Main Question or Discussion Point
how come light does not have mass, we know e=mc^2, so what gives; why is it that light doesn't have mass or rather what is the explanation for light not having mass?
Physics does rather poorly into explaining WHY Nature behaves the way it does...In this case,it cannot tell WHY the photon is massless...Experiments indicate that they are massless...Theories of light have been constructed on this assumption.The_Thinker said:how come light does not have mass, we know e=mc^2, so what gives; why is it that light doesn't have mass or rather what is the explanation for light not having mass?
This is a classical mistake in the way we need to look at physics. It is NOT the intention of physics to tell us why nature does what she does. Physics only describes nature it does NOT explain the behaiviour of nature. Physics does NOT teel us why there is gravity or why nature incorporated gravity (we only know massive objects interact via gravity, but we don't know why). Physics does not tell us why on the atomic scale, nature is probabilistic in "nature"...dextercioby said:Physics does rather poorly into explaining WHY Nature behaves the way it does..
The answer to your question lies in the definition of the "m" in that expression. The definition of "m" is a much discussed topic in most physics forums, this one being no diffferent.The_Thinker said:how come light does not have mass, we know e=mc^2, so what gives; why is it that light doesn't have mass or rather what is the explanation for light not having mass?
I have to disagree on that point.marlon said:This is a classical mistake in the way we need to look at physics. It is NOT the intention of physics to tell us why nature does what she does.
Pete...In other words, the nature of the questions changed. The questions became more fundamental. "Why?" was added to the "What?" and "How?" and "Where?". Alan Guth was one of the young pioneers of the new cosmology, asking the Whys, and his Inflationary Universe theory provided many answers.
This is wrong. Indeed, physics describes the motion of heavens and the concept of "the same force that gives you weight" is necessary for the description. But this is not the point. The why at most fundamental level (which we are talking about, i mean like the photonmass) are NOT answered by physics. Can you tell me why gravity is mg, can you tell me where gravity comes from (and don't say from massive objects, because then i'll just ask why it comes from massive objects???).Crosson said:Look at the great "why?"s that physics has solved in the past. "Why do the heavens move as they do?" got the answer "by the same force that gives you weight".
Perhaps not in your eyes, but in mine.marlon said:as to pmp : why you disagree ? the text you posted doesn't say anything in my eyes...
yes indeed i do...pmb_phy said:That is why I disagreed. However I assumed you disagreed with this philosophy. Is that correct?
This is wrong. Photons are massless because they do not interact with the Higgs-field. Why ?, Well, because they exhibit the U(1)-symmetry which is the local symmetry of the EM-interactions and which is the general symmetry of the QED (or QCD)-vacuum. This has nothing to do with gauge-invariance. It is quite the opposite, as a matter of fact, gauge-symmetries are broken in the spontaneous breaking of symmetry.Newton said:In the case of quantum electrodynamics; gauge invariane demands that the photon be massless!!!!
ha, that's a bit funny to be honest because we CAN answer that very clearly. Just read my journal (the "why fields"-entry) and you will find many explanations for that.you may say "why is electromagnetism a quantum field theory, etc etc". but that is a DEEPER question. at this point we do not have an answer to that.