What Is Scientific Discovery?

Science is divided into innumerable disciplines and subdisciplines, but within any single discipline the progress of science calls for the most diverse repertoire of activities - activities so numerous and diverse that it would seem that any person could find one to his or her taste. Outsiders often regard science as a sober enterprise, but we who are inside see it as the most romantic of all callings. Both views are right. The romance adheres to the processes of scientific discovery, the sobriety to the re­sponsibility for verification.

Histories of science put the spotlight on discovery. Everyone knows by what accident Fleming discovered penicillin, but only specialists can tell us much about how that discovery was subsequently put to the test. Everyone knows of Kekule's dream of the benzene ring, but only chem­ists can tell us why the structure of that molecule was problematic, and how and when it was finally decided that the problem had been solved. The story of scientific progress reaches its periodic climaxes at the mo­ments of discovery; verification is the essential but not very glamorous aftermath - the sorting out of facts that comes after the tale's denoue­ment and tells us that matters worked out all right (if only for a while, as in the story of phlogiston).

The philosophy of science has taken a very different tack than the discipline of the history of science. In the philosophy of science, all the emphasis is on verification, on how we can tell the true gold of scientific law from the fool's gold of untested fantasy. In fact, it is still the majority view among philosophers of science that only verification is a proper subject of inquiry, that nothing of philosophical interest can be said about the process of discovery.

In one respect the philosophers are right. What distinguishes science from the other works of the human imagination is precisely the insist­ence on testing, on subjecting hypotheses to the most intense scrutiny with the help of empirical evidence. If we are to distinguish science from poetry, we must have a theory of verification or confirmation that tells us exactly how to make that distinction.

But we believe that science is also poetry, and - perhaps even more heretical - that discovery has its reasons, as poetry does. However ro­mantic and heroic we find the moment of discovery, we cannot believe cither that the events leading up to that moment are entirely random and chaotic or that they require genius that can be understood only by con­genial minds. We believe that finding order in the world must itself be a process impregnated with purpose and reason. We believe that the proc­ess of discovery can be described and modeled, and that there are better and worse routes to discovery - more and less efficient paths.

With that claim, we open ourselves to attack from the other flank. Do we think it is possible to write books of advice to poets? Are we not aware that writing poems (and making scientific discoveries) is a creative process, sometimes even calling for genius? But we can avoid dangerous terms like " genius" by asking more modest questions. We can at least inquire into the sufficient conditions for making a poem (or a discovery). If writing poetry calls for creativity, it also calls for craft. A poet becomes, a craftsman (if not a creative poet) by long study and practice. We might aspire to distill and write down what a poet learns in this arduous ap­prenticeship. If we did that, we would have a book on the writing of poetry (there are some such on the library shelves). Perhaps its advice would take us merely to the level of superior doggerel, but we could determine that only after we had tested the advice by experiment - by writing poetry on its principles. Thus, the question of how poetry is writ­ten (or can or should be written) becomes a researchable question, one that can be approached with the standard methods of scientific inquiry. This is no less true of scientific discovery than it is of poetry. Wheth­er there is method in discovery is a question whose answer is open to scientific study. We may fail to find methods that account for discovery, or for the greater success of some would-be discoverers than of others, but we are free to look for them. And if we arrive at some hypotheses about them, then we must test these just as we test any other hypotheses in science.

 

Ответьте на вопросы по тексту:

1. How many social sciences are mentioned in the passage?

2. What are they?

3. What does the term behaviour sciences” mean?

4. What do the social sciences deal with?

5. What disciplines do the social sciences include?

6. What is the philosophy of science?

7. What is scientific discovery?

Текст 2

Art

Art, the use of skill and imagination in the creation of aesthetic ob­jects, environments, or experiences that can be shared with others. The term " art" may also designate one of a number of modes of expression conventionally categorized by the medium utilized or the form of the product; thus we speak of painting, sculpture, filmmaking, music, dance, literature, and many other modes of aesthetic expression as arts and of ill of them collectively as the arts. The term " art" may further be em­ployed in order to distinguish a particular object, environment, or expe­rience as an instance of aesthetic expression, allowing us to say, for ex­ample, that that drawing or tapestry is art.

Traditionally, the arts are divided into the fine and the liberal arts. The latter are concerned with skill of expression in language, speech, and reasoning. The fine arts, a translation of the French beaux-arts, are more Concerned with purely aesthetic ends, or, in short, with the beautiful. Many forms of expression combine aesthetic concerns with utilitarian purposes; pottery, architecture, metalworking, and advertising design may be cited as examples. It may be useful to conceive of the various arts as occupying different regions along a continuum that ranges from pure­ly aesthetic purposes at one end to purely utilitarian purposes at the oth­er. This polarity of purpose is reflected also in the related terms " artist" and " artisan", the latter understood as one who gives considerable at­tention to the utilitarian. This should by no means be taken as a rigid scheme, however. Even within one form of art, motives may vary wide­ly; thus a potter or a weaver may create a highly functional work - a salad bowl, for example, or a blanket - that is at the same time beautiful or he may create works that have no purpose whatever beyond being admired.

Another traditional system of classification applied to the fine arts. Wishes such categories as literature (including poetry, drama, story, and so on), the visual arts (painting, drawing, sculpture, etc.), the graph­ic arts (painting, drawing, design, and other forms expressed on flat surfaces), the plastic arts (sculpture, modeling), the decorative arts (enamelwork, furniture design, mosaic, etc.), the performing arts (theatre, dance, music), music (as composition), and architecture (often including interior design).

Physics. Period I (1900-1945)

The decisive events of the first period have been the conception of the Theory of Relativity and that of Quantum Mechanics. Rarely in the history of science have two complexes of ideas so fundamentally influ­enced natural science in general.

There are important differences between the two achievements. Relativity theory should be regarded as the crowning of classical physics of the eighteenth and nineteenth centuries. The special theory of relativity brought about a unification of mechanics and electromagnetism. These two fields were inconsistent with each other, when dealing with fast-moving electrically charged objects. Of course, relativity created new notions, such as the relativity of simultaneity, the famous mass-energy relation, the idea that gravity can be described as a curvature of space. But, altogether, the theory of relativity uses the concepts of classical phys­ics, such as position, velocity, energy, momentum, etc. Therefore it must be regarded as a conservative theory, establishing a logically coherent system within the edifice of classical physics.

Quantum mechanics was truly revolutionary. It is based on the recog­nition that the classical concepts do not fit the atomic and molecular world: a new way to deal with that world was created. Limits were set to the applicability of classical concepts by Heisenberg's uncertainty relations. They say 'down to here and no further can you apply classical concepts'. This is why it would have been better to call them 'Limiting Relations'. It would also have been advantageous to call relativity theory 'Absolute Theory', since it describes the laws of Nature independently of the systems of reference. Much philosophical abuse would have been avoided.

It took a quarter of a century to develop non-relativistic Quantum Mechanics. Once conceived, an explosive development occurred. With­in a few years most atomic and molecular phenomena could be under­stood, at least in principle. It is appropriate to quote a slightly altered version of a statement by Churchill praising the Royal Air Force: 'Never have so few done so much in so short a time'.

A few years later, the combination of relativity and quantum me­chanics yielded new unexpected results. P.A.M. Dirac conceived his relativistic wave equation which contained the electron spin and the fine structure of spectral lines as a natural consequence. The application of quantum mechanics to the electromagnetic field gave rise to Quantum Electrodynamics with quite a number of surprising consequences, some of them positive, others negative.

The positive ones included Dirac's prediction of the existence of an antiparticle to the electron, the positron, which was found afterwards in 1932 by C.D. Anderson and S.H. Nedermeyer. Most surprising were the predictions of the creation of particle - antiparticle pairs by radiation or other forms of energy and the annihilation of such pairs with the emis­sion of light or other energy carriers. Another prediction was the exist­ence of an electric polarization of the vacuum in strong fields. All these new processes were found experimentally later on.

The negative ones are consequences of the infinite number of degrees of freedom in the radiation field. Infinities appeared in the coupling of an electron with its field and in the vacuum polarization when the contri­bution of high-frequency fields is included. These infinities cast a shad­ow on quantum electrodynamics until 1946 when a way out was found by the so-called renormalization method.

Parallel to the events in physics during Period I, chemistry, biology, and geology also developed at a rapid pace. The quantum mechanical explanation of the chemical bond gave rise to quantum chemistry that allowed a much deeper understanding of the structure and properties of molecules and of chemical reactions. Biochemistry became a growing branch of chemistry. Genetics was established as a branch of biology, recognizing the chromosomes as carriers of genes, the elements of inher­itance. Proteins were identified as essential components of living sys­tems. The knowledge of enzymes, hormones, and vitamins vastly in­creased during that period. Embryology began to investigate the early development of living systems: how the cellular environment regulates the genetic program. Darwin's idea of evolution was considered in greater detail, recognizing the lack of inheritance of acquired properties. A kind of revolution was also started in geology by A. Wegener's concept of plate tectonics and continental drift. W. Elsasser's suggestion of eddy currents in the liquid-iron core of the Earth as the source of the Earth's magnetism was published at the end of Period I, and led to the solution o! a hitherto unexplained phenomenon.

The year 1932 was a miracle year in physics. The neutron was discovered by J. Chadwick, the positron was found by Anderson and Neddermeyer, a theory of radioactive decay was formulated by E. Fermi in analogy with quantum electrodynamics, and heavy water was discovered by H. Urey. The discovery of the neutron initiated nuclear physics; theatomic nucleus was regarded as a system of strongly interacting protons and neutrons. This interaction is a consequence of a new kind of force, the 'nuclear force', besides the electromagnetic and gravity forces, and the 'weak force' that Fermi introduced in his theory of radioactivity. Nuclear physics in the 1930's was a repeat performance of atomic quantum mechanics albeit on a much higher energy level, about a million times the energies in atoms, and based on a different interaction. It led to an understanding of the principles of nuclear spectroscopy and of nuclear reactions. Artificial radioactivity, and later nuclear fission and fusion were discovered with fateful consequences of their military applications. One of the most important insights of nuclear physics in Period I was the explanation of he sources of solar and stellar energy by fusion reactions in the interior of stars.

What is most striking was the small number of experimental and theoretical physicists who dealt with the new developments. The yearly Copenhagen Conferences, devoted to the latest progress in quantum mechanics and relativity, were attended by not more than fifty or sixty people. There was no division into specialities. Atomic and molecular physics, nuclear physics, condensed matter, astronomy, and cosmology were discussed and followed up by all participants. In general, every­body present was interested in all subjects and their problems. Quantum mechanics was regarded as an esoteric field; practical applications were barely mentioned.

Most characteristic of pre-World-War II science were small groups и ml low costs of research, primarily funded by universities or by foundations and rarely by government sources. Foundations had a great influence on science. Some of the impressive developments of the thir­ties in biology can be traced to the decision of the Rockefeller Foun­dation under Warren Weaver to support biology more than other sciences.

 

Ответьте на вопросы по тексту:

1. What is art?

2. What is the difference between an artist and an artisan?

3. How many systems of classification exist?

4. What was so revolutionary about the Quantum Mechanics?

5. What other sciences developed rapidly during the first period?

6. What was the beginning of nuclear physics?

7. Why is the Theory of Relativity the integral part of classical physics?

Текст 3

Physics. Period II (1946-1970)

The time from 1946 to about 1970 was a most remarkable period for all sciences. The happenings of World War II had a great influence, especially on physics. Physicists became successful engineers in some large military research and development enterprises, such as the Radi­ation Laboratory at MIT, the Manhattan Project, the design of the proximity fuse, to the astonishment of government officials. Scientists who previously were mainly interested in basic physics, conceived and constructed the nuclear bomb under the leadership of one of the most 'esoteric' personalities J.R. Oppenheimer, E. Fermi constructed the first nuclear pile, E. Wigner was instrumental in designing the reactors that produced plutonium, J. Schwinger developed a theory of waveguides, essential for radar. It was more than that: some of these people were excellent organizers of large-scale research and development projects having good relations with industry, such as the aforementioned mili­tary projects.

The progress of natural science in the three decades after the war was outstanding. Science acquired a new face. It would be impossible in the frame of this essay to list all the significant advances. We must restrict ourselves to an account of a few of the most striking ones with­out mentioning the names of the authors. The choice is arbitrary and influenced by my restricted knowledge. In quantum field theory: the invention of the renormalization method in order to avoid the infini­ties of field theory that made it possible to extend calculations to any desired degree of accuracy. In particle physics: the recognition of the quark structure of hadrons establishing order in their excited states, the existence of unstable heavy electrons and of several types of neutri­nos (two were discovered in Period II, the third in the next period), the discovery of parity violation in weak interactions, and the unification of electromagnetic and weak forces as components of one common force field. In nuclear physics: the nuclear shell model, an extensive and detailed theory of nuclear reactions, and the discovery and analy­sis of rotational and collective states in nuclei. In atomic physics: the Lamb shift, a tiny displacement of spectral lines which could be ex­plained by the new quantum electrodynamics, the maser and the laser with its vast applications, optical pumping, and non-linear optics. In condensed matter physics: the development of semiconductors and tran­sistors, the explanation of superconductivity, surface properties, and new insights into phase transitions and the study of disordered sys­tems. In astronomy and cosmology: the Big Bang and its consequences for the first three minutes of the Universe, the galaxy clusters and the 3⁰ radiation as the optical reverberation of the Big Bang, and the dis­covery of quasars and pulsars. In chemistry: the synthesis of complex organic molecules, the determination of the structure of very large molecules with physical methods such as X-ray spectroscopy and nuclear magnetic resonance, the study of reaction mechanisms using molecular beams and lasers. In biology: the emergence of molecular biology as a fusion of genetics and biochemistry, the identification of DNA as carrier of genetic information followed by the discovery of its double helical structure, the decipherment of the genetic code, the proc­ess of protein synthesis, the detailed structure of a cell with its cellular organelles, the study of sensory physiology investigating orientation of homing birds and fish. In geology: the development and refinement of plate tectonics using newly available precision instruments, and the discovery of ocean floor spreading by means of sonar and other elec­tronic devices.

Many of the new results and discoveries were based upon the in­strumental advances in the field of electronics and nuclear physics due to war research. One of the most important new tools decisive for all Huences was the computer. The development and improvements of this tool are perhaps the fastest that ever happened in technology.

Important changes in the social structure of science took place, es­pecially in particle physics, nuclear physics, and astronomy. The rapid developments in these fields required larger and more complex acceler­ators, rockets and satellites in space, sophisticated detectors, and more complex computers. The government funding was ample enough to provide the means for such instruments. The size and complexity of the new facilities required large teams of scientists, engineers, and tech nicians, to exploit them. Teams of up to sixty members were organized, especially in particle physics. (In Period III the sizes of teams reached several hundred.) Other branches of science, such as atomic and condensed matter physics, chemistry and biology, did not need such large groups; these fields could continue their research more or less in the old-fashioned way in small groups at a table top with a few exceptions, for example, in the biomedical field, where larger teams are sometimes necessary.

The large teams brought about a new sociology. A team leader was needed who had the responsibility not only for intellectual leadership, but also for the organization of subgroups with specific tasks, and for financial support. A new type of personality appeared in the scientific community with character traits quite different from the scientific lead­ers of the past. The participation in these large teams of many young people, graduate students and post-graduates, creates certain problems. It is hard for them to get recognition for their work, since their contri­butions get lost in the overall effort of the team. In order to attract young researchers to join big teams, the subgroups must have some independent initiative for well-defined tasks, so that the performers of these tasks can claim credit for their work.

The development of huge research enterprises caused a split in the character of science into 'small' science and 'big' science. Small science consists of all those fields that can be studied with small groups at relatively small cost, whereas big science is found in particle phys­ics, in some parts of nuclear physics and astronomy, in space explo­ration, and in plasma physics. There is also big science in condensed matter physics and in biology: the use of synchrotron radiation in the former and the human genome project in the latter. Big science needs large financial support, so that the question of justification plays a decisive role.

 

Ответьте на вопросы по тексту:

1. What is the difference between “big science” and “small science”?

1. What weapons and equipment which are products of science were used in the Second World War?

2. Why was science supported after the war and who supported it?

3. Which scientific achievements mentioned by the author are connected to some extent with future profession?

4. What were many of the new results and discoveries based upon?

5. What was one of the most important new tools decisive for all sciences?

What did the development of huge research enterprises cause?

 

Вариант 4

Текст 1

Physics. Period III (from 1970 to the end of the 20th century )

Basic and applied science are interwoven; they are like a tree whose loots correspond to basic science. If the roots are cut, the tree will degenerate.

Another intellectual value is the role that basic science plays in the education of young scientists. It fosters a kind of attitude that will be most productive in whatever work the students will finally end up with. Experience has shown that training in basic science often produces the best candidates for applied work. Basic science also has ethical values. It fosters a critical spirit, a readiness to admit 'I was wrong', an antidogma attitude that considers all scientific results as tentative, open for improvements or even negation by future developments. It also engenders a closer familiarity with Nature and a deeper understanding of our position and role in the world nearby and far away.

Much too little effort is devoted by scientists to explaining simply and impressively the beauty, depth, and significance of basic science, not only its newest achievements, but also the great insights of the past. This should be done in books, magazine articles, television programmes, and in school education. The view should be counteracted that science is materialistic and destroys ethical value systems, such as religion. On the contrary, the ethical values of science should be emphasized. Final­ly, it would help to point out the positive achievements of applied sci­ence, the contribution to a higher standard of living, and the necessity of more science to solve environmental problems.

It looks as if we are facing a more pragmatic era, concentrating on applied science. Perhaps the end is nearing of the era of one hundred years full of basic discoveries and insights under the impact of the The­ory of Relativity and that of Quantum Mechanics. Even so, we will always need basic research based on the urge to understand more about Nature and ourselves.

Lasers

The story of the laser, a device that produces a powerful beam of very pure light able to slice through metal and pierce diamond, began when physicists were unraveling the secrets of the atom.

In 1913 the Danish physicist Niels Bohr pointed out that atoms can exist in a series of states and each state has a certain energy level. Atoms cannot exist between these states but must jump from one to another. An atom at a low-energy level can absorb energy to reach a high-energy level. When it changes from a high to a low-energy level, it gives out the surplus energy in the form of radiation. If the radiation is given in the form of visible light, the light will all be of the same wavelength (that is, colour). The atom at a high-energy level may emit this radiation spontaneously. Or, as the German-born physicist Albert Einstein pointed out in 1917, it may be triggered into doing so by other radiation. It is on this latter proc­ess, called the stimulated emission of radiation, that the laser depends.

Stimulated emission was not thought useful until the early 1950s, when the physicists C.H. Townes in the United States and N.G. Basov and A.M. Prokhorov in Russia suggested how it could be used to am­plify microwaves - electro-magnetic radiation with very short wave­lengths outside the visible spectrum - and used, for example, in radar.

In 1953 Townes built the first device to amplify microwaves using stimulated emission. He used ammonia gas as the source of high-ener­gy (or 'excited') atoms. Later it was found that a ruby crystal could be used as well. The device became known as the maser, from the initials of 'Microwave Amplification by Stimulated Emission of Radiation'. For their pioneering work on masers Townes, Basov and Prokhorov were jointly awarded the 1964 Nobel Prize for physics.

In 1958 Townes and his brother-in-law, Arthur Schawlow, out­lined a design for an optical maser - that is one producing visible light rather than microwaves. This idea gave birth to the laser - 'Light Am­plification by Stimulated Emission of Radiation'.

Two years later the American physicist Т.Н. Maiman built the first laser, using a cylindrical rod of artificial ruby whose ends had been cut and polished to be exactly flat and parallel. It produced brief, penetrat­ing pulses of pure red light with 10 million times the intensity of sun­light. The pulsed ruby laser is still the most powerful type of laser. The emergent laser beam differs from an ordinary light beam m several respects. Whereas ordinary light is made up of several wave lengths (colours), the laser light consists of a single wavelength. And whereas ordinary light spreads out from its source in all directions, a laser beam is almost perfectly parallel.

The ruby laser was followed, also in 1960, by a gas laser, developed by D.R. Herriott, A. Javan and W.R. Bennett at Bell Telephone Lab oratories in the United States. Gas lasers are not as powerful as rub\ lasers but emit a continuous beam that can be left on like a torch, m contrast to the ruby laser which emits its light in very short pulses.

The purity of wavelength and straight-line beam of lasers have main applications. In industry the heat of the beam is used for cutting, boring and welding. In tunnelling, lasers guide the boring machines on a perfectly straight line; the laser beam remains accurately focused over long distances. Even after travelling a quarter of a million miles from the earth to the moon, a laser beam would have spread only a few miles.

Using the laser in a way similar to radar - sending out a light pulse and timing when its reflection ('echo') returns - provides a very accu­rate method of distance measurement in space as well as on earth. By this means the distance to the moon at any time can be calculated to the nearest foot. Lasers are used in telecommunications by FIBRE OPTICS, and create three-dimensional photographic images in HOLOGRAPHY.

In medicine, lasers are used in eye surgery to weld back in place a detached retina - the light-sensitive screen at the rear of the eye-ball. The heat of a ruby laser pulse causes a 'burn' which, in healing, devel­ops scar tissue that mends the tear. Lasers can be used to treat glauco­ma, a condition in which pressure builds up in the eye-ball. The laser punches a tiny hole in the iris to relieve the pressure, the patient feeliny no more than a pinprick. Laser scalpels are also coming into use. They make a fine incision and at the same time cauterise (heat seal) the blood vessels, reducing bleeding.

Lasers are applied in art as well. It is possible to mention the fa­mous concert with laser effects of J.M. Jarrenear Egyptian pyramids at the beginning of the 3rd millennium.

Holography

A holographic image is a three-dimensional photograph of an ob­ject; but unlike a photograph made by a camera, it is seen as a ghostly image in space behind or in front of a photographic plate. On the plate is a hologram - a pattern of light and dark areas formed by beams of laser light. When pure light such as that from a laser is shone through the developed plate, the observer sees an exact three-dimensional image of (lie object beyond the plate. As the observer moves round the image, it changes its aspect as the object would have done. Using a curved plate, the top and bottom of an object can also be seen. In a development of holographic technique, it is possible to create an image that appears be­tween the observer and the plate.

Holography became practical after the laser, a source of sufficiently pure light, was invented in 1960. It was developed in 1963 by two Uni­versity of Michigan scientists, Emmett Leith and Juris Upatnieks. Ho­lography is used in industrial research to make three-dimensional pic­tures of rapidly moving objects such as turbine blades.

 

Ответьте на вопросы по тексту:

1. What is the role of basic science?

2. What is the role of applied science?

3. What is the connection between basic science and applied science?

4. What is the laser?

5. What did the Danish physicist Niels Bohr point out in 1913?

6. When did Townes build the first device to amplify microwaves using stimulated emission?

7. Who built the first laser?

 

Текст 2

An Oblique View of Climate.

One explanation for certain patterns of glaciation in the past invokes a large and comparatively swift decline in the tilt, or obliquity, of the Earth. A provocative hypothesis provides a mechanism by which such a decline could have occurred. How do variations in Earth's orbital and rotational geometry influence climate? Does the climate system, in turn, influence rotation? We all experience the radiative and thermal cycles of night and day, winter and summer. So we are familiar enough with the influence of Earth's rotational and orbital motions on the spatio-temporal pattern of light and temperature to make it easy to imagine how long-term variations in the orbit and rotation would affect climate. Much recent data and model­ling help confirm that principle.

Somewhat further removed from human experience is the notion hat climatic change itself could influence the rotational dynamics of the Earth. The basic idea is quite simple, and involves feedback between Earth's obliquity (the angular separation between the spin pole and or bit pole around the Sun) and its oblateness (departure from spherical symmetry).

First, however, it is useful to recall how orbital and rotational geometry influences climate. The main seasonal cycle is primarily determined by the orientations of the spin axis, and only secondarily by the eccen­tricity of the orbit. Currently, perihelion (Earth's closest approach to the Sun) occurs several weeks after winter solstice in the Northern Hemi­sphere (shortest daylight). However, neither the orbit nor the spin axis in fixed in space. Gravitational interaction with other planets (principally Venus) causes the shape and orientation of the orbit to change on a vari­ety of timescales, with the dominant period near 70, 000 years (70 kyr) and subsidiary oscillations at periods ranging from 50 kyr to 1.9 million years (Myr).

Gravitational torques exerted by the Moon and Sun on the oblate igure of the Earth cause the spin axis to precess with a period of 25.8 kyr. If the orbit plane were fixed, the path of the spin pole would be a circle centred on the orbit pole, keeping the obliquity fixed. However, because the orbit is also precessing, the obliquity oscillates by ± 1° about its present value of 23.5°, with a period of 41 kyr. These obliquity oscilla­tions modulate the seasonal and latitudinal pattern of incident radiation, and thus affect climatic variations.

How then does climate change influence rotation? One way is to change the spin precession rate by changing the oblateness of the Earth's! mass distribution. During major glacial cycles, mass transport between the oceans and ice sheets is sufficient to change the precession rate by about 1%. The net change includes accumulation of continental ice and partially compensating subsidence of the Earth's surface. If the obliquity and oblateness oscillations are exactly in phase, there is no long-term net effect. But if the oblateness lags behind the obliquity, there will be a secular change in obliquity, with a rate that depends on the amplitude and phase of the oblateness variations.

The long-term stability of Earth's climate system is an important question, but one that remains elusive. Despite progress in short-term weather prediction (based on improved quality and quantity of observa­tions, faster computers and better understanding of the system dynam­ics), our understanding of long-term climate dynamics is still quite primitive. Part of the problem, of course, is that the further back into the past we go, the more difficult it is to reconstruct which path the climate sys­tem has followed. When we still don't know what has happened, how can we reconstruct why? In this situation, the role of theoretical models is not so much to explain what actually happened as to broaden our perspectives on the types of behaviours that might have occurred. As always, more work is needed. In this case, distinguishing between the two competing climatic possibilities (equatorial versus global glaciation) should be easily resolvable by searching for contemporaneous high-latitude and low-latitude glacial deposits. Reconstructing an unambiguous obliquity history will be more of a challenge.

The Dead Sea.

There is such a sea in a country with a very ancient history. This, of course, is the famous Dead Sea in Palestine. Its water is so salty that nothing can live in it. Due to the local scorching rainless climate the surface water evaporates. Note, though, that it is only water as such which evaporates. The salt dissolved in it remains making the water still saltier. This explains why the Dead Sea has a salt content not of two or three per cent (by weight) as most seas and oceans but of 27 per cent and even more - the salt content increases with depth.

Thus a quarter of the Dead Sea is made up of the salt dissolved in its water. This sea has been estimated to have a total of 40 million tons of salt. The water of the Dead Sea exhibits a very curious property precisely because of its saltiness. Since it is much heavier than ordinary sea water, you will never sink in it because your body is much lighter.

We weigh noticeably less than an equal volume of very salty water. Hence, according to the law of buoyancy we would never drown in the Dead Sea; we would pop up to the surface just like an ordinary egg in salt water - which, incidentally, sinks in fresh water.

Mark Twain, the famous American humorist, visited the Dead Sea, and in one of his books he wittily describes the unusual sensations that he and his companions experienced when they bathed in it.

" It was a funny bath. We could not sink, one could stretch himself at full length on his back, with his arms on his breast, and all of his body above a line drawn from the corner of his jaw past the middle of his side, the middle of his leg and through his ankle-bone, would remain out of water. He could lift his head clear out if he chose... You can lie comfort­ably on your back, with your head out, and your legs out from your knees down... you can sit, with your knees drawn up to your chin and your arms clasped around them, but you are bound to turn over present­ly, because you are top-heavy in that position. You can stand up straight in water that is over your head, and from the middle of your breast up­ward you will not be wet. But you cannot remain so. The water will soon float your feet to the surface. You cannot swim on your back and make the progress of any consequences, because your feet stick away above the surface, and there is nothing to propel yourself with but your heels. If you swim on your face, you kick up the water like a sternwheel boat. You make no headway. A horse is so top-heavy that he can neither swim nor stand up in the Dead Sea. He turns over on his side at once."

The water of the Kara Bogaz Gol, a gulf in the Caspian, and of Lake Elton - with its 27-per-cent salt content - exhibits the same unusual prop­erties.

 

Ответьте на вопросы по тексту:

1. How does rotation influence climate?

2. How does climate influence rotation?

3. What is the modern understanding of long-term dynamics?

4. What sea is spoken about?

5. What helps people not to sink?

6. Why is Dead Sea the unique sea?

7. What sensations do people experience bathing in the Dead Sea?

 

Текст 3

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