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Richard P. FeynmanThe Nobel Prize in Physics 1965
Biography

Richard P. Feynman was born in New York City on the 11th May 1918. He studied at the Massachusetts Institute of Technology where he obtained his B.Sc. in 1939 and at Princeton University where he obtained his Ph.D. in 1942. He was Research Assistant at Princeton (1940-1941), Professor of Theoretical Physics at Cornell University (1945-1950), Visiting Professor and thereafter appointed Professor of Theoretical Physics at the California Institute of Technology (1950-1959). At present he is Richard Chace Tolman Professor of Theoretical Physics at the California Institute of Technology.Professor Feynman is a member of the American Physical Society, the American Association for the Advancement of Science; the National Academy of Science; in 1965 he was elected a foreign member of the Royal Society, London (Great Britain).He holds the following awards: Albert Einstein Award (1954, Princeton); Einstein Award (Albert Einstein Award College of Medicine); Lawrence Award (1962).Richard Feynman is married to Gweneth Howarth, they have a son, Carl Richard (born 22nd April 1961), and a daughter Michelle Catherine (born 13th August 1968).
From Nobel Lectures, Physics 1963-1970, Elsevier Publishing Company, Amsterdam, 1972
This autobiography/biography was first published in the book series Les Prix Nobel. It was later edited and republished in Nobel Lectures. To cite this document, always state the source as shown above.

(James Maxwell (1831-१८७९

James Maxwell (1831-1879

James Maxwell was a true genius and made several contributions to the scientific community. Indirectly, he made a significant contribution to the area of relativity. His equations for electromagnetic waves helped to aid the future work of Hendrik Lorentz.
James Maxwell was born on June 13, 1831 in Edinburgh, Scotland. Maxwell showed an early understanding and love for the field of mathematics. In fact, he can be classified as one of the most brilliant mathematicians of all time. He lost his mother at the early age of eight. It was the original thoughts of his parents that he would be educated at home by them. He composed his first formal paper at the age of fourteen and it was entitled "On the description of oval curves, and those having a plurality of foci." This paper was presented to the Royal Society and it was well received. However, at the age of sixteen, James attended the Edinburgh Academy. While he attended the college, Maxwell was given the nickname "Dafty." In 1854, James graduated with a degree in mathematics from Trinity College and also received a fellowship there. He was the first person to establish the three color model of ordinary vision and hence became the first person to create the world's first ever color photo. In April of 1856, Maxwell became the chairman at Marischal College. A few months later he accepted a professorial position in Aberdeen. In 1857, Maxwell competed for and won the Adam's Prize on the subject of the motion of the rings of Saturn. He proved that the rings are not solid, but are made of several tiny, rocky particles. In 1860, James took the position of chairman of Natural Philosophy at King's College in London. Maxwell was always respected by his students and thought to be a fine professor. In addition, he was recognized publicly as one of the wisest men of that time. In 1866, he helped to develop a theory of gases that showed that the movement of molecules was the root cause for heat and for temperature. This theory is now called the Maxwell-Boltzmann kinetic theory of gases. James Maxwell died on November 5, 1879 in Cambridge, England.
Maxwell made several contributions to the scientific community, but his most important achievement was his development of the equations of electromagnetic waves that were first envisioned by Michael Faraday. His theory was presented in 1873 and was entitled "Electricity and Magnetism." His four differential equations can be summarized as the following: 1. Electric fields come from a single charge (it has definite starting and ending point at the charge itself or at infinity). 2. Neither a starting nor an ending point for a magnetic field can be located. 3. If a magnetic field is altered, then over time it will become an electric field; however, no beginning or ending points can be located since the field was not created by charges. 4. Changing an electric field will convert it into a magnetic field over time, and it will retain its looping properties. This description of electromagnetism is at once simple and complex and is one of the greatest mathematical achievements of the 19th century. Even though these four equations were not directly intended for the theory of relativity, they have made a significant contribution in the development of the theories of relativity by later mathematicians and physicists. For example, Hendrik Lorentz used a slightly modified version of Maxwell's equations in order to develop the concept of length contraction when an object is traveling near the speed of light.
Though Maxwell did not envision relativity at the time of the development of his equations describing electromagnetism, they definitely made a significant impact during the early formation of the concepts of relativity

The problem with physics
Physics has become obsessed with strings, branes and multiple dimensions, yet the big questions remain fundamentally unanswered. Has the time come to admit these wild conjectures have failed, and move on?

I was recently talking with a colleague who was a fellow theoretical physics graduate student at Princeton University back in the early 1980s. He had been thinking about an obscure academic physics journal he would occasionally skim in the library during those years. This journal was filled with bizarre extra-dimensional models of particles and forces, esoteric ideas about cosmology, and a slew of highly speculative theorising, with little in common other than a lack of any solid evidence for a connection with reality.
"You know," he said, "at the time I thought these things were a joke, but now when I look at mainstream physics papers, they remind me a lot of what was in that journal."
Why is it that central parts of mainstream physics have started to take on aspects that used to characterise the outer fringes of the subject? At the very centre of the physics establishment, things have been getting more and more peculiar.
A QUARTER-CENTURY AGO, in the 1980s, it was clear to both of us what serious theoretical physics looked like. A hugely successful theory of elementary particles and the fundamental forces governing them had come to final form a few years earlier. It was referred to as the Standard Model (see "The whole shebang", p62), and evidence for it was pouring in from experiments around the world.
The Standard Model is a quantum theory of fields – of which the electromagnetic field was just one variety – and much of our time as students was spent trying to master the complex mathematical techniques needed to understand these quantum field theories. According to the Standard Model, there are three fundamental forces: electromagnetic, weak and strong. There are also a small number of fundamental particles carrying specified charges that determine which forces they experienced, such as photons for the electromagnetic force, and gluons for the strong nuclear force.
The mathematics of the theory is deep and highly sophisticated; the fields responsible for the forces are basic geometrical quantities that mathematicians call 'connections'. The excitations and interactions of these fields were also responsible for the fundamental particles. The whole thing satisfied a beautiful equation as presented to the world by British physicist Paul Dirac in 1928.
At the time, no experimental evidence had been found that contradicted the Standard Model, but it was clearly not complete, since it didn't address certain fundamental questions. The task for theorists was to find a better theory that could.
On of the key questions was regarding the origin and nature of mass. In the Standard Model, one conjectures the existence of something called a 'Higgs field' (named somewhat arbitrarily after Peter Higgs, one of several theorists responsible for the idea it implements). This field is responsible for giving particles their unique mass. Unfortunately, in many ways, the Higgs field just highlights our ignorance; the mass of a particle is determined by a number that characterises how strongly it interacts with the Higgs field, but we have no idea where these numbers come from.
Another crucial question was why we have this specific pattern of forces and fundamental particles. In particular we'd like to be able to explain the charges of the fundamental particles, as well as the three different numbers that determine the strengths of the three forces.
Then there's the question of the mysterious fourth force: gravity. We have an excellent theory of this force – Einstein's theory of general relativity – but this theory doesn't mesh with quantum mechanics, and there appears to be a problem of inherent inconsistency in treating one of the forces differently than the other three.
What neither my fellow student nor I would ever have guessed during our graduate student days was that, in our middle age some 25 years later, we'd be no closer to answering any of these questions, and ever more speculative attempts to find such answers would have taken on some of what used to be the characteristics of the fringes of science
HOW DID THIS SITUATION come about, and what are the prospects for it changing before my friend and I drift off into senility? By far the most important factor is that the Standard Model has turned out to be simply too successful. Clearly, having a beautiful, mathematically sophisticated theory that predicts exactly what every new experiment will see is something physicists should be proud of. However, had the Standard Model catastrophically failed somewhere along the line, at least it would have given physicists a starting point for a new approach.
Instead, as each new generation of accelerators has been turned on, with the ability to explore higher and higher energy ranges – or equivalently, shorter and shorter distances – experimentalists have found exactly what the Standard Model predicts. Every time. (There has been just one minor surprise: that neutrinos are massive. But this discovery didn't contradict the model, and eventually did little more than add to the list of masses we don't understand.) As a scientific field, fundamental particle physics has become very much a victim of its own success.
Although particle physics has been in the doldrums, during this same period the field of cosmology has moved forward at a brisk pace. The Standard Model tells us what the fundamental particles and forces are, while cosmology is the study of the large-scale structure of the universe. Wonderful advances in ground- and space-based astronomy have provided a wealth of dramatic evidence about the Big Bang and the early history of the universe. Just as particle physics converged on the Standard Model, Big Bang cosmology has recently been converging on something now called the Concordance Model. A bit like the Standard Model, it fits the data all too well, while leaving crucial questions open as a precise parameterisation of our ignorance.
The Concordance Model doesn't address the most fundamental questions about the origin of our universe, questions about what happened in the earliest moments of the Big Bang. Instead it just quantifies and places parameters on the resulting structure we are able to observe, with our most precise observations coming from the details of the cosmic microwave background that fills space with radiation at a temperature of about three degrees Celsius above absolute zero (–273°C). Particle physicists have great hopes that cosmology will help solve some of the problems left open by the Standard Model, but so far this has not happened. Instead, the success of the Concordance Model has just provided two extra puzzles.
The first new puzzle goes under the name of 'dark matter': there appears to be some sort of matter of completely unknown origin, which only interacts weakly with conventional matter particles (producing no electromagnetic radiation, like light, thus it's invisible, or 'dark'), but whose effects are detectable indirectly through the gravity.
This exotic matter has a dramatic effect on the structure of galaxies, as without it, stars in their outer reaches would be flung into deep space. It also affects the large-scale structure of the universe, but we know virtually nothing about it beyond observing its gravitational influence. One can come up with a wide array of compatible extensions of the Standard Model that include dark matter by doing little more than postulating a new stable particle that experiences appropriately weak interactions with known particles. In fact, it was once thought – and hoped – that neutrinos could be the culprit behind dark matter, as they effortlessly pass through most other forms of matter and seem to possess mass. However, it has since been discovered they're just too lightweight and travel at too high a velocity to account for the observed dark matter phenomenon.
Experiments are underway to search for rare collisions of other postulated weakly interacting dark matter candidates, but so far nothing has been seen. Collisions in high-energy particle accelerators might, in principle, produce these exotic particles, but again, all searches for evidence of this so far have been in vain. One possibility is that the mass of such particles is just so large that experiments to date have had insufficient energy to produce them.
The second of the new puzzles has a similarly ominous and mysterious name, 'dark energy' (see "Dark forces", p56), but is of even less help with the unresolved questions in particle physics. In the Concordance Model of cosmology, dark energy is little more than an additional constant term in Einstein's equations describing space-time. In physical terms, it has the interpretation of an energy density carried by the vacuum pervading space.
According to the Standard Model, the energy of the vacuum is an undetermined coefficient that theorists have to enter by hand into their equations. For many years physicists running through their calculations had assumed this number was zero, but the new mystery is that it has now been measured to have a small positive, non-zero value, providing one more fundamental number characterising physics, the origin of which remains an enigma.

Fifth Force

Fifth Force

Occasionally, physicists have postulated the existence of a fifth force in addition to the four known fundamental forces. The force is generally believed to have roughly the strength of gravity (i.e. it is much weaker than electromagnetism or the nuclear forces) and to have a range of anywhere from less than a millimeter to cosmological scales.
The idea is difficult to test, because gravity is such a weak force: the gravitational interaction between two objects is only significant when one has a great mass. Therefore, it takes very precise equipment to measure gravitational interactions between objects that are small compared to the Earth. Nonetheless, in the late 1980s a fifth force, operating on municipal scales (i.e. with a range of about 100 meters), was reported by researchers (Fischbach et al.)[1] who were reanalyzing results of Loránd Eötvös from earlier in the century. The force was believed to be linked with hypercharge. Over a number of years, other experiments have failed to duplicate this result, and physicists now believe that there is no evidence for a fifth force.[2]

Theory and experiment
There are at least three kinds of searches that can be undertaken, which depend on the kind of force being considered, and its range.
One way is to search for a fifth force with tests of the strong equivalence principle: this is one of the most powerful tests of Einstein's theory of gravity, general relativity. Alternative theories of gravity, such as Brans-Dicke theory, have a fifth force—possibly with infinite range. This is because gravitational interactions, in theories other than general relativity, have degrees of freedom other than the "metric," which dictates the curvature of space, and different kinds of degrees of freedom produce different effects. For example, a scalar field cannot produce the bending of light rays. The fifth force would manifest itself in an effect on solar system orbits, called the Nordtvedt effect. This is tested with Lunar Laser Ranging Experiment[3] and very long baseline interferometry.
Another kind of fifth force, which arises in Kaluza-Klein theory, where the universe has extra dimensions, or in supergravity or string theory is the Yukawa force, which is transmitted by a light scalar field (i.e. a scalar field with a long Compton wavelength, which determines the range). This has prompted a lot of recent interest, as a theory of supersymmetric large extra dimensions—dimensions with size slightly less than a millimeter—has prompted an experimental effort to test gravity on these very small scales. This requires extremely sensitive experiments which search for a deviation from the inverse square law of gravity over a range of distances[4]. Essentially, they are looking for signs that the Yukawa interaction is kicking in at a certain length.
Australian researchers, attempting to measure the gravitational constant deep in a mine shaft, found a discrepancy between the predicted and measured value, with the measured value being two percent too small. They concluded that the results may be explained by a repulsive fifth force with a range from a few centimetres to a kilometre. Similar experiments have been carried out onboard a submarine (USS Dolphin (AGSS-555)) while deeply submerged. A further experiment measuring the gravitational constant in a deep borehole in the Greenland ice sheet found discrepancies of a few percent, but it was not possible to eliminate a geological source for the observed signal [5] [6].
Some experiments used lake and a 320m high tower[7] A comprehensive review suggested there is no compelling evidence for the fith force[8], though scientists still search for it.
The above experiments search for a fifth force that is, like gravity, independent of the composition of an object, so all objects experience the force in proportion to their masses. Forces that depend on the composition of an object can be very sensitively tested by torsion balance experiments of a type invented by Loránd Eötvös. Such forces may depend, for example, on the ratio of protons to neutrons in an atomic nucleus, or the relative amount of different kinds of binding energy in a nucleus (see the semi-empirical mass formula). Searches have been done from very short ranges, to municipal scales, to the scale of the Earth, the sun, and dark matter at the center of the galaxy.

Other interactions
A few physicists think that Einstein's theory of gravity will have to be modified, not at small scales, but at large distances, or, equivalently, small accelerations. They point out that dark matter, dark energy and even the Pioneer anomaly are unexplained by the Standard Model of particle physics and suggest that some modification of gravity, possibly arising from Modified Newtonian Dynamics or the holographic principle. This is fundamentally different from conventional ideas of a fifth force, as it grows stronger relative to gravity at longer distances. Most physicists, however, think that dark matter and dark energy are not ad hoc, but are supported by a large number of complementary observations and described by a very simple model.