Учебное пособие Издание второе, переработанное и дополненное Москва Астрель • act 2005 удк 811. 111 (075. 8) Ббк 81. 2 Англ-923 К48 Компьютерный дизайн обложки студии «Дикобраз»
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We still don't know where ... .
We don't know yet how ....
Until now we know almost nothing about....
We still lack precise knowledge of... .
Think and say a few words about:
the fate of a finite small universe;
lack of scientific facts in favour of this scenario;
the fate of the intellectual beings.
HOMEWORK
(to be done in writing)
1. Translate into Russian.
Alongside the familiar four fields mentioned above, the unified theories include another kind of fields, so-called scalar fields which have some interesting and unusual properties.
All the four known forces of nature are vector fields having both magnitude and direction at every point of space.
A scalar field has only magnitude and we might think of a property such as temperature or density of a liquid as being represented by a scalar field associated with each point through the volume of the field.
A uniform homogeneous scalar field is almost unobscrvable but filling the whole universe it effects the properties of all elementary particles.
The idea of scalar fields is useful in constructing unified theories because it helps to determine masses of elementary particles and the way they interact with other particles.
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READING (6A)  There are a few hypotheses concerning the structure and origin of the Universe. One of them will be presented in the passage below. Before reading the passage look at the block-scheme where some of the problems in studying the Universe are presented. Think what you know about each ofthe problems. Then read the passage. Find the ideas that were not known to you before reading. Origin —> time/composition/evolution The Universe <^ > Structure —> matter distribution Matter —> principal constituents THE UNIVERSE IS A HONEYCOMB What docs our Universe look like? Docs it conform to the popularly held concept of a black abyss with islands of galaxies dispersed through it with no boundaries or shape? Apparently, it does not. "The Universe has a clear-cut •a met lire," says astronomer D.Sc. Jaan Einasto, who heads the sector of the physics ofgalaxicsat the Institute of Astrophysics and Atmospheric Physics ol'ihe Estonian Academy of Sciences. Imagine a honeycomb! This is not a hypothesis! Einasto says he has the evidence to prove it. What do wc know about the Universe? First, it came into being as a result of the " Big Bang" some 20 billion years ago. This creation was a fantastically quick, but precisely accurate process. In moments, the composition of all matter was formed: electrons, neutrons, protons, barions and other particles. Through subsequent expansion, this matter, which originally was in a state of Miperdcnsc and superhot plasma, cooled and condensed into the galaxies, •aars and planets.... Second, the "Big Bang" process continues. We arc still living in an expanding Universe. This is proved by the galaxies "running" away in different directions. What was there before the bang, before this "beginning of all beginnings"? Science still has no answer, because all the known laws of physics only became meaningful instants after the bang. What is in store? Shall wc continue to infinitely expand, or will the Universe, ■ ii some point, begin to contract again? The answer lies hidden in the matter contained in the Universe. What does the "honeycomb" have to do with the Universe? — The structure of the Universe discovered explains a great deal. At the beginning and in the first stage of expansion, matter was distributed uniformly. Scientists came to understand this in the 60s, when the relic electromagnetic radiation which lemaincd since the blast was discovered. This radiation originally had the same temperature as matter and, therefore, expanded along with it. But now it has cooled off, just as matter itself, and the temperature of this radiation (weak ladiowaves) that pierces space is the same everywhere — something about 3° Kelvin (approximately —270°C). In other words uniformity is a major property ol'thc Universe. And yet, at the very beginning, there were some processes which led to the formation of stars, galaxies, accumulations, i.e. to the condensation of matter. I hese non-uniformities show that a pattern something like a gigantic honeycomb with a diameter of 100-200 megaparsec (a megaparscc is 30 million light years) has been created. The "walls" of the cells are made of accumulations of galaxies, and where they meet, the accumulations are more numerous and the radiation in the X-range is more intensive. In other words, the comb is a real structure. How is it that the freely moving galaxies evolved into this particular lormation? Is this chance occurrence? —The "rigidity" of the structure indicates that the "combs" themselves appeared initially and then galaxies. How can this paradox be explained? — Most likely the "combs" came into being when the galaxies were still in theirgascous state. To use an analogy, imagine two gas bubbles expanding towards each other. The more they expand, the greater the compression between them. At a certain moment they collide. This is when a certain flat formation originates between them, which Academician Yakov Zel'dovich called a "pancake" in his hypothesis which led to the idea of the cellular structure ofthe Universe. The joining of a multitude of these "pancakes" represents the walls of the gigantic "combs" in which the galaxies have accumulated. Ifthere are "combs", one would assume there should be "honey"? Could it be that all the matter of the Universe went into the "walls" and the cells themselves arc empty? — There is no visible matter there. But it is very difficult to conceive of a physical process which would absolutely cleanse these tremendous cavities of everything. So, perhaps, we just don't sec this substance. We have to assume the existence of some invisible mass whose attraction influences the movement of galaxies, thus maintaining the structure ofthe "combs". This mass should be many times greater than the visible matter in the areas of accumulation, i.e. in the "walls". The density of the "invisible" substance should also be far higher. Do scientists mean the neutrinos? — Yes, they do. Until recently it has been believed that the neutrino has no rest mass and moves with the speed of light, without interacting with anything in its path. But the sensational findings of a group of investigators led by V. Lyubimov (the Institute of Experimental and Theoretical Physics) show that the rest mass ofthe neutrino is larger than zero. This means that the neutrino, which literally floods the Universe is, regardless of its negligible mass, the principal matter of the Universe and hence the principal part of its entire mass. The conventional matter in the Universe comprises but only three percent. It is most likely that the "combs" themselves and the entire cellular structure ofthe Universe is the result of their force of gravity. The future ofthe Universe is in its structure. We have to know whether it is finite. Within a "finite" Universe, the galaxies, after thousands of millions of years have passed, will inevitably begin a reverse process, and expansion will give way to contraction. Our Universe will again become a "dot" and everything will be repeated. And so on for ever and ever... • Find English equivalents for the following Russian phrases. общепринятое представление; масса покоя; буквально наводняет; сверхплотная плазма; распределялась однородно; гигантские соты; основное свойство; со времени взрыва; в мгновение ока; первая стадия расширения; на смену расширению придстежатие; навсегда; во много раз больше; появилась первоначально; невзирая на пренебрежимо малую массу; неизбежно начнет обратный процесс; всего ли:.л> 3%; общепринятая концепция; черпая бездна • Mutch each word in Л with its synonym in B. Л. relic, evidence, moment, to reverse, to conform, multitude, to occur, to come into being H. instant, to correspond, something surviving from the past, a great number, to turn in an opposite direction, to originate, proof, to happen • Match each word in Л with its antonym in B. Л. expansion, meaningful, conventional, relic, rigidity, to contract, to disagree B. to expand, uncommon, modern, flexibility, meaningless, contraction, to conform • Complete the sentences with information from the text or any other sources. I. The passage deals with... .
• Think and find arguments lo prove that:
• What would you say of our current knowledge of
CLASSWORK RF.ADING (6B) • Read the passage (4 min.) and answer the questions.
SCENARIO 1. A FINITE SMALL UNIVERSE The universe can only be finite if there is enough matter inside it to curve space-time so that it closes on itself. We do not know whether there is enough matter to do this. *We do know that the amount of visible matter is at least one-tenth as much as we calculate is necessary for this to happen — and that there may be enough matter that is presently invisible to make up the difference. Some of this invisible matter may exist in the form of neutrinos, neutral particles that interact only very weakly. Neutrinos exist in the universe in large enough numbers so that if they have a small mass they could provide enough energy density to close the Universe. *The same may be true about other, presently unknown, subatomic particles. If there is enough matter present to make the universe finite then there is also enough to cause the expansion to eventually stop and be replaced by a contraction. If this is the actual condition in our universe then we would like to know when this changeoverWxW occur. We cannot say this precisely, because of lack of information about the actual amount of matter in the universe, but we can say that it will not happen for a longtime, probably at least as long as the time since the Big Bang — 10 to 15 billion years. *It is usually assumed that the size of a finite universe would only be a few times larger than the size of that part we are presently aware of, about lO" kilometers in radius. Yet there is no good reason for believing this cither on the basis of observation or of theoretical cosmology. If it were true, then the universe would begin contracting at a time in the future that is not much longerthan it has already lived, so that our universe could be said to be middle-aged. In this scenario, which I call the finite small universe, the future of the universe does not depend much on the details of particle physics. We know that nothing much can happen to change the properties and distribution of the subatomic particles in the universe over the next few tens of billions of years, until the density of matter becomes very high through the prolonged contraction of space-time. For example, we know that if protons are unstable, their lifetime isat least 10-'"timcsgrcatcrthan the present age ofthe universe, sothat in the scenario under discussion, very few protons would have time to decay before I he universe contracts back to the Big Crunch. Even the behaviour of much larger constituents of the universe, such as many stars and galaxies, would remain pretty much as they are now during the remaining expansion time for lhe universe. The study of particle physics as it relates to the future of the finite small universe is interesting only at two points: when the expansion is reversing to a collapse, and when the collapse reaches its final stages. Long before the collapse reaches its final stages, any of the large material structures such as stars, planets and their inhabitants that exist in the current universe will have been destroyed by the increase in temperature and density I hat will take place duringthe period of contraction. Perhaps the most significant question about any finite universe is whether there is some way that intelligent beings could avoid being caught up in the eventual Crunch. Even optimistic writers, such as the American physicist Freeman Dyson, have asserted that this is probably hopeless. Yet I think that even in this scenario, the ultimate future for intelligence may not be completely bleak (мрачный). The basis for my optimism is the notion that the space-time that we inhabit is not all there is, a view that a number of physicists have considered seriously, both for finite and infinite space-times. *For example, it is intellectually irresistible to think of a finite universe as embedded in some larger universe, with a higher number of dimensions, just as the two-dimensional, finite surface of the earth lies in ilnee-dimensional space. *Indeed, the mathematical description of a finite universe makes use of such an embedding into a five-dimensional space-time. I nis approach to the idea of extra dimensions is different from the one discussed previously, because here the extra dimensions are not tiny in extent. *Conceivably, both types of extra dimensions might exist. If there are large extra dimensions we are free to speculate that other realms lie in this larger universe, and that their evolution need not parallel that of our own. At present, this is no more than a science-fiction plot. However, if there are more dimensions than those wc know, or four-dimensional space-times in addition to the one we inhabit, then I think it very likely that there are physical phenomena that provide connections between them. *lt seems plausible that if intelligence persists in the universe, it will, in much less time than the many billions of years before the Big Crunch, find out whether there is anything to this speculation, and if so how to take advantage of it.
I. Until now we don't know whether.... |
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