Space aliens and extraterrestrials have long been popular subjects of Hollywood movies and science fiction literature. But the idea of intelligent life in outer space is no longer limited to fiction. For the last 50 years, scientists and astronomers have been training their telescopes into space in the search for signs of intelligent life. Frank Drake is a trailblazer in that quest. The question of whether we are alone in the Universe has haunted humanity for centuries, but we may now stand poised on the brink of the answer to that question, as we search for radio signals from other intelligent civilizations. This search, often known by the acronym SETI (search for extra-terrestrial intelligence), is a difficult one. Although groups around the world have been searching intermittently for three decades, it is only now that we have reached the level of technology where we can make a determined attempt to search all nearby stars for any sign of life.
A The primary reason for the search is basic curiosity-the same curiosity about the natural world that drives all pure science. Few will deny the profound importance, practical and philosophical, which the detection of interstellar communications will have. We want to know whether we are alone in the Universe. We want to know whether life evolves naturally if given the right conditions, or whether there is something very special about the Earth to have fostered the variety of life forms that we see around us on the planet. The simple detection of a radio signal will be sufficient to answer this most basic of all questions. In this sense, SETI is another cog in the machinery of pure science which is continually pushing out the horizon of our knowledge. However, there are other reasons for being interested in whether life exists elsewhere. For example, we have had civilisation on Earth for perhaps only a few thousand years, and the threats of nuclear war and pollution over the last few decades have told us that our survival may be tenuous. Will we last another two thousand years or will we wipe ourselves out? Since the lifetime of a planet like ours is several billion years, we can expect that, if other civilizations do survive in our galaxy, their ages will range from zero to several billion years. Thus any other civilisation that we hear from is likely to be far older, on average, than ourselves. The mere existence of such a civilisation will tell us that long-term survival is possible, and gives us some cause for optimism. It is even possible that the older civilisation may pass on the benefits of their experience in dealing with threats to survival such as nuclear war and global pollution, and other threats that we haven’t yet discovered.
B In discussing whether we are alone, most SETI scientists adopt two ground rules. First, UFOs (Unidentified Flying Objects) are generally ignored since most scientists do not consider the evidence for them to be strong enough to bear serious consideration (although it is also important to keep an open mind in case any really convincing evidence emerges in the future). Second, we make a very conservative assumption that we are looking for a life form that is pretty well like us, since if it differs radically from us we may well not recognise it as a life form, quite apart from whether we are able to communicate with it. In other words, the life form we are looking for may well have two green heads and seven fingers, but it will nevertheless resemble us in that it should communicate with its fellows, be interested in the Universe, live on a planet orbiting a star like our Sun, and perhaps most restrictively, have a chemistry, like us, based on carbon and water. We therefore feel that a discriminating search for signals deserves a considerable effort. The probability of success is difficult to estimate; but if we never search, the chance of success is zero.
C Even when we make these assumptions, our understanding of other life forms is still severely limited. We do not even know, for example, how many stars have planets, and we certainly do not know how likely it is that life will arise naturally, given the right conditions. However, when we look at the 100 billion stars in our galaxy (the Milky Way), and 100 billion galaxies in the observable Universe, it seems inconceivable that at least one of these planets does not have a life form on it; in fact, the best educated guess we can make, using the little that we do know about the conditions for carbon-based life, leads us to estimate that perhaps one in 100,000 stars might have a life-bearing planet orbiting it. That means that our nearest neighbours are perhaps 100 light years away, which is almost next door in astronomical terms.
D An alien civilisation could choose many different ways of sending information across the galaxy, but many of these either require too much energy, or else are severely attenuated while traversing the vast distances across the galaxy. It turns out that, for a given amount of transmitted power, radio waves in the frequency range 1000 to 3000 MHz travel the greatest distance, and so all searches to date have concentrated on looking for radio waves in this frequency range. So far there have been a number of searches by various groups around the world, including Australian searches using the radio telescope at Parkes, New South Wales. Until now there have not been any detections from the few hundred stars which have been searched. The scale of the searches has been increased dramatically since 1992, when the US Congress voted NASA $10 million per year for en years to conduct a thorough search for extra-terrestrial life. Much of the money in this project is being spent on developing the special hardware needed to search many frequencies at once. The project has two parts. One pa rt is a t a rge t ed search using the world’s largest radio telescopes, the American-operated t e l e s c o p e i n Ar e c i b o , Puerto Rico and the French telescope in Nancy in France. This part of the project is searching the nearest 1000 likely stars with high sensitivity for signals in the frequency range 1000 to 3000 MHz. The other part of the project is an undirected search which is monitoring all of space with a lower sensitivity, using the smaller antennas of NASA’s Deep Space Network.
E There is considerable debate over how we should react if we detect a signal from an alien civilisation. Everybody agrees that we should not reply immediately. Quite apart from the impracticality of sending a reply over such large distances at short notice, it raises a host of ethical questions that would have to be addressed by the global community before any reply could be sent. Would the human race face the culture shock if faced with a superior and much older civilisation? Luckily, there is no urgency about this. The stars being searched are hundreds of light years away, so it takes hundreds of years for their signal to reach us, and a further few hundred years for our reply to reach them. It’s not important, then, if there’s a delay of a few years, or decades, while the human race debates the question of whether to reply, and perhaps carefully drafts a reply
Questions 14-17 Reading Passage 2 has five paragraphs, A-E. Choose the correct heading for paragraphs B-E from the list of headings below. Write the correct number, i-vii, in boxes 14-17 on your answer sheet.
List of Headings
i. Seeking the radio signals coming from other planets
ii. Technical difficulty in replying a short notice immediately
iii. The best strategies of responding to signals from other civilisations
iv. Enormous distances to our planet’s closest neighbours
v. The expected and established assumptions underlying as to
vi. the search for extra-terrestrial intelligence
vii. Significances for the seeking for extra-terrestrial intelligence
viii. Knowledge of extra-terrestrial life forms
ix. Likelihood of extra-terrestrial life-forms on other planets
x. Financial investment into a field that seems no return
14 Paragraph B
15 Paragraph C
16 Paragraph D
17 Paragraph E
Questions 18-20 Answer the questions below. Choose NO MORE THAN THREE WORDS AND/OR A NUMBER from the passage for each answer. Write your answers in boxes 18-20 on your answer sheet.
18 What is the life expectancy (in years) of Earth?
19 What kind of signals from other intelligent civilizations are SETI scientists searching for?
20 How many stars are the world’s most potent and enormous radio telescopes searching?
Questions 21-26 Do the following statements agree with the views of the writer in Reading Passage 2? In boxes 21-26 on your answer sheet, write
TRUE if the sataement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this
21 Alien civilizations may be able to help the human in our planet to cope with problems that seriously matter.
22 SETI scientists are trying to find a life form that resembles humans in many ways.
23 The Americans and Australians have joined together into cooperative research projects.
24 signals from several stars have already been obtained by SETI scientists
25 The NASA project was bombarded with criticism from some members of Congress.
26 If human being receives a signal from outer space, it would be important to respond as swiftly as possible.