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    The Fundamental Nature Of Light
    By Sascha Vongehr | February 3rd 2011 01:29 AM | 102 comments | Print | E-mail | Track Comments
    About Sascha

    Dr. Sascha Vongehr [风洒沙] studied phil/math/chem/phys in Germany, obtained a BSc in theoretical physics (electro-mag) & MSc (stringtheory)...

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    Did you ever wonder why both, Einstein’s relativity theory and quantum physics, in theory as well as experiment, seem obsessed with the nature of light? The velocity of light, light clocks, entangled photons, and so on – why is it always light? This preoccupation is no coincidence. It comes directly from the fact that light does not actually exist. Think I am nuts yet?


    Today, I will tell you why relativity theory makes the non-existence of light obvious. The next time, I will show that this odd seeming fact only confirms what is known from entirely unrelated quantum mechanics: classical relativity and non-relativistic quantum physics both agree on that light does not exist for entirely different reasons!


    In a third part, I will explain why I personally find all this rather unsurprising. In short: it could not be any other way! The measure of all measures may not be allowed to have any internal properties that could possibly change and thereby change the measure. Hence, it best has no properties at all. Optimally, it does not even exist. That is why light has become the measure of all measures in the cutting edge of fundamental physics: It does not itself exist!


    Light is in a sense the very connection between nothingness and something and it is thus just the thing to be explored if we want to ever discover the fundamental basis of physics, how dreams about reality dream themselves. But lets get to the relativistic aspect of the non-existence of light.

              Relativity-

           Light has no time to see

           nor any space to be,

           nor even any energy.


    Relativity theory is all about the problematic of that if you want to know the properties of any system, say the weight or length of a rocket ship, you need to take some care in case that system is moving fast relative to you. You need to distinguish the contribution that your movement relative to the rocket for example adds into your measurements.


    In other words, if you want to know the system’s own properties without any relativistic contributions, you will have to best move along with the object of interest. I will now explain that the light’s own time, length, and energy are none at all and that all the light’s properties are nothing but relativistic contributions.


    Consider that we wish to know the mass, length, and energy of a flash of light that we just shone out of an electric torch and into the night sky. If we want to attain the point of view of the light, that is, if we want to experience the world from the light’s own point of view, from its so called ‘rest frame’, we will find that the more we accelerate to travel along with the light, the shorter the travel time between any two positions along its path becomes.


    Light travels with light velocity “c”. If we do not move relative to the earth, the travel time of the light from the upper atmosphere to the moon for example is about one second. We know this because if it hits a mirror on the moon, it will be back on earth after two seconds. However, these seconds is what it takes us to wait for the light. How long does it take the light to go anywhere?


    If we travel along that same path, the time that it takes us to get to the moon becomes shorter and shorter the faster we go. “Of course” you may say, “because you are faster and faster.” But that is not what I mean. What I mean is that we will experience a travel time below one second before we even reach the velocity of light relative to the earth-moon system. This is due to time dilation.


    In fact, we would experience about one second of travel time between earth and moon, if we moved with a velocity v that equals light velocity divided by the square root of two: v=c/√2. At 90% light velocity, i.e. at v=9c/10, our travel time will be only a third of a second! At 99.9% of the speed of light, the travel time we would experience has reduced to a thirtieth of a second, or 33.3 milliseconds.


    In fact, although we cannot ever reach light velocity, we would soon even by pure experimentation find out that if we could reach light velocity and travel along side by side with the light, time would stop and the travel time between any two points, even between here and the edge of the observable universe, would be exactly zero. Relativity theory tells us that light has no time at all to exist because it moves at the speed of light.


    The light comes to existence in the torch and it may cease to exist in an alien’s eye. The time in between these two events is the light’s life time. For the light, it is its own experienced travel time. There is none. I have a few decades between birth and my inevitable demise, some insects only a single day, but light has no time at all to be. Therefore: It is never! It is not!


    The same contraction of travel time also holds for the travel distance. If we want to attain the point of view of the light, that is, if we want to experience the world from the light’s own point of view, its so called rest frame, we will find that the more we accelerate to travel along with the light, the more the measured travel distance contracts via the so called Lorentz-contraction.


    The faster we go in between A and B, trying to keep up with the light, the shorter the distance becomes for us. This is easily misunderstood and most physicists even explain it incorrectly. So let me not try to explain it in any detail here. Nevertheless, it is true, and moreover, the factor with which the world contracts relative to a moving object is the same factor as that of the time dilation discussed above.


    The conclusion is similar, too: For the light itself, the whole universe is only zero millimeters long. There is no distance between A and B. There is no space in between its birthplace in the torch and its death bed in the alien’s eye. There is no place for the light to be, and therefore it cannot be: It is not!

    Moreover: the more we accelerate to travel along with the light, although the distances traveled become shorter, the light’s wavelength becomes ever longer relative to us. The light becomes ever more reddish because the light’s energy becomes less and less. The faster we hurry along with the beam of light, the more it red-shifts away to being undetectable. If we could race along with it, there would be nothing left at all. There is no light from the light’s own point of view! It is not!

    It should thus not surprise that we can never reach the velocity of light, that we cannot attain the light’s own point of view. There is no such point of view; it does not exist!

    And on to the next part in this series.

     

    Comments

    .. so what do we see then .. ? .. :-) ..

    Axel (from Germany)

    vongehr
    That is in a sense a good question, as we never "see the light". I will come back to this the next time around, because the interaction aspect of observation is of course the quantum mechanical aspect of the non-existence of light.
    rholley
    I got the idea of how it takes zero proper time from Sirius to Earth if you’re riding a photon from reading "The Nature of the Physical World" (1928) by A.S.Eddington.

    If, however, one were taking ‘conventional’ transport, say a spaceship travelling at 0.99 c relative to Earth or Sirius, the light from Sirius would be enormously redshifted as it caught up with one.  That agrees with what you are saying, but expressing it from what is (to me) an easier point of view.

    T.H.Huxley was known as "Darwin’s Bulldog" – I like to refer to Eddington as "Einstein’s Collie" because of the way he rounded up support for Einstein and the theory of General Relativity.
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    Samshive
    Hi Sascha
    Quick question, I think I read an article a few years back where light was slowed down. In this scenario, did the light experience either time or space?
    vongehr
    The slowing down due to a refractive index is best be modeled by a repeated absorption and re-emission with slight time delay by many particles in the medium. So, while it is in between absorptions, it still goes at v = c. But anyways - thus are models of complicated interactions where the interaction is in a sense not observed. It is certainly not about the phenomenon of free light.
    Ladislav Kocbach
    In one of his countless interviews Einstein also considered sitting on the electromagnetic wave. He somehow concluded that it would not be possible, because the oscillating field as we know it would "look" like a frozen landscape. From this propagating field pattern he somehow came to the conclusion that nothing can go as fast as light, and in that interview he somehow stated that these thoughts were sort of starting point of thoughts leading eventually to the special relativity theory. I wish I would have it in front of me now! 
    So it is sort of turned around here. Sascha starts from relativity and comes to the photon's standing time. When I talk to the students about these things, I do not say that the light does not exist, I prefer to say that the photon remains forever as young as newborn, and then perhaps that I might wish to be like a photon, since my time seems to be running too fast now at my age. The students smile politely. 

    Claiming that what remains forever young does not exist - no, I do not expect any polite smiles from the students there. 
    vongehr
    Claiming that what remains forever young does not exist - no,
    does not exist for itself! It does not have any experience of anything whatsoever. What kind of existence is that? Certainly none for itself - there is not even anything for it.
    Ladislav Kocbach
    And what about the "life" of the schizophrenic neutrino with multiple personalities, what type of existence must that be? Nonexistent and even mentally unstable. I already imagine that we two write a book about the personalities and private lives of elementary particles.
    vongehr
    Neutrinos interact weakly and have rest mass, so I am not sure why you think they do not exist. Something to do with handedness?
    Ladislav Kocbach
    Neutrinos - speed of light - and their rest mass:
    As I am told, they only get their rest mass due to their schizophrenia, also called oscillations. And I do not think they can rest, in spite of their rest mass. But I do not really know.
    It is like light which can be stopped, but then it is sort of not the same light as the free light, and there is a lot to discuss here when one starts personifying those poor little guys. On the other hand, light can be big, just yesterday night we had a winter thunderstorm here. It was  big and noisy. 

    ( and we have not yet mentioned the poor quarks, which are more like Siamese triplets, and no surgery can be successful there. We are told that if such surgery is attempted, an opposite one grows up immediately and they become sort of  Siamese twins, where the new one is anti- )

    But I do not see any great enthusiasm for that mentioned book - The private lives of particles in fields.


    Perhaps you are really serious about this non-existence of light?
    Is Time Dilation/Lorentz contraction predicted for massless objects at the speed of light by GR, too? (I'm an eejit, I have no idea indeed... Just seems to me that light in some of the non-vacuum mediums, where it moves a tad faster, should be going backwards in time and space, which I don't think was observed...)

    vongehr
    Is Time Dilation/Lorentz contraction predicted for ... too?
    These phenomena are plainly due to a kind of rotation inside space-time, i.e. they are a purely kinematic fact that is as such more fundamental than the dynamics (i.e. masses curving space-time) on top of it. So the short answer is: Yes.
    What an interesting version of the Zeno's paradox!

    Quentin Rowe
    So what is it that creates the universe's time&distance, mass & inertia, space & matter etc... is it the act of observation, as per quantum mechanics?

    so .. ummm .. for light, all time occurs instantaneously .. and that goes for (from our point of view) whereever it has existed and will exist. So the light experience is that the entire life of the universe is instantaneous.

    .. and .. all light experienced distance is zero. The totallity of all light experience of the universe is as an instantaneous dimensionless point of zero energy. And this is a particular quality of Nothing. It sort of contains the existing universe within its instantaneous zero-dimensional existence.

    ?? .. so .. what are we experiencing when we see light travel about the place? But light itself isn't travelling, is it. It's not taking part in our game. It's like we're seeing an apeture being mapped around the place.

    ... lol, sorry ... 8-) ... random, ill-educated meandering

    MikeCrow
    I can only imagine we are seeing light at our sense of time.

    I know how it propagates away from a radio antenna over time, But I also know there's nothing stopping it from taking a trip across the universe before it reaches my radio.

    This is one of the reasons I keep thinking the orientation of time's dimension(s) changes compared to the 3 space dimensions based on the curvature of gravity/acceleration.
    Never is a long time.
    so, is light responsible for time?

    vongehr
    No, but there is certainly a sense in which time and light are 'responsible' for space.
    blue-green
    The operative phrase here is RELATIVIVE to ITSELF. Relative to itself, light has no momentum and no energy. Furthermore, because of the duality betwixt momentum-energy descriptions and space-time ones, light also has no space or time unto itself. This truism about light, however, can apply to most anything. Unto myself, I have no momentum and no potential energy. The Universe as a whole, has no momentum nor energy, relative to itself. So where’s the beef? Happy New Year to you Sascha! Thanks for remembering us. I sense you have been getting plenty of action without approaching the red light zone. There’s a lightness in your step … a lightness of being unto yourself … no matter how heavy you may seem to others 3 states removed.

    Edit: by momentum (above)... I mean linear momentum.  Unto itself, a lonely photon has angular momentum with the same physical units as Planck's constant (gratuitous name drop there) and
    in precise indivisible chunks of Planck's irreducible unit of action.
    Whole integer, bosonic angular momentum for photons.
    Half-integer, fermionic angular momentum for neutrinos and particles with non-zero rest mass and Pauli's inherent repulsion. Three more name drops there, one for Bose (not the stereo), one for Fermi and one for the Pauli Exclusion Principle (not applicable to photons (bosons) except in exceptional media/Bohrian circumstances).

    The magnitude and full-integer nature of the spin is inherent to each photon.
    The direction of the spin is relative to the experimental framework in which it is measured.
    No framework, no coordinates, no specific direction. Nothing new here.
    vongehr
    This truism about light, however, can apply to most anything.
    Unto myself, I have no momentum and no potential energy.
    No - sorry, but that is just totally wrong. You have lots and lots of internal momenta and rest mass.
    blue-green
    Inherent in the Ferimi-Dirac or Bose-Einstein statistics (two more name drops) is the fact that these "particles" (bosons or fermions) have no particularity or individuality or distinguishability or History carried within themselves. They all be virgins.
    Maybe that's where the Zen notion of them not existing takes root.
    There is an Identity/Symmetry across all photons of equal energy ...
    just as there is an Identity (sameness under altered scrutiny) across all fundamental particles of equal mass, spin, charge and a few more characteristics ... sometimes called dimensions into which one can do abstract rotations ... aka transmutations ...
    Hank
    Carl Wieman, a guest columnist here, got a Nobel for his work on BECs so he'd be surprised to be told his prize does not exist, according to Zen.
    vongehr
    the fact that these "particles" (bosons or fermions) have no particularity or individuality or distinguishability or History carried within themselves.
    4-He atoms are bosons that can collectively make a super-fluid once you have about 60 of them together. They are basically able to form a BEC this way. That does not mean that the helium atom is nothing internally. It is electrons and protons and neutrons and quarks and photons (existing light!) .... You can go on to compare as much as you want with nonsense "Zen" stuff, but you won't discredit my article in the slightest. Your nonsense and what I am talking about have nothing in common, so please stop telling people that they are somehow similar. They are not.
    There is an Identity/Symmetry across all photons of equal energy ...
    Double mistake! 1) Photons are spin degenerate. 2) The very symmetry that is relativity is their symmetry across different energies.
    MikeCrow
    Do the waves on the surface of a pond exist as a thing?

    It isn't the water, or the air, nor the interface between them.
    Never is a long time.
    vongehr
    It is the water. Moreover, the wave shape usually changes over time even in an ideal frictionless one dimensional channel (if it is not some very particular solitonic excitation as similarly sometimes observed in some Dutch 'grachts' if I remember correctly), so water waves do 'experience' time. The wave shape of EM radiation cannot change in this way (It would be going too far into difficult territory to discuss how they change without a medium changing - the point is basically that their waves are actually the quantum wave functions of the photons).
    Slight comment. Solitons are usually not observed in Amsterdam grachts, but they were mathematically described by Korteweg en de Vries, after whom the Amsterdam mathematical institute is named.
    Solitons were first observed by John Scott Russell in the Union Canal near Edinburgh, which was a narrow, shallow canal for transportation of coal. I don't know exactly when, but he did the observation on horseback.
    A related confusion here is that some nerds insist on calling the Roetersgracht, where the Korteweg-deVries institute is housed, "Routersgracht", because they only know their network architecture and not the history of Amsterdam, where the Roeters family played important roles. ( in dutch Roeters is pronounced "Rooters", just as "routers".)

    vongehr
    Yes, you are right. [And I actually knew that, but forgot - must have to do with the other stuff around the Amsterdam grachts. ;-) ]
    Aitch
    It's OK, ....It doesn't exist, really....  ;-)




    Aitch
    vongehr
    He he - cute little thing. If I have had this before I would have put it into the post. I disagree however: It does exist.
    Bonny Bonobo alias Brat
    The light comes to existence in the torch and it may cease to exist in an alien’s eye. The time in between these two events is the light’s life time. For the light, it is its own experienced travel time. There is none. I have a few decades between birth and my inevitable demise, some insects only a single day, but light has no time at all to be. Therefore: It is never! It is not!
    I like this idea of light having no time to experience its own journey and therefore having no life span, which means that it doesn't really exist in reality, if you just use those terms of reference. It fits in nicely with the 'cogito ergo sum' concept. My latin is very rusty but I imagine it would be something like 'lux tempus nescit ergo non est' but then I was always dreadful at latin.

    Does this mean that a spacecraft traveling at not quite the speed of light could experience an extremely quick journey regardless of how far it traveled? For example, even though it was traveling to a galaxy 48 light years away at just short of the speed of light, could the passengers on board experience it as a one day trip?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    vongehr

    Does this mean that a spacecraft traveling ... 48 light years away at just short of the speed of light, could the passengers on board experience it as a one day trip?
    Yes, but using the formula in the post above, you can confirm that you need a velocity of about v = c (306950399/306950400)0.5 which is basically equal to c (try getting it with a calculator).
    Bonny Bonobo alias Brat
    Does this mean that a spacecraft traveling ... 48 light years away at just short of the speed of light, could the passengers on board experience it as a one day trip?

    Yes, but using the formula in the post above, you can confirm that you need a velocity of about v = c (306950399/306950400)0.5 which is basically equal to c (try getting it with a calculator).
    You’re right Sascha, that maths is too hard for me and my calculator. According to Wiki the speed of light is exactly 299,792,458 metres per second and a light-year is the distance light travels in one year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. The parsec being a unit of length, equal to just under 31 trillion (31×1012) kilometres, 206265 AU, or about 3.26 light-years.

    Proxima Centauri, is the closest star to Earth after the Sun, at around 4.2 light-years away, but let’s say for the purpose of this hypothetical example that it is just 3.27 light years away, so about 31 trillion kilometres away from Earth. If a spaceship was traveling at 99% of the speed of light, how would you calculate how long the journey would seem to the passengers on board traveling from Earth to Proxima Centauri? Would you also have to take into account the Lorentz contraction apparently shortening the distance traveled when you do this calculation or does that somehow follow on?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam
    Helen

    You can just use the calculation Sasha provided in the article.  Since the speed will be 99% that of light you don't need to do anything except replace (v2/c2) with (992/1002). 

    When you plug in all the numbers it comes out that the time experienced by the travelers will be 0.0199 that of the observer or 0.0199 * 3.27 years or about 23.7 days (if I did that right).

    Sorry ... screwed up and forgot the square root.
    Mundus vult decipi
    Bonny Bonobo alias Brat
    Sorry ... screwed up and forgot the square root.
    Thanks Gerhard, but I'm not sure if you are happy with your solution or not? I've given a fairly simple example can someone just give me a simple formula and solution for those figures please?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam
    3.27 years * SQRT(1 - (.99c)2/c2) = T0

    3.27 yrs * SQRT(1 - .9801) = T0

    3.27 yrs * SQRT(.0199) = T0

    3.27 yrs * .141 = T0 =  0.46 yrs  or 167.9 days
    Mundus vult decipi
    Bonny Bonobo alias Brat
    Thanks Gerhard :) So that means that the elapsed time experienced by passengers on board a spaceship traveling to let's say Zeta Reticuli which is 39 light years away from Earth, at 99.99% of the speed of light, would be about 201 days.

    39 yrs * SQRT(1 - (.9999c)2/c2) = T0
    39 yrs * SQRT(1 - .99980001) = T0
    39 yrs * SQRT(.00019999) = T0
    39 yrs * . 0.014141782065920829342951413716372 = T0 = 0.5515295005709123443751051349385 yrs or about 201 days

    If aliens have already mastered the ability to travel in spaceships at close to the speed of light, then these journey times are probably quite feasible. One of the arguments used against aliens visiting Earth is that it would take them too long to travel here, even at close to the speed of light, but now it seems that's not necessarily so, at least for them anyway. Does the Lorentz contraction also shorten the distance traveled or will that be covered in another blog?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    blue-green
    Interstellar travel for anything remotely like us is extremely difficult … virtually impossible. Besides the energetic demand to speed up to 99.99% of c and then to slow back down so that you can land ... and get off … besides all of that … here is yet another huge difficulty. When you are traveling that fast, any matter you smack into, even the hydrogen atoms that are diffused at about 1 atom per cubic meter are going to be blasting your ship as if you were plowing right into an intensely powerful particle accelerator beam. The never stopping radiation is going to kill you, if nothing else. It would be great to see all of the math worked out … I saw a calculation decades ago that said you would need many meters thick of dense lead to shield you from such radiation … and that all adds up to weight that has to be accelerated to 99.99% of c. It can’t be done … and teleporting isn’t going to work either … for a host of other reasons. The best we can do is get you a one way flight to Mars.
    Gerhard Adam
    Well besides time dilation and the Lorentz contraction, you all have the increase in inertia which makes it correspondingly more difficult to move your spaceship as you approach the speed of light.  As a result, the fuel requirements become phenomenally large in a short period of time.
    Mundus vult decipi
    Gerhard,

    From the viewpoint of a non travelling observer the mass of the fuel in the rocket - and therefore its energy potential has increased also.

    Gerhard Adam
    Does the Lorentz contraction also shorten the distance traveled or will that be covered in another blog?
    No, the Lorentz contraction deals with the object shortening in the direction of motion and not the distance traveled.
    Mundus vult decipi
    Bonny Bonobo alias Brat
    So why did Sascha say this?
    (W)e will find that the more we accelerate to travel along with the light, the more the measured travel distance contracts via the so called Lorentz-contraction.The faster we go in between A and B, trying to keep up with the light, the shorter the distance becomes for us. This is easily misunderstood and most physicists even explain it incorrectly. So let me not try to explain it in any detail here.
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    vongehr
    Well, but the distance from A to B might as well be a long space ship, so yes, the travel distance shortens. To the traveler this is the very reason why she needs shorter time.
    Halliday
    Yes, but using the formula in the post above, you can confirm that you need a velocity of about v = c (306950399/306950400)0.5 which is basically equal to c (try getting it with a calculator).
    v = c (306950399/306950400)0.5 ~= c(0.99999999837107232827443157505881) (depending upon how "exact" you consider those integers, of course).  So, yes, 99.9999998% of the speed of light.  :)
    Gerhard Adam
    Actually a question that I'm interested in is whether the point about light having no time or distance has any significance to the classic "spooky action at a distance" problem, since technically there's no violation (from light's perspective) regarding an immediate reaction between any entangled particles.
    Mundus vult decipi
    vongehr
    No, not really, because the entanglement 'interaction' (if you want to call it that) is going on between two particles A and B that have a space-like distance to each other. This means that the 'interaction' goes faster than light. That is not a problem because there is one specific reference system to which it goes faster relatively, namely the one reference system whose spatial direction cuts through both events A and B. That means causality cannot be violated as there is no 'interaction' able to jump onto another reference system and then go backwards inside anybody's past directed light-cone. This in turn you can understand in two different ways:
    1) You believe in some sort of Einstein aether (say the cosmic background or standard model Higgs vacuum) with relativity being an emergent symmetry at low energies and the 'interaction' being a real shock-wave like interaction through the aether (this also ensures there is only one specific reference system, namely the aether).
    2) Many minds interpretation (much better)! I.e., the entangled events, say up-down or down-up spins for a pair of particles A and B left and right of you, they split into two branches once their information about the spin direction meets you in the middle. Then you split into two minds, one seeing up-down, one seeing down-up. So, the 'interaction' did not happen faster than light but rather right there were you observe it with no distances involved at all!
    Does that answer your question?
    Gerhard Adam
    Actually yes ... thank you
    Mundus vult decipi
    Conlusion: So the light only exists in the observers eye. It doesn't exist for itself (in its own experience), OK. It is the observer who gives reality to the things,* not the observed object.
    (To be or not to be - it just depends on the point of view - Quantum-Philosophy is really a very nice topic! )
    *Because we are slow enough to be a little self-conscious..
    But still unsure: How to measure the measure?

    vongehr
    It is the observer who gives reality to the things,* not the observed object.
    That would not be anything to do with my post though. In general, the interaction exchange particle may well itself do have structure and an existence for itself rather than being mere interaction. This only applies to light.
    But still unsure: How to measure the measure?
    That is exactly the question that most people who do apparently understand relativity do never really ask and thus they really do not understand relativity. Light is the fundamental measure because it is the only one that cannot internally change as it does not exist (in the sense that I discussed). Thus, we take light as the measure and the only measure that you measure it with is light.
    You will have to forgive my ignorance, I am not a scientist, but I do believe scientific theories are becoming increasingly bizarre as fact continues to elude scientists. Light does not exist relative to itself, yet it undeniably exists relative to everything else? Please correct me if I am mistaken, but I do believe "relative to itself" is an impossibility, at the very least a paradox. The very nature or relativity requires "something" to be relative to "something else", just as time and space are relative to one another.

    Light does exist, it can be measured and broken down into its component parts. Nothing can simultaneously exist and not exist, no matter how much theoretical nonsense is involved.

    vongehr
    Forgiven ;-)
    "relative to itself" is common, as in "I have velocity 6km/h relative to the street and 0km/h relative to my jacket, and also 0km/h relative to myself. No problem there. "Light does exist", of course it does, but it is all made up of relativistic correction between sender and absorber and none is due to anything that would be the system 'photon particle traveling along the path' itself.
    Nothing can simultaneously exist and not exist
    Quantum mechanics has lead to a very similar problem with our understanding of "exist" versus "possible" as relativity did with "past" and "future". Schroedinger cat states are not nonsense. But I should not actually say quantum mechanics. Philosophers (not necessarily the big names, I mean profound ones) knew all along.
    I mostly agree with professor Sascha Vongehr here. Only the phrase "Light is in a sense the very connection between nothingness and something" is a point of interest.

    Can light exist if there is no material sender AND material recipient?

    In my opinion light only has a causal meaning between objects that show a reaction to it.
    In the process "photons" or the information they "contain" are "destroyed". [ a lot of "", I know :-) ]

    Can light really exists between nothingness and something? I don't think so.

    You should always have material recipients to exchange information.

    blue-green
    Completely separate from Sascha’s relativistic arguments or the wave mechanics to come, is the much older realization at the dawn of fundamental chemistry that the fundamental building blocks are Universal objects and not individual objects. Electrons can trade places; photons (of equal energy) can trade places; entire atoms (of gold for instance) or molecules (of water) can be swapped … with no observable difference except for the statistical accounting that goes into whether they are behaving as bosons or fermions. There is no parallel to this in the classical world or in art … where everything has its unique thumbprint of history. Existence without individuality is … is like traveling in a city and repeatedly coming upon one cookie-cutter chain store after another. It is as if you have never left or gone anywhere.
    And yes, unto myself, I have no linear momentum. My potential energy is naught, if I cannot interact with something else. It would be like being a billionaire with no one with whom to trade. Yes, a single photon has zero rest mass. However, two photons, traveling in opposite directions (or any nonzero angle relative to each other) DO have a non-zero rest-mass m^2 = E^2-P^2. You add up all the energies of the individual photons to get a cumulative E, you add up all of their momenta to get a cumulative P, and only then do you do the E^2-P^2 calculation to get the square of the photons' rest-mass. Photons in the plural have zero-rest mass only if they are moving exactly parallel to each other ... which is a concept that does not hold up well except in flat and empty spaces.  The rest-mass of the system is not the sum of the rest-masses of its components.

    This multiparticle case in a nice example of where nothing AND nothing can be Something.

    OK. Now back to Sascha æther @#%&¿
    vongehr
    However, two photons, traveling in opposite directions DO have a non-zero rest-mass
    Together, yes, and one relative to the other is even infinitely energetic, as it is infinitely blue shifted (plenty of energy for electron-positron pair creation one could think). Yet, they still do not interact but just go through each other. Why? Because there is nothing to interact with! If you want to excite the vacuum to create something with pure light, you have to be adding something more to the mix. Light does not scatter light before you do not have at least as much energy as necessary to make electron-positron pairs as intermediates (or weak interactions may be possible, too, well, at some point even black hole creation). An electron-positron pair however is not nothing relative to itself.
    Light is too busy moving forward, it has no time to waste on any physical events that could possible measure the flow of time. Light is totally deprived from any experience of time. I would claim that after being emitted, light experiences a single unchanging physical state. Which maybe counts as some sort of existence, compared to your claim of not existing at all.

    vongehr
    light experiences a single unchanging physical state.
    That does not sound like experience to me, well certainly not like time if nothing happens at all. Experience is not a state, it is a process.
    Some remarks.

    "...the more we accelerate to travel along with the light, although the distances travelled become shorter, the light’s wavelength becomes ever longer relative to us. The light becomes ever more reddish because the light’s energy becomes less and less."

    One has to be very careful here choosing the right words here. Because when we move close to lightspeed we are changing the conditions of this universe. Lightspeed always has the same "speed" for baryonic matter. I suppose you consider the observer here needs to be immaterial?.

    Then this is OK for me. I think that lightspeed is not determined by the properties of light [if it exists] itself, but by the maximum difference in speed for baryonic matter within the visible universe. Outside it can reach beyond lightspeed.

    For being an immaterial observer there is no distance and no redshift at all in the end. Only a causal bond between all objects in this universe. There is only a 'reservoir' of 'change' when there is 'time'.

    We are merely mortals experiencing "change" in general.

    blue-green
    Fiber Optic cables fully utilize the fact that the light pulses in them are not going to interact with each over. Photons are ideal couriers.
    MikeCrow
    I have a thought experiment.

    Imaging you're riding a solar sail to another star system. The sail is going to be powered by a large laser.

    Instead of just a plain laser beam, this beam is going to project a moving picture image, and they design the sail like a giant movie screen.
    Your ship also has a movie laser pointed back at earth, both lasers send the outputs from 2 atomic clocks that are synchronized.

    What do you see (as well as earth) as your velocity becomes a large % of C?


    For this experiment ignore red-shift.
    Never is a long time.
    Gerhard Adam
    I'm not sure where you're going with this, but the images you see on the sail (assuming you're traveling with it) would all be in the same reference frame so everything would appear normal.  The images arriving at earth would be subject to the same time constraint as any signal traveling over a specified distance (since they are in a different reference frame).

    In other words, the whole point is that there are no privileged reference frames from which one could detect a difference that would allow them to pinpoint any differences in their velocity from anyone else.   More to the point, if two craft were approaching each other and sent a laser signal towards each other, the signal would not travel at 2c.
    Mundus vult decipi
    MikeCrow
    Right, both signals would travel away from their crafts at c, as would the signal they're receiving from the other ship. But the data rate of the incoming signal would be 2x. Until they pass, at which time it'd drop to 0.5x. Your outgoing speed would always be 1x.
    Never is a long time.
    vongehr
    He wants us to neglect the red-shift, which is like the only thing that does anything in the problem as he poses it. I am out of here. ;-)
    Aitch
    OK, if you INCLUDE the red shift, what then?

    I'd also like to know, what if the 'movie' projected were an on-board 'real-time clock'....and the images were side-by-side?

    Surely the one projected the farthest distance merely delays, relative to the on-board....?

    Aitch
    MikeCrow
    I was trying to prevent the answer "it red-shifts out of visible, and you can't see it" or some such variant. So jumping ahead, if you put both on the screen, and then let's say you're going ~ 2 lt yr's away, and back. A) From Earth orbit to light speed in a second, travel 2 light years distance, zip around the star we find there, fly 2 lt yr's distance back to Earth orbit. or B)From Earth orbit to light speed in 1 year(let say this is possible @1G accel), plus 1.5 years at c, zip around the star 1.5 years at c, then 1 year to slow down.
    With whichever of these examples you'd rather pick, What do the clocks say along the way and at the end?
    Never is a long time.
    vongehr
    I came once more back to see whether I can understand your question today.
    The sail is going to be powered by a large laser ... both lasers send the outputs from 2 atomic clocks that are synchronized.
    Hmm - no, I still may not get it. If the sail is accelerated ("powered"), the clocks cannot stay synchronized!
    Anyway, the movie (send from earth to the starship without any strange synchronizations) would become very slow because of redshift, because redshift is no more than the Doppler effect on the frequency (= beats or movie frames per time). The redshift is more than a change of color, like from rose to brown, it is the very effect you are asking for I believe. Just imagine to send the frames per second with the frequency of the light itself.
    MikeCrow
    So, let's say both the ship and earth (or leo) has a laser connected to synchronized atomic clocks. The lasers pulse out an encoded time signal at 1x10-100 of a sec. the ships laser points at earth, earths laser points at the ship, so both earth and the ship can see each others time. When the ship hits C, the light from earth will be traveling right beside the ship not moving forward or backwards. If the entire trip was at C, there's 2 years of time encoded in the light stream from earth to the ship. How long did it seem for the astronauts to go that 2 light years? How long is their light stream? I guess where I get bound up is, if you're going say 2 light years distance, and you're traveling at C, doesn't the trip seem like it takes 2 years? I can see how a standard clock in two different inertial frames when exchanging the time with the propagation limited to C, get's different rates of time, but I don't get how the standard clocks would run at a different local rate.
    Never is a long time.
    vongehr
    You are somehow having difficulty to fully embrace the relativity of time. Time is a measurement of changes with a clock (= comparing to somehow standardized changes). Just think through what I said about red shift and the picture frame rate more carefully; the answers are all in there.
    Mike, this image from Wikipedia might help:
    https://secure.wikimedia.org/wikipedia/en/wiki/File:Rstd4.gif
    The left-hand picture shows the transmission from Earth. On the outward trip, the transmission is redshifted, but you only receive the very first part of the movie (the opening credits.) On the return trip, the transmission from Earth is blueshifted and you get to watch the entire rest of the movie.
    The right-hand picture shows the transmission from your ship. On the outward trip your transmission back to Earth is redshifted, and its reception on Earth takes almost the entire time (4 years). On your return trip your transmission is blueshifted and is received on Earth almost all at once just before you land.
    The total subjective time experienced aboard ship (proper time) can be made as small as you choose (but not zero) provided you quickly accelerate and get close enough to c.

    MikeCrow
    Sascha, You're right, that's where I get bogged down.
    I totally understand how redshift/blueshift will alter the rate of time I can see while optically monitoring a remote object(like earth from my starship).

    But I don't see how local time changes, because that would alter the signal that earth see's radiating from my ship. If time stops at C, my emitter will stop changing from my point of view, not just earths.

    If my ship travels 2 light years distance, and I'm traveling at C, shouldn't that take 2 years subjective time, all of which time my laser is radiating my local time back at earth.

    Bill, it's the last sentence I can't rationalize, because I keep seeing how easily the propagation of light delay would explain relativestic (my understanding anyways) time dilation.

    Hence I think I've finely found some people who might really understand GR/SR and would understand my question/confusion.
    Never is a long time.
    vongehr
    But I don't see how local time changes
    This statement reveals your main difficulty. You need to let go of that 'local time' can somehow change. That does not mean anything. Changes are compared/measured with a clock (standardized, periodic changes). There are methods to compare/synchronize clocks that are apart from each other, moving, and so on. There is no "time flowing here differently from there" at all.
    my emitter will stop changing from my point of view
    Your emitter will always be the same to you, you two are at rest relative to each other. No changes at all, that is the very core of relativity. Anything else is violating relativity.
    MikeCrow
    Great, That is what I keep figuring will happen, but I thought I was wrong.

    So, this blog is in part about light not having time, yet in my light speed traveling spaceship, it'd take 2 years subjective time to travel 2 light years, correct?
    And that would be about 2 years on earth (+/- the difference in the rate of time at the different inertial/gravitational frames)?
    Never is a long time.
    Argg, this conversation is quickly reaching thermal equilibrium. What Sascha said, and meant, is that life aboard the spaceship appears perfectly normal. The movie plays at a normal rate, your heart continues to beat at 60 bpm, etc. All the laws of physics appear unchanged. You cannot tell you're moving without looking out the window. That's the relativity principle. But -- you do get to your destination sooner. It does not, not, not, take you two full years.

    MikeCrow
    Bill, Thanks for your reply!
    Never is a long time.
    Halliday
    Sascha:
    I've often been amused at how many scientists, that claim to understand relativity, get so incensed when I say things like "light", meaning photons, particles of "light", does not exists.  I have been saying this for a couple of decades now, for quite the same reason you are saying here (with the addition that since photons travel on null geodesics, whether in the flat spacetime of Special Relativity, or in any curved spacetime of General Relativity, the spacetime separation between their "birth" and "death" is zero [zero "distance", and zero proper time]---no need to "accelerate up to the speed of light").

    The "existence" of "light", then, has nothing to do with any form of existence of particles like photons, but a direct interaction between "source" and "sink" over zero spacetime separation ("distance"), by way of a null spacetime geodesic (path).  What we observe is not the "particle" we call a "photon", but only the direct interaction.  (After all, there has never been a problem having direct interactions between "things" that have zero distance between them.  The one thing that appears to be missing form many peoples' [scientists'] minds is that the indefinite nature of our spacetime metric allows for spatially and temporally separated points to have zero distance between them, over these null geodesic paths.  [Even light bouncing back and forth between perfect mirrors, with no delay at the mirror surfaces, forms a total spacetime path-length of zero.])

    Incidentally, there has been at least one group of physicists that have been working on reformulating relativistic Quantum Mechanics (QM) to respect the non-existence of photons:  Photons, or the electromagnetic field, is replaced with direct interaction between charged particle over null geodesics (this does, however, lead to non-linearities in the QM).  (The real challenge, is to be able to do the same for other massless particles, like gluons, since they, ostensibly, form a "self interacting" field.)

    Anyway, even though I don't see a lot of acceptance within the comments, here, I just wanted to let you know that you are far from being alone.

    David

    vongehr
    I've often been amused at how many scientists, that claim to understand relativity, get so incensed when I say things like "light", meaning photons, particles of "light", does not exists.
    I suspect it is the same reason very many physicists cannot grasp the Everrett relative state description or its multiple worlds interpretation. Once the word 'exist' comes into play, especially physicists are people who cannot easily overcome direct realism. After all, realism is the castle they grew up in and learned to defend against esoteric pseudo science and religion. If they did not love realism as kids, they probably would have not ended up doing exact sciences in the first place.
    It may also have to do with plain misunderstanding of relativity. How many understand that not all v greater c signals do not violate causality, how many understand that accelerated hubble expansion leads to frame dragging, and so on and so forth. Most who claim to understand only understand the very first step of that SR does not need an absolute background, and they have had so much difficulty with that little step, that they defend it as their religion. GR already brings the background back in a sense, but that is where they do not follow and the whole becomes dogma.

    After all, there has never been a problem having direct interactions between "things" that have zero distance between them.
    Very good point and basically what I wrote about to Gerhard above is the solution to the entanglement problem.

    this does, however, lead to non-linearities in the QM
    I am unsure whether it must really be so that QM is the only theory known ever that stays linear and does not get corrections at some point. We are still far away from the Diosi-Penrose criterion for example.
    rholley
    It should, by now, be evident to all readers that the proper time between the emergence of a photon from Sirius and its reception at Earth is zero.

    However, should not the path in Minkowskian spacetime between the two events be regarded, not as ‘non-existent’, but rather as an isotropic vector whose dot product with itself is zero.

    I first came across these things when reading The Nature of Spinors, where it is stated:
    A vector X is said to be isotropic if X·X=0. Isotropic vectors could be said to be orthogonal to themselves, but that terminology causes mental distress.
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    vongehr
    said to be orthogonal to themselves
    On the danger that most people will think I gone totally nuts: Some A that is 'orthogonal' to B is in a sense not at all to do with B, like not going in any of the directions that B is going (vector) or being counter-factual (Everett state description), mutually exclusive. In a sense, A does not 'exist' for B. Now if something is orthogonal to itself, it does not exist relative to itself, exactly as I claim.
    javaquantron
    We know that local mechanics are Einsteinian Mechanics and nonlocal mechanics are Newtonian and Quantum Mechanics.Because of we can not combine Theory of Relativity with Quantum Mechanics.They have different logical foundations. The light of Theory of Relativity isn't same with the light of Quantum Mechanics.Namely the quantization of Quantum Mechanics is nonlocal ,But we haven't a local quantization for Theory of Relativity.I have studied on local quantization for this mechanics.Best Regards.Cebrail Hasimi
    the article might be out of my grasp, but the idea of:

    "..if you want to know the system’s own properties without any relativistic contributions, you will have to best move along with the object of interest. ." sounds like the system can only be understood from inside itself

    so, might this not also explain dark matter?
    and, I reluctantly add, "god" ?

    but, on the flip side, it also sounds like the teenage battle cry "you don't know what it's like to be me"
    and we've all been there.

    vongehr
    I was not after dark matter, god, philosophical "can only be understood from within", let alone teenage battle cries. The main point is just a boring technical "without any relativistic contributions".
    David Yerle
    Funnily enough, in fact no particles have mass -they acquire it when interacting with the Higgs boson- so they all travel at the speed of light and hence act like photons. The mass is the result of the average speed being less than c, due to constant bumping into Higgs bosons.
    Therefore, our theories of Nature are very good at predicting how the Universe looks for a particle traveling at less than c, which is none of them!
    Also, the fact that one of the dimensions disappears when traveling at c -because of length contraction- seems to be related to the holographic principle, the fact that information in 3d is contained in a 2d sheet. Photons would see the Universe as precisely a 2d sheet with all the necessary information.
    So I think there are a lot of insights to be gained by thinking about how the Universe must look from the point of view of a photon, even though Special Relativity tells us that's not possible.
    David Yerle
    vongehr
    You are aware of the fact that still no Higgs bosons have been found? And even if they should be found, writing
    The mass is the result of the average speed being less than c, due to constant bumping into Higgs bosons.
    goes a little too far off. If they would bump, they would change paths. Your bumping is that of virtual interaction, which you could just as well say makes photons interact with gravity (bumping into gravitons), however, that does not slow down light. Light is slowed by refractive index media because the atoms that they bump into do absorb and re-emit, leading to a delay. Are you claiming the Higgs boson absorbs protons and neutrons? Surely not. Little mass comes from Higgs interaction even in the Higgs standard model. Most mass is still from QCD interaction.

    David Yerle
    Sure, most mass comes from QCD interaction. However, the point is still valid that elementary particles (not protons and neutrons!) are supposed to be massless before interaction.
    David Yerle
    vongehr
    That "before" means "before I put the Higgs into the theory"; it is not somehow time-like. The Higgs mass is not being slowed down via a time delay due to absorption. Your argument with why massive particles are going slower than c is a confusion with the mechanism that slows down light in refracting media. It does not work that way even if the Higgs existed. What one could argue is that anything that has charge needs to have paths curled around compactified space-time directions and thus the velocity inside the non-compactified ones cannot ever be c.
    David Yerle
    Yes, that "before" means "before I put the Higgs in". Maybe my visualization gets in the way of my Physics. I've always thought about interaction with the Higgs as something that doesn't give the naked particle mass, but the renormalized particle. That is, the underlying Physics has masless particles, but on average they look as if they had mass. As you increase the energy (the resolution), reality emerges and you'll see a bunch of particles which actually have no mass. Same as with electron's charge in QED, which changes with the resolution.
    The curling around compactified space-time dimensions doesn't work. I tried it myself during my phd and you get a linear mass spectrum, which can't account for observed particle masses. Then I read a number of papers from people who tried the same, also with the same problem. That would be a beautiful solution, though. Hopefully we missed something.
    David Yerle
    blue-green
    Before I comprehend anything about Higg’s field and particle(s), I’ll have to wait until you professionals slug it out … and we get a lot more hard data. The following note above from David Y is worth revisiting: “the fact that one of the dimensions disappears when traveling at c -because of length contraction- seems to be related to the holographic principle, the fact that information in 3d is contained in a 2d sheet. Photons would see the Universe as precisely a 2d sheet with all the necessary information. So I think there are a lot of insights to be gained by thinking about how the Universe must look from the point of view of a photon, even though Special Relativity tells us that's not possible.” Sounds good until "not possible". The “not possible” bit reminds me of the Schwarzschild metric. It breaks down at the Schwarzschild radius (which is synonymous with the 2d null-sheet of light-like geodesics around a black hole). Back in Schwarzschild’s day, I suppose that it was presumed that the required extremes for the breakdown would never be physically attained, and so the Schwarzschild radius was just a mathematical curiosity. It was not until the 1960s that Penrose and Hawking proved using general topological considerations that the formation of a horizon is inevitable for burnt out stars only a little larger than our sun. The breakdown of the Schwarzschild metric is simply a matter of a poor choice of coordinates … With a coordinate transformation one can make the zero and infinite terms disappear (although one is then working within an unfamiliar way of framing things) … The freedom to shift to other coordinates (to give the point of view from a photon, for instance) is entirely in the spirit of General Relativity and Special Relativity. That's my impression.
    blue-green you said "Existence without individuality is … is like traveling in a city and repeatedly coming upon one cookie-cutter chain store after another.
    It is as if you have never left or gone anywhere.

    I am troubled by this. I know I am off topic with this, but i am compelled...if all the protons and all electrons are identical...then all the atoms of elements, within isotopes, are identical...and so on to molecules of say glycine et al. and so on to macromolecules of haemoglobin ...but somewhere we have the introduction of differences. Where and how could variation emerge among say for example a cell line. I know that all e.coli are not alike, but what about the virus that infect them? are bacteriophage (that can be crystalized just like protein or salt crystals) are they identical in the same sense as protons. by what mechanism does variation manifest? this is a fantastic concept, that any material object is indistinquishable from another. i believe it is profound without understanding why i "feel" that way and it bothers me. I am not a believing/feeling type of fellow. Of course it is 3:40 in the am and perhaps I should not sleep with my computer! I will submitthis anyway in hope of some illumination by light that does not see. What would be the consequence of two identical persons? not clones or twins but actually indistinquishable, atom for atom identical people? why am I an insomniac in NZ and not a dreamer in New Delhi? thanks for your indulgence.

    Procyan said, "I am troubled by this. I know I am off topic with this, but i am compelled...if all the protons and all electrons are identical...then all the atoms of elements, within isotopes, are identical...and so on to molecules of say glycine et al. and so on to macromolecules of haemoglobin ...but somewhere we have the introduction of differences. "

    This may not be off topic since space, time, and location may not be an introducable differences. See this paper by Tetrode: http://nonloco-physics.000freehosting.com/interaction.pdf
    In 1922 Hugo Tetrode wrote a prescient paper about how a charged particle in a distant star can momentarily share its identity in every way with a charged particle in the retina of one's eye and in doing so we “see” the star. For example, two electrons widely separated in space and time can share the same wave function, energy level, location, and even the same moment in time and, when their common wavelike connection is broken, some of the energy from the electron in the star can remain with the electron in one's eye. Tetrode's reasoning was strictly mathematical but we see examples of this sort of non-local connectedness in the experiments of Bell and Aspect and in experiments with quantum teleportation where two remote particles can become “entangled” and their locations “indeterminate” and when their wavelike connection collapses their “identities” (including energy levels) can swap locations. Thus we have a "fiat lux" without photons.
    Tetrode used this same reasoning of particles being identical in his calculations to solve a paradox involving entropy. If you have a tank of fluid with a partition in the middle, does the entropy level of the molecules in the tank increase if you remove the partition and allow the molecules on both sides to mix and achieve a greater level of disorder. Tetrode said there would be no change in entropy if the molecules on both sides of the tank are indistinguishable so the entropy remains the same. With light related phenomenon, we may be seeing the same non-local swapping of identities because we can't identify particles on the quantum level by their locations.

    rholley
    Hugo Tetrode – the name immediately brings to mind the Sackur-Tetrode equation

    Following links from there to the two biographies, I find that they developed the equation independently.  Both died in their 30s, Tetrode of tuberculosis and Sackur from an explosion after mixing two chemicals in the laboratory of Fritz Haber (of the ammonia process.)
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    rholley
    This quantum indistinguishability can be a bit unsettling.

    I wonder, did Heisenberg come by the idea through seeing how some of his fellow quantum geniuses swapped wives so readily?
    The special circle in which they lived in Zurich had enjoyed the sexual revolution a generation before [the United States]. Extramarital affairs were not only condoned, they were expected, and they seemed to occasion little anxiety. 
    http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Weyl.html
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    vongehr
    You mean they could not distinguish their wives because they were identical? Why swap if you get the same?
    Hugo Tetrode...what a cool name, like a little poem. I was not able to open that link. If that paper is public domain I would like to take a stab at it. What you have written captures the essence of my conflict. I mentioned this on another blog recently and am told that David Bohm had similar thoughts on the subject. Sadly, I am a biochemist and anything beyond slope and intercept...well the mist decends and it all goes pear shaped. Nevertheless, I do appreciate the leads and i shall see how I go. Maybe I'll come back here for rescue when the partitial differentials deal to me. The chain rule rules!

    Photons only exist because there is measurement. Without that they cannot show any history indeed.

    There is no way to observe a photon without interaction with the observer. "History" always means interaction - which involves multiple measurements also. But light has no history at all - its observation is limited to a single event.

    The point here is - light cannot exist without measurement from an observer. Light is an emergent phenomenon. And its roots are "non sequitur". Without observer it has no physical existance. There is only involvement at the deepest fundamental level.

    MikeCrow
    light cannot exist without measurement from an observer

    When you say this, it reminds me of the philosophical "If a tree falls in a forest and no one is around to hear it, does it make a sound?"
    Does our Sun pour photons into space, even if we don't see them?

    From an experimental point of view, depending on the experiment, you might convince me that if you don't detect an expected photon it didn't exist, but I don't think it's true for all possible system. Maybe you have to account for the probability on a particular axis, ie the Sun emits in all directions, other systems might only emit in a single direction, which I think makes it a probability (ie QM) question.
    Never is a long time.
    Well, you are completely right - there is a kind of philosophical question at stake here. A photon is not needed at all if you can proof it has an existance beyond the measurement alone.

    With sound you can proof it is incapable of travelling beyond a vacuum, to establish a kind of proof of its existance. But "light" must also incorporate an electromagnetic component to explain magnetic fields. There have to be photons everywhere because a field is never really non present anywhere. It would be like explaining why gravitons need to be omnipresent, connecting any single baryonic atom to every other particle in this universe. And it needs a continuous stream of gravitons or photons to do so.

    To see a photon as a representation of a process has more meaning in my opinion. It shows we are part of the process and cannot independently see the hidden nature. But we can make a scheme to try to understand the "logic" behind it [in our view as an observer] .

    I pondered this and came to the same conclusion. However I interpreted it the other way round and concluded that light is everything, rather than nothing. Would that also make sense?

    Also (and forgive my ignorance) but could light possibly be an artifact of some higher dimensional transformation? In the same way that 'teleportation' appears possible when viewing the 3D world from a 2D perspective.

    I love this stuff :)

    Thanks,
    Dave

    I love this! I am not trained in physics or serious maths so I can't discuss easily but, given the effects of relativity, what you are saying is an unavoidable conclusion. You have expressed it beautifully if I may say so.

    I just have one questions. Please bear with me, as it is convoluted.

    Taking light emerging from the sun's surface and falling warmly on my cheek, I understand that the light from its own point of view does not have any time to be, (nor distance to travel, nor energy to warm me with). Yet, in my reference terms, it has a start time and an end time. Before its start time, it did not exist. From the light's reference, the start time and the end time are the same, and all the events along its path (which take 8 hours I think of my time) are a single snapshot.

    Now, here is my question. What is in that snapshot? Surely, what is in the snapshot is not the entire life of the universe, but must be a subset of the 8 hours of events which occur in my reference frame? Or perhaps if I could go slow enough could I expand that 8 hours of my reference frame to be the whole lifetime of the universe? During that time the earth goes around the sun many times... Please excuse me, I am out of my depth here.

    Either way, the atomic reactions in the sun produce the light, from my reference point of view. Before the particular atomic reaction which produced the light which instantly falls on my cheek, that light could not have existed. In fact, if one could prevent that reaction, that particular light would never have existed at all in any reference frame. Therefore the light's own perceived universe can include nothing earlier than that moment of its birth? Or does everything in the universe's life time happen at the same moment, from the point of view of light? Or to put it another way, is light itself something outside of time which we experience as light in our time?

    Please excuse me if I am asking ridiculous questions here, thank you very much.

    Rather than saying light does not exist while space and time do,
    wouldn't it be equally valid to say that light DOES exist while space and time do not?
    i.e. that space and time are illusions?

    Hello, I'd like to pose some questions which I struggle with in the hopes that it will help me understand phenomenon and concepts which have already been established and verified. I struggle with the relativity, length contraction, time dilation a lot among many other things with regards to the cosmos. I'm a 3rd year aerospace engineering student with a minor in astrophysics and I feel like I should have already understood this quite well by now but I don't. It's very easy to answer problems on my tests with my cheat sheet full of lorentz transformation equations but the concept itself, I have failed to understand. I hope some of you will bear with me and follow my thought process and correct me or provide more insight in parts where my logic fails me.

    Let's start with the speed of light. We know it is 300,000 km/s in vacuum. There are many ways to experimentally determine the speed of light. Here we start my building a space ship that takes us to the moon where an astronaut will place a prismatic reflector at particular coordinates on the side facing earth. Later, an observatory on Earth will fire a laser beam of particular frequency and wavelength at this reflector on the moon and measure the time between firing the laser and detecting the reflected laser beam. Then using our simple formula of Speed=Distance/Time and neglecting effects of Earth's atmosphere and the prismatic reflector's refractive index, we have an approximate estimate of the speed of light. Cool, I just passed my 7th grade exam!

    Now let' get to time specifically with regard to the speed of light. Regardless of the more complicated nature, existence or non existence of light relative to itself, light takes time to travel. The light from the Sun takes 8 minutes to reach us. This also effectively means that at any given instant we look at the sun, we are actually looking at it as it was 8 minutes ago.

    Here we dive into time dilatation. Let's say there are 2 twin brothers who are very heavy smokers but during their lifetimes, technology has become very advanced and cancer is as curable as the common cold. Also, Virgin Galactic regularly operates a shace ship which instantaneously achieves a velocity of 0.99c upon take off. One twin (TWIN A) did not graduate with a physics degree and is poor while the other one (TWIN B) did and hence is rich in a discriminatory world, thereby being able to afford a trip on Virgin's luxury space cruises. The 2 share one last cigarette at the spaceport before A see's B off. They will not meet until the ship returns back but B is perplexed about time dilation and convinces A to participate in an experiment to verify time dilation. Apart from being twins, A and B are also similar in their smoking habits. Both smoke one cigarette per hour. The point of the experiment is to see if they would have both smoked the same amount of cigarettes by the time the ship returns. After seeing the ship take off, A lights up and so does B while enjoying a fine VirginTM Cosmo. The space ship cruises to center of the milky way and returns back.

    I realize that this is just another version of the twins paradox but with regards to doing the same activity at the same rate and knowing that in their own respective frames, time does not change, Then a journey which takes 10 hours to complete (based on earth time) since the spaceport would display the earth departure time and the earth arrival time, Twin A should have smoked 10 cigarettes. How many did Twin B smoke?

    To add to it, let's assume they had identical precise atomic clocks. I know that upon returning, B's clock would be lagging behind A's. How then did they experience the same rate of time of smoking cigarettes/unit time. Assuming that an alien observer in the Andromeda galaxy with advanced alien technology has telepathically learned of the Twins experiment since its civilization remotely monitors other intelligent, alien civilizations and has somehow managed to get live streaming video feeds (with no delays) of twin A on earth and twin B in space but isn't really looking at them directly but through cameras focusing on the twins. His screens also have the local Andromeda based planet's time displayed and obviously synchronized. He decided to count the cigarettes that each twin smoked before the ship returns back and instantaneously decelerates to 0. What would he see?

    Also let's assume at 4:21 AM this morning, I fire a laser beam into the night sky. The beams moves away from Earth at light-speed. Does this mean that relative to it, the earth is moving away at light speed assuming its existence and it's ability to perceive?

    Lastly, if the answer is the obvious one in which B smoked less cigarettes than A and the alien simply saw A smoke more cigarettes than B, then why exactly is the time dilation occurring at all. This seems like an absurd question to ask but I can't fathom the implications of time dilation. Assuming you are sleeping on a trip from the Sun to Earth, it still is going to take 8 minutes to cover the distance simply because based on the formula, Speed=Distance/Time, Time=Distance/Speed. The distance between the earth and sun isn't changing and the speed of light is always constant at 300,000 km/s. Does the slow down of time in the space ship even matter in the grand scheme or in the Andromeda's alien reconnaissance mission?

    To more practical, assume we had genetically engineered a mouse to die exactly 70 years after birth and put this mouse on the voyager 1 probe. The voyager is now traveling quite fast and if it turns back now and returns by 70 years to earth, will the mouse have died immediately upon retrieval or will it live a few more seconds?

    Also, the whole concept of aging slower on a spacecraft seems incomprehensible to me. Aging does occur over time but in the twins case, their reference frames still feel the same to them and aging occurs because of wear and tear of cells and their eventual decline in the ability to replicate. Shouldn't aging still occur at the same rate? if shaving in space and earth takes the same 5 minutes of time?

    how does this speed of light actually came in existence means how was it firstly calculated????

    vongehr
    If I understand your question correctly: The velocity of light as first calculated (rather than specifically looking for it and in that sense specifically measured, say via Jupiter moon transit) follows from electrodynamics, i.e. the constant c is a combination of electrical and magnetic field constants, epsilon and mu respectively, that has clearly the role of a velocity inside the equation that describes the propagation of electromagnetic disturbances (waves).
    on what basis.....

    can you eleborate a li'l bit more?

    and can you tell me observing what conditions was it calculated....?