Newtonian physics

How is physics, as it is currently practiced, deficient in its description of nature Certainly, as popularizations of physics frequently reniiiid us, theories such as Quantum Electrodynamics are successful to a reinarkiible degree in predicting the results of experiments. However, any reasonable measure of success requires that wc add the caveat, ...in the domain (or domains) for which the theory was developed. For example, classical Newtonian physics is perfectly correct in its description of slow-moving, macroscopic objects, but is fundamentally incorrect in its description of quantum and/or relativistic systems. 

The British physicist and mathematician Sir Isaac Newton formulated his laws of motion in the 17th century. These laws predict the course of an object when subjected to various forces, such as a push, pull, or a collision with another object. In Newtonian physics, physicists can predict the motion of an object with any desired degree of accuracy if all the forces acting on it are precisely known. 

Reducing each component would, in principle, create a miniaturized instrument or device, but in most cases, this simple idea probably would not work. Quantum mechanics becomes important at the scale of nanotechnology, and as described in the sidebar on page 20-21, its laws are different from Newtonian physics. 

The geometric description of the light propagation and the kinetics description of motion were closely correlated in the history of science. Among the main evidence of classical Newtonian mechanics is Euclidean geometry based on optical effects. In Newtonian physics, space has an affine structure but time is absolute. The basic idea is the inertial system, and the relations are the linear force laws. The affine structure allows linear transformations in space between the inertial coordinate systems, but not in time. This is the Galilean transformation ... 

One of the most important requirements for an axiomatic theory is to determine the validity-round of the laws, and to verify of the self-consistency in the theory. The M-M experiment proved that the prediction of the classical physics was not valid for light propagation, or rather, for Maxwell s theory of electromagnetism. This is an applicability limit of Newtonian physics. Beyond this limit, Newtonian physics becomes incomplete. 

According to Newtonian physics, the universe and all of the objects in it are simply an extremely complicated collection of masses and charges. This implies that if you knew the state of the universe at any one time (exactly), you could predict (exactly) the future. Of course it is unrealistic to actually do a set of measurements which define the conditions at one time with enough accuracy, but it is in principle possible. Therefore, Newtonian mechanics predicts that the future is perfectly determined by the past. There is no such thing as free will , and you need not worry about studying for the next examination it has already been determined how much you will study, and what you will score on the test ... 

There were critics who thought that chemistry could never be more than a combination of laboratory practice, which they viewed as a kind of cookery, and classification, which they saw as the essence of natural history, including botany and zoology. Those same critics regarded natural history as unscientific, lacking the rigor of mathematical physics or astronomy. Chemistry was indeed far from Newtonian physics. We have already seen the failure of attempts to assimilate chemistry to Newton s program. But to dismiss chemistry for this reason was to adopt too narrow a definition of science and to undervalue the role of classification in the scientific enterprise as a whole. Natural historians have to classify what they observe or collect so do chemists. 

Chemistry lacked prestige, and chemists often worked in isolation, with little recognition from the wider community of science. Newtonian physics and... 

Mechanical motion—the motion of macroscopic bodies—is described by simple Newtonian physics. The study of mechanical motion is a logical precursor to the study of molecular displacements. It is useful to highlight the principal similarities and differences here. 

Alternatively, Einstein thought mostly outside the box of the prevailing wisdom of his day, or what was known at the time, and such exploration is the essence of solving problems in untried and untested ways. His theory of relativity questioned key assumptions of Newtonian physics. Einstein even characterized himself as a little strange—but strangeness is what it takes to solve ill-defined problems, or to solve fairly well-defined problems in new and unusual ways. 

Momentum is a property of motion that in classical physics is a vector (directional) quantity that in closed systems is conserved during collisions. In Newtonian physics momentum is measured as the product of the mass and component velocity of a body. For massless... 

The Cognitive Correspondence Principle Named after the inspiration of Neils Bohr in tying quantum physics to Newtonian physics, this principle recognizes the mathematical hierarchy required in modeling complex systems and need to make simplifying assumptions. It states that each assumption must, in the limit, be found to be a valid truncation of a more precise mathematical description of the overall system. 

Now suppose a chamber of slow and hence cold molecules is connected with a chamber of warm, fast moving molecules. Soon, the two chambers will have the same mix of fast and slow molecules. But if you begin with two chambers containing the same mixture and connect them, you will never find one chamber collecting all the fast molecules and the other the slow ones. Newtonian physics was reversible, but the world he was describing was not. To cope with this fact, enshrined of course in the second law of thermodynamics and the entropy concept, we need to introduce directional time designated here as -ft. 

One may ask why the expression for the non-relativistic current density is so very much more complicated than the corresponding relativistic expression. The answer is that it reflects the attempt to merge equations (Schrodinger and Maxwell) with incompatible transformation properties. When Poincar6 studied the transformation properties of Maxwell s equations, he found that they did not transform according to the Galilei transformation as the equations of the Newtonian physics, and they were in fact termed non-relativistic until Einstein with the introduction of the theory of special relativity showed that they indeed possessed the physically correct transformation properties ... 

FIGURE 233. Title page from Dr. John Freind s 1712 book in which he attempted to use Newtonian physics to explain physical and chemical properties of matter. Newton suspected that the forces holding matter together were electrical and magnetical. 

Biomechanics considers safety and health implications of mechanics, or the study of the action of forces, for the human body (its anatomical and physiological properties) in motion (at work) and at rest Mechanics, which is based on Newtonian physics, consists of two main areas statics or the study of the human body at rest or in equilibrium, and dynamics or the study of the human body in motion. Dynamics is further subdivided into two main parts, kinematics and kinetics. Kinematics is concerned with the geometry of motion, including the relationships among displacements, velocities, and accelerations in both translational and rotational movements, without regard to the forces involved. Kinetics, on the other hand, is concerned with forces that act to produce the movements. 

As far back as Bohr s doctoral dissertation he had decided that some of the phenomena he was examining could not be explained by the mechanical laws of Newtonian physics. One must assume that there are forces in nature of a kind completely different from the usual mechanical sort, he wrote then. He knew where to look for these different forces he looked to the work of Max Planck and Albert Einstein. 

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