1.How has special theory of relativity been unified/reconciled with Quatum mechanics? \n\n2. Why, and where, has the general theory of relativity of not been reconciled with Quantum mechanics?\n\n3. What things has Feynman proved in QED?\n\nA 3-4 line answer for each question will be ok too.
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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).
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The universal field theory is still being attempted. You see the field theory which governs large things like planets doesn't cover things which are small. By small we are talking molecular. You see when Hawking first realized that black holes aren't persistant and that they do burn out he realized that the particles within them must act differently that those of larger size (planets) and now he and some others are trying to prove a universal field theory that covers all of them. \n\nThat's about as simple as I can make it man without filling page after page.
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i like to contemplate the coming together of Heisenberg"s uncertainty principle, string theory, and the theory of relativity (special edition).\n\ni feel it was best described and visualized in the TV series farscape.\nthe explanation was wonderful.\nthe visuals helpful.\nputting aside fiction, i think the universe maker breaker force is essential to defining the glue of everything.\n\n\n"In quantum physics, the Heisenberg uncertainty principle states that one cannot assign, with full precision, values for certain pairs of observable variables, including the position and momentum, of a single particle at the same time even in theory. It furthermore precisely quantifies the imprecision by providing a lower bound (greater than zero) for the product of the standard deviations of the measurements. The uncertainty principle is one of the cornerstones of quantum mechanics and was discovered by Werner Heisenberg in 1927.\n\nIt is sometimes called the Heisenberg indeterminacy principle (a name preferred by Niels Bohr)."\n\n"string theory \n \ndescription of elementary particles based on one-dimensional curves, or "strings," instead of point particles. Superstring theory, which is string theory that contains a kind of symmetry known as supersymmetry, shows promise as a way of unifying the four known fundamental forces of nature. The strings are embedded in a space-time having as many as 10 dimensions–the three ordinary dimensions plus time and seven compactified dimensions. The energy-scale at which the stringlike properties would become evident is so high that it is currently unclear how any of the forms of the theory could be tested.\n\nSee P. C. W. Davies and J. Brown, ed., Superstrings (1988)."\n\n"Special Relativity\nNewton's laws of motion give us a complete description of the behavior moving objects at low speeds. The laws are different at speeds reached by the particles at SLAC. \n\nEinstein's Special Theory of Relativity describes the motion of particles moving at close to the speed of light. In fact, it gives the correct laws of motion for any particle. This doesn't mean Newton was wrong, his equations are contained within the relativistic equations. Newton's "laws" provide a very good approximate form, valid when v is much less than c. For particles moving at slow speeds (very much less than the speed of light), the differences between Einstein's laws of motion and those derived by Newton are tiny. That's why relativity doesn't play a large role in everyday life. Einstein's theory supercedes Newton's, but Newton's theory provides a very good approximation for objects moving at everyday speeds. \n\nEinstein's theory is now very well established as the correct description of motion of relativistic objects, that is those traveling at a significant fraction of the speed of light.\n\nBecause most of us have little experience with objects moving at speeds near the speed of light, Einstein's predictions may seem strange. However, many years of high energy physics experiments have thoroughly tested Einstein's theory and shown that it fits all results to date."
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First of all, it is fundementally impossible to go at the speed of light. Therefore, the question as stated is invalid.\n\nHowever, it may or may not surprise you that, indeed, it is THAT VERY QUESTION that Albert Einstein surmised in 1896.  Here is his quote:\n"If I pursue a beam of light with the velocity c (velocity of light in a vacuum), I should observe such a beam of light as a spatially oscillatory electromagnetic field at rest.  However, there seems to be no such thing, whether on the basis of experience or according to Maxwell's equations.  From the very beginning it appeared to me intuitively clear that, judged from the standpoint of such an observer, everything would have to happen according to the same laws as for an observer who, relative to the earth, was at rest.  For how, otherwise, should the first observer know, i.e., be able to determine, that he is in a state of fast uniform motion?  One sees that in this paradox the germ of the special relativity theory is already contained.  Today everyone knows, of course, that all attempts to clarify this paradox satisfactorily were condemned to failure as long as the axiom of the absolute character of time, viz., of a simultaneous, unrecognizedly was anchored in the unconscious.  Clearly to recognize this axiom and its arbitrary character really implies already the solution to the problem."\n\nTherefore, In 1905 he realised how it could be that light always goes at the same speed no matter how fast you go.  Events that are simultaneous in one reference frame will happen at different times in another that has a velocity relative to the first.  Space and time cannot be taken as absolute.  On this basis Einstein constructed the theory of special relativity, which has since been well confirmed by experiment.\n\nNow, I can't explain any more than that.  So there :P
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Wow.\n\nA few people here know what they're talking about.  A few.  Very few.\n\nMost of these responses are absolutely hilarious.  Most of them are from people trying to sound smart, in which case they do NOT.  Other cases are from kids with big imaginations, with "Anything is possible!"\n\nEinstein was brilliant, no question.  But all great scientists are capable of mistakes, and Einstein was no exception.\n\nHis theory on time travel was based on the speed of light and the "paradox" in which light travels at a fixed rate of speed.  This is true; light moves at 186,000 mps no matter what conditions are in place.\n\nHis theory's flaw is accounted to the fact that light has NO mass.  Light, in it's fixed movement, cannot be compared to any living organism (which is made up of mass) or any other object.  Any object made up of mass (for example, a human being, or any kind of lightspeed-capable rocket ship) does NOT have a fixed speed; therefore the velocity equation paradox that Einstein based his theory on does not apply to them.\n\nThis is all I want to say tonight.  Anyone who understands his theories will understand what I've said here, so think about my statements.  Let me know what you think (again, only those of you who understand what Einstein's theories were all about), as I'm no expert on relativity.  Like everyone else posting on a Yahoo answers forum about Albert Einstein and his theories on time travel, I'm just a fan.  Don't act like any of us are any more.\nEveryone else:  Please don't worry about it.\n\nAlthough I am skeptical by nature, like any smart person, it is NOT my goal to bash the idea of time travel.  After I spotted the flaw in Einstein's theory I presented it to many professionals in the field (or the few that I know, anyway) and have so far received very positive feedback.  I searched online as well and have discovered that others seem to have come up with the same idea, or similar.  Let me know what you think about the whole deal.\n\nBeing proven wrong only makes you smarter.
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This is serious:\n\n1. It's up to him to prove it is shrinking, not up to you to prove it isn't.  He, after all, is the one who supports the hypothesis he read on the internet.  Just say "Prove it".  \n\n2. You gave the source of his information as "the internet".  That's too vague.  Where on the interent?  What web site?  What "expert(s)" in what fields(s)?  What proof did the internet article(s) present in support of the hypothesis?  How can anyone support or deny those proofs if we don't know what they are?\n\n2. What is meant by "getting smaller"?  As you can see from the other responses, different people have different ideas about which quantity is decreasing.  One person, who understands nothing about Einstein's Special and General Theories of Relativity, thought the mass was "getting smaller".  Another thought you meant the size, as in the diameter and/or volume.  Another seemed to think the entire universe is involved in the shrinkage.\n\nThe problem here is not so much your friend's outlandish claim as your inability to ask a critical question.
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Ask around if any of your friends have a GPS system.  There is your example of a daily-life example of the theory of relativity.  The Global Positioning System would not be able to give you very accurate locations if it did not take the corrections to time and distance from both special, and general reletivity into account.  I am pretty sure that it is the first piece of public consumer-grade equiptment that relies on our understanding of General Relativity.
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Don't you think that relativity dictates that those two things are the same?\nEdited my old answer after thinking-\nmy answer is:\nIt doesn't make a difference if I say I'm going 65 miles/hr or if I say everything else is and I'm going 0.  For all intents, purposes, and consequences, it's the same.  It's the same in this case, frame of reference is crucial in measurement, and so essentially, there is no difference in macro scale physics.\nGeneral theory of relativity wise, I'm still not sure about.  It seems like there might be serious consequences for this idea due to the speed of light/space relationship.  It also seems like I'm not really qualified to do those calculations, and the people who are could very well have already thought of this.  They are rather bright.\nSo my rating for viability of the idea is: (drum roll)\n23%
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I too would be veeerrrrry interested in seeing some evidence for this claim from a non-creationist source. I keep an eye out for this sort of thing out professional as well as personal interest and I can't recall seeing anything like it.\n\nRoger are you absolutely certan that you haven't misundertsood the phase velocity experiments of Wang? They were done around that time (published 2000 IIRC). But they never shattered the speed of light or anything like that, no  did Wang et al ever make such a claim.\n\nTo help you out Roger, folow the link below? Is that what you arehtinkng of? If so you have misunderstood the results entirely.\n\n" Wang et al. (2000), who produced a laser pulse in atomic cesium gas with a group velocity of 310+/- 5 C. In each case, the observed superluminal propagation is not at odds with causality, and is instead a consequence of classical interference between its constituent frequency components in a region of anomalous dispersion (Wang et al. 2000)."\n\nIOW the speed of light wasn't exceeded by a particle, massless or not. It was the speed of the frequency change wihtin the medium that was 300 times faster than light. Perhaps the easiest way for a layman to understand this is to imagine one of those Newton's Cradle's toys. (see link 2). \n\nWhen you let go of one ball the motion is tranferred through the two intervening balls to the other end, causing that ball to fly up. That motion is is transmitted at near enough the speed of sound. IOW when the dropped ball hits the suspended balls the motion is passed along at the speed of sound. \n\nBut, and this is important, the ball itself wasn't travelling at the speed of sound. Nor did the ball on the end fly out at Mach 1 just because the motion was tranferred at MAch 1. The motion of the drooped ball was transferred at Mach 1, but at no stage was the ball or anyhting else actually travelling at Mach 1.\n\nWang's experiments did approximately the same thing using photons rather than metal balls. By some very clever work they managed to induce a phase change within the Cesium medium. In essence the Cesium atoms became the middle balls in newtons cradle. When light  hit an atom on one side it caused a phase change that was then passed on to the next atom, then the next and so forth, all at 300*C. But it was the phase change that was moving at that speed, not photons, not even electrons, just a phase change.
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I came across the Heisenberg Principle when doing some light reading ("A Brief History of Time" - SH)and thought that it would be a great joke, if I should ever need a defense of a speeding ticket.\nBut I'll simply use it here, instead, as I'm sick of waiting for that opportunity to arise ;)\n"In another uncertainty principle joke, a quantum physicist is stopped on the highway by a police officer who asks "Do you know how fast you were going, sir?", to which the physicist responds, "No, but I know exactly where I am!"."
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Einsteins theories and the related mathematical equations seemed to have held up to experimental data for both special and general relativity. In that way, it seems he was at least right in the way he described reality. It may turn out that there is a theory out there somewhere that is even righter.\n\nWhat he may not have been right about is calling the Cosmological Constant his "biggest blunder". It now seems that it is in fact needed in GR.\n\nThere is a theory circulating the internet currently that Einsteins Special Relativity may have mathematical inconsistencies, but I have not verified this.
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The equations imply that it is impossible for any object with >0 rest mass to accelerate from below the speed of light up to exactly the speed of light. This is because, as has been mentioned, that would take an infinite amount of energy.\n\nThe equations don't prohibit an object traveling faster than the speed of light from the outset though. Photons have zero rest mass, and the instant they are created they are traveling at exactly c. If it were possible for a particle to exist that was traveling faster than c from the instant it was created, this would not be a problem for relativity. I'm not sure what it would imply about it's mass though. The name for such a particle is a tachyon (although there is no evidence these actually exist as far as I'm aware).
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Yes, Richard Feynman suggested this way back when. \n\nThe original paper is available here: http://prola.aps.org/abstract/PR/v76/i6/p749_1\n\nWithout a subscription you'll only be able to read the abstract.
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yikes, everyone is giving you the wrong formula. it's not e=mc^2. that would be converting energy into mass and back which is done like when subatomic particles crash into each other really fast and such... the mass dialation formula you are looking for is \nm'= m/sqrt(1-v^2/c^2)\nwhere m' is the mass you would be not moving at the high velocities, m is the mass moving at the high velocities, v is the velocity you're traveling at, c is the speed of light, sqrt means we're square rooting everything in those parenthesis, and ^2 means squared. if you were to plug numbers in for velocity, you can see that this effect is absolutely neglagible unless you are moving very very close to the speed of light. and it is impossible to actually move at the speed of light, because then v^2/c^2 would be 1, and 1-1=0 so you would have a 0 in the denominator of that equation, which is impossible.  that equation is actually very interesting in that it is part of the lorentz factor which also effects time and length. in fact, as you increase speeds close to the speed of light, not only does mass increase, but time moves slower for you and length shrinks.  I've had to derive these equations in physics class, it's very interesting to do it yourself and come up with the equation proving that things like velocity, mass, and length are affected by velocity.  but again, you need to be going very very close to the speed of light for the velocity to have any effect on these things.\n\nas far as practicality, instances of the lorentz factor have been proven. there are these particles that have a certain lifespan before they disintigrate.  so now, we know how fast they are going and we know how long before they disintegrate, so theoretically, we should easily be able to figure out how much distance they cover before they disintigrate, right? but somehow, the particles go a lot farther than they should... if we plug their velocity into the lorentz transformation formula however, and put in how far they should travel (but don't), they we come up with how far they actually do travel.  this proves the validity of the lorentz factor.\n\nthere is no practical application of the mass increase since objects of great mass would require way too much energy to accelerate to speeds great enough to see this effect, so therefore it can't really happen.. if ever it did though, the only thing this mass expansion would serve to do would be to limit time travel. i mean, if time is slowing down for us at high speeds, technically we could make it slow down so much so that it would be going slower for you than everyone else and so you could basically travel forward in time. but if your mass was expanding and length shrinking, then either the pressure would kill you, or your blood would get so dense it couldnt carry oxygen to your cells and that would kill you, so there goes the time travel thing.
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Not sure that i can agree with Messrs Santras. Photons that do not have a mass? \nhmmm.. no mass, no energy, no time, no light. Anyway.. The  idea about photons that i find interesting are that they only have mass while they are moving. The mass disappears as a result of trying to observe it.\nMaybe the giving up of mass and the subsequent conversion of this mass to energy gives us the equal and opposite force to power...............TIME.\nAs for the rest of this question? Well if light is not electromagnetic then what is it? Are photons spots of energy or waves? This has been an argument for a long time. Maybe they are both. Each having their own laws to drive them.\nIf we consider the double slit experiments with light, we come up with some interesting results. One of which talks about the possibility that photons can communicate with each other! That there is some clandestine signalling goes on between a source of a photon and a recipient of a photon. This would have to happen at a super-light speed and therefore involve time travel of the signals! Maybe? The crux could be following the simplest form of physical law "the path of least resistance" how does a photon (light) know which direction is a straight line?\nPhoton theory isnt easy to think about. there are many established experiments out there to prove many things about photons but to manipulate photons in order to make something invisible? We would have to understand the fundementals of time, as yet this has not been achieved. We can only hope to observe its effect rather than it's mechanics.
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Two views on the space and time.\n1.\n There are an independent space and independent time:\nWe notice it on our planet - Earth.\nIt is a fhree - dimensional space.\n2.\nThere is simultaneous union of space and time:\nIt is negative four-dimensional (Minkowski) space.\nHerman Minkowski :\n“ Henceforth, space by itself, and time by itself, \nare doomed to fade away into mere shadows,\n and only a kind of union of the two will preserve an independent reality.”\nQuestion.\nWhat  is the “a kind of union of the two “?\nThe answer.\nIt is Vacuum. T=0K.\n=========================\nhttp://www.socratus.com
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NO!!  If people would stop (mis)quoting half-remembered precepts here, and do a spot of THINKING, instead, we might get somewhere.\n\n1.  If a moving spherical ball directly hits an identical free, stationary ball head on in an elastic collision, the moving ball STOPS, and the previously stationary one heads off with the original velocity of the other.  So ALL of the moving ball's K.E. has been transferred to the other ball.  \n\nHere are two ways to see this:\n\n1a.  The device known somewhat indelicately to British schoolboys as "Newton's balls" (but in squeamish America as "The Swinging Wonder") provides an excellent table-top demonstration of this.  Most undergraduate physics instructors must haul this out from time to time.\n\n1b.  You can easily solve it analytically, but a thought experiment will also demonstrate it.  In the originally stationary ball's frame, let the other ball approach with speed v.  Now shift (with an appropriately directed speed of v/2) to the frame in which the two equal balls are simply approaching each other, each with a speed in this frame of that same v/2 (oppositely directed, of course)!  Clearly, from the symmetry of the situation, they'll bounce off each other with the same (oppositely directed) speeds in this frame, still of v/2.  Now go back to the original frame: the previously moving ball is now completely stationary, while the originally stationary one is haring off with speed v.  (You may need to make little sketches of what is happening as viewed successively from each of these frames, to see this; I admit that that's what I did.)\n\n2a.  A similar approach can be used to solve the general case for an arbitrary ratio of masses, m (initially moving)/M (initially stationary).  Hint: have the balls approach one another in their center of mass frame with equal but opposite momenta of mv and  MV.  They'll clearly bounce off one another in such a frame, retaining the same values of their respective (but now oppositely directed) speeds.  Then you can do the other frame-jugglings from there. \n\nHowever, this analytical approach, done accurately, is a tedious mess.  So, to appreciate the general problem more physically, consider just the following:\n\n2b.  The case of m << M.\n\nConsider the "equal but opposite momentum" frame for these two balls, in which MV = mv.  This means that if ball M is VERY MASSIVE, the speed it will have in such a frame, V = (m/M)v; that is, it's VERY SMALL compared to little puny m's high speed.\n\nSo, transforming to the frame in which M itself (the big guy) is initially stationary takes only a speed shift of O(m/M)v.  (In fact identically so.)  This only affects the speed of puny m minutely, so m's initial K.E. is still of order O(m v^2).  (There's no need to do picky constant book-keeping for these purposes.)  \n\nNow after the collision: In the original frame, Big M is now moving (and in fact at 2V if you think about it.)  But, being loose about the constants, M's K.E is only O(MV^2).  \n\nSo, the ratio (m's K.E.)/(M's K.E.) ~ (mv^2)/(MV^2)\n\n= (m/M)(M/m)^2 (since mv = MV)\n\n= M/m.\n\nBINGO!  The little bugger still carries by far the larger amount of the kinetic energy.  The massive ball (i) moves sluggishly, and (ii) because  K.E. involves both mass but also the SQUARE of the speed, the TWO POWERS of (small) speed more than cancel out the effect of its (large) mass.\n\nThis is a well-known fact in particle collision theory, that little particles basically bounce off big ones.  \n\nYou could also say that it's well-known in "space billiards": when spacecraft head close to Jupiter to receive a "gravitational sling-shot effect" that sends them off to the outermost planets.  \n\nIt's more complicated because of 3-D effects there, but analogous frame-shifting methods can be used to show that the spacecraft can pick up considerable speed AND change