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Thread: What makes light so special?

  1. #1 What makes light so special? 
    Forum Freshman Kyleg's Avatar
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    So if i have understood this well light is a constance to all observers no matter the difference in their frame of reference, but for example motion is not if you're travelling on a train and you throw a ball to an observer a the ball would look as though it was traveling the speed it was in the reference frame of the train and the speed at which the actual reference frame was traveling itself... i may have not fully understood this, it could be a very silly question but...

    What makes light so special, do we know why it occurs or just know that it (should) occur?


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    Light speed is constant in all inertial reference frame is part of the foundation of special relativity. It has been experimentally verified in numerous experiments, starting with Michelson-Morley.


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    Yes, i understand that-well kind of... my question was ment to ask why? do we know why it is constant to even observers outside the reference frame it is in?
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    Quote Originally Posted by mathman View Post
    Light speed is constant in all inertial reference frame is part of the foundation of special relativity. It has been experimentally verified in numerous experiments, starting with Michelson-Morley.
    "do we know why it occurs or just know that it (should) occur?" thanks for your reply but it really only answered the second part of the question it didn't answer the first part.
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    The answer appears to be, that's the way our Universe works. Electromagnetic radiation moves at "the speed of light".
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    Quote Originally Posted by Kyleg View Post
    So if i have understood this well light is a constance to all observers no matter the difference in their frame of reference, but for example motion is not if you're travelling on a train and you throw a ball to an observer a the ball would look as though it was traveling the speed it was in the reference frame of the train and the speed at which the actual reference frame was traveling itself... i may have not fully understood this, it could be a very silly question but...

    What makes light so special, do we know why it occurs or just know that it (should) occur?
    The reason is that all massless particles travel at the speed of light; this does not just apply to photons, it is a universal consequence of the maths behind the models describing them. If a photon had a rest mass it couldn't travel at the speed of light. Likewise, a particle travelling at the speed of light implies that is has no rest mass. So, to answer your question - the photon travels at the speed of light, because it's rest mass is exactly zero.
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    The speed of light is a fundamental constant of the universe, but, and I think that is what Kyleg is asking, is why, uniquely, is the speed of light observed to be the same from any reference frame?

    If I had to guess, I'd think that because every change in observed speed of objects with mass from different frames are due to time dilation and that no time dilation occurs to massless objects? When you work out time dilation there is a mass component and the equation becomes meaningless if the mass entered is zero. Is that correct? For instance, if you work out the travel time of a photon from it's own perspective, you find that from it's own perspective it travels at infinite speed, no?
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  9. #8  
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    Quote Originally Posted by KALSTER View Post
    The speed of light is a fundamental constant of the universe, but, and I think that is what Kyleg is asking, is why, uniquely, is the speed of light observed to be the same from any reference frame?

    If I had to guess, I'd think that because every change in observed speed of objects with mass from different frames are due to time dilation and that no time dilation occurs to massless objects? When you work out time dilation there is a mass component and the equation becomes meaningless if the mass entered is zero. Is that correct? For instance, if you work out the travel time of a photon from it's own perspective, you find that from it's own perspective it travels at infinite speed, no?
    Well, if you formulate the question in this way, then the answer is simply this - c is the same for all observers, because the laws of physics need to be the same for all observers, regardless of their frame of reference. Remember, all physical laws in their relativistic form are expressed in terms of c ( as a scale factor or otherwise ). If c wasn't the same for all observers, then everyone would experience different physical laws, which of course isn't the case.
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    Quote Originally Posted by Kyleg View Post
    So if i have understood this well light is a constance to all observers no matter the difference in their frame of reference, but for example motion is not if you're travelling on a train and you throw a ball to an observer a the ball would look as though it was traveling the speed it was in the reference frame of the train and the speed at which the actual reference frame was traveling itself... i may have not fully understood this, it could be a very silly question but...
    One part of the answer is related to this addition of relative velocities. If you are on a train travelling at 100mph and throw a ball at 100mph (implausible, I know) then you imagine that someone stationary outside the train would see the ball travelling at 200mph. In fact, velocities don't quite add linearly so the total velocity will be ever so slightly less than200mph. In everyday life we rarely have to take this into account (GPS systems do though, because the relative velocity of the satellites is significant).

    If the train were travelling at 100mph less than c (the speed of light) and you threw the ball at 100mph, the total speed (to an outside observer) would still be less than c. If you threw the ball at 200mph, the total speed would still be less than c.

    Light is just the limiting case of this. It is already travelling at c so whatever relative velocity you to add to it, it will still be travelling at c.

    What makes light so special, do we know why it occurs or just know that it (should) occur?
    Why is the universe like that? Why don't velocities add linearly as we naively assume? Why does light travel at c? Why does c have the value it has?

    Dunno. It is just the way it is. Could be design, could be chance, could be the result of some underlying physical laws we haven't found yet.
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  11. #10  
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    The exact value of the speed of light in vacuum is determined by the vacuum's permittivity and permeability like so : c2 = 1/(ε0μ0). This of course does not answer the question as to why these constants have their specific values either.
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  12. #11  
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    I would say that light isn't special, it just helps to illustrate the special relationship between space and time.
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    screwed the comment and can't delete it? ;/
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  14. #13  
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    Quote Originally Posted by KALSTER View Post
    The speed of light is a fundamental constant of the universe, but, and I think that is what Kyleg is asking, is why, uniquely, is the speed of light observed to be the same from any reference frame?
    that is correct
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  15. #14  
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    Quote Originally Posted by Kyleg View Post
    Quote Originally Posted by KALSTER View Post
    The speed of light is a fundamental constant of the universe, but, and I think that is what Kyleg is asking, is why, uniquely, is the speed of light observed to be the same from any reference frame?
    that is correct
    Refer to post # 8 for an answer to this...
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    Doesn't gravity also travel at light speed? So the speed of visible light describes all electromagnetic radiation and gravity, so it's not the light itself, but this constant that's special. Right?
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    The basic problem underlying this thread is that physical laws are what they are because that is the way it is. Why is a question that has no answer. Why is the speed of light constant - because special relativity says so.
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    Quote Originally Posted by brody View Post
    Doesn't gravity also travel at light speed? So the speed of visible light describes all electromagnetic radiation and gravity, so it's not the light itself, but this constant that's special. Right?
    You are right, all EM and gravitational radiation travels at the speed of light, so in that sense light really isn't special at all.
    By "gravitational radiation" I mean specifically gravitational waves - a static gravity field acts instantaneously.
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  19. #18  
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    Quote Originally Posted by mathman View Post
    The basic problem underlying this thread is that physical laws are what they are because that is the way it is. Why is a question that has no answer. Why is the speed of light constant - because special relativity says so.
    You are right in a way - the laws of physics are what they are because it couldn't really be any other way. If the laws of physics were different in any appreciable way we more than likely wouldn't be here to ponder this question. However, physical laws are also interrelated - the constancy of the speed of light is a direct consequence of other physical laws needing to be the same for any observer.
    Last edited by Markus Hanke; January 8th, 2012 at 06:46 AM.
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  20. #19  
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    Quote Originally Posted by Markus Hanke View Post
    a static gravity field acts instantaneously.
    Heh, you won't believe the trouble I caused here when I tried to explain that!
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    Quote Originally Posted by SpeedFreek View Post
    Quote Originally Posted by Markus Hanke View Post
    a static gravity field acts instantaneously.
    Heh, you won't believe the trouble I caused here when I tried to explain that!
    Yeah, I suppose it depends a little bit which angle you are coming from; from the geometrical standpoint of GR it is quite intuitive that static fields act instantaneously. From a quantum gravity standpoint it is much less clear and actually quite hard to visualize why this is the case.
    Anyway, I can very well imagine certain members of this forum objecting to this idea !
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    It gets even worse when you try to explain how gravity also acts instantaneously for uniformly accelerating objects, but changes in acceleration cause gravitational waves.
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  23. #22  
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by SpeedFreek View Post
    Quote Originally Posted by Markus Hanke View Post
    a static gravity field acts instantaneously.
    Heh, you won't believe the trouble I caused here when I tried to explain that!
    Yeah, I suppose it depends a little bit which angle you are coming from; from the geometrical standpoint of GR it is quite intuitive that static fields act instantaneously. From a quantum gravity standpoint it is much less clear and actually quite hard to visualize why this is the case.
    Anyway, I can very well imagine certain members of this forum objecting to this idea !
    I would think it would be just like if you had a constant radio wave emitting into space at a set power level. It appears to be acting "instantaneously" at all points in space where the transmission extends to, but really that's just because the same signal has been getting repeated so many times that copies of it are filling all of that space. If you were far away from it and someone were to turn off the radio emitter, it would be a while before all the previously emitted copies of the old signal reached you.

    However, I'm not sure if that's how gravity waves work. Is there something else to them beyond that?
    Some clocks are only right twice a day, but they are still right when they are right.
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    Quote Originally Posted by kojax View Post
    However, I'm not sure if that's how gravity waves work. Is there something else to them beyond that?
    Interestingly, your description actually helps to describe the problem, rather than the solution!

    But firstly, the term "gravitational waves" has a specific meaning and here is my attempt to describe it! They are the ripples that propagate across the curvature of spacetime caused when an object accelerates.

    The Earth is causing gravitational waves as it orbits, speeding up as its orbit takes it closer to the Sun and slowing down as it heads away again, but the gravitational waves are so small as to be unmeasurable. We need to look at dramatic events in order to find them, so we look for extreme places like binary pairs of white dwarves or neutron stars, where the accelerations involved would cause large gravitational waves. By the time the waves reach here their magnitude would be much reduced, but theoretically measurable in the way they make everything on Earth "flex" in different directions by a tiny amount as they pass by. Gravitational waves are theorised to propagate at c, across the curvature of spacetime.

    Now, on to the curvature itself, which acts kind of like a static field, and this is where your description comes in. What if the source of gravity is moving, relative to you? If there is a delay in your signal (which presumably propagates at c), then surely you would be gravitationally attracted towards the place the source was when the signal left, rather than where the source actually is when the signal arrives? This would have measurable repercussions (solar system orbits would change over time for instance), and we have measured them - they don't seem to happen.

    So, gravity seems to act instantaneously in that sense. The Earth is not falling around the place in the sky where we see the Sun to be, as it was 8 minutes ago, it is falling around the place in the sky the Sun is "now" (approximately). Apparently we have evidence for this from measurements taken during a solar eclipse, where peak acceleration happened not when the Moon and Sun were lined up in the sky at totality, but when the Moon was closest to the "instantaneous" position of the Sun.

    How General Relativity describes this apparent miracle of instantaneous-ness is very hard to understand (and I admit I don't really understand it!), but it is worth remembering that the curvature is not just caused by mass alone, there are many factors that contribute, including energy and momentum. All those various factors combine with the velocities involved to cause gravity to point to an "extrapolated" instantaneous position of the gravitational source, except when an object has changing acceleration, in which case gravity "misses" and causes gravitational radiation in the form of gravitational waves!

    Or something like that!
    Last edited by SpeedFreek; January 9th, 2012 at 08:30 PM.
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    Quote Originally Posted by Kyleg View Post
    Yes, i understand that-well kind of... my question was ment to ask why? do we know why it is constant to even observers outside the reference frame it is in?
    Kyleg: the velocity of the source of a sound wave isn’t added to that wave’s velocity either. And at least in this case I think we can safely say why: the wave is propagated through a medium (air, water etc); so despite the fact that the source of the wave front (maybe a car or plane engine) is moving, the medium in which that wave front travels is not. Now why the wave travels at the speeds it does is merely a fact (the “way it is”, as some other posters might put it) and is related I suppose (among other things) to the density of that medium. Of course, this isn’t an explanation for the isotropic nature of electromagnetic radiation, but it does show that the velocity of other wave phenomena relative to their source diverges from the “common sense” view of adding velocities.

    As to the “why” of your question about light waves: that is a tough one: Please check out the link below. It provides to some extent a suggested explanation for the isotropic nature of light waves.


    http://www.classicalmatter.org/Class...Relativity.doc
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    This is why the higgs boson hunt has become so important. The higgs field is the field that interacts with particles, giving them mass and drag. Photons, however, do not interact with this field, meaning they travel at the speed of light ALWAYS, as they have no method of de-acceleration to any observer. Finding the higgs boson would prove this theory, and tell us that the higgs boson is the particle that means that all the others don't whizz around at the speed of light like photons.
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    /A photon has no rest mass' is what I read. Does a photon acquire mass as it moves?
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    Quote Originally Posted by Aristarchus in Exile View Post
    /A photon has no rest mass' is what I read. Does a photon acquire mass as it moves?
    No, but it does have momentum which is also related to energy in the same way that mass is. (Alternatively, I suppose you can say it has a certain energy which gives it its momentum).
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    /A photon has no rest mass' is what I read. Does a photon acquire mass as it moves?
    No, but it does have momentum which is also related to energy in the same way that mass is. (Alternatively, I suppose you can say it has a certain energy which gives it its momentum).
    I thought you were finished with me, Strange. Thanks for answering though. So if photon does not have mass, it cannot be affected by the normal idea of what gravity is .. which, I suppose, is what gave Einstein a clue about the curvature of space. But, regardless of the curvature, the curving path of photons means they are affected by something .. that space has a pathway for them to follow, or else they would travel right through the curvature. I think that thinking of gravity as a force takes physics in a wrong direction .. or am I wrong in thinking that gravity is thought of a a force?
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    Quote Originally Posted by Aristarchus in Exile View Post
    I thought you were finished with me, Strange.
    I know. I just can't stop being helpful (I just need to stay out of the religion/philosophy threads and we will be fine)

    So if photon does not have mass, it cannot be affected by the normal idea of what gravity is ..
    Well, actually, surprisingly perhaps, Newton considered that light consisted of "corpuscles" (particles) with no mass and he demonstrated that such things would be affected by gravity. I seem to remember that it is quite an simple proof; I'll see if I can dig it up.

    which, I suppose, is what gave Einstein a clue about the curvature of space.
    One of many things. Interestingly, under GR light is deflected twice as much by gravity as it is under the Newtonian model. We can measure this and it is Yet Another (yawn) confirmation of GR - actually, I seem to remember that it was one of the first ... during an eclipse or something ...

    But, regardless of the curvature, the curving path of photons means they are affected by something .. that space has a pathway for them to follow, or else they would travel right through the curvature.
    Yes, they follow the shortest curved path (a null geodesic) through spacetime. In fact, everything follows a geodesic in spacetime which is what causes the effects we perceive as gravity.

    I think that thinking of gravity as a force takes physics in a wrong direction .. or am I wrong in thinking that gravity is thought of a a force?
    It was thought of as a force when Newtonian physics ruled (and still can be, as a good approximation in many circumstances). But it is now more accurately modelled as curvature of spacetime.

    And I say "modelled" specifically because, although GR is based on the geometry of spacetime as a 4-dimensional surface, it isn't clear that "spacetime" has a real existence as rubbery "stuff"; it is just a mathematical description (model) that works.
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    Quote Originally Posted by Aristarchus in Exile View Post
    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    /A photon has no rest mass' is what I read. Does a photon acquire mass as it moves?
    No, but it does have momentum which is also related to energy in the same way that mass is. (Alternatively, I suppose you can say it has a certain energy which gives it its momentum).
    I thought you were finished with me, Strange. Thanks for answering though. So if photon does not have mass, it cannot be affected by the normal idea of what gravity is .. which, I suppose, is what gave Einstein a clue about the curvature of space. But, regardless of the curvature, the curving path of photons means they are affected by something .. that space has a pathway for them to follow, or else they would travel right through the curvature. I think that thinking of gravity as a force takes physics in a wrong direction .. or am I wrong in thinking that gravity is thought of a a force?
    In General Relativity energy and mass are equivalent; a photon does not possess rest-mass, but it does possess energy. Therefore gravity will act upon it. Likewise, all forms of energy are a source of the gravitational field, so the photon has its own gravitational field, albeit a very small one of course.
    In general, all moving objects must follow geodesics through curved spacetime, since the very notion of movement implies energy. It is not possible to somehow avoid the spacetime curvature, except of course by acceleration, which doesn't apply to photons.
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    Problem about staying out of philosophy and religion is that religious people and philosophers were among the greatest of discovers of scientific facts .. a chief example is the philosopher who determined that the fuzzy patches in the night sky were not nebula, but galaxies beyond our own, only later confirmed by Mount Palomar .. I can't remember the name of the Philosopher .. another was Michael Farraday who derived his Field ideas which he proved from scripture. Also, quantum mechanics is basically philosophy rather than empirical observation.

    I recall that the bent light experiment (Venus?) Einstein relied on for proving GR was later proven erroneous in, but by the time the error was discovered other so-called proofs were established.



    The Death of Socrates by Jacques-Louis David (1787). The painting depicts the philosopher Socrates about to take poison hemlock.



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    Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language.[1][2] Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational argument.[3] The word "philosophy" comes from the Greek φιλοσοφία (philosophia), which literally means "love of wisdom".[4][5][6]



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    Quote Originally Posted by Aristarchus in Exile View Post
    I recall that the bent light experiment (Venus?) Einstein relied on for proving GR was later proven erroneous in, but by the time the error was discovered other so-called proofs were established.
    I believe what you are looking for is any one of these multitudes of images :

    gravitational lensing images - Google Search
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    Quote Originally Posted by Aristarchus in Exile View Post
    I recall that the bent light experiment (Venus?) Einstein relied on for proving GR was later proven erroneous in, but by the time the error was discovered other so-called proofs were established.
    No it was numerous stars behind the sun during a solar eclipse, and it confirmed Einstein's predictions precisely.
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    Quote Originally Posted by MeteorWayne View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    I recall that the bent light experiment (Venus?) Einstein relied on for proving GR was later proven erroneous in, but by the time the error was discovered other so-called proofs were established.
    No it was numerous stars behind the sun during a solar eclipse, and it confirmed Einstein's predictions precisely.
    I recall it was one star or planet, and that it was later proven miscalculated. Wouldn't it be ducky if we could back up our statements, eh.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    I recall that the bent light experiment (Venus?) Einstein relied on for proving GR was later proven erroneous in, but by the time the error was discovered other so-called proofs were established.
    I believe what you are looking for is any one of these multitudes of images :

    gravitational lensing images - Google Search
    Thanks Markus .. that's a slightly different thing than what we were talking about, but yes, proof that somehow light does get around objects. Am I understanding it correctly that the warp of space collects light that would normally go flying past to the left, right, up and down of our normal observation .. with the mass causing the warp blocking the normal straight though path?
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    Quote Originally Posted by Aristarchus in Exile View Post


    I recall it was one star or planet, and that it was later proven miscalculated. Wouldn't it be ducky if we could back up our statements, eh.
    Your recollection is incorrect.

    "After the war, Eddington travelled to the island of Príncipe near Africa to watch the solar eclipse of 29 May 1919. During the eclipse, he took pictures of the stars in the region around the Sun. According to the theory of general relativity, stars with light rays that passed near the Sun would appear to have been slightly shifted because their light had been curved by its gravitational field. This effect is noticeable only during eclipses, since otherwise the Sun's brightness obscures the affected stars. Eddington showed that Newtonian gravitation could be interpreted to predict half the shift predicted by Einstein. (Somewhat confusingly, this same half-shift was initially predicted by Einstein with an incomplete version of general relativity. By the time of the 1919 eclipse Einstein had corrected his calculations.)

    Eddington's observations published the next year[4] confirmed Einstein's theory, and were hailed at the time as a conclusive proof of general relativity over the Newtonian model. The news was reported in newspapers all over the world as a major story. Afterward, Eddington embarked on a campaign to popularize relativity and the expedition as landmarks both in scientific development and international scientific relations.

    It has been claimed that Eddington's observations were of poor quality and he had unjustly discounted simultaneous observations at Sobral, Brazil which appeared closer to the Newtonian model.[5] The quality of the 1919 results was indeed poor compared to later observations, but was sufficient to persuade contemporary astronomers. The rejection of the results from the Brazil expedition was due to a defect in the telescopes used which, again, was completely accepted and well-understood by contemporary astronomers.[6]

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    Quote Originally Posted by MeteorWayne View Post
    Quote Originally Posted by Aristarchus in Exile View Post


    I recall it was one star or planet, and that it was later proven miscalculated. Wouldn't it be ducky if we could back up our statements, eh.
    Your recollection is incorrect.

    "After the war, Eddington travelled to the island of Príncipe near Africa to watch the solar eclipse of 29 May 1919. During the eclipse, he took pictures of the stars in the region around the Sun. According to the theory of general relativity, stars with light rays that passed near the Sun would appear to have been slightly shifted because their light had been curved by its gravitational field. This effect is noticeable only during eclipses, since otherwise the Sun's brightness obscures the affected stars. Eddington showed that Newtonian gravitation could be interpreted to predict half the shift predicted by Einstein. (Somewhat confusingly, this same half-shift was initially predicted by Einstein with an incomplete version of general relativity. By the time of the 1919 eclipse Einstein had corrected his calculations.)

    Eddington's observations published the next year[4] confirmed Einstein's theory, and were hailed at the time as a conclusive proof of general relativity over the Newtonian model. The news was reported in newspapers all over the world as a major story. Afterward, Eddington embarked on a campaign to popularize relativity and the expedition as landmarks both in scientific development and international scientific relations.

    It has been claimed that Eddington's observations were of poor quality and he had unjustly discounted simultaneous observations at Sobral, Brazil which appeared closer to the Newtonian model.[5] The quality of the 1919 results was indeed poor compared to later observations, but was sufficient to persuade contemporary astronomers. The rejection of the results from the Brazil expedition was due to a defect in the telescopes used which, again, was completely accepted and well-understood by contemporary astronomers.[6]

    from Wiki:
    Arthur Eddington - Wikipedia, the free encyclopedia
    Excellent work, Meteor. Thank you for correcting me without disdain. However, "[5] The quality of the 1919 results was indeed poor compared to later observations, but was sufficient to persuade contemporary astronomers. The rejection of the results from the Brazil expedition was due to a defect in the telescopes used which, again, was completely accepted and well-understood by contemporary astronomers."

    I'm not saying GR is wrong or right .. but I do see political correctness at work. Einstein was brilliant, I love the man for his method of work especially (immagination is more important than knowledge) and for his view of life .. but he was hailed as a demi-god instead of a man, resulting in his worshippers also balking at his baliking at the reality of non-locality/entanglement and setting up a huge wall for others to get over even though it was part of quantum theory from the start. I also think that the term "contemporary astronomers" at the tail end of the paragraph above would read "consensus astronomers" if used correctly.
    Einstein's elevation of 'C' to law "for this specific purpose" has also been a huge wall to thought, being chipped at only now with the faster-than-C neutrinos. Einstein, I believe, never intended to make 'C' a totality in itself. What effects this has on GR I don't know, but I see its effects in mentality of those who consider Einstein the last word, the concept of which he himself abhored.
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    Quote Originally Posted by Aristarchus in Exile View Post
    Thanks Markus .. that's a slightly different thing than what we were talking about, but yes, proof that somehow light does get around objects. Am I understanding it correctly that the warp of space collects light that would normally go flying past to the left, right, up and down of our normal observation .. with the mass causing the warp blocking the normal straight though path?
    Yes, basically this is what happens. Due to the presence of a mass spacetime is curved in that area according to GR; light travelling in that vicinity must follow the curvature, and therefore gets "bent". The visible effect looks ( and works ) like a giant lens. The effect is the same as the light bending in the experiment you were referring to.
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    Quote Originally Posted by Aristarchus in Exile View Post
    Michael Farraday who derived his Field ideas which he proved from scripture.
    How on earth did he prove them from scripture? He was an experimentalist: he measured things and derived an explanation (theory) based on that. Which Maxwell then formalized.

    Also, quantum mechanics is basically philosophy rather than empirical observation.
    The only possible response to that is: bollocks. It is entirely based on observational and experimental science.. Do you think the LHC is a big "philosophy machine"?
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    Thanks Markus .. that's a slightly different thing than what we were talking about, but yes, proof that somehow light does get around objects. Am I understanding it correctly that the warp of space collects light that would normally go flying past to the left, right, up and down of our normal observation .. with the mass causing the warp blocking the normal straight though path?
    Yes, basically this is what happens. Due to the presence of a mass spacetime is curved in that area according to GR; light travelling in that vicinity must follow the curvature, and therefore gets "bent". The visible effect looks ( and works ) like a giant lens. The effect is the same as the light bending in the experiment you were referring to.
    And so because photons have no mass they don't accelerate going round the bend as spacecraft to, that technique know as 'slingshotting' I believe.
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    Quote Originally Posted by Aristarchus in Exile View Post
    I see its effects in mentality of those who consider Einstein the last word, the concept of which he himself abhored.
    No one considers Einstein "the last word" - except some pseudo-scientists who frequently focus on individuals like Einstein instead of the science.

    The reason GR is widely accepted (at the moment) is because every experiment and observation confirms it; no experiment contradicts it. In short: it works.
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    Quote Originally Posted by Aristarchus in Exile View Post
    Einstein, I believe, never intended to make 'C' a totality in itself.
    You are right, he didn't. The constancy of c is a natural consequence of the fact that the laws of physics are the same for all observers, regardless of their frame of reference - that is all that Einstein postulated. Because these relativistic laws are expressed in terms of c, this must therefore be the same for all observers. It's really quite simple. If c wasn't constant then different observers would notice different physical laws, which obviously isn't the case.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    Einstein, I believe, never intended to make 'C' a totality in itself.
    You are right, he didn't. The constancy of c is a natural consequence of the fact that the laws of physics are the same for all observers, regardless of their frame of reference. Because these relativistic laws are expressed in terms of c, this must therefore be the same for all observers. It's really quite simple. If c wasn't constant then different observers would notice different physical laws, which obviously isn't the case.
    But the quantum world does away with laws. Einstein was one of the founders of quantum mechanics. He raised C to a law for simple purposes of convenience, which others have applied as a universal law, and so find evidence for that law in everything they see and do. When faster than light neutrinos come along they balk and deny rather than seeing new evidence for the quantum realities.
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    Quote Originally Posted by Aristarchus in Exile View Post
    And so because photons have no mass they don't accelerate going round the bend as spacecraft to, that technique know as 'slingshotting' I believe.
    You are correct, they do not accelerate. They simply follow the shortest line between two points, which now just so happens to be a curved geodesic because spacetime is no longer flat.
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    Quote Originally Posted by Aristarchus in Exile View Post
    But the quantum world does away with laws.
    Of course it doesn't. If it did, your computer wouldn't work and we wouldn't be having thos conversation. In fact we probably wouldn't even exist.

    When faster than light neutrinos come along they balk and deny rather than seeing new evidence for the quantum realities.
    No one has "denied seeing" new evidence. It is just doubted until it is confirmed or explained.

    That is the way science works: when extraordinary new evidence appears it is tested, sceptically. You wouldn't want us leaping off in different directions with every new hint of a result, which then turns out to have been an error.
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    Farraday proved nothing from scriptures .. he derived his ideas from scriptures. Read his story. there are books.
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    Aristarchus in Exile, stop spreading your nonsense in the Physics forum.
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  49. #48  
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    Quote Originally Posted by Aristarchus in Exile View Post
    Farraday proved nothing from scriptures
    Quote Originally Posted by Aristarchus in Exile View Post
    Michael Farraday who derived his Field ideas which he proved from scripture.
    Care to admit you were wrong? (I know you won't, you are incapable, but I thought it was worth asking).

    And it is "Faraday".
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    Quote Originally Posted by Aristarchus in Exile View Post
    But the quantum world does away with laws. Einstein was one of the founders of quantum mechanics. He raised C to a law for simple purposes of convenience, which others have applied as a universal law, and so find evidence for that law in everything they see and do. When faster than light neutrinos come along they balk and deny rather than seeing new evidence for the quantum realities.
    Well, you see, it really is too early to concern ourselves too much with FTL neutrinos. At the moment the statistics of those results are not yet significant enough to confidently say that those neutrinos really were moving at FTL speeds. That is not denial, but they are simply being careful. If it was denial they would never have published the results in the first place.
    All the various quantum field theories are formulated relativistically, by the way, meaning quantum mechanics also obey relativistic laws.
    Should it turn out however that the FTL neutrinos are real, then a re-think of basic physical laws will indeed be needed. Bear in mind though that these laws in their current form are well verfied experimentally, so at most a minor adjustment would be needed.
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    Quote Originally Posted by Vexspits View Post
    Quote Originally Posted by Kyleg View Post
    Yes, i understand that-well kind of... my question was ment to ask why? do we know why it is constant to even observers outside the reference frame it is in?
    Kyleg: the velocity of the source of a sound wave isn’t added to that wave’s velocity either. And at least in this case I think we can safely say why: the wave is propagated through a medium (air, water etc); so despite the fact that the source of the wave front (maybe a car or plane engine) is moving, the medium in which that wave front travels is not.
    Well "The medium in which that wave front travels" if i've understood you correctly is contained within a reference frame, for example the train so yes to people within the train the medium would appear to not be moving but to people outside the train it would be. so i don't really think it answers the question as to why it is the same to all observers reguardless.
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    Quote Originally Posted by SpeedFreek View Post
    I would say that light isn't special, it just helps to illustrate the special relationship between space and time.
    A reason that the speed of light in a vacuum is always measured to be c, relative to the measurer, regardless of the measurers speed relative to anything else, is because space and time are relative.

    Our rulers and our clocks are not absolute, they are relative. One man's space is another man's time.

    If you are at rest in relation to me, then your time is passing the same as mine is and our rulers are the same length. If you are moving in relation to me, your time will be passing slower than mine, and your ruler is now shorter than mine, as you have converted some of your motion through time into motion through space, relative to me. This means you will still measure the speed of light to be the same as I measure it.
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    Quote Originally Posted by Kyleg View Post
    so i don't really think it answers the question as to why it is the same to all observers reguardless.
    Refer to post 42
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    Quote Originally Posted by SpeedFreek View Post
    Our rulers and our clocks are not absolute, they are relative. One man's space is another man's time.

    If you are at rest in relation to me, then your time is passing the same as mine is and our rulers are the same length. If you are moving in relation to me, your time will be passing slower than mine, and your ruler is now shorter than mine, as you have converted some of your motion through time into motion through space, relative to me. This means you will still measure the speed of light to be the same as I measure it.
    Interesting way to look at it...I like your way of thinking
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    I stole that way of looking at it from Brian Greene, by the way.
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    Quote Originally Posted by Kyleg View Post
    Quote Originally Posted by Vexspits View Post
    Quote Originally Posted by Kyleg View Post
    Yes, i understand that-well kind of... my question was ment to ask why? do we know why it is constant to even observers outside the reference frame it is in?
    Kyleg: the velocity of the source of a sound wave isn’t added to that wave’s velocity either. And at least in this case I think we can safely say why: the wave is propagated through a medium (air, water etc); so despite the fact that the source of the wave front (maybe a car or plane engine) is moving, the medium in which that wave front travels is not.
    Well "The medium in which that wave front travels" if i've understood you correctly is contained within a reference frame, for example the train so yes to people within the train the medium would appear to not be moving but to people outside the train it would be. so i don't really think it answers the question as to why it is the same to all observers reguardless.
    No, this had nothing to do with a comparison between reference frames, it had to do with comparing a sound wave propagated away from the front of a moving train vs say a cannon ball fired away from the front of a moving train—both from the point of view of a ground observer (single reference frame). And by no means was I suggesting that this was an explanation for the isotropic nature of light waves (as the rest of post #24, not cited here should make clear). I only wanted to point out that electromagnetic waves are not unique in failing to yield entirely to the “…‘common sense” view of adding velocities,” and I chose the example of sound waves because I thought it was a nice preamble to Robert Close’s paper which discusses applying Lorenz transformations to sound waves propagating through a water medium (again see link onpost #24). I should have replied directly to your original post. My bad.
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