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Fstablisled 18-17 AN February 1.970 Volume 222 Number 2 ARTICLES 13, THE ASSESSMENT OF TECHNOLOGY, by Ilarvey Brooks and Raymond Bowers How can technology be fostered while avoiding undesirable effects? 22 LARGE-SCALE INTEGRATION IN ELECTRONICS, by F. C. Heath Thousands Of circuit elements can now be simultaneously made onasingle "chip." 32 THE AFAR TRIANGLE, by Maroon Tazieff A fantastic landscape beside the Red Sea appears to be an ocean in the making. 52 TIIE PHYSIOLOGY OF IIICII ALTITUDE, by Raymond J. Hock How do men and other animals adapt to permanent residence above 6,000 feet? 68 PARTICLES THAT GO FASTER THAN LIGHT, by Gerald Feinberg They have not been discovered, but there are reasons to believe they may exist. 82 PIIOSPIIENES, by Gerald Oster The patterns eve see when we close our eyes are clues to how the eye works. 88 THE RANGELANDS OF THE WESTERN U.S., by R. Alerton Love These vast tracts normally reserved for grazing can have other humane uses. 98 CELL SURGERY BY LASER, by Michael W. Berns and Donald E. Rounds A tiny, intense spot of light is used to probe the physiology of the living cell. 9 10 42 112, 116 122 126 LETTERS 50 AND 100 YEARS AGO THE AUTHORS SCIENCE AND TIIE CITIZEN MATHEMATICAL GAMES TIIE AMATEUR SCIENTIST BOOKS BIBLIOGRAPHY ? OF EDITORS Gerard PICT (Publisher), Dennis Flanagan (Editor), Francis Bello (Associate Editor), Philip Morrison (Book Editor), Jonathan B. Piel, John Purcell, James T. Rogers, Armand Schwab, Jr., C. L. Stong, Joseph \t 'isnovsky ART DEPARTMENT Jerome Snyder (Art Director). Samuel L. I toward (Associate Art Director) PRODUCTION DEPARTMENT Richard Sasso (Production Manager), Arnold P. Shindler and Doreen Trager (Assistant Production Managers), Pauline Ray COPY DEPARTMENT Sally Porter Jenks (Copy Chief), Sally S. Fields, Dorothy Patterson, Julio E. Xavier GENERAL MANAGER Donald II. Miller, Jr. ADVERT151NO MANAGER Allan Wittman ASSISTANT TO THE PUBLISHER Stephen ..Fischer FV5115/tEA Ly^, ,tVyMME( YaI.A~S~Ptllt T`P![1 A1~N;rlVOYV / ARD i1CN?L IDILR V' INC. A. I V-VG78, 0RIiE000100030001-9 OND?CLA.SS MAIL BY IHE PC,51 OFFICE O0AR1MENT, OTSAWA, CANADA, AND FOR PATMENS OF POSTAGE IN CASH. SUBSCRIPTION F.555,310 FER YEAR. ` %ige 2000/08/10 : CIA-RDP96-00WR000100030001-9 Approved For Rel a 2000/08/10C1ARDP96-007t00010003001=.9 Approved For Re1eaase,`2000108/10, `CIA-RbP9 Efforts to etect such particles, named tucllyo s, have yielded only 71e~;atice results. C07111'(11) '"[0 conrrno71 belief. however, their existence would not be inconsistent with the theory of relativity by Gerald Feinberg unce the formulation of the special Stheory of relativity by Einstein in 1905 and its subsequent verifica- tion by innumerable experiments, physi- cists have generally believed that the speed of light in a vacuum (about 300,- 000 kilometers per second) is the maxi- nium speed at which energy or informa- tion can travel through space. Indeed, Einstein's first article on relativity con- tains the statement that "velocities great- er than that of light... have no possibil- ity of existence." The basis of Einstein's conclusion was his discovery that the equations of rela- tivity implied that the mass of an object increases as its speed increases, becom- ing infinite at the speed of light (which is usually denoted c). Since the mass of a body measures its resistance to a change of speed, when the mass be- comes infinite the body cannot be made to go any faster. Stated somewhat differ- ently, the relation between energy and speed implied by relativity is such that as the speed of a body approaches c its energy becomes infinite. Since this ener- gy must be supplied by whatever is ac- celerating the body, an infinite source of energy would be needed to speed up a body to the speed of light from any low- er speed. No such infinite energy source is available, and so it is impossible to make a body go from less than c to c. Furthennore, if a body could some- how be made to go from a speed less than c to one greater than c, the same relativity equations imply that its energy and momentum would become imagi- nary numbers, that is, numbers contain- ing a square root of a negative number. This situation does not seem to have any physical meaning. Objects with imagi- nary energy clearly cannot exchange energy with objects having real energy and hence cannot affect them. Accord- ingly, such objects could not be detected by real instruments, and can be said not to exist. Within the context in which Einstein worked, where the properties of objects varied continuously and where the creation of new objects was not con- sidered, it therefore seemed a logical conclusion that no form of energy, and hence no matter, could travel faster than light. With the development of subatom- ic physics, however, the context has changed considerably. We now know that the subatomic particles can easily be created or destroyed, and that in their mutual interactions their energies and other properties change discontinuously, rather than in the smooth way envi- sioned in classical physics. Therefore one can imagine the creation of particles al- ready traveling faster than light, and so avoid the need for accelerating them through the "light barrier" with the at- tendant expenditure of infinite energy. In addition, one can consistently re- quire that such particles always travel at speeds greater than c, which obviously cannot be the case for known particles. If one assumes these conditions, there is no problem in satisfying the require- ment that the particles carry real en- ergy and momentum. This can be done mathematically by allowing a certain constant that appears in the relation be- tween energy and speed to be an imagi- nary number, rather than a real number as it is for ordinary particles [see top il- lustration on next two pages]. This con- stant is usually known as the rest mass, because for ordinary objects, which can be slowed to rest, it gives the value of the object's mass when at rest. For the hypothetical faster-than-light particles, which can never be brought to SEARCH FOR TACIIYONS led the author and his colleagues at Columbia University to scrutinize thousands of bubble chamber photographs such as the one on the opposite page for indirect evidence of the occurrence of neutral tachyons among the by-products of cer- tain subatomic interactions. The photographs, which were originally made at the Brook- haven National Laboratory for another experiment, were analyzed by means of the "miss- ing mass" method. In this approach the energy and momentum of the charged particles in the reaction are measured directly from the configuration of the tracks they make in the bubble chamber. Although neutral particles are usually not observed directly, it is possible to tell from the values measured for the charged particles whether or not any neutral parr ticles have been produced, and also what the missing mass of these particles is. In this case a negative K meson (K-) was allowed to come to rest and be captured by a proton in the hydrogen bubble chamber (see diagram at left). One neutral particle, a lambda hyperon (Al), was produced and was detected through its decay into two charged particles, a nega- tive pion (--') and a proton tp+). In order to conserve energy and momentum, another neutral particle (xa) had to be produced in this reaction, but the experimenters were able p ro vedFor Release`I2bfbiofo '! 'a` ' 1 =I ~ ~='b$il'${f 'O ~d d Pt'9(t) EQUATIONS OF RELATIVITY pertinent to a discussion of the possible existence of tachyons are shown on these two pages. The relation between energy and speed that must be satisfied by any object obeying the special theory of relativity is given by equation a, where E is the energy of the object, v is its speed and c is the speed of light. The quantity in is known as the rest mass of the ob- ject and is related to the energy E0 that the object has at rest by equation b. For a body traveling faster than light v-'/c" is greater than one; consequently the quantity under the square-root sign in equation a is negative, and the denominator of the quantity that is equal to E in the same equation is an imaginary number (that is. a number containing a square root of a negative number). In order to make E a real number one must choose in to be an imaginary number, say m= As long as the object always travels at more than the speed of light, its energy, which can be written in the form shown in equation c, will then be real, because (v'/c) - I rest, this constant is not directly measur- trast, an increase in speed results in a able, and there is no need for it to be decrease in energy. Hence a tachyon real. The square of the rest mass, how- that was losing energy by interacting ever, can be expressed in terms of the with matter or by radiating light would measurable energy and momentum of an speed up, whereas a tachyon that was object and hence can be directly mea- gaining energy from some outside source sured. For ordinary objects the rest mass would slow down, and its speed would squared is found to be a positive real approach c from above rather than be- number. For faster-than-light particles low. Thus c acts as a limiting speed for it would be a negative number; indeed, tachyons also, but the limit is a lower this fact is the basis of one attempt to de- limit, rather than the upper limit that tect such particles. It should be men- it is for ordinary objects. tioned that there is a third class of parti- In the limiting case of a tachyon mov- cles, including photons (light quanta) ing at infinite speed its total energy and neutrinos, for which the rest mass is would be zero, although its momentum zero and which always travel at c. would remain finite. It should be empha- The possibility therefore seems to sized that for a tachyon at infinite speed exist that there is a new kind of natural it is the total energy that is zero and not object: one that always travels faster just the kinetic energy. For an ordinary than light. The latter statement is in- particle with nonzero rest mass the total variant, in the sense that if a body tray- energy can never vanish. els faster than light with respect to one The condition of infinite speed is, observer, it will do so with respect to any however, not invariant but depends on other observer himself traveling in rela- the observer. If a tachyon were moving tion to the first at less than the speed of at infinite speed as seen by one observer, light. These are the only observers of its speed as measured by another ob- which we have any knowledge. It must server in motion with respect to the first be stressed that all the considerations would not be infinite but rather some given here and below are consistent with finite value between c and infinity. This the special theory of relativity, and as- is another way of phrasing Einstein's sume the validity of its equations for de- discovery that simultaneity for events at scribing particles, even if the particles different points in space has only a rela- travel faster than light. tive and not an absolute nicaning. ~n anticipation of the possible discovery of faster-than-light particles, I named them tachyons, from the Greek word tachys, meaning swift. In order to show how physicists have gone about search- ing for tachyons, I shall describe some of the properties that would distinguish them from ordinary particles. One such property follows directly from the relation between energy and speed given in the equations of relativ- ity. We have seen that for ordinary par- ticles, as theirspeed increases, their en- cause of the ce nation of relativity that n r r~ rf ~s!~~1~t"j n the absorption of a er~}pprey. F+Qfl Re*ap a 2QDWAWA, ; tT~E' ^ "Y'PC`t!4,497, ~I n{1~c6 ii 7i 00 G~i l f. - tCR4'?'11'l`T .n A second property of tachyons that substantially distinguishes them from or- dinary particles comes about from the way measurements of energy and time change with the relative motion of ob- servers. For ordinary particles the ener- gy is a slumber whose value will change from observer to observer but that will always be positive. A tachyon whose en- ergy is positive for one observer, how- ever, might appear to be negative to oth- er observers in motion with respect to the first. This can occur for tachyons be- ways less than its momentum multiplied by c; this ambivalence does not apply to ordinary particles. if negative-energy tachyons were emitted by the unexcited atoms of ordinary matter, this would cause the emitting atoms to be unstable, and hence the existence of such tachyons would contradict the Imown stability of ordinary matter. The change in the sign of the energy of a tachyon from observer to ob- server is. connected to another peculiar property of,tachyons. If an ordinary par- ticle is seen by one observer to be emit- ted (say by an atom A) atone time and absorbed elsewhere (by atom 13) at a later time, then any other observer in relative motion will see this process in the same way-as emission by atom A followed at a later time by absorption by atom B-although the time interval will vary from observer to observer. Tachy- ons, however, because they would travel. faster than light, would move between points in "space time" whose time-order- ing can vary from observer to observer. Therefore if one observer saw a tachyon emitted by atom A at one time $t and absorbed by atom B at a later time t?,, another observer could find that the time t1' that he measures corresponding to tl is later than the time t4' that he pleasures corresponding to t_ If this occurs, the latter observer would naturally want to interpret what happens in the following way: The tachyon is emitted by atom 13 at the earlier time t,' and absorbed by atom A at the later time tt'. It can be seen that this interchange of emission and absorption also removes the problem of negative-energy tachy- ons, since the reversal betwccti observers of the sign of the energy occurs if and only if the reversal in time-ordering oc- curs. Since the emission of a negative- ~41eetwt 2000/08/10: CIA-RD4 E2 - p2c2 = m2c4 -0078ZRC~010Q9 001-9 c E will in this case be a positive quantity. The momentum p of any body obeying the special theory of relativity can be expressed in terms of its speed by means of equation d, in which in is indepen- dent of v. It follows from a combination of this equation and equa- tion a that the quant.ity represented by equation e does not depend on v and hence is the same for all observers. The quantity ni' (called the rest crass squared) is then a constant for each object, even for bodies such .as photons (light quanta) or tachyons, which opposite direction produce the same ef- fect on the energy of a system, it is al- ways possible for any observer to insist that all tachyons have positive energy, and that emission and absorption take place in the familiar time-ordering, thus removing the instability problems that negative-energy tachyons would present. This interpretation of the negative-ener- gy states of the tachyon was first pro- posed in 1962 by 0. M. Y. Bilaniuk, E. C. G. Sudarshan and V. K. Deshpande of the University of Rochester. The description given above is in agreement with the principle of relativ- ity requiring that any process that can be seen by one observer must also be a are never at rest. One can also deduce from these relations equation f, which implies that if v/c is less than one (as it is for ordinary objects), then pc/E is less than one, E2 - psc- is greater than zero and hence m2 is positive. On the other hand, for objects that go faster than light v/c is greater than one, E2 - p'c2 is less than zero and hence nis is negative. In either case the rest mass squared should always have the same value for a given object and can be measured by measuring the energy and momentum for the object. possible process for any other observer. The principle does not require, however, that different observers agree on the in- terpretation of any individual process. Hence there is no contradiction of the principle of relativity involved in the fact that one observer views as absorp- tion what another views as emission, since both absorption and emission can be witnessed by either observer under suitable conditions. The novelty of tachy- ons is that emission and absorption must be converted into each other by a change in the observer's velocity, and this im- plies a closer connection between the two processes than exists for ordinary particles. TIME - I PECULIAR PROPERTY OF TACHYONS arises from the fact that the time-ordering of points in "space time" between which a faster?than-light particle would move could vary from observer to observer. Thus a process that appears to one observer as emission of a taehyon by one atom followed by absorption of the tachyon by another atom could be reversed for another observer moving with respect to the first. In this schematic representation of such a phenomenon the first observer (left) sees atom A at rest in its ground state and atom B at rest in all excited state at time te. At ti atom B emits a taehyon (color), dropping to its ground state and recoiling (broken arrow). At t_ this tachyou is absorbed by atom .4, which jumps to all excited state and also recoils. In this sit.nation the tine-ordering would be tar, tt, t.,. To another observer (right), for whom emission and absorption have been exchanged, the same process would appear as follows: Atom A is now moving at time to but is still in its ground state. It emits a tachyon at t.,' and jumps to an excited state, losing some of its translational energy. Atom 11, which is moving and in an excited Mate at to', absorbs the taehyon at tt', dropping to the ground state and gaining translational energy. For this observer the time sequence would be to', t..', tn'. Approved For Release 2000/08/10 : CIA-RDP96-00787R000100030001-9 It also implies that the number of tachyons in some region of space must vary from observer to observer. Suppose one observer views the process of emis- sion of a taehyon by an atom, with the subsequent escape of the tacltyon to in- finity. A second observer may view the same process as the tachyon's coming in from outer space and being absorbed by the atom. Hence the two observers will disagree on the number of tachyons present in the past and in the future. Again this situation differs from that for ordinary particles, where the number of particles present at any time is inde- pendent of the observer. A detailed theo- ry of the interaction of tachyons with Approved For Relewe 2000/08/10 : CIA-RDP96-007 2000100030001-9 CO) TIME to POPULATION OF TACHHYONS in a region of space at any given time would also vary from observer to observer. One observer (left) would view the emission of a tachyon by an atom at rest, with the subsequent recoil to the atom and the escape of the tachyon to infinity. A second observer (right) would view the tachyon coining in from outer space and being absorbed by a moving atom, causing the atom to lose translational energy. matter, which has not yet been worked out, would have to take these features into account. Having convinced ourselves that the existence of faster-than-light parti- cles does not imply any contradiction of relativity, we must nevertheless leave the determination of whether such ob- jects really happen in nature to the ex- perimental physicist. In the present state of theoretical physics there are few cir- cumstances in which theories flatly pre- dict that certain objects must exist. In- stead these theories generally enable us to describe various hypothetical objects, and we must determine by experiment which objects exist in reality. For exam- ple, present theories allow for the de- scription of particles with an electric charge equal to half the electron's charge and a mass six times the electron's mass, but we are fairly confident from experi- ments that no such objects are to be found in nature. We do not, however, know why this is so, and we may not know until we have more fundamental theories than we have now. The situation with tachyons is similar; to settle the issue of their existence one turns to the experimentalist. This is not to say, however, that he must hope to stumble on them somewhere in the uni- verse. One feature of all particle theories based on relativity is that they imply that if particles of some type exist at all, it must he possible to create them from other particles, provided that enough energy is available. For tachyons this condition of having enough energy is particularly easy to satisfy, because fast tachyons have very low.. eneirgy. Itt is coed 1e~~NcYe~ ltic~r ~~ ~t