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Natural Science Forum / Physics / Relativity / March 2007Can Light quata to stop its moving?
Can Light quata to stop its moving? ========== Quantum mechanics describes the bizarre rules of light and matter on atomic scales. In that realm, matter can be in two places at once. Objects can be particles and waves at the same time. And nothing is certain -- only probable or improbable. This improbable feat -- stopping light -- was accomplished by two teams. One was led by Ron Walsworth, a physicist at the Harvard-Smithsonian Center for Astrophysics, and the other by Lene Hau of Harvard University's Department of Physics. Walsworth's group used warm rubidium vapors to pause their laser beam; Hau's group used a super- cold sodium gas to do the same thing. ============== http://science.nasa.gov/headlines/y2002/27mar_stoplight.htm > Can Light quata to stop its moving? > ========== [quoted text clipped - 5 lines] > This improbable feat -- stopping light -- was accomplished by two > teams. Not according to the article. I hate these cutesy articles that completely distort the physics. We're still suffering from the "fast than light" article from several years ago. Somebody pops up with that one every few weeks. > One was led by Ron Walsworth, a physicist at the Harvard-Smithsonian > Center for Astrophysics, and the other by Lene Hau of Harvard > University's Department of Physics. Walsworth's group used warm > rubidium vapors to pause their laser beam; Hau's group used a super- > cold sodium gas to do the same thing. > ==============http://science.nasa.gov/headlines/y2002/27mar_stoplight.htm And if you read the article, the photon isn't "stopped", it's absorbed into spin states of electrons. - Randy > Can Light quata to stop its moving? > ========== > Quantum mechanics describes the bizarre rules of light and matter > on atomic scales. In that realm, matter can be in two places at once. No it can't. It does not have a definite position - there is a difference. > Objects can be particles and waves at the same time. Yes. > And nothing is certain -- only probable or improbable. Yes. > This improbable feat -- stopping light -- was accomplished by two > teams. It is a real problem when what seems to be authoritative articles do not get their facts exactly correct - which is why I always recommend studying proper texts. Thanks Bill > One was led by Ron Walsworth, a physicist at the Harvard-Smithsonian > Center for Astrophysics, and the other by Lene Hau of Harvard [quoted text clipped - 3 lines] > ============== > http://science.nasa.gov/headlines/y2002/27mar_stoplight.htm Bill Hobba wrote: > > Can Light quata to stop its moving? > > ========== [quoted text clipped - 6 lines] > > Yes. That's only when you aren't looking. When you are looking it's always one or the other: http://atoptics.co.uk/rainbows/supform.htm > > And nothing is certain -- only probable or improbable. > > Yes. The probabilities are 100% certain, otherwise you wouldn't have much to work with. Isn't QED the most precisely confirmed theory known to humankind? Quantum Theory says mass increases with speed increase and becomes infinite when a mass reaches speed of light:c=1. Which is against the "Law of conservation and transformation energy/mass". But we know the quantum of light is real particle and its mass is particular and not infinite. How to understand this contradiction? And the scientists invented an artful way: the quantum does not possess the mass of rest and it is always in motion. ============== The quantum of light has not mass of rest equal to zero. But....... ============= The Soviet/Russian academic S. Vavilov suggested an interesting idea. In his book ' Isaac Newton' he wrote. The force, according to the Newton,s Second Law, is equal to : F= ma. This force is possible to consider as absolute independent quantity - impulse. When in case with light quanta the impulse is equal to: mc. He continued. Let us now imagine that light quanta falls on a black body, and it absolutely absorbs this light quanta ( it means light quanta stops). Then, according to the Lebedev,s law, light quanta renders pressure on the black body: E/c. Therefore it is possible to write: mc=E/c. It means that according to Classic physics the stopping light quanta has not mass of rest equal to zero, but it has potential energy/mass: M=E/c^2. (E=Mc^2). ========================= The potential energy/mass of light quanta can transform in its kinetic energy. =============== > Quantum Theory says mass increases with speed increase > and becomes infinite when a mass reaches speed of light:c=1. No that's relativity. How can you confuse the two? > Which is against the > "Law of conservation and transformation energy/mass". No it isn't, and the argument is irrelevant in the first place because it simply isn't possible for a massive particle to reach c. > But we know the quantum of light is real particle and > its mass is particular and not infinite. Photons are massless. E^2 = [mc^2] + [pc]^2 reduces nicely to E = pc. Photons travel along null geodesics - all c, all the time. > How to understand this contradiction? Start by realizing that ignorance is not a contradiction. > And the scientists invented an artful way: the quantum > does not possess the mass of rest and it is always in motion. It isn't artful - conservation of charge demands it via Maxwell's equations. > ============== > The quantum of light has not mass of rest equal to zero. [quoted text clipped - 4 lines] > The force, according to the Newton,s Second Law, > is equal to : F= ma. F = dp/dt. F = ma is a special case. Why is classical mechanics being invoked? > This force is possible to consider as absolute independent > quantity - impulse. When in case with light quanta > the impulse is equal to: mc. Cute, but wrong. Photons are massless. > He continued. > Let us now imagine that light quanta falls on a black body, [quoted text clipped - 3 lines] > renders pressure on the black body: E/c. > Therefore it is possible to write: mc=E/c. Not if photons are massless. > It means that according to Classic physics the stopping > light quanta has not mass of rest equal to zero, but > it has potential energy/mass: M=E/c^2. (E=Mc^2). Good ol' classical mechanics - you can get whatever you want if you start from the right spot. > ========================= > The potential energy/mass of light quanta > can transform in its kinetic energy. > =============== To Eric Gisse . =========== Photons are massless. ============ 1. Yes. Photon mass doesnt zero. Good ol' classical mechanics - you can get whatever you want if you start from the right spot. ============ 2. The right spot. If you want to understand the right spot, if you want to understand photon, you must to think from beginning, from the VACUUM. 3. Quantum of light is a privileged particle. Only the speed of a light quantum has a maximal, constant, absolute quantity of c=1. Other particle can travel only with the speed s=d/t. And I was taught at school from the first class: that the incommensurable quantities cannot be compared. To connect incommensurable quantities it is similar to the decision of a problem: "What will be if the whale will attacks the elephant?" ==================================== |
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