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Thread: What light really is?

  1. #1 What light really is? 
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    I know that light sometimes behave like wave and sometimes like particles depend on the condition we measure it.
    But What photon really is?
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    Quote Originally Posted by johnzxcv View Post
    I know that light sometimes behave like wave and sometimes like particles depend on the condition we measure it.
    But What photon really is?
    We don't have access to that kind of information. All we can do is tell you what happens when we make a certain kind of observation. By that I mean that the only thing that can be said to be "real" is what can be deduced from experiments.

    This is by far an easy subject to study. Great philosophers have tried. Here is a good book to look at

    The Feynman Lectures on Physics Vol 3 by Feynman, Leighton and Sands
    Feynman Lectures on Physics Vol 3 - Feynman, Leighton and Sands | | digital library BookOS

    For students who are able to absorb some heavy stuff there's also

    The Logic of Scientific Discovery by Karl Popper
    The Logic of Scientific Discovery | Popper | digital library BookOS

    The Structure of Scientific Revolutions by Thomas Kuhn
    The structure of scientific revolutions (third edition) | Thomas S. Kuhn | digital library BookOS

    The philosophy of quantum mechanics; the interpretations of quantum mechanics in historical perspective by Max Jammer
    The philosophy of quantum mechanics; the interpretations of quantum mechanics in historical perspective. | Max Jammer | digital library BookOS

    I don't mean to come across as condescending when I say this is for students able to absorb heavy stuff. Even I have a hard time absorbing this stuff. It's very difficult to read for us meat and potatoes quantum mechanics folks. Lol!
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    Quote Originally Posted by johnzxcv View Post
    I know that light sometimes behave like wave and sometimes like particles depend on the condition we measure it.
    But What photon really is?
    As Physicist noted, your question is an excellent one, and one for which there isn't a simple, readily expressed answer. First, it's not just light that has both a wave and particle character; all matter does.

    Second, if one were to give you some sort of answer, it would almost certainly trigger yet another question: What is {answer} really? And another...At some point, you'd just tire of the enterprise.

    When most people ask questions like yours, they're really looking for an analogy in terms of things they think they're familiar with. For example, you might ask "What holds atoms together in a molecule?" A textbook answer is "electric forces." But why stop there? What are electric forces? Another textbook might say that they're the result of the exchange of virtual photons. Then you would ask about those, and so on.

    Only crackpots pretend to have an ultimate answer to such questions.
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  4. #4  
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    Quote Originally Posted by johnzxcv View Post
    I mean aplly the ideal of distortion space time. Light is a distortion space time just like gravity. If you don't want to talk in this post ,You don't have to be rude
    I don't understand. Why are you accusing me of being rude? All I said was that the books I listed are hard to read even for physicists and even for myself. That's all. Why would you accuse me of being rude?

    I typically never discuss physics with those who openly accuse me of being rude just to make sure it doesn't happen again. Therefore if you have any plans on saying something like that again then please do it in a PM. Otherwise I won't respond to anything you post again to assure I don't get accused of being rude again.
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    Quote Originally Posted by Physicist View Post
    I don't understand. Why are you accusing me of being rude? All I said was that the books I listed are hard to read even for physicists and even for myself. That's all. Why would you accuse me of being rude?

    I typically never discuss physics with those who openly accuse me of being rude just to make sure it doesn't happen again. Therefore if you have any plans on saying something like that again then please do it in a PM. Otherwise I won't respond to anything you post again to assure I don't get accused of being rude again.
    I'm sorry . I won't make that mistake again.Forgive me Ok?
    I just want to tell the ideal that light is distortion space time.
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  6. #6  
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    Quote Originally Posted by johnzxcv View Post
    I'm sorry . I won't make that mistake again.Forgive me Ok?
    No problem my friend. All is forgiven and forgotten. On to bigger and better things.

    Quote Originally Posted by johnzxcv View Post
    I just want to tell the ideal that light is distortion space time.
    No. Light is not a distortion in spacetime. Do you know what a curved spacetime is? It's merely a gravitational field with tidal forces in it. That's all. Just because a beam of light is moving through spacetime it doesn't mean that it's curving the spacetime.

    In reality there is an extremely small spacetime curvature due to the energy of the light beam. However its so small as to be immeasurable in practice. Maybe in a few hundred or thousand years we might be sophisticated to measure something that small. But not today. However if you're thinking that the light curves spacetime for any other reason then you're wrong. At least according to general relativity.
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    Quote Originally Posted by Physicist View Post
    No problem my friend. All is forgiven and forgotten. On to bigger and better things.


    No. Light is not a distortion in spacetime. Do you know what a curved spacetime is? It's merely a gravitational field with tidal forces in it. That's all. Just because a beam of light is moving through spacetime it doesn't mean that it's curving the spacetime.

    In reality there is an extremely small spacetime curvature due to the energy of the light beam. However its so small as to be immeasurable in practice. Maybe in a few hundred or thousand years we might be sophisticated to measure something that small. But not today. However if you're thinking that the light curves spacetime for any other reason then you're wrong. At least according to general relativity.
    Let me simple my point: Light is energy and energy is mass and mass is distortion space time. In conclude light is a distortion of space time.
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  8. #8  
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    Quote Originally Posted by johnzxcv View Post
    Let me simple my point: Light is energy and energy is mass and mass is distortion space time. In conclude light is a distortion of space time.
    You're wrong. But at least now I know what you're talking about.

    Light is not energy. That's a very common misconception among non-physicists. Light is a property of energy. It can only be said that light has energy. So light is not a curvature in spacetime. It merely curves spacetime.

    Note: The term "distortion" is a misnomer. The correct term is "curvature/curved"
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    Quote Originally Posted by Physicist View Post
    You're wrong. But at least now I know what you're talking about.

    Light is not energy. That's a very common misconception among non-physicists. Light is a property of energy. It can only be said that light has energy. So light is not a curvature in spacetime. It merely curves spacetime.

    Note: The term "distortion" is a misnomer. The correct term is "curvature/curved"
    Ha ha ha funny ." Photon is not energy" . That is the most stupid thing I have ever heard.
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  10. #10  
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    Quote Originally Posted by johnzxcv View Post
    Ha ha ha funny ." Photon is not energy" . That is the most stupid thing I have ever heard.
    This is the second time within a week that you've said something rude to me for no valid reason. The proper thing to do if you disagree with someone is to state that you disagree and then prove that you're right and they're wrong. You don't insult them by saying that what the wrote was stupid. That's the best way to get onto my ignore list so that I never read anything you write again or respond to anything you post. I gave you a second chance. There won't be a third one.

    Is there are reason you chose to insult me? When people insult me like that I never help them again. Was that your goal? I'm a very good physicist and know this subject very well and know exactly the difference between something that "is" energy and something that "has" energy. And nothing "is" energy. They only "have" energy. Especially photons.

    I've been a professional physicist for some twenty five years now, not including my time as an undergraduate and in graduate school. Why exactly do you think you'd know better than I do regarding one of the most basic facts of all physics? What I said is not an opinion but a universally accepted fact that every single physicist that has been alive for the last 100 years knows.

    Since you claim to know differently then prove to us that you're right and I'm wrong. For example, search for a text athttp://bookzz.org/ and find either a quantum mechanics text, an electromagnetism text or a modern physics text that shows that you're right.
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  11. #11  
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    Quote Originally Posted by Physicist View Post
    This is the second time within a week that you've said something rude to me for no valid reason. The proper thing to do if you disagree with someone is to state that you disagree and then prove that you're right and they're wrong. You don't insult them by saying that what the wrote was stupid. That's the best way to get onto my ignore list so that I never read anything you write again or respond to anything you post. I gave you a second chance. There won't be a third one.

    Is there are reason you chose to insult me? When people insult me like that I never help them again. Was that your goal? I'm a very good physicist and know this subject very well and know exactly the difference between something that "is" energy and something that "has" energy. And nothing "is" energy. They only "have" energy. Especially photons.

    I've been a professional physicist for some twenty five years now, not including my time as an undergraduate and in graduate school. Why exactly do you think you'd know better than I do regarding one of the most basic facts of all physics? What I said is not an opinion but a universally accepted fact that every single physicist that has been alive for the last 100 years knows.

    Since you claim to know differently then prove to us that you're right and I'm wrong. For example, search for a text athttp://bookzz.org/ and find either a quantum mechanics text, an electromagnetism text or a modern physics text that shows that you're right.
    Man you make me so mad
    Ok I will prove to you .
    Have you watched Stephen Hawking Grand Design The key to the comos?
    Stephen Hawking himself said that light is a distostion of space time.
    Here it link
    stephen.hawkings.grand.design.s01e02.the.key.to.th e.cosmos.hdtv.mw.xvid.avi | Sockshare
    Watch it at minute 24!
    Let the greatest physicist explain it to you.
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  12. #12  
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    Quote Originally Posted by johnzxcv View Post
    Man you make me so mad
    That's because you have a poor understanding of general relativity. Hawking should never have phrased it like that. He made a mistake. A distortion is an action whereas curvature is a state of being. One can't be replaced for the other.

    Quote Originally Posted by johnzxcv View Post
    Ok I will prove to you .
    I don't need proof of something I know infinitely better than you do.

    Frankly I've grown tired of your poor insulting attitude. You're going on my ignore list. That means that when you respond to this post with claims that you're understanding of GR is superior to mine and that it's impossible for Hawking to phrase someone poorly I'll never see it. Most people continue to keep responding to people when they're on their ignore list for reasons I can't understand. They can't be seen but that never seems to matter to the people posting. All they end up doing is talking to the rest of the forum and themselves. So if you find that either useful or a comfortable thing to do then feel free. But know that you'll be wasting your time.
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    Quote Originally Posted by Physicist View Post
    That's because you have a poor understanding of general relativity. Hawking should never have phrased it like that. He made a mistake. A distortion is an action whereas curvature is a state of being. One can't be replaced for the other.


    I don't need proof of something I know infinitely better than you do.

    Frankly I've grown tired of your poor insulting attitude. You're going on my ignore list. That means that when you respond to this post with claims that you're understanding of GR is superior to mine and that it's impossible for Hawking to phrase someone poorly I'll never see it. Most people continue to keep responding to people when they're on their ignore list for reasons I can't understand. They can't be seen but that never seems to matter to the people posting. All they end up doing is talking to the rest of the forum and themselves. So if you find that either useful or a comfortable thing to do then feel free. But know that you'll be wasting your time.
    Wait ,please don't put me into ignore list.
    You watch that and you see my point.
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  14. #14  
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    Quote Originally Posted by Physicist
    No. Light is not a distortion in spacetime.
    In retrospect I should have explained that while people do speak of spacetime distortion that's typically something a physicist would say in a book or article written for the layman and not for a professional. Distortion in this case means being distorted, i.e. to changing something from its original state. The problem with this term is that in general it doesn't mean the same thing as curved. Therefore its bad practice to substitute distortion for curved.

    For example; if you take a flat piece of paper and roll it into the shape of a cone then you're not introducing any curvature, the intrinsic curvature of the cone is still flat (and that's the kind of curvature one speaks of in GR). As I said, I doubt that term can be found in a GR textbook because textbooks teach professionals and not layman. A good professional would pick up on the difference.
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    Quote Originally Posted by Physicist View Post
    In retrospect I should have explained that while people do speak of spacetime distortion that's typically something a physicist would say in a book or article written for the layman and not for a professional. Distortion in this case means being distorted, i.e. to changing something from its original state. The problem with this term is that in general it doesn't mean the same thing as curved. Therefore its bad practice to substitute distortion for curved.

    For example; if you take a flat piece of paper and roll it into the shape of a cone then you're not introducing any curvature, the intrinsic curvature of the cone is still flat (and that's the kind of curvature one speaks of in GR). As I said, I doubt that term can be found in a GR textbook because textbooks teach professionals and not layman. A good professional would pick up on the difference.
    So you mean stephen Hawking was wrong?
    Anyway thanks for not putting me into irnog list. I join this forum to study, and I need a lot of help.
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    I think, only real entities make sensory perception. Light is sensed by sensory organs. Hence, light is a real entity. In material world all real entities are made of matter. It means light should be made of (corpuscles of) matter. Matter is the fundamental substance that provides objective reality and positive existence to real entities. If light is made of matter, what relation it has to space, which is a functional entity?
    Nainan
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    Quote Originally Posted by matterdoc View Post
    I think, only real entities make sensory perception. Light is sensed by sensory organs. Hence, light is a real entity. In material world all real entities are made of matter. It means light should be made of (corpuscles of) matter. Matter is the fundamental substance that provides objective reality and positive existence to real entities. If light is made of matter, what relation it has to space, which is a functional entity?
    Nainan
    Can you explain your point, I don't get it
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    in reply to johnzxcv, re: your posts.

    Physicist is correct with the explanation of light (although I have a different interpretation)

    What he wrote is far removed from "stupid", it is, with some elements of doubt involved, the most recent info regarding "light as energy". You asked a question, he answered.

    You did not care for the answer, and disregard the concept...okay then.

    Show me what you think is correct (I always like new stuff)

    .....

    Yes, Stephen Hawking can be wrong! So can Einstein, or anyone else...no one knows the "secrets of all things". The best anyone can do is their best, and it would be difficult to fault them

    for it...sometimes the best that can be done is "guess" as verified by experiment and mathematics.

    No one will ever travel to a "blackhole", so virtually everything about them is a "best guess"...the same is true for our own Sun. (how close do you think anything made could ever hope to

    get in terms of examining the Sun? And the Sun is practically in our laps compared with everything else!)

    .....

    There is still NO ABSOLUTE PROOF of what "light" is, of itself...everything that is known is assumed. It's all a "best guess".

    So don't be so quick to ridicule something...it just might be right in some way, or wrong in some other.


    (Thanks for reading!)
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    Quote Originally Posted by Gerry Nightingale View Post
    in reply to johnzxcv, re: your posts.

    Physicist is correct with the explanation of light (although I have a different interpretation)

    What he wrote is far removed from "stupid", it is, with some elements of doubt involved, the most recent info regarding "light as energy". You asked a question, he answered.

    You did not care for the answer, and disregard the concept...okay then.

    Show me what you think is correct (I always like new stuff)

    .....

    Yes, Stephen Hawking can be wrong! So can Einstein, or anyone else...no one knows the "secrets of all things". The best anyone can do is their best, and it would be difficult to fault them

    for it...sometimes the best that can be done is "guess" as verified by experiment and mathematics.

    No one will ever travel to a "blackhole", so virtually everything about them is a "best guess"...the same is true for our own Sun. (how close do you think anything made could ever hope to

    get in terms of examining the Sun? And the Sun is practically in our laps compared with everything else!)

    .....

    There is still NO ABSOLUTE PROOF of what "light" is, of itself...everything that is known is assumed. It's all a "best guess".

    So don't be so quick to ridicule something...it just might be right in some way, or wrong in some other.


    (Thanks for reading!)
    Oh man
    Light is a distotion of space-time. Stephen Hawking himself said that.
    That is the ideal of theodo calypso , a German theorist. That will unify graviton and photon.
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    Quote Originally Posted by Gerry Nightingale View Post
    in reply to johnzxcv, re: your posts.

    Physicist is correct with the explanation of light (although I have a different interpretation)

    What he wrote is far removed from "stupid", it is, with some elements of doubt involved, the most recent info regarding "light as energy". You asked a question, he answered.

    You did not care for the answer, and disregard the concept...okay then.

    Show me what you think is correct (I always like new stuff)

    .....

    Yes, Stephen Hawking can be wrong! So can Einstein, or anyone else...no one knows the "secrets of all things". The best anyone can do is their best, and it would be difficult to fault them

    for it...sometimes the best that can be done is "guess" as verified by experiment and mathematics.

    No one will ever travel to a "blackhole", so virtually everything about them is a "best guess"...the same is true for our own Sun. (how close do you think anything made could ever hope to

    get in terms of examining the Sun? And the Sun is practically in our laps compared with everything else!)

    .....

    There is still NO ABSOLUTE PROOF of what "light" is, of itself...everything that is known is assumed. It's all a "best guess".

    So don't be so quick to ridicule something...it just might be right in some way, or wrong in some other.


    (Thanks for reading!)
    Can you show me where that ideal is wrong? Light is a distotion of space time .That ideal can explain why photon behave like particle and like wave.
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    In reply to johnzxcv, re: your # 20 post.

    "Which idea do you want me to comment on"...light is a distortion of the spacetime continuum?"

    You would be better informed by Physicist or Jilan<she knows what's current in QM far better than I do, and I don't think you would "get" my answer, as it's far from doctrine.

    .....

    By the bye...Hawking creates hypothesis for dealing w/ specific circumstances, usually as mathematical expressions. General "theory" is different in that it usually involves the

    "basic nature" of things and forces, a broader spectrum...this would be Einstein territory.

    (Thanks for reading!)
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  22. #22  
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    Quote Originally Posted by Gerry Nightingale View Post
    In reply to johnzxcv, re: your # 20 post.

    "Which idea do you want me to comment on"...light is a distortion of the spacetime continuum?"

    You would be better informed by Physicist or Jilan<she knows what's current in QM far better than I do, and I don't think you would "get" my answer, as it's far from doctrine.

    .....

    By the bye...Hawking creates hypothesis for dealing w/ specific circumstances, usually as mathematical expressions. General "theory" is different in that it usually involves the

    "basic nature" of things and forces, a broader spectrum...this would be Einstein territory.

    (Thanks for reading!)
    You didn't tell where that ideal wrong.Moreover Stephen Hawking said so in his book Stephen Hawking Grand design the key to the comos. That book is very famous. How can you miss it?
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    Quote Originally Posted by Gerry Nightingale View Post
    In reply to johnzxcv, re: your # 20 post.

    "Which idea do you want me to comment on"...light is a distortion of the spacetime continuum?"

    You would be better informed by Physicist or Jilan<she knows what's current in QM far better than I do, and I don't think you would "get" my answer, as it's far from doctrine.

    .....

    By the bye...Hawking creates hypothesis for dealing w/ specific circumstances, usually as mathematical expressions. General "theory" is different in that it usually involves the

    "basic nature" of things and forces, a broader spectrum...this would be Einstein territory.

    (Thanks for reading!)
    stephen.hawkings.grand.design.s01e02.the.key.to.th e.cosmos.hdtv.mw.xvid.avi | Sockshare
    Please watch that and you will believe me Light is a distotion of space time. Stephen Hawking will explain it.
    Watch at minute25.Physicist didn't watch that so he did't believe me.
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    John, Kaluza Klein theory operates in 5 dimensions, the usual four with one compactified curled up dimension. There were issues with it so the string theorists moved to 11 dimensions to sort out the issues. String Theory is still just a theory when all said and done. It cannot be proved or disproved.
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    Quote Originally Posted by johnzxcv View Post
    I know that light sometimes behave like wave and sometimes like particles depend on the condition we measure it. But What photon really is?
    It's a lemon-like singleton soliton "pulse" of electromagnetic four-potential spatial pressure that propagates through space without dissipating. Field is the derivative of potential, so it's also a field variation propagating at c. You could say it's a wave in space where E=hf applies, h being action, and the dimensionality of action can be expressed as momentum x distance. Think in terms of a subterranean seismic wave, but in space. Have a look at Displacement current on Wikipedia and note the Maxwell quote: "light consists of transverse undulations in the same medium that is the cause of electric and magnetic phenomena”. Because action is momentum x distance, think of the displacement as being the same regardless of wavelength. Something like a guitar pluck being the same regardless of the position of your left hand on the frets. Yeah, I know it sounds weird. But take a look at some pictures of the electromagnetic spectrum. Regardless of frequency, the amplitude is always depicted as being the same. Trust me, this isn't just some coincidence, it's idiot savant.
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    Wow, don´t belive Farsight John :-) Easiest way is just wikipedia Light - Wikipedia, the free encyclopedia . No hardcore physics here.
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    Quote Originally Posted by Farsight View Post
    But take a look at some pictures of the electromagnetic spectrum. Regardless of frequency, the amplitude is always depicted as being the same. Trust me, this isn't just some coincidence, it's idiot savant.
    Are you recommending that rather than learn physics we just look as a few pictures? Can you show us the equations that govern photons and then explain what you mean by amplitude?
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    The equation is E=hf where h is action, and action has the dimensionality of energy x time or momentum x distance. That's how it really is. If you look around the internet you can find Leonard Susskind in a video talking about angular momentum and rolling his finger round and round. You can roll your finger round fast or slow, but it's always going round the same path. It really isn't totally unlike the wind wave gif. If the wavelength is longer, the red dot goes round slower. But it still goes round the same path:


    CCBYSA image by Kraaiennest, see wiki

    Of course for space you have to mentally copy then invert this image, and slap it on top of the image above, such that there is no surface. If you've ever been scuba diving deep in a gin-clear sea, you'll know what I mean.
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    That doesn't really make sense. Can you give us an example scenario with some simple numbers where there is this wave and then show us what you are referring to as "amplitude"?
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    Quote Originally Posted by PhysBang View Post
    That doesn't really make sense. Can you give us an example scenario with some simple numbers where there is this wave and then show us what you are referring to as "amplitude"?
    What are they talking about? What kind of wave are they referring to? I.e. wave as in wave function from quantum mechanics or wave as in electromagnetic wave where there are two amplitudes, one for the electric field and one for the magnetic field?
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    I presume this thread is about classic electromagnetic radiation in vacuum, rather than quantum field theories, or radiation in the presence of sources. In this context, the answer to the question in the OP is quite simply that light is an electromagnetic 4-potential that satisfies the wave equation



    With an appropriate choice of gauge ( e.g. Lorentz gauge ), Maxwell's equations connect this with our usual concepts of electric and magnetic fields, but ultimately what light is in the classic domain all boils down to a specific form of 4-potential in space-time.
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    Quote Originally Posted by Farsight View Post
    It's a lemon-like singleton soliton "pulse" of electromagnetic four-potential spatial pressure that propagates through space without dissipating. Field is the derivative of potential, so it's also a field variation propagating at c. You could say it's a wave in space where E=hf applies, h being action, and the dimensionality of action can be expressed as momentum x distance. Think in terms of a subterranean seismic wave, but in space. Have a look at Displacement current on Wikipedia and note the Maxwell quote: "light consists of transverse undulations in the same medium that is the cause of electric and magnetic phenomena”. Because action is momentum x distance, think of the displacement as being the same regardless of wavelength. Something like a guitar pluck being the same regardless of the position of your left hand on the frets. Yeah, I know it sounds weird. But take a look at some pictures of the electromagnetic spectrum. Regardless of frequency, the amplitude is always depicted as being the same. Trust me, this isn't just some coincidence, it's idiot savant.
    You mean the idea "light is a distotion of space time" was wrong. I'm a very good listener, If you can tell where it was wrong or it isn't nessary to know what light really is? We will have to tell Stephen Hawking that he was wrong about light.
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    Quote Originally Posted by johnzxcv View Post
    You mean the idea "light is a distortion of space time" was wrong.
    Not really. Have a look at The role of the potentials in electromagnetism by Percy Hammond and note the bit that says "We conclude that the field describes the curvature that characterizes the electromagnetic interaction". Then ask yourself what curvature?. The other guys here might give you answers like "curvature of a fibre bundle". And when you ask what that is, you won't get a clear answer. IMHO it's a curvature of space. That's fairly close to what you said Hawking said.

    Quote Originally Posted by johnzxcv View Post
    I'm a very good listener, If you can tell where it was wrong or it isn't necessary to know what light really is?
    I think it's essential to know what light is. But if you ask around, you don't get a clear idea. Markus gave a stock answer, but it doesn't really satisfy.

    Quote Originally Posted by johnzxcv View Post
    We will have to tell Stephen Hawking that he was wrong about light.
    I don't think so.
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    Quote Originally Posted by PhysBang View Post
    That doesn't really make sense. Can you give us an example scenario with some simple numbers where there is this wave and then show us what you are referring to as "amplitude"?
    No, sorry. But see Leonard Susskind trying to explain the Higgs boson. At 2 minutes 50 second he was waving his marker round saying angular momentum is quantized. That's like the rotational motion associated with the red dots in the ocean waves gif. Roll your finger around fast or slow, but roll it round the same circumference, because the waves are the same height. You're emulating the h in E=hf.
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    Quote Originally Posted by Farsight View Post
    No, sorry. But see Leonard Susskind trying to explain the Higgs boson. At 2 minutes 50 second he was waving his marker round saying angular momentum is quantized. That's like the rotational motion associated with the red dots in the ocean waves gif. Roll your finger around fast or slow, but roll it round the same circumference, because the waves are the same height. You're emulating the h in E=hf.
    How about Physicist ideal? He said light is not energy.so itn't a distotion of space time. Light is property of energy.Is he right? If so he is the one will tell stephen Hawking wrong
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    I've just been looking at what was said. I think there's been some confusion here between curved space and curved spacetime. Curved spacetime isn't the same thing as curved space. Let me try to explain using an analogy:

    Imagine you're standing on a headland looking out to sea. You are gazing upon a flat calm ocean which is disturbed by one single wave coming towards you. After a while you appreciate that the path of this wave is curved. That's like curved spacetime, wherein light curves when it traverses a gravitational field. However look closely at the ocean where the wave is. It's curved. That's like curved space. It's not the same thing as curved spacetime.

    Also, since Einstein described radiation as energy, I think it's OK to say light is energy. And whilst "distortion of spacetime" isn't quite the same thing as curved space, I wouldn't complain too much about it myself.
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    Quote Originally Posted by Farsight View Post
    I've just been looking at what was said. I think there's been some confusion here between curved space and curved spacetime. Curved spacetime isn't the same thing as curved space. Let me try to explain using an analogy:

    Imagine you're standing on a headland looking out to sea. You are gazing upon a flat calm ocean which is disturbed by one single wave coming towards you. After a while you appreciate that the path of this wave is curved. That's like curved spacetime, wherein light curves when it traverses a gravitational field. However look closely at the ocean where the wave is. It's curved. That's like curved space. It's not the same thing as curved spacetime.

    Also, since Einstein described radiation as energy, I think it's OK to say light is energy. And whilst "distortion of spacetime" isn't quite the same thing as curved space, I wouldn't complain too much about it myself.
    I see now. You mean light is curved space.And the object it affect is Curved spacetime. Oh man that is really confusing.
    Thanks for explain it to me.
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    Quote Originally Posted by Farsight View Post
    No, sorry. But see Leonard Susskind trying to explain the Higgs boson. At 2 minutes 50 second he was waving his marker round saying angular momentum is quantized. That's like the rotational motion associated with the red dots in the ocean waves gif. Roll your finger around fast or slow, but roll it round the same circumference, because the waves are the same height. You're emulating the h in E=hf.
    So you can't explain yourself, but you want us to trust you anyways?

    That is pathetic.
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    I see now. You mean light is curved space.And the object it affect is Curved spacetime. Oh man that is really confusing.
    Thanks for explain it to me.
    Light "is" neither curved space nor "is" it curved space-time in the sense that this is its defining characteristic; rather, it is an excitation of the electromagnetic field. Obviously, since there is energy-momentum associated with an electromagnetic field, this will have a ( very tiny ) effect on the local geometry of space-time - but then, so does a rock, or dust particle, or the electric field of an electron, or anything else that has energy-momentum associated with it, for that matter. The geometric effect light has on space-time is not its defining characteristic; it is the specific form of the electromagnetic 4-potential that forms the source of this effect which defines light and distinguishes it from other sources of energy-momentum, and that specific form is just the wave constraint I gave in my last post. Light is just that - electromagnetic potential of a very specific type.
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    Quote Originally Posted by johnzxcv View Post
    I see now. You mean light is curved space. And the object it affect is curved spacetime. Oh man that is really confusing.
    No, the object it affects is space. Curved spacetime isn't an object, because spacetime isn't an object, it's a mathematical model which is a static representation of space and motion through it over time. I didn't mean to cause any confusion.


    Quote Originally Posted by Markus Hanke
    Light "is" neither curved space nor "is" it curved space-time in the sense that this is its defining characteristic; rather, it is an excitation of the electromagnetic field.
    But Percy Hammond really did refer to curvature. Go and look at electromagnetic geometry. So again the question is this: what curvature? When a seismic wave travels through the ground, the ground waves. When an ocean wave travels through the sea, the sea waves. When an electromagnetic wave travels through space, what waves?

    Quote Originally Posted by Markus Hanke
    Obviously, since there is energy-momentum associated with an electromagnetic field, this will have a ( very tiny ) effect on the local geometry of space-time...
    You seem to be conflating curved space with curved spacetime Markus. You know spacetime is static. You know that space isn't curved where a gravitational field is. You've missed the point of the wave analogy and what Percy Hammond was saying. And what Maxwell said when he talked about displacement current and transverse undulations. What curvature? What's displaced? What's undulating? What waves?

    Quote Originally Posted by Markus Hanke
    ...it is the specific form of the electromagnetic 4-potential...
    And what is that? Explain it to your grandmother, Markus.
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    Quote Originally Posted by Farsight View Post
    And what is that? Explain it to your grandmother, Markus.
    Any grandmother willing to learn the mathematics of the theory can understand that.

    It is the pathetic assholes, like you Farsight, who are unwilling to learn and still want to pontificate about science as if they knew something.

    We know that you cannot understand mathematics. We know that you have been peddling your self-published book for over a decade without trying to learn physics. We can go back and look at your pathetic early posts trying to demonstrate mathematical claims with horrible mistakes. You, and nobody else, decided that it was too hard for you to keep going and learn the math. You, and nobody else, decided to say that the scientists describing galaxies were making basic mathematical errors when you can't be bothered to work through the math yourself.
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    But Percy Hammond really did refer to curvature. Go and look at electromagnetic geometry.
    I am not familiar with the details of Born-Infeld theory, so I will need to study this in more detail. At first glance all that this seems to be implying is that there is a very specific relationship between the electromagnetic field and local geometry, which is no different from what I was saying anyway. This doesn't imply that light and curvature are the same thing, any more than the earth and the Kerr metric outside of it are the same thing.

    You seem to be conflating curved space with curved spacetime Markus.
    I am not conflating anything. Electromagnetic radiation comes with a non-vanishing stress-energy tensor, and hence a local metric that is not Minkowskian via the Einstein equations. No conflations here.

    And what is that? Explain it to your grandmother, Markus.
    What is it with you and grandmothers ? Can you explain the blueprints of your computer's CPU to your grandmother ? No ? Does that make computers any less real ?
    Despite what you might think, "understandability by grandmothers" is not a requirement of physics theories.
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    I honestly can explain my computer to my grandmother. I have a computer science degree, I'm an IT guy.

    And honestly Markus, you are conflating curved space with curved spacetime. The metric isn't what space is. It's your plot of your measurements. Such as your plot of light-clock readings in an equatorial slice of space around the Earth. Like the Baez article says, that space isn't curved. However spacetime is. Your metric is. Your plot of light-clock readings is. Pay attention to the analogy:

    Imagine you're standing on a headland looking out to sea. You are gazing upon a flat calm ocean which is disturbed by one single wave coming towards you. After a while you appreciate that the path of this wave is curved. That's like curved spacetime, wherein light curves when it traverses a gravitational field. However look closely at the ocean where the wave is. It's curved.

    The path of the wave is curved because your headland is next to an estuary. There's a salinity gradient in the water. The water is inhomogeneous, so wave motion through it is curved. If you don't like that analogy look to sonar. Waves follow a curved path when the medium is inhomogeneous. And where those waves actually are, the medium is distorted / displaced / curved. This is what electromagnetic geometry is all about. It's different to the spacetime geometry you're familiar with. Do study it. And remember we call them electrons. Not geons. Because curved space is a savage thing that can curve the path of light through 720 degrees in a picosecond using only 511keV of self-energy. When it comes to curved spacetime, the whole mass-energy of the Earth can barely curve light at all.

    PS: please do something about the abuse. It's getting out of hand.
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    Quote Originally Posted by Farsight View Post
    I honestly can explain my computer to my grandmother. I have a computer science degree, I'm an IT guy.
    But you are not a physics expert, for all your lies to the contrary.

    PS: please do something about the abuse. It's getting out of hand.
    The abuse here is from you: you know that you cannot do the math, yet you lie and claim that you have done some sort of analysis of the math.
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    In reply to AIP's this thread.

    So...a true science defense consists ultimately of calling other people "pathetic a-holes" (just as I suspected! ain't theory grand?) And this assessment from a "quote-miner" who has nothing

    to add to anything except personal conjecture.
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    OH...I forgot the maths! 1+1=2...everything else is a derivation of this.
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    I honestly can explain my computer to my grandmother.
    I wasn't talking about your computer, I was talking about the CPU circuitry blueprints. But even if you can - good for you ! That still doesn't make this a requirement for a physics model to be valid. That's what the scientific method is for, not your grandmother, with all respect that is due to her.
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    Quote Originally Posted by Markus Hanke View Post
    Light "is" neither curved space nor "is" it curved space-time in the sense that this is its defining characteristic; rather, it is an excitation of the electromagnetic field. Obviously, since there is energy-momentum associated with an electromagnetic field, this will have a ( very tiny ) effect on the local geometry of space-time - but then, so does a rock, or dust particle, or the electric field of an electron, or anything else that has energy-momentum associated with it, for that matter. The geometric effect light has on space-time is not its defining characteristic; it is the specific form of the electromagnetic 4-potential that forms the source of this effect which defines light and distinguishes it from other sources of energy-momentum, and that specific form is just the wave constraint I gave in my last post. Light is just that - electromagnetic potential of a very specific type.
    Markus ,I will have to ask you what is electromagnetism?Is it some kind of energy? If it is energy then it is mass and it is curved spacetime
    Moreover isn't electromagnetic potential . Electromagnetism cannot explain it's particle behavior.
    One more thing ,Stephen Hawking said that "Light is curved spacetime" . Why don't you talk to him that he was wrong about this?
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    One more thing ,Stephen Hawking said that "Light is curved spacetime" . Why don't you talk to him that he was wrong about this?
    You end every one of your posts with this. It is the 'appeal to authority' invoked because you don't understand
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    Quote Originally Posted by AlexG View Post
    You end every one of your posts with this. It is the 'appeal to authority' invoked because you don't understand
    I only told the true. Stephen himself told that
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    Quote Originally Posted by AlexG
    You end every one of your posts with this. It is the 'appeal to authority' invoked because you don't understand
    My first question is who are you quoting? You didn't make it clear who you were quoting. If it was johnzxcv, PhysBang, Farsight or x0x then they're in my ignore list and I can't see their posts. Next time please state whom you're quoting.

    My second question starts off with this; I don't understand your objection. Authority (an expert other than ourselves) can be a valid source of knowledge in a logically sound argument. Why would you have a problem with it?
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    But he's not making a sound argument. He's invoking 'prove me wrong' in abstentia.
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    Quote Originally Posted by AlexG View Post
    But he's not making a sound argument. He's invoking 'prove me wrong' in abstentia.
    Okay. I see now. Who is "he" anyway?
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    Markus ,I will have to ask you what is electromagnetism?Is it some kind of energy? If it is energy then it is mass and it is curved spacetime
    Moreover isn't electromagnetic potential . Electromagnetism cannot explain it's particle behavior.
    One more thing ,Stephen Hawking said that "Light is curved spacetime" . Why don't you talk to him that he was wrong about this?
    I don't think you read my post very carefully. Electromagnetism is a form of energy, so there is space-time curvature involved. That is exactly what I said. However, I also said that the curvature is not its defining characteristic, because I could choose a different source of energy-momentum to arrive at the exact same curvature.
    Can you see the difference ?
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    It is the pathetic assholes, like you Farsight
    MODERATOR NOTE : Not acceptable ! Regardless of what our feelings are towards a particular poster, this level of language will not be tolerated on this forum. This is an official warning, and any repeat will be an automatic three day suspension.
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    Quote Originally Posted by Markus Hanke View Post
    I don't think you read my post very carefully. Electromagnetism is a form of energy, so there is space-time curvature involved. That is exactly what I said. However, I also said that the curvature is not its defining characteristic, because I could choose a different source of energy-momentum to arrive at the exact same curvature.
    Can you see the difference ?
    Markus ,I will have to ask you what is electromagnetism? Is it some kind of energy? If it is energy then it is mass and it is curved spacetime
    Moreover isn't electromagnetic potential . Electromagnetism cannot explain it's particle behavior.
    I'll take a crack at this myself. Electromagnetism is a branch of physics dealing with electricity and magnetism, the laws governing their behavior being Maxwell's equations. It can be shown that the electromagnetic field can store energy and an electromagnetic wave has energy. That energy can be thought of as kinetic energy.

    When it comes to static fields it gets tricky. It's one of the reasons why we say that energy is not a real thing. The way the energy of an electric field is defined is to calculate the amount of work done to create the field. It we try to say that the energy is in the field then we have a problem. It can be shown that the work W done to create an electric field by bringing charges in from infinity is



    where is the charge density and V the potential. This can be shown to equal



    If we were to ask "where" the energy is then how would we use these results to make that determination uniquely. The fact is that we can't. That's why one form is not superior over the other and we can't say that there is physically energy at any particular place. In the second expression we could express it as



    where



    is an energy density. When we do this we can say that the energy is where the field is. When the field is an electromagnetic one and changes with time then its a bit different.

    Now go back and look at both of the first two integrals and ask yourself what region your integrating over. In the first case you're integrating over the region where the charge density is non-zero. In the second expression we're integrating where E is not zero, i.e. over all space.

    You can read all about this in Griffiths text on electrodynamics in section 2.4.3
    Last edited by Physicist; 08-10-2014 at 12:10 AM.
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    Quote Originally Posted by Markus Hanke View Post
    MODERATOR NOTE : Not acceptable ! Regardless of what our feelings are towards a particular poster, this level of language will not be tolerated on this forum. This is an official warning, and any repeat will be an automatic three day suspension.
    You've given free rein to the abuse, and in doing so you have actively encouraged it. And you said yesterday that you will move all my posts to personal theories. So this "moderator" note of yours is spectacularly unconvincing. And there was I thinking you were interested in sincere discussion. More fool me.
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    Quote Originally Posted by Markus Hanke View Post
    I don't think you read my post very carefully. Electromagnetism is a form of energy, so there is space-time curvature involved. That is exactly what I said. However, I also said that the curvature is not its defining characteristic, because I could choose a different source of energy-momentum to arrive at the exact same curvature.
    Can you see the difference ?
    I see now. Thanks.
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    Quote Originally Posted by johnzxcv
    I see now. Thanks.
    No problem.
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