have to admit that our conception of material reality today is more wavering and uncertain than it has been for a long time. we know a great many interesting details, learn new ones every week. but to construct a clear, easily comprehensible picture on which all physicists would agree — that is simply impossible. physics stands at a grave crisis of ideas. in the face of this crisis, many maintain that no objective picture of reality is possible. however, the optimists among us ( of whom i consider myself one ) look upon this view as a philosophical extravagance born of despair. we hope that the present fluctuations of thinking are only indications of an upheaval of old beliefs which in the end will lead to something better than the mess of formulas which today surrounds our subject. since the picture of matter that i am supposed to draw does not yet exist, since only fragments of it are visible, some parts of this narrative may be inconsistent with others. like cervantes ’ tale of sancho panza, who loses his donkey in one chapter but a few chapters later, thanks to the forgetfulness of the author, is riding the dear little animal again, our story has contradictions. we must start with the well - established concept that matter is composed of corpuscles or atoms, whose existence has been quite " tangibly " demonstrated by many beautiful experiments, and with max planck ’ s discovery that energy also comes in indivisible units, called quanta, which are supposed to be transferred abruptly from one carrier to another. but then sancho panza ’ s donkey will return. for i shall have to ask you to believe neither in corpuscles as permanent individuals nor in the suddenness of the transfer of an energy quantum. discreteness is present, but not in the traditional sense of discrete single particles, let alone in the sense of abrupt processes. discreteness arises merely as a structure from the laws governing the phenomena. these laws are by no means fully understood ; a probably correct analogue from the physics of palpable bodies is the way various partial tones of a bell derive from its shape and from the laws of elasticity to which, of themselves, nothing discontinuous adheres. the idea that matter is made up of ultimate particles was advanced as early as the fifth century b. c. by leucippus and democritus, who called these particles atoms. the corpuscular theory of matter was lifted to physical reality in the theory of gases developed during the 19th century by james clerk maxwell


as the fifth century b. c. by leucippus and democritus, who called these particles atoms. the corpuscular theory of matter was lifted to physical reality in the theory of gases developed during the 19th century by james clerk maxwell and ludwig boltzmann. the concept of atoms and molecules in violent motion, colliding and rebounding again and again, led to full comprehension of all the properties of gases : their elastic and thermal properties, their viscosity, heat conductivity and diffusion. at the same time it led to a firm foundation of the mechanical theory of heat, namely, that heat is the motion of these ultimate particles, which becomes increasingly violent with rising temperature. within one tremendously fertile decade at the turn of the century came the discoveries of x - rays, of electrons, of the emission of streams of particles and other forms of energy from the atomic nucleus by radioactive decay, of the electric charges on the various particles. the masses of these particles, and of the atoms themselves, were later measured very precisely, and from this was discovered the mass defect of the atomic nucleus as a whole. mass of a nucleus is less than the sum of the masses of its component particles ; the lost mass becomes the binding energy holding the nucleus firmly together. this is called the packing effect. the nuclear forces of course are not electrical forces — those are repellent — but are much stronger and act only within very short distances, about 10 - 13 centimeter. here i am already caught in a contradiction. didn ’ t i say at the beginning that we no longer assume the existence of force fields apart from matter? i could easily talk myself out of it by saying : well, the force field of a particle is simply considered a part of it. but that is not the fact. the established view today is rather that everything is at the same time both particle and field. everything has the continuous structure with which we are familiar in fields, as well as the discrete structure with which we are equally familiar in particles. this concept is supported by innumerable experimental facts and is accepted in general, though opinions differ on details, as we shall see. in the particular case of the field of nuclear forces, the particle structure is more or less known. most likely the continuous force field is represented by the so - called pi mesons. on the other hand, the protons and neutrons, which we think of as discrete particles, indisputably also have a continuous wave structure, as is shown by the interference patterns


field is represented by the so - called pi mesons. on the other hand, the protons and neutrons, which we think of as discrete particles, indisputably also have a continuous wave structure, as is shown by the interference patterns they form when diffracted by a crystal. the difficulty of combining these two so very different character traits in one mental picture is the main stumbling - block that causes our conception of matter to be so uncertain. neither the particle concept nor the wave concept is hypothetical. the tracks in a photographic emulsion or in a wilson cloud chamber leave no doubt of the behavior of particles as discrete units. the artificial production of nuclear particles is being attempted right now with terrific expenditure, defrayed in the main by the various state ministries of defense. it is true that one cannot kill anybody with one such racing particle, or else we should all be dead by now. but their study promises, indirectly, a hastened realization of the plan for the annihilation of mankind which is so close to all our you can easily observe particles yourself by looking at a luminous numeral of your wrist watch in the dark with a magnifying glass. the luminosity surges and undulates, just as a lake sometimes twinkles in the sun. the light consists of sparklets, each produced by a so - called alpha particle ( helium nucleus ) expelled by a radioactive atom which in this process is transformed into a different atom. a specific device for detecting and recording single particles is the geiger - muller counter. in this short resume i cannot possibly exhaust the many ways in which we can observe single particles. now to the continuous field or wave character of matter. wave structure is studied mainly by means of diffraction and interference — phenomena which occur when wave trains cross each other. for the analysis and measurement of light waves the principal device is the ruled grating, which consists of a great many fine, parallel, equidistant lines, closely engraved on a specular metallic light impinging from one direction is scattered by them and collected in different directions depending on its wavelength. but even the finest ruled gratings we can produce are too coarse to scatter the very much shorter waves associated with matter. the fine lattices of crystals, however, which max von laue first used as gratings to analyze the very short x - rays, will do the same for " matter waves. " directed at the surface of a crystal, high - velocity streams of particles manifest their wave nature. with crystal


max von laue first used as gratings to analyze the very short x - rays, will do the same for " matter waves. " directed at the surface of a crystal, high - velocity streams of particles manifest their wave nature. with crystal gratings physicists have diffracted and measured the wavelengths of electrons, neutrons and protons. what does planck ’ s quantum theory have to do with all this? planck told us in 1900 that he could comprehend the radiation from red - hot iron, or from an incandescent star such as the sun, only if this radiation was produced in discrete portions and transferred in such discrete quantities from one carrier to another ( e. g., from atom to this was extremely startling, because up to that time energy had been a highly abstract concept. five years later einstein told us that energy has mass and mass is energy ; in other words, that they are one and the same. now the scales begin to fall from our eyes : our dear old atoms, corpuscles, particles are planck ’ s energy quanta. the carriers of those quanta are themselves quanta. one gets dizzy. something quite fundamental must lie at the bottom of this, but it is not surprising that the secret is not yet understood. after all, the scales did not fall suddenly. it took 20 or 30 years. and perhaps they still have not fallen completely. the next step was not quite so far reaching, but important enough. by an ingenious and appropriate generalization of planck ’ s hypothesis niels bohr taught us to understand the line spectra of atoms and molecules and how atoms were composed of heavy, positively charged nuclei with light, negatively charged electrons revolving each small system — atom or molecule — can harbor only definite discrete energy quantities, corresponding to its nature or its constitution. in transition from a higher to a lower " energy level " it emits the excess energy as a radiation quantum of definite wavelength, inversely proportional to the quantum given off. this means that a quantum of given magnitude manifests itself in a periodic process of definite frequency which is directly proportional to the quantum ; the frequency equals the energy quantum divided by the famous planck ’ s constant, h. according to einstein a particle has the energy mc2, m being the mass of the particle and c the velocity of light. in 1925 louis de broglie drew the inference, which rather suggests itself, that a particle might have associated with it a wave process of frequency mc2 divided by h. the particle for which he postulated


particle and c the velocity of light. in 1925 louis de broglie drew the inference, which rather suggests itself, that a particle might have associated with it a wave process of frequency mc2 divided by h. the particle for which he postulated such a wave was the electron. within two years the " electron waves " required by his theory were demonstrated by the famous electron diffraction experiment of c. j. davisson and l. h. germer. this was the starting point for the cognition that everything — anything at all — is simultaneously particle and wave field. thus de broglie ’ s dissertation initiated our uncertainty about the nature of matter. both the particle picture and the wave picture have truth value, and we cannot give up either one or the other. but we do not know how to that the two pictures are connected is known in full generality with great precision and down to amazing details. but concerning the unification to a single, concrete, palpable picture opinions are so strongly divided that a great many deem it altogether impossible. i shall briefly sketch the connection. but do not expect that a uniform, concrete picture will emerge before you ; and do not blame the lack of success either on my ineptness in exposition or your own denseness — nobody has yet succeeded. one distinguishes two things in a wave. first of all, a wave has a front, and a succession of wave fronts forms a system of surfaces like the layers of an onion. you are familiar with the two - dimensional analogue of the beautiful wave circles that form on the smooth surface of a pond when a stone is thrown in. the second characteristic of a wave, less intuitive, is the path along which it travels — a system of imagined lines perpendicular to the wave fronts. these lines are known as the wave " normals " or " rays. " we can make the provisional assertion that these rays correspond to the trajectories of particles. indeed, if you cut a small piece out of a wave, approximately 10 or 20 wavelengths along the direction of propagation and about as much across, such a " wave packet " would actually move along a ray with exactly the same velocity and change of velocity as we might expect from a particle of this particular kind at this particular place, taking into account any force fields acting on the particle. here i falter. for what i must say now, though correct, almost contradicts this provisional assertion. although the behavior of the wave packet gives us a more or less intuitive picture of a particle,


any force fields acting on the particle. here i falter. for what i must say now, though correct, almost contradicts this provisional assertion. although the behavior of the wave packet gives us a more or less intuitive picture of a particle, which can be worked out in detail ( e. g., the momentum of a particle increases as the wavelength decreases ; the two are inversely proportional ), yet for many reasons we cannot take this intuitive picture quite seriously. for one thing, it is, after all, somewhat vague, the more so the greater the wavelength. for another, quite often we are dealing not with a small packet but with an extended wave. for still another, we must also deal with the important special case of very small " packelets " which form a kind of " standing wave " which can have no wave fronts or wave normals. one interpretation of wave phenomena which is extensively supported by experiments is this : at each position of a uniformly propagating wave train there is a twofold structural connection of interactions, which may be distinguished as " longitudinal " and " transversal. " the transversal structure is that of the wave fronts and manifests itself in diffraction and interference experiments ; the longitudinal structure is that of the wave normals and manifests itself in the observation of single particles. however, these concepts of longitudinal and transversal structures are not sharply defined and absolute, since the concepts of wave front and wave normal are not, the interpretation breaks down completely in the special case of the standing waves mentioned above. here the whole wave phenomenon is reduced to a small region of the dimensions of a single or very few wavelengths. you can produce standing water waves of a similar nature in a small basin if you dabble with your finger rather uniformly in its center, or else just give it a little push so that the water surface undulates. in this situation we are not dealing with uniform wave propagation ; what catches the interest are the normal frequencies of these standing waves. the water waves in the basin are an analogue of a wave phenomenon associated with electrons, which occurs in a region just about the size of the atom. the normal frequencies of the wave group washing around the atomic nucleus are universally found to be exactly equal to bohr ’ s atomic " energy levels " divided by planck ’ s constant h. thus the ingenious yet somewhat artificial assumptions of bohr ’ s model of the atom, as well as of the older quantum theory in general, are superseded by the far more natural idea of


energy levels " divided by planck ’ s constant h. thus the ingenious yet somewhat artificial assumptions of bohr ’ s model of the atom, as well as of the older quantum theory in general, are superseded by the far more natural idea of de broglie ’ s wave phenomenon. phenomenon forms the " body " proper of the atom. it takes the place of the individual pointlike electrons which in bohr ’ s model are supposed to swarm around the nucleus. such pointlike single particles are completely out of the question within the atom, and if one still thinks of the nucleus itself in this way one does so quite consciously for reasons of expediency. what seems to me particularly important about the discovery that " energy levels " are virtually nothing but the frequencies of normal modes of vibration is that now one can do without the assumption of sudden transitions, or quantum jumps, since two or more normal modes may very well be excited simultaneously. the discreteness of the normal frequencies fully suffices — so i believe — to support the considerations from which planck started and many similar and just as important ones — i mean, in short, to support all of quantum the theory of quantum jumps is becoming more and more unacceptable, at least to me personally, as the years go on. its abandonment has, however, far - reaching consequences. it means that one must give up entirely the idea of the exchange of energy in well - defined quanta and replace it with the concept of resonance between vibrational frequencies. yet we have seen that because of the identity of mass and energy, we must consider the particles themselves as planck ’ s energy quanta. this is at first frightening. for the substituted theory implies that we can no longer consider the individual particle as a well - defined permanent entity. that it is, in fact, no such thing can be reasoned in other ways. for one thing, there is werner heisenberg ’ s famous uncertainty principle, according to which a particle cannot simultaneously have a well - defined position and a sharply defined velocity. this uncertainty implies that we cannot be sure that the same particle could ever be observed twice. another conclusive reason for not attributing identifiable sameness to individual particles is that we must obliterate their individualities whenever we consider two or more interacting particles of the same kind, e. g., the two electrons of a helium atom. two situations which are distinguished only by the interchange of the two electrons must be counted as one and the same ; if they are counted as two equal situations,


particles of the same kind, e. g., the two electrons of a helium atom. two situations which are distinguished only by the interchange of the two electrons must be counted as one and the same ; if they are counted as two equal situations, nonsense obtains. this circumstance holds for any kind of particle in arbitrary numbers without exception. most theoreticians will probably accept the foregoing reasoning and admit that the individual particle is not a well - defined permanent entity of detectable identity or sameness. nevertheless this inadmissible concept of the individual particle continues to play a large role in their ideas and discussions. even deeper rooted is the belief in " quantum jumps, " which is now surrounded with a highly abstruse terminology whose common - sense meaning is often difficult for instance, an important word in the standing vocabulary of quantum theory is " probability, " referring to transition from one level to another. but, after all, one can speak of the probability of an event only assuming that, occasionally, it actually occurs. if it does occur, the transition must indeed be sudden, since intermediate stages are disclaimed. moreover, if it takes time, it might conceivably be interrupted halfway by an unforeseen disturbance. this possibility leaves one completely at sea. the wave v. corpuscle dilemma is supposed to be resolved by asserting that the wave field merely serves for the computation of the probability of finding a particle of given properties at a given position if one looks for it there. but once one deprives the waves of reality and assigns them only a kind of informative role, it becomes very difficult to understand the phenomena of interference and diffraction on the basis of the combined action of discrete single particles. it certainly seems easier to explain particle tracks in terms of waves than to explain the wave phenomenon in terms of corpuscles. " real existence " is, to be sure, an expression which has been virtually chased to death by many philosophical hounds. its simple, naive meaning has almost become lost to us. therefore i want to recall something else. i spoke of a corpuscle ’ s not being an individual. properly speaking, one never observes the same particle a second time — very much as heraclitus says of the river. you cannot mark an electron, you cannot paint it red. indeed, you must not even think of it as marked ; if you do, your " counting " will be false and you will get wrong results at every step — for the structure of line spectra, in thermod


you cannot paint it red. indeed, you must not even think of it as marked ; if you do, your " counting " will be false and you will get wrong results at every step — for the structure of line spectra, in thermodynamics and elsewhere. a wave, on the other hand, can easily be imprinted with an individual structure by which it can be recognized beyond doubt. think of the beacon fires that guide ships at sea. the light shines according to a definite code ; for example : three seconds light, five seconds dark, one second light, another pause of five seconds, and again light for three seconds — the skipper knows that is san sebastian. or you talk by wireless telephone with a friend across the atlantic ; as soon as he says, " hello there, edward meier speaking, " you know that his voice has imprinted on the radio wave a structure which can be distinguished from any other. but one does not have to go that far. if your wife calls, " francis! " from the garden, it is exactly the same thing, except that the structure is printed on sound waves and the trip is shorter ( though it takes somewhat longer than the journey of radio waves across the atlantic ). all our verbal communication is based on imprinted individual wave structures. and, according to the same principle, what a wealth of details is transmitted to us in rapid succession by the movie or the television picture! this characteristic, the individuality of the wave phenomenon, has already been found to a remarkable extent in the very much finer waves of particles. one example must suffice. a limited volume of gas, say helium, can be thought of either as a collection of many helium atoms or as a superposition of elementary wave trains of matter waves. both views lead to the same theoretical results as to the behavior of the gas upon heating, compression, and so on. when you attempt to apply certain somewhat involved enumerations to the gas, you must carry them out in different ways according to the mental picture with which you approach it. if you treat the gas as consisting of particles, then no individuality must be ascribed to them, as i said. if, however, you concentrate on the matter wave trains instead of on the particles, every one of the wave trains has a well - defined structure which is different from that of any other. it is true that there are many pairs of waves which are so similar to each other that they could change roles without any noticeable effect on the gas. but if


the wave trains has a well - defined structure which is different from that of any other. it is true that there are many pairs of waves which are so similar to each other that they could change roles without any noticeable effect on the gas. but if you should count the very many similar states formed in this way as merely a single one, the result would be quite wrong. in spite of everything we cannot completely banish the concepts of quantum jump and individual corpuscle from the vocabulary of physics. we still require them to describe many details of the structure of matter. how can one ever determine the weight of a carbon nucleus and of a hydrogen nucleus, each to the precision of several decimals, and detect that the former is somewhat lighter than the 12 hydrogen nuclei combined in it, without accepting for the time being the view that these particles are something quite concrete and real? this view is so much more convenient than the roundabout consideration of wave trains that we cannot do without it, just as the chemist does not discard his valence - bond formulas, although he fully realizes that they represent a drastic simplification of a rather involved wave - mechanical situation. if you finally ask me : " well, what are these corpuscles, really? " i ought to confess honestly that i am almost as little prepared to answer that as to tell where sancho panza ’ s second donkey came from. at the most, it may be permissible to say that one can think of particles as more or less temporary entities within the wave field whose form and general behavior are nevertheless so clearly and sharply determined by the laws of waves that many processes take place as if these temporary entities were substantial permanent beings. the mass and the charge of particles, defined with such precision, must then be counted among the structural elements determined by the wave laws. the conservation of charge and mass in the large must be considered as a statistical effect, based on the " law of large numbers. " simultaneously with the development of wave mechanics, heisenberg evolved a different mathematical analysis known as matrix mechanics. according to heisenberg ’ s theory, which was developed in collaboration with the german physicists max born and ernst pascual jordan, the formula was not a differential equation but a matrix : an array consisting of an infinite number of rows, each row consisting of an infinite number of quantities. matrix mechanics introduced infinite matrices to represent the position and momentum of an electron inside an atom. also, different matrices exist, one for each observable physical property associated with the motion of an electron,


each row consisting of an infinite number of quantities. matrix mechanics introduced infinite matrices to represent the position and momentum of an electron inside an atom. also, different matrices exist, one for each observable physical property associated with the motion of an electron, such as energy, position, momentum, and angular momentum. these matrices, like schrodinger ’ s differential equations, could be solved ; in other words, they could be manipulated to produce predictions as to the frequencies of the lines in the hydrogen spectrum and other observable quantities. like wave mechanics, matrix mechanics was in agreement with the earlier quantum theory for processes in which the earlier quantum theory agreed with experiment ; it was also useful in explaining phenomena that earlier quantum theory could not explain. schrodinger subsequently succeeded in showing that wave mechanics and matrix mechanics are different mathematical versions of the same theory, now called quantum mechanics. even for the simple hydrogen atom, which consists of two particles, both mathematical interpretations are extremely complex. the next simplest atom, helium, has three particles, and even in the relatively simple mathematics of classical dynamics, the three - body problem ( that of describing the mutual interactions of three separate bodies ) is not the energy levels can be calculated accurately, however, even if not exactly. in applying quantum - mechanics mathematics to relatively complex situations, a physicist can use one of a number of mathematical formulations. the choice depends on the convenience of the formulation for obtaining suitable although quantum mechanics describes the atom purely in terms of mathematical interpretations of observed phenomena, a rough verbal description can be given of what the atom is now thought to be like. surrounding the nucleus is a series of stationary waves ; these waves have crests at certain points, each complete standing wave representing an orbit. the absolute square of the amplitude of the wave at any point is a measure of the probability that an electron will be found at that point at any given time. thus, an electron can no longer be said to be at any precise point at any given time. the impossibility of pinpointing an electron at any precise time was analyzed by heisenberg, who in 1927 formulated the uncertainty principle. this principle states the impossibility of simultaneously specifying the precise position and momentum of any particle. in other words, the more accurately a particle ’ s momentum is measured and known, the less accuracy there can be in the measurement and knowledge of its position. this principle is also fundamental to the understanding of quantum mechanics as it is generally accepted today : the wave and particle character of electromagnetic radiation can be understood


momentum is measured and known, the less accuracy there can be in the measurement and knowledge of its position. this principle is also fundamental to the understanding of quantum mechanics as it is generally accepted today : the wave and particle character of electromagnetic radiation can be understood as two complementary properties of radiation. another way of expressing the uncertainty principle is that the wavelength of a quantum mechanical principle is inversely proportional to its momentum. as atoms are cooled they slow down and their corresponding wavelength grows larger. at a low enough temperature this wavelength is predicted to exceed the spacing between particles, causing atoms to overlap, becoming indistinguishable, and melding into a single quantum state. in 1995 a team of colorado scientists, led by national institutes of standards and technology physicist eric cornell and university of colorado physicist carl weiman, cooled rubidium atoms to a temperature so low that the particles entered this merged state, known as a bose - einstein condensate. the condensate essentially behaves like one atom even though it is made up of thousands. - physicists condense supercooled atoms, forming new state of matter a team of colorado physicists has cooled atoms of gas to a temperature so low that the particles entered a merged state, known as a " bose - einstein condensate. " this phenomenon was first predicted about 70 years ago by the theories of german - born american physicist albert einstein and indian physicist satyendra nath bose. the condensed particles are considered a new state of matter, different from the common states of matter — gas, liquid, and solid — and from plasma, a high temperature, ionized form of matter that is found in the sun and other stars. physicists have great expectations for the application of this discovery. because the condensate essentially behaves like one atom even though it is made up of thousands, investigators should be able to measure interactions at the atomic and subatomic level that were previously extremely difficult, if not impossible, to study the condensate was detected june 5 by a colorado team led by national institutes of standards and technology physicist eric cornell and university of colorado physicist carl wieman. their discovery was reported in the journal science on july 14. cornell and wieman formed their condensate from rubidium gas. several groups of physicists, including the teams in texas and colorado and a group at the massachusetts institute of technology, have been working to form pure condensate in recent years. the goal of the investigations has been to create a pure chunk of condensate out of atoms in


including the teams in texas and colorado and a group at the massachusetts institute of technology, have been working to form pure condensate in recent years. the goal of the investigations has been to create a pure chunk of condensate out of atoms in an inert medium, such as a diffuse, nonreactive gas. the effort began when methods of cooling and trapping became refined enough that it seemed possible to reach the required conditions of temperature and density. the colorado team used two techniques : first laser cooling and then evaporative cooling. the laser technique used laser light whose frequency was carefully tuned to interact with the rubidium atoms and gently reduce their speeds. a number of lasers were aimed at the gas to slow the motion of the atoms in different directions. the colorado physicists then switched to evaporative cooling. in this method, the gas is " trapped " by a magnetic field that dwindles to zero at its center. atoms that are moving wander out of the field, while the coldest atoms cluster at the center. because a few very cold atoms could still escape at the zero field point of the trap, the physicists perfected their system by adding a second slowly circling magnetic field so that the zero point moved, not giving the atoms the chance to escape through it. physicists will now begin to explore the properties of the condensate and see what other materials they can use to form it. one unusual characteristic of the condensate is that it is composed of atoms that have lost their individual identities. this is analogous to laser light, which is composed of light particles, or photons, that similarly have become indistinguishable and all behave in exactly the same manner. the laser has found a myriad of uses both in practical applications and in theoretical research, and the bose - einstein condensate may turn out to be just as important. some scientists speculate that if a condensate can be readily produced and sustained, it could be used to miniaturize and speed up computer components to a scale and quickness not possible before. the prediction that a merged form of matter will emerge at extremely low temperatures is based on a number of aspects of the quantum theory. this theory governs the interaction of particles on a subatomic scale. the basic principle of quantum theory is that particles can only exist in certain discrete energy states. the exact " quantum state " of a particle takes into consideration such factors as the position of the particle and its " spin, " which can only have certain discrete values.


principle of quantum theory is that particles can only exist in certain discrete energy states. the exact " quantum state " of a particle takes into consideration such factors as the position of the particle and its " spin, " which can only have certain discrete values. a particle ’ s spin categorizes it as either a boson or a fermion. those two groups of particles behave according to different sets of statistical rules. bosons have spins that are a constant number multiplied by an integer ( e. g., 0, 1, 2, 3 ). fermions have spins that are that same constant multiplied by an odd half - integer ( 1 / 2, 3 / 2, 5 / 2, etc. ). examples of fermions are the protons and neutrons that make up an atom ’ s nucleus, and composite particles, such as nuclei and atoms, are classified as bosons or fermions based on the sum of the spins of their constituent particles. for instance, an isotope of helium called helium - 4 turns out to be a bose particle. helium - 4 is made up of six fermi particles : two electrons orbiting a nucleus made up of two protons and two neutrons. adding up six odd half - integers will yield a whole integer, making helium - 4 a boson. the atoms of rubidium used in the colorado experiment are bose particles as well. only bose atoms may form a condensate, but they do so only at a sufficiently low temperature and high density. at their lab in colorado, cornell and wieman cooled a rubidium gas down to a temperature as close to absolute zero, the temperature at which particles stop moving, as they could get. the slower the particles, the lower their momentum. in essence, the cooling brought the momentum of the gas particles closer and closer to precisely zero, as the temperature decreased to within a few billionths of a degree kelvin. ( kelvin degrees are on the scale of degrees celsius, but zero kelvin is absolute zero, while zero celsius is the freezing point of water. ) as the temperature, and thus the momentum, of the gas particles dropped to an infinitesimal amount, the possible locations of the atom at any given moment increased proportionally. the goal of the experiment was to keep the gas atoms packed together closely enough that during this process — as their momentum got lower and lower, and their wavelengths got larger and larger — their waves would begin to overlap. this interplay of position and movement in three dimensions with the


was to keep the gas atoms packed together closely enough that during this process — as their momentum got lower and lower, and their wavelengths got larger and larger — their waves would begin to overlap. this interplay of position and movement in three dimensions with the relative distances between particles is known as the phase - space density and is the key factor in forming a condensate. in essence, the momentum of the atoms would become so precisely pinpointed ( near zero ) that their position would become less and less certain and there would be a relatively large amount of space that would define each atom ’ s position. as the atoms slowed to almost a stop, their positions became so fuzzy that each atom came to occupy the same position as every other atom, losing their individual identity. this odd phenomenon is a bose - einstein as their experimental conditions neared the realm of bose - einstein condensation, cornell and wieman noticed an abrupt rise in the peak density of their sample, a type of discontinuity that strongly indicates a phase transition. the colorado physicists estimated that after progressive evaporative cooling of the rubidium, they were left with a nugget of about 2, 000 atoms of pure condensate. and wieman then released the atoms from the " trap " in which they had been cooling and sent a pulse of laser light at the condensate, basically blowing it apart. they recorded an image of the expanding cloud of atoms. prior to the light pulse, when the density dropped after the atoms were released, the physicists believed the temperature of the condensate fell to an amazing frigidity of 20 nanokelvins ( 20 billionths of one degree above absolute zero ). the image showed a larger, expanding sphere of particles with a smaller, more concentrated elliptical - looking center. cornell and wieman observed that when a gas is constrained and then released ( in an extreme example, as in a bomb ), thermodynamics specifies that it will expand outward equally in all directions regardless of the shape in which it had been contained. this occurs because the particles in that gas, even if the gas was very cold, were moving in all different directions with various energies when the gas was this rule of uniform expansion does not hold for a bose - einstein condensate. because the particles were all acting in exactly the same manner at the time of the light pulse, their expansion should give some indication of the shape of the space they had previously inhabited. the uneven, elliptical - looking clump of atoms in the


discussion. in the 1930s the application of quantum mechanics and special relativity to the theory of the electron ( see quantum electrodynamics ) allowed the british physicist paul dirac to formulate an equation that referred to the existence of the spin of the electron. it further led to the prediction of the existence of the positron, which was experimentally verified by the american physicist carl david anderson. the application of quantum mechanics to the subject of electromagnetic radiation led to explanations of many phenomena, such as bremsstrahlung ( german, " braking radiation, " the radiation emitted by electrons slowed down in matter ) and pair production ( the formation of a positron and an electron when electromagnetic energy interacts with matter ). it also led to a grave problem, however, called the divergence difficulty : certain parameters, such as the so - called bare mass and bare charge of electrons, appear to be infinite in dirac ’ s equations. ( the terms bare mass and bare charge refer to hypothetical electrons that do not interact with any matter or radiation ; in reality, electrons interact with their own electric this difficulty was partly resolved in 1947 - 49 in a program called renormalization, developed by the japanese physicist shin ’ ichiro tomonaga, the american physicists julian s. schwinger and richard feynman, and the british physicist freeman dyson. in this program, the bare mass and charge of the electron are chosen to be infinite in such a way that other infinite physical quantities are canceled out in the equations. renormalization greatly increased the accuracy with which the structure of atoms could be calculated from first principles. theoretical physicist c. llewellyn smith discusses the discoveries that scientists have made to date about the electron and other elementary particles — subatomic particles that scientists believe cannot be split into smaller units of matter. scientists have discovered what smith refers to as sibling and cousin particles to the electron, but much about the nature of these particles is still one way scientists learn about these particles is to accelerate them to high energies, smash them together, and then study what happens when they collide. by observing the behavior of these particles, scientists hope to learn more about the fundamental structures of the universe. electrons : the first hundred years the discovery of the electron was announced by j. j. thomson just over 100 years ago, on april 30, 1897. in the intervening years we have come to understand the mechanics that describe the behavior of electrons — and indeed of all matter on a small scale — which is called quantum mechanics.


. j. thomson just over 100 years ago, on april 30, 1897. in the intervening years we have come to understand the mechanics that describe the behavior of electrons — and indeed of all matter on a small scale — which is called quantum mechanics. by exploiting this knowledge, we have learned to manipulate electrons and make devices of a tremendous practical and economic importance, such as transistors and lasers. meanwhile, what have we learned of the nature of the electron itself? from the start, electrons were found to behave as elementary particles, and this is still the case today. we know that if the electron has any structure, it is on a scale of less than 1018 m, i. e. less than 1 billionth of 1 billionth of a meter. however, a major complication has emerged. we have discovered that the electron has a sibling and cousins that are apparently equally fundamental. the sibling is an electrically neutral particle, called the neutrino, which is much lighter than the electron. the cousins are two electrically charged particles, called the mu and the which also have neutral siblings. the mu and the tau seem to be identical copies of the electron, except that they are respectively 200 and 3, 500 times heavier. their role in the scheme of things and the origin of their different masses remain mysteries — just the sort of mysteries that particle physicists, who study the constituents of matter and the forces that control their behavior, wish to resolve. we therefore know of six seemingly fundamental particles, the electron, the mu, the tau and their neutral siblings, which — like the electron — do not feel the nuclear force, and incidentally are known generically as leptons. what about the constituents of atomic nuclei, which of course do feel the nuclear force? at first sight, nuclei are made of protons and neutrons, but these particles turned out not to be elementary. it was found that when protons and neutrons are smashed together, new particles are created. we now know that all these particles are made of more elementary entities, called quarks. in a collision, pairs of quarks and their antiparticles, called antiquarks, can be created : part of the energy ( e ) of the incoming particles is turned into mass ( m ) of these new particles, thanks to the famous equivalence e = mc2. the quarks in the projectiles and the created quark - antiquark pairs can then rearrange themselves to make various different sorts of new particles. today


) of these new particles, thanks to the famous equivalence e = mc2. the quarks in the projectiles and the created quark - antiquark pairs can then rearrange themselves to make various different sorts of new particles. today, six types of quarks are known which, like the leptons ( the electron and its relations ) have simple properties, and could be elementary. in the past 30 years a recipe that describes the behavior of these particles has been developed. it is called the " standard model " of particle physics. however, we lack a real understanding of the nature of these particles, and the logic behind the standard model. what is wrong with the standard model? first, it does not consistently combine einstein ’ s theory of the properties of space ( called general relativity ) with a quantum mechanical description of the properties of matter. it is therefore second, it contains too many apparently arbitrary futures — it is too baroque, too byzantine — to be complete. it does not explain the role of the mu and the tau, or answer the question whether the fact that the numbers of leptons and quarks are the same — six each — is a coincidence, or an indication of a deep connection between these different types of particles. on paper, we can construct theories that give better answers and explanations, and in which there are such connections, but we do not know which, if any, of these theories is correct. third, it has a missing, untested, element. this is not some minor detail, but a central element, namely a mechanism to generate the observed masses of the known particles, and hence also the different ranges of the known forces ( long range for gravity and electromagnetism, as users of magnetic compasses know, but very short range for the nuclear and the so - called weak forces, although in every other respect these forces appear very similar ). on paper, a possible mechanism is known, called the higgs mechanism, after the british physicist peter higgs who invented it. but there are alternative mechanisms, and in any case the higgs mechanism is a generic idea. we not only need to know if nature uses it, but if so, how it is realized in detail. luckily the prospects of developing a deeper understanding are good. the way forward is to perform experiments that can distinguish the different possibilities. we know that the answer to the mystery of the origin of mass, and the different ranges of forces, and certain other very important questions, must lie in an energy


are good. the way forward is to perform experiments that can distinguish the different possibilities. we know that the answer to the mystery of the origin of mass, and the different ranges of forces, and certain other very important questions, must lie in an energy range that will be explored in experiments at the large hadron collider, a new accelerator now under construction at cern [ also known as the european laboratory for particle physics ] near geneva. the fundamental tools on which experimental particle physics depends are large accelerators, like the large hadron collider, which accelerate particles to very high energies and smash them together. by studying what happens in the collisions of these particles, which are typically electrons or protons ( the nuclei of hydrogen atoms ), we can learn about their natures. the conditions that are created in these collisions of particles existed just after the birth of the universe, when it was extremely hot and dense. knowledge derived from experiments in particle physics is therefore essential input for those who wish to understand the structure of the universe as a whole, and how it evolved from an initial fireball into its present the large hadron collider will therefore not only open up a large new window on the nature of matter, when it comes into operation in 2005, but also advance our understanding of the structure of the universe. however, although it will undoubtedly resolve some major questions and greatly improve our knowledge of nature, it would be very surprising if it established a " final theory. " the only candidate theory currently known which appears to have the potential to resolve all the problems mentioned above — the reason for the existence of the mu and tau, reconciliation of general relativity with quantum mechanics, etc. — describes the electron and its relatives and the quarks, not as pointlike objects, but as different vibrating modes of tiny strings. however, these strings are so small ( 10 - 35 m ) that they will never be observed if this is so, the electron and the other known particles will continue forever to appear to be fundamental pointlike objects, even if the — currently very speculative — " string theory " scores enough successes to convince us that this is not the case! future prospects : quantum mechanics underlies current attempts to account for the strong nuclear force and to develop a unified theory for all the fundamental interactions nevertheless, doubts exist about the completeness of quantum theory. the divergence difficulty, for example, is only partly resolved. just as newtonian mechanics was eventually amended by quantum mechanics and relativity, many scientists — and einstein was among them — are convinced


nevertheless, doubts exist about the completeness of quantum theory. the divergence difficulty, for example, is only partly resolved. just as newtonian mechanics was eventually amended by quantum mechanics and relativity, many scientists — and einstein was among them — are convinced that quantum theory will also undergo profound changes in the future. great theoretical difficulties exist, for example, between quantum mechanics and chaos theory, which began to develop rapidly in the 1980s. ongoing efforts are being made by theorists such as the british physicist stephen hawking, to develop a system that encompasses both relativity and quantum mechanics. breakthroughs occurred in the area of quantum computing in the late 1990s. quantum computers under development use components of a chloroform molecule ( a combination of chlorine and hydrogen atoms ) and a variation of a medical procedure called magnetic resonance imaging ( mri ) to compute at a molecular level. scientists used a branch of physics called quantum mechanics, which describes the activity of subatomic particles ( particles that make up atoms ), as the basis for quantum computing. quantum computers may one day be thousands to millions of times faster than current computers, because they take advantage of the laws that govern the behavior of subatomic particles. these laws allow quantum computers to examine all possible answers to a query at one time. future uses of quantum computers could include code breaking and large database queries. quantum time waits for no cosmos the intriguing notion that time might run backwards when the universe collapses has run into difficulties. raymond laflamme, of the los alamos national laboratory in new mexico, has carried out a new calculation which suggests that the universe cannot start out uniform, go through a cycle of expansion and collapse, and end up in a uniform state. it could start out disordered, expand, and then collapse back into disorder. but, since the cobe data show that our universe was born in a smooth and uniform state, this symmetric possibility cannot be applied to the real universe. physicists have long puzzled over the fact that two distinct " arrows of time " both point in the same direction. in the everyday world, things wear out - - cups fall from tables and break, but broken cups never re - assemble themselves spontaneously. in the expanding universe at large, the future is the direction of time in which galaxies are further apart. many years ago, thomas gold suggested that these two arrows might be linked. that would mean that if and when the expansion of the universe were to reverse, then the everyday arrow of time would also reverse, with broken cups re - assem


apart. many years ago, thomas gold suggested that these two arrows might be linked. that would mean that if and when the expansion of the universe were to reverse, then the everyday arrow of time would also reverse, with broken cups re - assembling themselves. more recently, these ideas have been extended into quantum physics. there, the arrow of time is linked to the so - called " collapse of the wave function ", which happens, for example, when an electron wave moving through a tv tube collapses into a point particle on the screen of the tv. some researchers have tried to make the quantum description of reality symmetric in time, by including both the original state of the system ( the tv tube before the electron passes through ) and the final state ( the tv tube after the electron has passed through ) in one mathematical description. murray gell - mann and james hartle recently extended this idea to the whole universe. they argued that if, as many cosmologists believe likely, the universe was born in a big bang, will expand out for a finite time and then recollapse into a big crunch, the time - neutral quantum theory could describe time running backwards in the contracting half of its life. unfortunately, laflamme has now shown that this will not work. he has proved that if there are only small inhomogeneities present in the big bang, then they must get larger throughout the lifetime of the universe, in both the expanding and the contracting phases. " a low entropy universe at the big bang cannot come back to low entropy at the big crunch " ( classical and quantum gravity, vol 10 p l79 ). he has found time - asymmetric solutions to the equations - - but only if both big bang and big crunch are highly disordered, with the universe more ordered in the middle of its life. observations of the cosmic microwave background radiation show that the universe emerged from the big bang in a very smooth and uniform state. this rules out the time - symmetric solutions. is that even if the present expansion of the universe does reverse, time will not run backwards and broken cups will not start re -


glucose is a type of sugar. it comes from food, and is also created in the liver. glucose travels through the body in the blood. it moves from the blood to cells with the help of a hormone called insulin. once glucose is in those cells, it can be used for energy. diabetes is a condition that makes it difficult for the body to use glucose. this causes a buildup of glucose in the blood. it also means the body is not getting enough energy. type 2 diabetes is one type of diabetes. it is the most common type. medication, lifestyle changes, and monitoring can help control blood glucose levels. type 2 diabetes is often caused by a combination of factors. one factor is that your body begins to make less insulin. a second factor is that your body becomes resistant to insulin. this means there is insulin in your body, but your body cannot use it effectively. insulin resistance is often related to excess body fat. the doctor will ask about your symptoms and medical history. you will also be asked about your family history. a physical exam will be done. diagnosis is based on the results of blood testing. american diabetes association ( ada ) recommends diagnosis be made if you have one of the following : symptoms of diabetes and a random blood test with a blood sugar level greater than or equal to 200 mg / dl ( 11. 1 mmol / l ) - fasting blood sugar test — done after you have not eaten for eight or more hours — showing blood sugar levels greater than or equal to 126 mg / dl ( 7 mmol / l ) on two different days - glucose tolerance test — measuring blood sugar two hours after you eat glucose — showing glucose levels greater than or equal to 200 mg / dl ( 11. 1 mmol / l ) - hba1c level of 6. 5 % or higher — indicates poor blood sugar control over the past 2 - 4 months mg / dl = milligrams per deciliter of blood ; mmol / l = millimole per liter of blood treatment aims to : - maintain blood sugar at levels as close to normal as possible - prevent or delay complications - control other conditions that you may have, like high blood pressure and high cholesterol food and drinks have a direct effect on your blood glucose level. eating healthy meals can help you control your blood glucose. it will also help your overall health. some basic tips include : if you are overweight, weight loss will help your body use insulin better. talk to your doctor about a healthy weight goal. you and


" we believe this is the first time bacterial horizontal gene transfer has been observed in eukaryotes at such scale, " says senior author igor grigoriev of doe jgi. " this study gets us closer to explaining the dramatic diversity across the genera of diatoms, morphologically, behaviorally, but we still haven ' t yet explained all the differences conferred by the genes contributed by the other taxa. " from plants, the diatom inherited photosynthesis, and from animals the production of urea. bowler speculates that the diatom uses urea to store nitrogen, not to eliminate it like animals do, because nitrogen is a precious nutrient in the ocean. what ' s more, the tiny alga draws the best of both worldsit can convert fat into sugar, as well as sugar into fatextremely useful in times of nutrient shortage. the team documented more than 300 genes sourced from bacteria and found in both types of diatoms, pointing to their ancient origin and suggesting novel mechanisms of managing nutrientsfor example utilization of organic carbon and nitrogenand detecting cues from their environment. diatoms, encapsulated by elaborate lacework - like shells made of glass, are only about one - third of a strand of hair in diameter. " the diatom genomes will help us to understand how they can make these structures at ambient temperatures and pressures, something that humans are not able to do. if we can learn how they do it, we could open up all kinds of new nanotechnologies, like for building miniature silicon chips or for biomedical applications, " says bowler. diatoms reside in fresh or salt water and can be divided into two camps, centrics and pennates. the centric thalassiosira resemble a round " camembert " cheese box ( only much smaller ) and pennates like phaeodactylum look more like a cross between a boomerang and a narrow three - cornered hathence the species name, tricornutum. not only is their shape and habitat dive | contact : david gilbert | doe / joint genome institute


first ever direct measurement of the earth ’ s rotation geodesists are pinpointing the orientation of the earth ’ s axis using the world ’ s most stable ring laser a group with researchers at the technical university of munich ( tum ) and the federal agency for cartography and geodesy ( bkg ) are the first to plot changes in the earth ’ s axis through laboratory measurements. to do this, they constructed the world ’ s most stable ring laser in an underground lab and used it to determine changes in the earth ’ s rotation. previously, scientists were only able to track shifts in the polar axis indirectly by monitoring fixed objects in space. capturing the tilt of the earth ’ s axis and its rotational velocity is crucial for precise positional information on earth – and thus for the accurate functioning of modern navigation systems, for instance. the scientists ’ work has been recognized an exceptional research spotlight by the american physical society. the earth wobbles. like a spinning top touched in mid - spin, its rotational axis fluctuates in relation to space. this is partly caused by gravitation from the sun and the moon. at the same time, the earth ’ s rotational axis constantly changes relative to the earth ’ s surface. on the one hand, this is caused by variation in atmospheric pressure, ocean loading and wind. these elements combine in an effect known as the chandler wobble to create polar motion. named after the scientist who discovered it, this phenomenon has a period of around 435 days. on the other hand, an event known as the “ annual wobble ” causes the rotational axis to move over a period of a year. this is due to the earth ’ s elliptical orbit around the sun. these two effects cause the earth ’ s axis to migrate irregularly along a circular path with a radius of up to six meters. capturing these movements is crucial to create a reliable coordinate system that can feed navigation systems or project trajectory paths in space travel. “ locating a point to the exact centimeter for global positioning is an extremely dynamic process – after all, at our latitude, we are moving at around 350 meters to the east per second, ” explains prof. karl ulrich schreiber, meanwhile as station director of the geodetic observatory wettzell where the ring laser is settled. karl ulrich schreiber had directed the project in tum ’ s research section satellite geodesy. the geodetic observatory wettzell is run together by tum and bkg. the researchers have succeeded in corrobor


special thanks to our guest blogger, chris myers, u. s. space and rocket center®, huntsville, al for this post bringing the cosmos to space camp®! at the u. s. space and rocket center® and space camp, we are constantly looking for fun and innovative ways to teach our museum guests and trainees about space history and the science and math concepts that surround it. naturally, we were excited to participate in the harvard - smithsonian center for astrophysics series of instructional webinars in order to get some fresh ideas and content. the creativity started to flow as we reviewed the background material, but the amount and quality of the lesson plans and information presented to us by mary dussault and erin braswell was impressive. by the end of the first hour of the webinar, we had solid ideas and lesson plans that could be implemented in every program from summer day camp for 5 - year - olds to advanced space academy® for high - school seniors. and they meet both state and national curriculum guidelines! in this case, our target subject was astronomy. for our younger trainees, we adapted the activities that dealt with colors and filters into a hands - on component for our astronomy briefing “ tenacious telescopes. ” we use pvc pipe, colored felt and theater lighting gel in the primary colors to teach the trainees about how real telescopes like the hubble space telescope use filters to look for specific information, and how scientists can put these single - color images together to make a full - color picture. in addition to making it look more like a real telescope, mounting the color filter inside a pvc pipe telescope has the added bonus of keeping our filters fingerprint and wrinkle free. for our advanced academy ( junior high to high school ) trainees, we added an image processing component into our existing astronomy curriculum which is made up of four components. at the beginning of the week, the trainees participate in a lecture called “ exploring the night sky ” where they learn the basics of astronomy and focus on finding and naming the constellations and deep space objects. our second astronomy block is the “ micro observatory lab, ” where our trainees use the mobs software to compile full - color images of deep space objects. our third astronomy block is a “ night telescope ” activity, where the trainees use real telescopes to find the same objects in the sky of which they compiled images the day before. and for our final astronomy block, our advanced academy trainees learn the stories behind selected constellations in our infl


songwriting for beginners : ‘ just enough ’ music theoryby jeff oxenford • category : how to write songs, songwriting articles ( this is an article in the series “ songwriting for beginners ”. we are filing the series under the songwriting basics category. ) question : how do you stop a guitarist from playing? answer : put music in front of him. that ’ s me. i can ’ t read music and i doubt i ever will. however, over the last three years, i ’ ve learned just enough about music theory to be dangerous. what i ’ ve found is that by understanding some basic concepts, i ’ ve been able to find that next chord i was always searching for. the first step in understanding is that most songs are played in a single key and that the chords in the come from that key. the formula ( i. e. what order ) you use for the chords is what make up the song. for example, blues often uses the 1, 4, and 5 chords. if you ’ re playing blues in e, the chords are e, a, b ( or b7 ). the blues progression in the key of c, uses c, f, and g. if you can understand the table below, you ’ ve got the majority of theory you need. | 1 ( root ) | | 2 | | 3 | | 4 | | 5 | | 6 | | 7 | | 8 ( root ) | | major | | minor | | minor | | major | | major or dominant | | minor | | diminished | | major | here ’ s how to understand this table : guitar frets are in half ( h ) step intervals. in other words, moving up one fret is moving up a half ( h ) step. moving up 2 frets is a whole ( w ) step. notes and intervals on a guitar, the open string and the 12th fret on the same string are the same note ( just different octave ). if you look at the a string, the notes are : | a note | | a | | a # or bb | | b | | c | | c # or db | | d | | d # oreb | | e | | f | | f # orgb | | g | | g # orab | | a | to go from a to b is a whole ( w ) step. to go from a to a # ( or bb ) is a half ( h ) step. also, note that for b to c


excerpt of how to read and why by harold bloom ( page 2 of 5 ) printer friendly excerpt i turn to reading as a solitary praxis, rather than as an educational enterprise. the way we read now, when we are alone with ourselves, retains considerable continuity with the past, however it is performed in the academies. my ideal reader ( and lifelong hero ) is dr. samuel johnson, who knew and expressed both the power and the limitation of incessant reading. like every other activity of the mind, it must satisfy johnson ' s prime concern, which is with " what comes near to ourself, what we can put to use. " sir francis bacon, who provided some of the ideas that johnson put to use, famously gave the advice : " read not to contradict and confute, nor to believe and take for granted, nor to find talk and discourse, but to weigh and consider. " i add to bacon and johnson a third sage of reading, emerson, fierce enemy of history and of all historicisms, who remarked that the best books " impress us with the conviction, that one nature wrote and the same reads. " let me fuse bacon, johnson, and emerson into a formula of how to read : find what comes near to you that can be put to the use of weighing and considering, and that addresses you as though you share the one nature, free of time ' s tyranny. pragmatically that means, first find shakespeare, and let him find you. if king lear is fully to find you, then weigh and consider the nature it shares with you ; its closeness to yourself. i do not intend this as an idealism, but as a pragmatism. putting the tragedy to use as a complaint against patriarchy is to forsake your own prime interests, particularly as a young woman, which sounds rather more ironical than it is. shakespeare, more than sophocles, is the inescapable authority upon intergenerational conflict, and more than anyone else, upon the differences between women and men. be open to a full reading of king lear, and you will understand better the origins of what you judge to be patriarchy. ultimately we read - - as bacon, johnson, and emerson agree - - in order to strengthen the self, and to learn its authentic interests. we experience such augmentations as pleasure, which may be why aesthetic values have always been deprecated by social moralists, from plato through our current campus puritan


- - in order to strengthen the self, and to learn its authentic interests. we experience such augmentations as pleasure, which may be why aesthetic values have always been deprecated by social moralists, from plato through our current campus puritans. the pleasures of reading indeed are selfish rather than social. you cannot directly improve anyone else ' s life by reading better or more deeply. i remain skeptical of the traditional social hope that care for others may be stimulated by the growth of individual imagination, and i am wary of any arguments whatsoever that connect the pleasures of solitary reading to the public good. the sorrow of professional reading is that you recapture only rarely the pleasure of reading you knew in youth, when books were a hazlittian gusto. the way we read now partly depends upon our distance, inner or outer, from the universities, where reading is scarcely taught as a pleasure, in any of the deeper senses of the aesthetics of pleasure. opening yourself to a direct confrontation with shakespeare at his strongest, as in king lear, is never an easy pleasure, whether in youth or in age, and yet not to read king lear fully ( which means without ideological expectations ) is to be cognitively as well as aesthetically defrauded. a childhood largely spent watching television yields to an adolescence with a computer, and the university receives a student unlikely to welcome the suggestion that we must endure our going hence even as our going hither : ripeness is all. reading falls apart, and much of the self scatters with it. all this is past lamenting, and will not be remedied by any vows or programs. what is to be done can only be performed by some version of elitism, and that is now unacceptable, for reasons both good and bad. there are still solitary readers, young and old, everywhere, even in the universities. if there is a function of criticism at the present time, it must be to address itself to the solitary reader, who reads for herself, and not for the interests that supposedly transcend the self. copyright © 2000 by harold bloom. all rights reserved. reproduced by permission of the publisher, simon & schuster.


buildings don ’ t work they way they used to. 1 folks are always saying stuff like this. but let me make the case regarding just one factor and you decide. there are other factors of course, but i want to focus on only one for the moment. this one over - arching factor is the amount of energy exchange across the building enclosure. i think that higher levels of thermal resistance and reduced heat gain across building enclosures has forever changed the performance of buildings — and not necessarily in a good way. and things are going to get worse before they get better. sound familiar? the lens i am going to use to look at this factor is moisture. why? it is one of the principal damage functions acting on materials along with heat and ultra - violet radiation. 2 i think moisture is the key to understanding the performance of buildings in general — and in this particular case — in specific. the consequence of this reduced energy exchange is beginning to be seen all over the place : mold, part load humidity problems, rot, and corrosion. highly insulated building enclosures with reduced heat gain have low drying potentials and increased interior moisture loads. when they get wet they don ’ t dry. stuff is beginning to stink, rot, break and annoy. there are two things to look at here. levels of insulation and airtight assemblies and heat gain through glazing, roof assemblies and interior loads. adding insulation and providing airtight assemblies reduces energy flow. that is a good thing right? well, no — not always. less energy flow from the inside to the outside the colder things on the outside of the building get in the winter. the colder these things, the wetter these things get and the wetter they stay. this is not good. less energy flow from the outside to the inside in the summer and the less heat that is generated inside in the summer the less the air - conditioning system runs. this is a good thing right? well, no — not always. we create something called “ the part load humidity problem. ” higher levels of thermal resistance how do we dry wet wood? we kiln dry it. we heat the wood so that the water in the wood is warmer than its surroundings. we add energy to the water and it evaporates. there is a huge exchange of energy. when we put warm wet coffee beans in a room with very cold surfaces we call it freeze - drying. the moisture leaves the coffee beans and accumulates on the cold surfaces. there is a huge exchange of energy. the greater the


exchange of energy. when we put warm wet coffee beans in a room with very cold surfaces we call it freeze - drying. the moisture leaves the coffee beans and accumulates on the cold surfaces. there is a huge exchange of energy. the greater the rate of energy exchange the greater the rate of moisture movement. drying cannot happen with out an exchange of energy. when my mom and dad bought their first house in toronto, canada in 1957 there was no insulation in the walls and the house was leaky to air — it had a high air change driven by a traditional chimney. we lived in a 1, 200 square foot house and in january, when the outside temperature dropped to 0 degrees f., momma cranked up the 300, 000 btu oil furnace to maintain an interior temperature of 70 degrees f. the energy flow across the building enclosure was enormous, but oil was cheap, and we were comfortable and happy. the energy flow was so enormous the building enclosure was simultaneously kiln dried and freeze - dried. in fact, the drying potential was so high, we were uncomfortably dry. as a result poppa insisted that the furnace have a new fangled gadget attached to it — called a humidifier. how things have changed. well what changed? we ’ ve begun to insulate — and insulate exceptionally well — and we ’ re getting the assemblies “ tighter ” to air change and convection. that results in two things — less energy exchange therefore less drying potential — and things on the exterior side of the enclosure are colder in the winter. things being colder on the outside lead to something most folks don ’ t consider. many building materials are hygroscopic ( figure 1 ). this means they absorb moisture based on relative humidity. even more strangely, they don ’ t care about vapor pressure except if it affects relative humidity. this is a big deal. in fact it is a huge deal. figure 1 : sorption curve for common building materials — note that moisture content goes up as relative humidity goes up. there is no temperature dependence or vapor pressure dependence except where temperature affects relative humidity or where vapor pressure affects relative humidity. quick, snap quiz, psychrometric chart stuff …. as the temperature drops, and vapor pressure is kept constant, what happens to the relative humidity? buzz / clang / bell. yes, folks, you are correct, the relative humidity goes up. the implications are staggering. just making things on the outside of your building cold, hygroscopic things, makes them wetter


humidity? buzz / clang / bell. yes, folks, you are correct, the relative humidity goes up. the implications are staggering. just making things on the outside of your building cold, hygroscopic things, makes them wetter. period, end of story. but, but, the moisture content of the outside air in the wintertime is low. yes, grasshopper, it is, but its ’ relative humidity is high. the amount of moisture in the absolute sense is low, but in the relative sense it is high. and hygroscopic materials don ’ t care about the absolute sense ; they only care about the relative sense. why? second law stuff — isn ’ t it always? check out photograph 1. nice, normal, everyday type of house in cleveland, oh. twenty years old, no insulation in the wall cavities, built in 1965 ( yes, the photograph was taken in 1985 — we did have camera ’ s back then... ). the house was perfectly happy at this point for twenty years. then the homeowner decides to do something crazy, he decides to insulate the exterior walls to save energy and has the cavities blown with dry cellulose. what a dumb idea in 1985 eh? but, never the less, it was a beautiful job, no voids, yes it can be done, and yes it was done. no voids, no convection ( photograph 2 — notice how young this engineer once was ). next thing you know, the paint falls off, and the siding gets smelly, moldy and begins to decay ( photograph 3 ). huh? the insulation did this? yup. the drying potential is reduced due to the addition of the insulation so that the moisture entering the cladding assembly from the exterior due to rain and capillarity does not evaporate and this is further exacerbated by the colder siding having a higher local relative humidity and thus a higher equilibrium moisture content due to the sorption properties of wood. bummer. how to fix this? easy, wedges were used to create a gap at the overlaps of the siding reducing capillary uptake at the laps and increasing evaporation despite the cladding being colder ( photograph 4 ). this early lesson in sorption and drying potentials taught this engineer to drain and back - ventilate claddings – especially those on highly insulated assemblies ( photograph 5 ). photograph 1 : the “ typical house ” —


why insulating sheathing is pretty much the name of the game for highly insulated wall assemblies — or at a minimum claddings should be back ventilated and back - drained — or better, do both. this is easy for new construction. the problem is what to do with the existing building stock? what are we going to do if oil ever goes above $ 100 / barrel? dumb comment. yes, but now we have a real problem. folks cannot just go and blow / spray / fill cavities with a bunch of insulation without appreciating the consequences. this is not just a cold climate problem. it is a problem everywhere. in fact it gets worse when we go far south. read on mcduff … reduced heat gain i am going to let you in on a little secret that us mechanical engineers don ’ t often share with the rest of the world — air conditioning systems only dehumidify when they run. yup, when they don ’ t run, they don ’ t dehumidify. if there is no load, there is no dehumidification. 4 well, just make them run longer. how? they still make the air cold no matter how you run them. that is good if you need cold air. but what if you don ’ t need cold air? what if you only need dry air? well, you still have to make the air cold to get it to drop its water, and when you are done you still have cold air. so now what? well, you have to heat it back up if you want to use it. this is sometimes called cooling with re - heat. there are other tricks we can do — read on — but at the end of the day we have to add energy back to the air that we cooled. there is no other practical way to do it. it gets worse when we over - ventilate with humid air — especially when it is cloudy and not so hot. now all you are doing is bringing in moisture. but you are doing it when there is not much of a load — not much of a “ sensible load ” ( heat gain across the enclosure and heat gain from lights and appliances and people — the load you can “ sense ” ) to run the air conditioning system. this moisture that you are bringing in with the ventilation air is also a “ load ” — but it is a different kind of load that we have pretty much been ignoring up till now and getting away with it. the operative phrase to note is


system. this moisture that you are bringing in with the ventilation air is also a “ load ” — but it is a different kind of load that we have pretty much been ignoring up till now and getting away with it. the operative phrase to note is : “ getting away with it. ” mechanical engineers like me call this the “ hidden load ” or the “ latent load ” ( as in “ latent defect ” or “ hidden defect ” ) and our heads explode when we try to explain this problem to the indoor air crazies who think that only dilution is the solution to indoor pollution. i mean how can too much outside air be bad? 5 arrargah … to take the water out of the air you need to use energy. to make the air comfortable / useful the air can ’ t be too cold after you have taken the water out of it. typically heat ( energy ) has to be added back to the air. traditionally this heat ( energy ) was available through lousy glazing systems, too much glass, black roofs with no insulation, poorly insulated walls, energy inefficient lights, and crappy appliances. well, this traditional “ re - heat ” due to inefficiency and poor practice is disappearing. now we are stuck. if we don ’ t warm up the air after we dry it we are going to get into trouble. we haven ’ t been, and we are getting into trouble. the buildings are now getting too cold or too humid or worse, both. ah, this is easy you say. just make the air conditioning systems smaller — “ right size ” them. don ’ t make me scream. i am getting tired of being told by energy weenies that my equipment is too big. 6 i still have to satisfy the “ full load ” requirement. if you make the equipment too small it doesn ’ t satisfy the cooling requirements under full load. let the people be uncomfortable you say. people should suffer you say ; we have had it too good you say. yeah, sure, another greenie weenie value judgment that also makes me scream. i don ’ t think we should suffer. i like it being good. i don ’ t have a problem with using energy. i have a problem with wasting energy. until now we have gotten pretty good at dealing with this part - load problem with face - bypass, run - around coils, hot gas bypass and heat pipes but we have reached our limits. building enclosures have gotten so good, gla


. until now we have gotten pretty good at dealing with this part - load problem with face - bypass, run - around coils, hot gas bypass and heat pipes but we have reached our limits. building enclosures have gotten so good, glazing systems so good, interior load management so good, that we can ’ t use the same equipment to handle the “ sensible load ” and the “ latent load. ” did i mention just how good the glazing systems have become? did i mention the low shgc thing? we used to just install air conditioners and only cared about making it cold inside. we used one piece of equipment to handle the sensible and latent load. the reason this worked is that the latent load was small compared to the sensible load. not any more. the sensible load has gotten smaller big time. and, much to my chagrin, the latent load has gone up due to over ventilation. the old systems can ’ t handle the new sensible to latent ratios. we have to separate the two loads. we need separate systems for the sensible load and the latent load. this is a big deal and it results from the low heat gain in the modern enclosure. in other words energy conservation and good construction practice is biting us on the butt. we sometimes refer to this second separate latent load control system as supplemental dehumidification — and we need it when we have a low heat gain enclosure and efficient lighting and appliances. others call it “ preconditioning ” of outside air since the largest component of the latent load is the ventilation air or the outside air. whatever you call it, we need this second system. we don ’ t often get it and it hurts us. but, but these systems use energy. yes, as the saying goes — there is no thermodynamic free lunch. you need to use energy to make air cold and you need to use energy to make air dry. we have been very good at making air cold. we now have to get good at making air dry. think of it this way. for every 100 units of energy you save on the efficiency and on the cooling side, you are going to have to give back about 20 units of energy to be dry. you are still 80 units ahead. problem is, if you are greedy and want the entire 100 units your building fails and your occupants get very uncomfortable and probably very annoyed. it is pretty amazing to me but the hotel industry figured this out first. they pretty much had


80 units ahead. problem is, if you are greedy and want the entire 100 units your building fails and your occupants get very uncomfortable and probably very annoyed. it is pretty amazing to me but the hotel industry figured this out first. they pretty much had the problem first, so it stands to reason that they would also figure it out first. think about the typical hotel room. the drapes are pretty much closed all the time, the room is empty during the day, and you know the unit has been sized for the full load, with the drapes open, and the room full, and everything on and you know that someone in some bureaucracy somewhere wants way too much outside air. most of the time your latent load dwarfs your sensible load. so what do you do? you reduce the amount of outside air by installing timers on the exhaust fans and you pretty much ignore the faceless bureaucrat. then you only run the through - wall unit to control the temperature ( i. e. make it the “ sensible ” system ) and install a dehumidifier in each unit control the humidity ( the “ latent ” system ) ( photograph 6 ). a pretty primitive but effective “ fix. ” in new design we just “ hide ” the dehumidifier better — or better still make it part of the ventilation system. photograph 6 : hotel room fix — the through - wall unit controls the temperature ( the “ sensible ” system ). the dehumidifier controls the humidity ( the “ latent ” system ). guess where this technology is now making an impact — condos and apartments. small houses are next. we are already separating the latent from the sensible on most commercial design — after all it is the sensible thing to do. north versus south so how come it is worse in the south than the north? besides the south loosing the civil war? in the north, it still gets cold and the outside cold air is pretty dry — and walls tend to dry to the outside in the north - so the size of the moisture drying “ sink ” so to speak — has not changed. but in the south, walls also dry to the inside — and if the inside is humid because of the part load problem — the walls stay wetter because the moisture drying “ sink ” is smaller. additionally, in the south the moisture drive from the exterior into the wall is greater while at the same time the moisture drive from the wall into the interior is smaller as compared to the corresponding drives in opposite directions in the


functions ( water, heat and uv radiation ) with 80 percent of the 80 percent being water. i don ’ t know who said this. can someone help me out? i might have just made it up, but i have been saying it so long i no longer remember if i did or not. aren ’ t footnotes great … air flow — air change and convection — increases energy exchange therefore increases drying potential. my canadian friends heads are now going to explode because they have been taught that air leakage leads to “ wetting ” from interior sources. yes, in extreme climates with high interior moisture loads. think humidified buildings in canada. not everywhere else. come visit the united states, the dollar exchange now works for you and air leakage improves drying potentials. sensible load. i know you knew that i knew this, but some of the email i have been getting from you folks has been quite picky, which is good, but i want to head off the obvious emails, so continue to be picky, but not on this … some folks don ’ t seem to care about the energy thing either. i mean health is paramount and we should always err on the side of caution. how can we argue against health? easy, when the “ healthy ” measures are “ unhealthy. ” over - ventilation can be unhealthy — and energy wasteful. read on. this is leading to interesting discussions in the standard 62 committees. apparently the standard 62 committees are not about energy. apparently energy security is not a 62 problem nor is climate change nor are operating costs. apparently, it is some other committee ’ s problem. how about the energy committee ( standard 90. 1 )? except that the energy committee does not want to touch ventilation. cowards. my insider ’ s perspective ( on 62. 2 at least ) is that there is a lot of mileage to be made by scaring people about under ventilation, and folks are rising to the occasion. unfortunately, over ventilation in hot humid climates and in mixed humid climates has led to more indoor air problems due to mold resulting from part load issues than under ventilation anywhere else — in my not so humble opinion. and speaking of health and under ventilation where are all the dead bodies? where is the causal link between health and specific levels of specific indoor contaminants? in my not so humble opinion all of the rates have been just wild assed guesses without a sound epidemiological basis. but the resulting mold from over ventilation is real and demons


the immune system because the human body provides an ideal environment for many microbes, they try to pass your skin barrier and enter. your immune system is a bodywide network of cells, tissues, and organs that has evolved to defend you against such " foreign " invasions. the proper targets of your immune system are infectious organisms - - bacteria such as these streptococci ; fungi ( this one happens to be candida, the cause of yeast infections ) ; parasites, including these worm - like microbes that cause malaria ; and viruses such as this sars virus. markers of self at the heart of the immune response is the ability to distinguish between " self " and " non - self. " every cell in your body carries the same set of distinctive surface proteins that distinguish you as " self. " normally your immune cells do not attack your own body tissues, which all carry the same pattern of self - markers ; rather, your immune system coexists peaceably with your other body cells in a state known as self - tolerance. this set of unique markers on human cells is called the major histocompatibility complex ( mhc ). there are two classes : mhc class i proteins, which are on all cells, and mhc class ii proteins, which are only on certain specialized cells. markers of non - self any non - self substance capable of triggering an immune response is known as an antigen. an antigen can be a whole non - self cell, a bacterium, a virus, an mhc marker protein or even a portion of a protein from a foreign organism. the distinctive markers on antigens that trigger an immune response are called epitopes. when tissues or cells from another individual enter your body carrying such antigenic non - self epitopes, your immune cells react. this explains why transplanted tissues may be rejected as foreign and why antibodies will bind to them. markers of self : major histocompatibility complex your immune cells recognize major histocompatibility complex proteins ( mhc ) when they distinguish between self and non - self. an mhc protein serves as a recognizable scaffold that presents pieces ( peptides ) of a foreign protein ( antigenic ) to immune cells. an empty " foreign " mhc scaffold itself can act as an antigen when donor organs or cells are introduced into a patient ' s body. these mhc self - marker scaffolds are also known as a patient ' s " tissue type " or as human leukocyte antigens ( h


effective in killing bacteria. scientists long wondered how all the genetic information needed to make millions of different antibodies could fit in a limited number of genes. the answer is that antibody genes are spliced together from widely scattered bits of dna located in two different chromosomes. each antibody molecule is made up of two separate chains, a heavy chain and a light chain. the heavy chain is where the binding of antigens occurs, so much genetic variation is involved in its assembly. for example, to form a heavy chain, 1 of 400 possible variable gene segments ( v ) combines with 1 out of 15 diversity segments ( d ) and 1 out of 4 joining ( j ) segments. this makes 24, 000 possible combinations for the dna encoding the heavy chain alone. as this part of the gene assembles, it joins the variable coding segments with those for the constant - c segments of the heavy - chain molecule. t cells contribute to your immune defenses in two major ways. some help regulate the complex workings of the overall immune response, while others are cytotoxic and directly contact infected cells and destroy them. chief among the regulatory t cells are helper t cells. they are needed to activate many immune cells, including b cells and other t cells. cytotoxic t cells ( sometimes called killer t cells ) help rid your body of cells that have been infected by viruses as well as cells that have been transformed by cancer but have not yet adapted to evade the immune detection system. they are also responsible for the rejection of tissue and organ grafts. cytokines are diverse and potent chemical messengers secreted by the cells of your immune system. they are the chief communication signals of your t cells. cytokines include interleukins, growth factors, and interferons. lymphocytes, including both t cells and b cells, secrete cytokines called lymphokines, while the cytokines of monocytes and macrophages are dubbed monokines. many of these cytokines are also known as interleukins because they serve as a messenger between white cells, or leukocytes. interferons are naturally occurring cytokines that may boost the immune system ' s ability to recognize cancer as a foreign invader. binding to specific receptors on target cells, cytokines recruit many other cells and substances to the field of action. cytokines encourage cell growth, promote cell activation, direct cellular traffic, and destroy target cells - - including cancer cells. when cytokines attract specific


on target cells, cytokines recruit many other cells and substances to the field of action. cytokines encourage cell growth, promote cell activation, direct cellular traffic, and destroy target cells - - including cancer cells. when cytokines attract specific cell types to an area, they are called chemokines. these are released at the site of injury or infection and call other immune cells to the region to help repair damage and defend against infection. killer cells : cytotoxic ts and nks at least two types of lymphocytes are killer cells - - cytotoxic t cells and natural killer cells. both types contain granules filled with potent chemicals. both types kill on contact. they bind their targets, aim their weapons, and deliver bursts of lethal chemicals. to attack, cytotoxic t cells need to recognize a specific antigen bound to self - mhc markers, whereas natural killer ( nk ) cells will recognize and attack cells lacking these. this gives nk cells the potential to attack many types of foreign cells. phagocytes and their relatives some immune cells have more than one name. for example, the name " phagocytes " is given to the large immune cells that can engulf and digest foreign invaders, and the name " granulocytes " refers to immune cells that carry granules laden with killer chemicals. phagocytes include monocytes, which circulate in the blood ; macrophages, which are found in tissues throughout the body ; dendritic cells, which are more stationary, monitoring their environment from one spot such as the skin ; and neutrophils, cells that circulate in the blood but move into tissues when they are needed. macrophages are versatile cells ; besides acting as phagocytic scavengers, they secrete a wide variety of signaling cytokines ( called monokines ) that are vital to the immune response. neutrophils are both phagocytes and granulocytes : they contain granules filled with potent chemicals. these chemicals, in addition to destroying microorganisms, play a key role in acute inflammatory reactions. other types of granulocytes are eosinophils and basophils, which degranulate by spraying their chemicals onto harmful cells or microbes. the mast cell is a twin of the basophil, except it is not a blood cell. rather, it is responsible for allergy symptoms in the lungs, skin, and linings of the


spraying their chemicals onto harmful cells or microbes. the mast cell is a twin of the basophil, except it is not a blood cell. rather, it is responsible for allergy symptoms in the lungs, skin, and linings of the nose and intestinal tract. a related structure, the blood platelet, is a cell fragment. platelets, too, contain granules. they promote blood clotting and wound repair, and activate some immune defenses. phagocytes in the body if foreign invaders succeed in getting past your skin barriers and manage to reach body tissues, they are usually recognized, ingested, and killed by phagocytes strategically positioned throughout the body. macrophages and neutrophils are the main phagocytes involved, with macrophages as the first line of defense. monocytes stop circulating in the blood and mature into specialized macrophages that migrate into the tissues of the body and prepare for invasion. large numbers of mature macrophages reside in connective tissue, along the digestive tract, in the lungs, in the spleen, and even along certain blood vessels in the liver, where they are known as kupffer cells. neutrophils are short - lived immune cells that remain circulating in the blood. when tissue - based macrophages encounter an invader, neutrophils soon reinforce their immune response by coming to the site of infection in large numbers. the complement system consists of a series of about 25 proteins that work to " complement " the work of antibodies in destroying bacteria. complement also helps rid the body of antigen - antibody complexes. complement proteins are the culprits that cause blood vessels to become dilated and leaky, causing redness and swelling during an inflammatory response. complement proteins circulate in the blood in an inactive form. the so - called " complement cascade " is set off when the first complement molecule, c1, encounters antibody bound to antigen in an antigen - antibody complex. each of the complement proteins performs its specialized job, acting, in turn, on the molecule next in line. the end product is a cylinder that punctures the cell membrane and, by allowing fluids and molecules to flow in and out, dooms the target cell. mounting an immune response microbes attempting to get into your body must first get past your skin and mucous membranes, which not only pose a physical barrier but are rich in scavenger cells and iga antibodies. next, they must elude a series of nonspec