Ordinary matter

As far as is known, ordinary matter is made of tiny building blocks called elementary particles. For example, an atom is made up of a nucleus surrounded by one or more electrons. As far as scientists have been able to determine, the electrons are elementary particles, not made of anything simpler. Fdowever, an atomic nucleus is not clcmcntai y, but is a composite particle made up of simpler particles called protons and neutrons. (The lightest nucleus is the nucleus of ordinai y hydrogen, which consists of only a single proton.) Today, physicists believe that even protons and neutrons are not elementai y but are composite particles made up of still simpler building blocks called quarks. 

In addition to ordinai y matter, scientists have evidence for the existence in the universe of dark matter. Some of the dark matter is ordinai y matter, such as dust in outer space and planets going around other stars. Astronomers cannot see ordinai y dark matter because any light coming from such matter is too faint to be observed in telescopes. However, most of the dark matter in the universe is believed not to be ordinary matter. At the present time it is not known what this mysterious dark matter is, or what it is made of. Scientists know that this dark matter exists because it exerts a gravitational force on stars (which are made of ordinary matter), causing the stars to move faster than they otherwise would. According to present estimates, there is perhaps five times as much dark matter in the universe as ordinary matter. 

Earth and the sun, and, as far as is kno wn, the stars and planets in the rest of the visible universe, are made of ordinai y matter. However, according to a theoi y fir.st proposed by Paul Dirac in 1928, for every kind of particle of ordinary matter that exists in nature, there can exist an antiparticle made of antimatter. Some antiparticles have been discovered for example, the antiparticle of the electron, called the positron, was discovered in 1932 in cosmic rays falling on earth and have also been created in experiments performed in the laboratory. Antimatter is very simi-... 

The main reason particle accelerators were invented and developed is so that scientists can observe what happens when beams of particles strike ordinary matter. However, particle accelerators are also used in a wide variety of applications, such as irradiating cancers in people. 

Of all electrical phenomena electrolysis appears the most likely to furnish us with a real insight into the true nature of the electric current, because we find currents of ordinary matter and currents of electricity forming essential parts of the same phenomenon. 

On the other hand, the permanent EDM of an elementary particle vanishes when the discrete symmetries of space inversion (P) and time reversal (T) are both violated. This naturally makes the EDM small in fundamental particles of ordinary matter. For instance, in the standard model (SM) of elementary particle physics, the expected value of the electron EDM de is less than 10 38 e.cm [7] (which is effectively zero), where e is the charge of the electron. Some popular extensions of the SM, on the other hand, predict the value of the electron EDM in the range 10 26-10-28 e.cm. (see Ref. 8 for further details). The search for a nonzero electron EDM is therefore a search for physics beyond the SM and particularly it is a search for T violation. This is, at present, an important and active held of research because the prospects of discovering new physics seems possible. 

A mechanical analogy can be done we must anticipate that there will be very little coupling between GW and ordinary matter. In fact, we know that sound waves in common materials couple efficiently from one body of density p, and sound velocity vx to another of density p2 and sound velocity v2 if the product p, p, = p2v2. The product pv is called the sound impedance per unit area and has dimension of kg/m2s. For an antenna made of copper with a surface area of 1 m2, the impedance is 3 x 107 kg/s. For space-time this would be ... 

This represents an upper limit for the dimensions of the nucleus. Compared with the estimates for the size of the atom, obtained from kinetic theory calculations on gases, which are typically 4x10 9 m. we can see that the nucleus is very small indeed compared to the atom as a whole - a radius ratio of 10-5, or a volume ratio of 10 15, which supports Rutherford s observation that most of an atom consists of empty space. We can also conclude that the density of the nucleus must be extremely high - 1015 times that encountered in ordinary matter, consistent with density estimates in astronomical objects called pulsars or neutron stars. 

Chemistry is the central science in the sense that it provides the tie between physics on the one hand and biology on the other. The world of physics, seen broadly, covers a wide spectrum. In general, the concerns of physics focus on entities smaller or larger than those of direct interest to chemistry. At the micro level physics unravels the mysteries of the elementary particles, known generally as fermions, which constimte all ordinary matter. Fermions include the quarks and their antiparticles, the antiquarks. There are six kinds of quarks, known as top, bottom, strange, charm,... 

No indeed The stars are not made from some incorruptible ether but of ordinary matter. The last post had sounded for the quintessence, the fifth and highest of the elements, along with earth, air, fire and water. Tycho enlisted the services of Kepler and in 1604 master and pupil were rewarded by the magnificent spectacle of a supernova. 

Luminous matter has revealed dark matter, but the new substance remains obscure. What is it made from Is it perhaps composed of known forms of matter Only partly Is dark matter made up of microscopic particles If the answer is affirmative, we may suppose that this unknown form of energy penetrates and permeates the galaxies, the Solar System and even our own bodies, just as neutrinos pass through us every second without affecting us in any way. And like the neutrinos, these unknown particles would hardly interact at all with ordinary matter made from atoms. To absorb its own neutrinos, a star with the same density as the Sun would have to measure a billion solar radii in diameter. Luminous and radiating matter is a mere glimmer to dark matter. 

The insufficient density of ordinary matter (i.e. yours, mine and the matter in stars) implies that there must be matter which is not nuclear, literally extraordinary matter which is not made up of atoms. The sky thus distances itself from the purely atomic and nuclear paradigm. So speaks the dark side of space. 

Anderson s particle, which is now called the muon after the Greek letter mu, was actually a kind of heavy electron. It had a large mass, but it otherwise exhibited electronlike properties. This was a great puzzle to the physicists of the day, because there seemed to be no reason it should exist. It was not a component of ordinary matter. It could be observed in the high-energy cosmic ray laboratory, but it quickly decayed (that is, disintegrated) into other particles. 

A recent development in nuclear medicine that illustrates how advances in basic research are transformed into practical applications is positron emission tomography or PET. PET creates a three-dimensional image of a body part using positron emitting isotopes. Positrons, positively charged electrons, are a form of antimatter. Antimatter consists of particles that have the same mass as ordinary matter, but differ in charge or some other property. For example, antipro-... 

Clearly there is something arbitrary abont defining the essence of discovery and attribnting it to a particular researcher at a particular time. In my mind, the identity of the electron as a building block of ordinary matter is a key part of the concept of the electron simply characterizing cathode rays as particles of a... 

This approach parallels our consideration of the equation of state that applies to ordinary matter, such as gases, liquids, and solids that exist in macrostructured materials. See also Equation of State. 

Smith, TP. Hidden Worlds Hunting for Quarks in Ordinary Matter. Princeton University Press, Princeton, NJ, 2003. 

A few years later the antielectron was found, and almost 30 years later, the antiproton. Antimatter indeed exists in nature, as Dirac predicted from Einstein s work. This theoretical prediction was one of the greatest intellectual achievements of science. Today, beams of antimatter are produced in many laboratories they run in carefully evacuated tubes m order not to hit any ordinary matter until they reach their target, where they annihilate with the target substance. 

In this case, regardless of the value of a, the value of the equation of state parameter w is always around —0.8 when Qq = 0.7. Let us note that this is far from the end of the story. In order to build a realistic model, we have in particular to (i) find a framework which can naturally account for an inverse power law potential, (ii) explain why the particle associated to this field have never been observed since V" is extremely low today, one expects that the associated particles are very light, so that if they are not detected experimentally, then they must be extremely weakly coupled to ordinary matter, a situation which may necessitate some new fine tuning in the model. For a much deeper discussion about all this, see for examples Refs. Brax Martin 1999 Brax et al. 2000 Brax et al. 2001 and references therein. 

Nothing is known about the nature of the energy component, which goes under the name of dark energy. Of the matter component, less than 2% is luminous, and no more than 20% is made of ordinary matter like protons, neutrons, and electrons. The rest of the matter component, more than 80% of the matter, is of an unknown form which we call non-baryonic. Finding the nature of non-baryonic matter is referred to as the non-baryonic dark matter problem. 

Living things are peculiar aggregates of ordinary matter and of ordinary force which in their separate states do not possess the aggregates of qualities known as life. 

Though the value of mv measured by the ITEP group is about 1/15,000 of the electron mass, the average concentration of neutrinos in the universe is so much greater than the average concentration of ordinary matter that more than 90% of the whole mass of the universe is due to neutrinos. So, in a way, we are living in a neutrino universe. 

Watt, like Black, was committed to one of three major views of heat extant at the time. The first of the three views was that heat was motion, or the vibration of the parts of ordinary material bodies. This mechanical theory of heat had been favoured by Boyle and had been endorsed by Newton. But the mechanical theory was not fashionable in the mid- to late eighteenth century. We know that a mathematical theory of heat as motion was developed by Henry Cavendish in the 1780s but, typically, not published.42 This type of theory was, of course, to become the correct view of heat by the mid-nineteenth century. The second and third accounts of heat are often collapsed together as material theories since in both heat was a special substance rather than the motion of ordinary matter. The distinction between these two material theories is clearly described by McCormmach ... 

Joseph Black subscribed to a version of the first material theory. He considered heat to be a special form of matter that combined with ordinary matter as a result of chemical forces of attraction. The phenomenon of cold produced by evaporation was explained by Black as follows. The cold experienced when water evaporates is the result of the water absorbing sensible heat as the water becomes vapour. The heat is not lost, rather the heat combines chemically with the vapour and it is this that gives the vapour the property of elasticity. Thus water absorbs the matter of heat, which becomes latent (or fixed as Black termed it initially) because it is now chemically combined with the water. Through this combination, the latent heat confers the property of fluidity or elasticity upon the vapour, that is upon the steam. 

This account seems strange to us. We are accustomed to thinking of Black as the discoverer of latent heat , and by this we usually mean the discoverer of what we understand by the term latent heat . But this is quite wrong. Our concept of latent heat is underwritten by a kinetic theory of heat Black s was based on a material (chemical) one in which latent heat was intrinsic to chemical reactions and was compounded with ordinary matter. The fact that Black has a conception of latent heat foreign to us is made clear by the terms in which Black s supporters stated and defended his claims. Thus, in his Encyclopaedia Britannica article on Steam Robison described Black as having justly concluded that,... 

The Nature of Atoms. Ail ordinary matter consists of atoms. The exceptional kinds of matter are. the elementary particles from which atoms are made (electrons, protons, neutrons), and other subatomic particles (positrons, mesons) these elementary particles will be dis cussed later (Chap. 33). But atoms are the units which retain their identity when chemical reactions take place therefore, they are im portant to us now. Atoms are the structural units of all solids, liquids, and gases. They are very small—only about 2 A to 5 A in diameter. 

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