how Max Plank were lead to Quantum mechanics?
359804
The so called ultraviolet catastrophe of the Rayleigh-Jeans law of black body radiation.\n\nhttp://en.wikipedia.org/wiki/Rayleigh-Jeans_law\n\n------------\n\nA similar question\nhttp://answers.yahoo.com/question/index;_ylt=AiSEt83vSVIv92vc9vsdCtzsy6IX?qid=1006022704468
340728
This is one of the best questions i have come across.In fact most Physicists have taken this cue for unravelling the problems of quantum mechanics. Look at the universe. Everything is moving in eleptical orbits. The sea shore is never straight and so are the trees, mountains and the rivers. The big bang and oscillating universe theory talks of tangential motion arrived through circular motion.\nStraightness is unnatiral!
471221
I am trying to give just a brief idea about these questions. Actual explanations need a lot of space. In any case, one can easily search the internet for these things.\n1. Special theory of relativity was combined with quantum mechanics to produce a new branch of physics called 'relativistic quantum mechanics'. This was done mainly by Dirac. He considered the wave functions of particles moving with very high velocities, and used Lorentz transformation equations in his mathematics. He considered also the imaginary (complex) solutions to the basic equations of motion (such as the Schrodinger equation, for example). The main contribution of this 'unification' was the theoretical discovery of anti-particles (which was varified later on from the experimental discovery of positrons).\n2. The 'unification' of general theory of relativity and quantum mechanics leads to the branch called 'quantum gravity'. The basic problem with this unification is the matching of length scales at which these two theories work. Quantum mechanics is designed and valid for subatomic length-scales, whereas, the general theory of relativity, which is the theory of gravity, deals with massive objects and large (astronomical) length-scales. Presently, scientists are looking for a suitable wavefunction for the universe, which is expected to provide information about the universe in the same way as the wavefunction of an electron gives many information about it.\n3. Feynman reconstructed almost the whole of quantum mechanics and electrodynamics in his own way, deriving a way to analyze atomic interactions through simple diagrams (now known as Feynman diagrams), a method that is still used widely. QED was the theory to which Feynman diagrams were first applied. For his work on quantum electrodynamics, Feynman was one of the recipients of the Nobel Prize in Physics for 1965, along with Julian Schwinger and Shin-Ichiro Tomonaga.\n\nI would also like to comment on the answers given by other users, such as Smart prash: \n1. In question 1 the user is asking about Dirac's relativistic quantum mechanics, and not about Bohr's elementry quanrum mechanics.\n2. Please don't get confused. Quarks are not coloured at all (how can they be?). Colour of a quark is just one of the many quantum numbers that is used in a way to number them in terms of their different energies. Moreover, the question is about QED (quantum electrodynimics), and the colour quantum number is a concept from QCD (quantum chromodynamics).
990811
Quantum mechanics is a fundamental physical theory which extends and corrects Newtonian mechanics, especially at the atomic and subatomic levels. It is the underlying framework of many fields of physics and chemistry, including condensed matter physics, quantum chemistry, and particle physics. The term quantum (Latin, "how much") refers to the discrete units that the theory assigns to certain physical quantities, such as the energy of an atom at rest.
453143
http://computer.howstuffworks.com/quantum-computer.htm
790211
This is one of the questions that led to the quantum theory.  Heisenberg proposed that there is an inherent uncertainty in certain attributes of a particle: if you know its momentum precisely, you can say nothing about its position, and vice versa.  The product of the uncertainties in position and momentum cannot be less than a certain number called Planck's constant.  So, if the electron were to be eaten by the proton, both its position and momentum would become known to high precision, and that would be a violation of Heisenberg.  There is, however, an interesting exception in which what you posit actually occurs: it is a form of radioactive decay called k-electron capture, in which an atomic nucleus eats an inner electron, and the remaining electrons cascade downward to fill the hole, emitting characteristic x-rays in the process.  This can happen only under special circumstances, and involves a significant amount of energy.
707791
Besides the classic standard model of quantum mechanics, there's the superspace version where all possibilities happen in alternate universes.  Then there's string theory and its higher dimensional cousin m-theory.  As far as I know, that last is most current.  Recent Nobel prize for it at Institute of Theoretical Physics at UC Santa Barbara.  But see link as well.
933058
Quantum leaps are only possible between orbitals that overlap each other and the probability of leaping is proportional to the amount of overlap (actually since the wave functions are complex numbers it's slightly more complicated than this).\n\nYou can see what the orbitals look like and how they would overlap in the section "visualizing the hydrogen electron orbitals" in the first reference.\n\nDon't worry about the non-overlapping parts of the orbits moving faster than light. Thats just how quantum mechanics works. Einstein didnt like this and wrote a paper about it in 1935 (second reference), but he turned out to be wrong.
498367
A good website on quantum mechanics: http://en.wikipedia.org/wiki/Quantum_mechanics\n\nAlso, if you are intrigued by the cosmological theory of the universe, The Life of the Cosmos by Lee Smolin is an excellent read.
362081
Not much;  quantum mechanics is pretty much taken for granted (by physicists, NOT philosophers!) as the framework of almost all of modern physics (but gravity's another story...).  In that sense almost all physics research these days is "quantum" physics.  However, there is still some interesting work being done with phenomena that are distinctly quantum mechanical, such as Bose-Einstein condensation, quantum entanglement, and the like.\n\nI'd just like to point out that in the past 100 years since quantum mechanics was "born", no experiment has been performed whose results are not consistent with quantum mechanics.
784965
It comes from \nE = Plank's constant * Speed of light / Wavelength\n\nPlank's constant = 6.63 x 10^-34J.s\nSpeed of light = 3 x 10^8 m/s\nWavelength = 475 x 10^-9 m\n\nand you'll get the answer in" jouls" =4.1873 X10^-19 Jouls\nyou can also express this energy in terms of electron volt; as 1.602 x 10-19 J = 1 eV and you get it equal to  2.6101945 eV
756937
for sure.\n\nbible is descriptive.... quantum physics is a snap.\n\naren't you glad..\n\nthat way its cover 11 or 12 diminsions where you only think in 3 or 4.
1151938
The expression is an attempt to bring the weird behaviors that are evident on a quantum mechanical scale to a macroscopic scale.  The theory in question here is that of tunneling.  Tunneling states that there is a non-zero probability of a particle passing through an energy barrier without going over it.  In essence, it's like the particle simply passed through the barrier.  Now, in theory, were you to try an infinite number of times, it is possible that at the instant that every particle in your body hit the wall, they would all quantum mechanically tunnel through the barrier.  It's so exceedingly unlikely though, that for all intents and purposes, it's impossible.  \n\nQuantum mechanics is filled with little things like that.  Things that make sense on an atomic scale don't necessarily work on a human scale.  If you are interested, look up a few books by Brian Greene, which gives a pretty good understanding of relativity and QM.  Also, if you would like another example, look up  the Schrodinger's Cat Paradox.
656145
Originally, it was a "fudge factor" that Planck used to explain certain phenomena in physics.\n\nAs we have matured in our understanding, it turns out to be a fundamental concept in quantum physics--don't recall its exact value, but it relates the energy of a quantum to its frequency.\n\nBelieve me, this is one TOTALLY horrible oversimplification of things, but it has a good deal of the basics...  OK, a little of the basics...
1067262
This is covered in most quantum mechanics textbooks. I'm looking at the appendix to Albert Messiah's Quantum Mechanics Vol I. The wavefunction for n=2,l=0 is:\n\n(1/(a^3/2)) * 1/sqrt(8pi) * (1-r/2a) * exp(-r/2a)\n\nwhere a is the Bohr radius. Let's use units in which a=1. The probability density is:\n\nP(x) = 1/(8pi) * (1-r/2)^2 * exp(-r)\n\nThe radial probability density is the above times the area of the sphere:\n\nR(r) = 4pi * r^2 * P(x) = 1/2 * r^2(1-r/2)^2 * exp(-r)\n\nIf you want the radius of the location in space at which P(x) is maximal solve:\n\ndP(r)/dr = 0 (a quadratic equation)\n\nIf you want the radius at which the radial probability density is maximal solve:\n\ndR(r)/dr = 0 (a cubic equation)\n\nR(r) has two relative maxima. I think the one farther out is bigger. The expectation value of the radius <r> is:\n\n<r> = &#92;int_0^oo R(r) r dr \n\nstraightforward using &#92;int_0^oo r^n e^(-r) dr = n! etc.. The answer <r> should be 6a.
429187
Heisenberg's Uncertainty Principle is science.  Allow me to explain why.\n\nIt was observed that there were limits on measurements made at the smallest levels.  When Planck pointed out that light acted as if it were small particles--quantum, in the singular, and quanta in the plural--Heisenberg used some of the stuff inherent in the physics developed from Planck's work to explain the uncertainties of the measurement, and indeed to go one step farther and show how using electromagnetic radiation to sense things imposed specific limits on how well you could measure things, a developement that matched what had been observed.\n\nSO!  We have observation; we have development of theory; we have measuring of theory against observation, and seeing whether or not it matched, which it did.\n\nAt the level of abstraction in that last paragraph, this is pretty much the same as science elsewhere...
6613
Quantum physics predicts the existence of an underlying sea of zero-point energy at every point in the universe. This is different from the cosmic microwave background and is also referred to as the electromagnetic quantum vacuum since it is the lowest state of otherwise empty space. This energy is so enormous that most physicists believe that even though zero-point energy seems to be an inescapable consequence of elementary quantum theory, it cannot be physically real, and so is subtracted away in calculations. \n\nA minority of physicists accept it as real energy which we cannot directly sense since it is the same everywhere, even inside our bodies and measuring devices. From this perspective, the ordinary world of matter and energy is like a foam atop the quantum vacuum sea. It does not matter to a ship how deep the ocean is below it. If the zero-point energy is real, there is the possibility that it can be tapped as a source of power or be harnassed to generate a propulsive force for space travel. \n\nThe propellor or the jet engine of an aircraft push air backwards to propel the aircraft forward. A ship or boat propellor does the same thing with water. On Earth there is always air or water available to push against. But a rocket in space has nothing to push against, and so it needs to carry propellant to eject in place of air or water. The fundamental problem is that a deep space rocket would have to start out with all the propellant it will ever need. This quickly results in the need to carry more and more propellant just to propel the propellant. The breakthrough one wishes for deep space travel is to overcome the need to carry propellant at all. How can one generate a propulsive force without carrying and ejecting propellant? \n\nThere is a force associated with the electromagnetic quantum vacuum: the Casimir force. This force is an attraction between parallel metallic plates that has now been well measured and can be attributed to a minutely tiny imbalance in the zero-point energy in the cavity between versus the region outside the plates. This is not useful for propulsion since it symmetrically pulls on the plates. However if some asymmetric variation of the Casimir force could be identified one could in effect sail through space as if propelled by a kind of quantum fluctuation wind. This is pure speculation. \n\nThe other requirement for space travel is energy. A thought experiment published by physicist Robert Forward in 1984 demonstrated how the Casimir force could in principle be used to extract energy from the quantum vacuum (Phys. Rev. B, 30, 1700, 1984). Theoretical studies in the early 1990s (Phys. Rev. E, 48, 1562, 1993) verified that this was not contradictory to the laws of thermodynamics (since the zero-point energy is different from a thermal reservoir of heat). Unfortunately the Forward process cannot be cycled to yield a continuous extraction of energy. A Casimir engine would be one whose cylinders could only fire once, after which the engine become useless. \n\nORIGIN OF ZERO-POINT ENERGY \n\nThe basis of zero-point energy is the Heisenberg uncertainty principle, one of the fundamental laws of quantum physics. According to this principle, the more precisely one measures the position of a moving particle, such as an electron, the less exact the best possible measurement of momentum (mass times velocity) will be, and vice versa. The least possible uncertainty of position times momentum is specified by Planck's constant, h. A parallel uncertainty exists between measurements involving time and energy. This minimum uncertainty is not due to any correctable flaws in measurement, but rather reflects an intrinsic quantum fuzziness in the very nature of energy and matter. \n\nA useful calculational tool in physics is the ideal harmonic oscillator: a hypothetical mass on a perfect spring moving back and forth. The Heisenberg uncertainty principle dictates that such an ideal harmonic oscillator -- one small