientists set up a gigantic, sensitive apparatus to collect radio waves from the far roaches of space, hoping to discover in them some mathematical pattern indicating that the waves were sent out by other intelligent beings. The first at tempt failed; but someday the experiment may succeed.
But is there intelligent life？ Life that has reached the stage of being able to send radio waves out-into space in a planned pattern？ Our own planet may have been in existence for five billion years and may have had life on it for two billion, but it is only in the last fifty years that intelligent life capable of sending radio waves into space has lived on earth. From this it might seem that even if there were no technical problems involved, the chance of receiving signals from any particular earth-type planet would be extremely small.
This does not mean that intelligent life at our level does not exist somewhere. There is such an unimaginable number of stars that, even with only a small chance, it seems certain that there are millions of intelligent life forms scattered through space. The only trouble is, none may be within hailing distance of us. Perhaps none ever will be; perhaps the huge distances that separate us from our fellow inhabitants of this universe will forever remain too great to be conquered. And yet it is conceivable that someday we may come across one of them or, frighteningly, one of them may come across us. What would they be bike, these extraterrestrial creatures？
Surely, it would seem, there is no way of telling. Here on earth alone, life has developed in many directions, taking on forms that could scarcely be invented by the wildest imagination if they were not already known to exist.
Who would dream that a mouse could fly if he had never seen a bat？ Who would predict blind lizards living in caves, or worms living in the intestines of other creatures？ Consider the giraffe, the humming-bird, the redwood tree, the Venus' flytrap, and see whether you can imagine any limit to various forms of life. Then how can anyone predict anything at all a bout extraterrestrial beings？
Ah, but all these variations and modifications that exist on earth are in some ways only superficial. In the chemist's test tube, all amazing differences in life forms vanish when we consider the basic similarity of those life forms, which is neither exciting nor amazing. Whatever appearance earth creatures may have, they are all made up of the same kinds of complex molecules; with minor variations, they all make use of the same chemical machinery.
For all its wonderful differences, life on earth is merely an imaginative variation on a single chemical structure. Life on any earthlike planet may prove to be similar.
As we understand life, it consists of molecules large enough and complex enough to meet the infinitely flexible requirements of living tissue. The molecules must be stable enough to retain their structure under some conditions, and unstable enough to change kaleidoscopically under other conditions. In living things on earth, the most important molecules of this type are the proteins, and as far as we know, nothing will substitute for them.
Furthermore, the changes these proteins undergo in the process of living can only take place against a watery back ground. Life began in the oceans, and even the various forms of land life are still from 50 to 80 percent water.
The chemical structure, then, upon which life is based, here and possibly on all earth-type planets, is protein-in water. If we are ever to meet up with creatures from an earth-type planet, we may not be able to predict their appearance, but we can predict that, whatever their shape, they will very likely be protein-in-water.
But what about life on planets that are not like the earth？ Wh
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The author says that silicones might replace protein on hot planets because silicones may
Friendship is one of the basic bonds between human beings. While the characteristics of friendship might vary from one country to another, people from all cultures not only enjoy friends but need them.
Many studies have shown that teenagers who have no friends often suffer from psychological disorders. It has been shown that teenagers, perhaps more than any other age group, need companionship and a sense of belonging. The negative consequences of loneliness have also been observed among the elderly. The death of a spouse often leaves a widow or a widower totally lonely. If, however, they are surrounded by friends and relatives and if they are able to articulate their feelings, they are more likely to recover from their grief.
"No man is an island." In other words, we are all parts of society. We all need the love, admiration, respect and moral support of other people. If we are fortunate, our friends will provide us with all of these necessary aspects of life.
As most people observe, there are many levels of friendship. The degree or intensity of friendship varies depending on the personality of the individuals involved and the context of the relationships. Extroverts enjoy being surrounded by many people whereas introverts are perhaps content with fewer but more intense friendships.
Everyone is not equally open with all their friends. The degree of intimacy is determined by many factors. Close friends can be formed at any stage in one's life but they are usually very rare. Not very many people have more than a few really close friends. Irrespective of the level of intimacy, all friendships are based on reciprocity, honesty and a certain a mount of love and affection.
The second paragraph implies that ______.
Modern theories of the development of stars suggest that almost every star has some sort of family of planets.
Scientists collect radio waves from space in hopes that they might receive planned messages sent by intelligent life on an other world.
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