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Thread: light and relativity

  1. #1 light and relativity 
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    ok, I'm not an expert on relativity althought I was in to it some 10 years ago. however, now there is a question keeping me awake. first of al, the question is: IF light is fastest form we know, does it go with the same speed everywhere? is it constant? and if so, and maybe more importantly, does it have the same speed no matter what the source is? i.o.w. can it be slowed down? reason why I ask this is the following:
    whe learn that light takes time to travel from A to B. depending on the speed of A an B relative 'to each other', we know if B is is getting closer, going faster or staying at the same distance from A. Simpel relativity theorie.
    ok now, imagine A an B in a concord plane. My speed is altered wether in the plane or outside. if A is in the plane and B outside, time will alter. imagine A and B outside the plane, they live at same speed, inside the plane also.
    but then I started asking the question: "imagine A and B moving at the speed of light (or almost) could they still see each other?
    here's the image:

    A and B go from left tot right at the speed of light:


    -----------> A ----------> B --------------->


    Does A see B? with twice the speed of light? and does it mean that B doesn't see A at all?


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    Let's keep this to A and B moving at "almost" the speed of light. (In relativity, it is improper to have a frame of reference that moves at the speed of light.

    Then what happens depend on the frame form which you are viewing things. If you are traveling with A and B, A and B see each other just the same as they would if they were "at rest". Light traveling from A to B would take the same amount of time to cross the distance as light traveling from B to A.

    If however, A and B were traveling at almost c with respect to you, the Light traveling from A to B would take much longer to cross the distance between Them than light going from B to A.

    This is what is meant by saying that the speed of light is constant; that everyone measures it as having the same speed relative to themselves. It is this property that leads to the effects of Time dilation, length contraction and the Relativity of simultaneity.


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    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    ok, great explanation! but now other questions arise... it seems that we contradict ourselfs. because if you says light take much longer to travel fram A to B then light going from B to A, it means that light, even constant, does have a variable speed in this extreem case! and even in cases les extreem, let's says 1/2 c
    and then, if light travels relative to ourselves. who says WE do not travel at speeds neering c? espacially if we consider the big bang and accelerating expation of the universe, it could mean that alot of light doesn't 'reach' us because we are in this A and B case...
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    Quote Originally Posted by Raymond van Hemert View Post
    ok, great explanation! but now other questions arise... it seems that we contradict ourselfs. because if you says light take much longer to travel fram A to B then light going from B to A, it means that light, even constant, does have a variable speed in this extreem case!
    The difference in time is due to the "closing speed" of the light and A or B; i.e. the difference in speed between c and the speed A and B are moving at. Think of it this way: if the light is travelling from A to B then by the time it gets to where B was, B will have moved so the light has to travel a longer distance than the distance between A and B. Similarly, if the light is travelling from B to A it will meet A sooner because A is moving towards it and so it doesn't have to travel so far.

    It is also important to note that, as Janus said, this is from "our" perspective. As far as A and B are concerned, the light takes the same time to go from A to B and B to A.
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    Quote Originally Posted by Raymond van Hemert View Post
    ok, great explanation! but now other questions arise... it seems that we contradict ourselfs. because if you says light take much longer to travel fram A to B then light going from B to A, it means that light, even constant, does have a variable speed in this extreem case! and even in cases les extreem, let's says 1/2 c
    and then, if light travels relative to ourselves. who says WE do not travel at speeds neering c? espacially if we consider the big bang and accelerating expation of the universe, it could mean that alot of light doesn't 'reach' us because we are in this A and B case...

    again, when we say that light is constant we mean "invariant", meaning that all frames measure it as being the same as measured relative to themselves.


    To illustrate, consider the following animations.

    We have A and B, which are at rest with respect to each other and a blue dot which both A and B have a relative velocity of 0.5c. at the moment that this dot is halfway between A and B a flash of light is emitted from that point. (for the purposes of this discussion it does not matter whether the source of the light is stationary to A and B or the dot. In fact we could say that it is a combination of a flash from both a source at rest with respect to the dot and a source at rest with respect to A and B.

    The first animation shows events according to the frame of the blue dot.




    The flash expands out as a circular wavefront (actually spherical, but we are only showing a 2D image here), which always maintains a constant distance from the blue dot. A is moving towards the blue dot and B is moving away. Thus A meets up with the wave front before the wave front catches up with B, and the light reaches A before B.


    The second animation shows the same light flash, but considered from the frame of A and B.



    Here, the light flash maintains a constant distance from the halfway point between A and B, while the blue dot moves off to the left away from the center of the wave front. The wave front hits A and B simultaneously.

    This is a demonstration of what is known as the Relativity of Simultaneity. Events that are simultaneous in one frame (the light reaching A and B in the the frame of A and B) are not simultaneous in another (the light reaching A and B at different times in the frame of the Blue Dot.)

    Now a couple of caveats:

    The animations do not factor in length contraction. In reality, in the frame of the Blue dot, the distance from A to B will be shorter than it is as measured by A and B. But since this contraction affects the distance between the center point between A and the distance between the center point and B equally, it doesn't effect the fact that according to the Blue dot frame the light reaches A before B.

    Above, I mentioned that it did not matter whether the source of the light was at rest with respect to the blue dot or A and B. While this is true in terms of the timing of the arrival of the light, it doesn't take into account Doppler shift. Doppler shift will tell you whether the source has a relative velocity with respect to you. For example, if the source is at rest with respect to the Blue dot, then A will see the light as blue shifted and B will see it as red shifted. If the source is at rest with respect to A and B, neither A or B will see a Doppler shift. This will tell A or B whether or not the Source is moving with respect to them.

    However, and this is important, it only tells them the relative motion between themselves and the source. They cannot tell if it is them or the source that is moving. In fact, there is no test that they can make that will tell them this. This is a cornerstone of Relativity, that not only is it impossible to test as to who is "really" moving, but that the very idea of the idea of absolute motion is meaningless.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Perhaps the following statements will help.. (or perhaps not).

    In a vacuum, it doesn't matter how fast you are moving, you will always measure the speed of light to be 299,792,458 metres per second faster than yourself.

    If you accelerate from rest to a speed of 150,000,000 metres per second, you will still measure light to be travelling 299,792,458 metres per second faster than yourself.

    In a vacuum, light always travels 299,792,458 metres per second faster than whoever is measuring it.
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    Janus, thanks alot for the animation and the explanation. same to you speedfreek. the first animation was exactly what I meant. with A and B moving at nearly the speed of light. we always calculate according to being A or B, so like you said "in relative motion between themselves and the source". I think that was is bothering me all this time is trying to see it like your first animation, a 'third' eye so to speak. taking into account velocity of A and the arrival speed of the wave does mean an addition of the speeds and thus a speed greater that c. But then again, like speedfreek says, if light always travels at the constant c, no matter how fast you move...
    still... it all seems so... incompleet... you know How I came to the idea? I thought: "how come al we see in the univers is 'dark' absence of light? and then I thought of the big bang and ever accelerating expantion of the univers and I thought... and what if accelaration was so fast (like speed of light) that it doesn't even reach us... and that's when I came up with this thing... and still I'm not 100% satisfied you know. that 'impossible' part bothers me... =) but thanks alot for the super great explanation! you're a teacher? scientist? or just a devoted lover of science?
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    Quote Originally Posted by SpeedFreek View Post
    Perhaps the following statements will help.. (or perhaps not).

    In a vacuum, it doesn't matter how fast you are moving, you will always measure the speed of light to be 299,792,458 metres per second faster than yourself.

    If you accelerate from rest to a speed of 150,000,000 metres per second, you will still measure light to be travelling 299,792,458 metres per second faster than yourself.

    In a vacuum, light always travels 299,792,458 metres per second faster than whoever is measuring it.
    This seems to infer that we can travel at 'warp' speeds (as in Star Trek) as even though we are travelling hundreds of times faster than the speed of light we never begin to approach the speed of light, so the effects of travelling at speed of light would not occur.
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    Quote Originally Posted by Aristarchus in Exile View Post
    This seems to infer that we can travel at 'warp' speeds (as in Star Trek) as even though we are travelling hundreds of times faster than the speed of light we never begin to approach the speed of light, so the effects of travelling at speed of light would not occur.
    Except you can't travel at hundreds of times faster than the speed of light. In fact, you can't even travel at the speed of light.
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    wel, there is a point at which speeds are so high that matter changes into energie...
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    Can matter change into energy? Matter and energy are as different as fire and water, and matter cannot reach the speed of "energy" (light). Matter is of course full of energy, which is what holds everything together. Maybe that energy can be removed as in e=mc2?
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    Quote Originally Posted by Raymond van Hemert View Post
    ok, great explanation! but now other questions arise... it seems that we contradict ourselfs. because if you says light take much longer to travel fram A to B then light going from B to A, it means that light, even constant, does have a variable speed in this extreem case! and even in cases les extreem, let's says 1/2 c
    and then, if light travels relative to ourselves. who says WE do not travel at speeds neering c? espacially if we consider the big bang and accelerating expation of the universe, it could mean that alot of light doesn't 'reach' us because we are in this A and B case...
    While matter cannot travel faster than light, two objects can move away from each other at a combined speed greater than light speed, so they are not visible to each other.
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    Quote Originally Posted by Cyberia View Post
    Can matter change into energy?
    Yes. That is the practical application of E=mc2.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    This seems to infer that we can travel at 'warp' speeds (as in Star Trek) as even though we are travelling hundreds of times faster than the speed of light we never begin to approach the speed of light, so the effects of travelling at speed of light would not occur.
    Except you can't travel at hundreds of times faster than the speed of light. In fact, you can't even travel at the speed of light.
    I will never accept that it's impossible to travel past light speed, which is really, really slow on the scale of the universe, especially IF it's true that no matter how fast you go light always travels away from you at the speed of light. Besides, it's been demonstrated in labs that light can be slowed down and speeded up, and I can't see why light should be any more special thatn sound waves which travel faster or slower through different mediums.
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    Quote Originally Posted by Aristarchus in Exile View Post
    I will never accept that it's impossible to travel past light speed...
    And I will never accept that a heavier than air plane can fly, or a steel ship can float. I promise to avoid all evidence to the contrary to satisfy my own private belief system.

    OK. It may be that faster than light travel is possible but (a) our best theories say it isn't and (b) we have no evidence (neutrinos notwithstanding) that it is.

    it's been demonstrated in labs that light can be slowed down and speeded up
    I put that down to bad reporting

    and I can't see why light should be any more special thatn sound waves which travel faster or slower through different mediums
    Light does travel at different speeds in different materials. That is why we get refraction. But that is hardly relevant.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    I will never accept that it's impossible to travel past light speed...
    And I will never accept that a heavier than air plane can fly, or a steel ship can float. I promise to avoid all evidence to the contrary to satisfy my own private belief system.

    OK. It may be that faster than light travel is possible but (a) our best theories say it isn't and (b) we have no evidence (neutrinos notwithstanding) that it is.

    it's been demonstrated in labs that light can be slowed down and speeded up
    I put that down to bad reporting

    and I can't see why light should be any more special thatn sound waves which travel faster or slower through different mediums
    Light does travel at different speeds in different materials. That is why we get refraction. But that is hardly relevant.
    Well, it's not important anyway, unless there's money to be made in it. I'm not trying to persuade anyone of anything, just expressing what I believe to be true, and I base my beliefs on evidence which includes numerous scientific examples of scientists who were derided and condemned before being proven right, even IN their own lifetimes. One example, Michael Faraday who demonstrated fields, but he could not do much math, and his peers thought him a lunatic, and talked openly of him as such, but when he proved himself right he was honoured by the higher up mucky mucks. A thread on lunatic scientists proven right (quasi science, right?)might help us all remain open minded.
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    Just because there are example of scientists who were later proved right doesn't mean that every half baked idea is right. That is not "evidence" of anything (except warped logic).

    There are also many, many more scientists who came up with ideas that didn't turn out to be right? Does that prove that every idea you have is wrong?

    "They laughed at me when I said I wanted to be a comedian. Well, they aren't laughing now." B. Monkhouse

    A thread on lunatic scientists proven right (quasi science, right?)might help us all remain open minded.
    A thread on lunatic scientists who were later proved to be lunatics might help us all remain suitably sceptical and demanding of evidence.
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    Quote Originally Posted by Strange View Post
    Just because there are example of scientists who were later proved right doesn't mean that every half baked idea is right. That is not "evidence" of anything (except warped logic).

    There are also many, many more scientists who came up with ideas that didn't turn out to be right? Does that prove that every idea you have is wrong?

    "They laughed at me when I said I wanted to be a comedian. Well, they aren't laughing now." B. Monkhouse

    A thread on lunatic scientists proven right (quasi science, right?)might help us all remain open minded.
    A thread on lunatic scientists who were later proved to be lunatics might help us all remain suitably sceptical and demanding of evidence.
    Okay .. I'll open one on lunatics who were not lunatics, and you open one on lunatics who have not yet been proven lunatics.
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    Quote Originally Posted by Raymond van Hemert View Post
    wel, there is a point at which speeds are so high that matter changes into energie...
    No, there isn't.

    One of the basic tenets of Relativity is that there is no such thing as a preferred frame of absolute rest by which motion can be measured. All you can co do is measure motion relative to some reference. Such a reference can be completely arbitrary, but is usually chosen by convenience. For instance, it is more convenient to measure a car's velocity with respect to the surface of the Earth instead of with respect to the to the Sun, though both are perfectly valid references by which to measure the car's motion.

    So you see that it makes no sense to say that there is a speed at which matter change to energy. It's speed to respect to what reference? An object would many different speeds as measured with respect to different references, and you can't have it turning to energy according to one reference and not according to another.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Quote Originally Posted by Aristarchus in Exile View Post
    Okay .. I'll open one on lunatics who were not lunatics, and you open one on lunatics who have not yet been proven lunatics.
    Why? It is flawed (utterly broken) logic. Do you really think that just because person A had an idea which later turned out to be right, then every idea that anybody has must also be right?

    So all those pseudo-scientists with their own personal arguments as to why relativity is wrong (all of which come down to "I don't understand it so it must be wrong") are all actually correct? Even though they contradict one another?

    Or is it the ridicule aspect? Do you think that just because person A had an idea which people laughed at but which later turned out to be right, then every idea that anybody has must also be right - as long as someone laughs at it? So we don't need physics labs, we can just put scientists on stage and see which theories get the biggest laughs. Well, it is cheaper than building another LHC, I suppose.
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    Quote Originally Posted by Aristarchus in Exile View Post
    [

    I will never accept that it's impossible to travel past light speed, which is really, really slow on the scale of the universe, especially IF it's true that no matter how fast you go light always travels away from you at the speed of light. Besides, it's been demonstrated in labs that light can be slowed down and speeded up, and I can't see why light should be any more special thatn sound waves which travel faster or slower through different mediums.
    Light travels away from you at c as measured by you, not as measured by some one that you are moving with respect to. The speed of light limit only applies to the speed of light in a vacuum. The fact that light can be slowed when traveling through a medium has no bearing on this, as it is the speed c that is special and no the light itself. It happens to be the speed at which light travels in a vacuum, and light is very convenient for us to use, which is why we tend to call it the "speed of light" rather than the "invariant speed of the universe".
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Quote Originally Posted by Janus View Post
    Quote Originally Posted by Raymond van Hemert View Post
    wel, there is a point at which speeds are so high that matter changes into energie...
    No, there isn't.

    One of the basic tenets of Relativity is that there is no such thing as a preferred frame of absolute rest by which motion can be measured. All you can co do is measure motion relative to some reference. Such a reference can be completely arbitrary, but is usually chosen by convenience. For instance, it is more convenient to measure a car's velocity with respect to the surface of the Earth instead of with respect to the to the Sun, though both are perfectly valid references by which to measure the car's motion.

    So you see that it makes no sense to say that there is a speed at which matter change to energy. It's speed to respect to what reference? An object would many different speeds as measured with respect to different references, and you can't have it turning to energy according to one reference and not according to another.
    Excellent post in almost every way .. but what happens to matter in conventional theory when it approaches close to light speed?
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    Quote Originally Posted by Aristarchus in Exile View Post
    but what happens to matter in conventional theory when it approaches close to light speed?
    Of course, you missed out the vital part: close to the speed of light from whose point of view? But anyway, nothing special happens to it.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Aristarchus in Exile View Post
    but what happens to matter in conventional theory when it approaches close to light speed?
    Of course, you missed out the vital part: close to the speed of light from whose point of view? But anyway, nothing special happens to it.
    Does relativity say the speed of light is the same for all observers?

    Okay .. so nothing special happens to matter near the speed of light. We cannot catch light as it is the same speed no matter how fast we go. Therefore we cannot catch the speed of light no matter how fast we go. Therefore we can go as fast as we want and not approach the speed of light. Therefore at 999999trillion gazillion galaxies per second we still cannot approach the speed of light. So .. i guess I've done the right thing not to take up jogging.
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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
    but what happens to matter in conventional theory when it approaches close to light speed?
    Of course, you missed out the vital part: close to the speed of light from whose point of view? But anyway, nothing special happens to it.
    Does relativity say the speed of light is the same for all observers?

    Okay .. so nothing special happens to matter near the speed of light. We cannot catch light as it is the same speed no matter how fast we go. Therefore we cannot catch the speed of light no matter how fast we go. Therefore we can go as fast as we want and not approach the speed of light. Therefore at 999999trillion gazillion galaxies per second we still cannot approach the speed of light. So .. i guess I've done the right thing not to take up jogging.

    The problem is that you cannot catch the light according to anyone. For example, you are zooming past the Earth and fire a light beam ahead of you. By your measurement, the light jumps ahead of you at ~300,000 kps. I also see the light travel ahead of you, but at ~300,000 kps relative to the Earth. Since neither of us can see you catch up to or pass the light, this means that no matter how hard you try, you will always travel at less than ~300,000 kps relative to the Earth.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    The problem is that you cannot catch the light according to anyone. For example, you are zooming past the Earth and fire a light beam ahead of you. By your measurement, the light jumps ahead of you at ~300,000 kps. I also see the light travel ahead of you, but at ~300,000 kps relative to the Earth. Since neither of us can see you catch up to or pass the light, this means that no matter how hard you try, you will always travel at less than ~300,000 kps relative to the Earth.[/QUOTE]

    You explained yourself VERY clearly. Thanks. What happens if the earth is taken out of the picture?
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    Quote Originally Posted by Aristarchus in Exile View Post
    The problem is that you cannot catch the light according to anyone. For example, you are zooming past the Earth and fire a light beam ahead of you. By your measurement, the light jumps ahead of you at ~300,000 kps. I also see the light travel ahead of you, but at ~300,000 kps relative to the Earth. Since neither of us can see you catch up to or pass the light, this means that no matter how hard you try, you will always travel at less than ~300,000 kps relative to the Earth.
    You explained yourself VERY clearly. Thanks. But it all seems impossible to me. QUOTE]
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    Quote Originally Posted by Aristarchus in Exile View Post
    The problem is that you cannot catch the light according to anyone. For example, you are zooming past the Earth and fire a light beam ahead of you. By your measurement, the light jumps ahead of you at ~300,000 kps. I also see the light travel ahead of you, but at ~300,000 kps relative to the Earth. Since neither of us can see you catch up to or pass the light, this means that no matter how hard you try, you will always travel at less than ~300,000 kps relative to the Earth.
    You explained yourself VERY clearly. Thanks. What happens if the earth is taken out of the picture?[/QUOTE]

    Nothing. The earth in this example just a "marker" for a reference frame, the reference frame still exists without the Earth being there, its just easier to keep track of the reference frame when you assign a physical object to it.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Quote Originally Posted by Janus View Post
    Nothing. The earth in this example just a "marker" for a reference frame, the reference frame still exists without the Earth being there, its just easier to keep track of the reference frame when you assign a physical object to it.
    Okay .. so we eliminate external references. We initiate a light beam. Within this beam we send information which either does not rely on light as a carrier, or in which the light quanta actually push the information ahead as we slip in between the light quanta in by corkscrewing the information similar to how polarized light is said to corkscrew. As the information moves through the beam, relativity says the light ahead of it is still travelling at the speed of light, so that no matter how fast the information moves the light ahead of it is still travelling at C. The infomation can then travel at infinite speed without breaking C. This could be how Non-Locality works .. as light appears to be everywhere in the known universe the beams are already there. I wonder, did I just come up with an original idea? (Please remembre that at one time the sound barrier was considered a physical barrier though which an aircraft could not pass.)
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    Yes light does slow down as it propagates through different transparentmaterials…hence the reason we have the ‘refractive index’ (i.e. n = c /v).
    For all the confusionon what happens to matter as it approaches the speed of light I give you theLorentz transforms straight out of Einstein’s original papers.
    lorentz03.gif


    These equations represent the idea that astationary observer measuring Einstein’s good old fashion measuring rod, as it approachesthe speed of light, would observe a decrease in length along the x axis with an increase in velocity. Nowimagine, if you will, a clock sitting on the measuring rod, the stationaryobserver would read the time on the clock as shortening (slowing down in termsof time t) with an increase invelocity as well… so what happens if you are ridding the measuring rod as ithits a velocity of c and I’m watchingyou go by? Let’s just say that’s the first and only time I’ll see someone flyup their own ass hole
    Lastly the debate about catching a beamof light. Let us not forget that relativity is all about reference point. So theidea is that an observer standing in a stationary system of co-ordinates wouldobserve the same c as an observerstanding in a moving system of co-ordinates, however the observers would vieweach other as changing throughout the motion. Hence the first postulate ofSpecial Relativity “Observers can never detect their uniform motion exceptrelative to other objects. The laws of physics are the same for all observers,no matter what their motion.”
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    Quote Originally Posted by Aristarchus in Exile View Post
    We initiate a light beam. Within this beam we send information which either does not rely on light as a carrier, or in which the light quanta actually push the information ahead as we slip in between the light quanta in by corkscrewing the information similar to how polarized light is said to corkscrew.
    This is meaningless on so many levels. You cannot treat the beam of light as a reference frame (try putting v = c in the Lorentz transform and you will see why). Information cannot travel faster than c. And the last part of that sentence is just gibberish.

    As the information moves through the beam, relativity says the light ahead of it is still travelling at the speed of light
    No it doesn't.

    The infomation can then travel at infinite speed without breaking C.
    No it can't.

    It seems the problem is that you are trying to apply "common sense" to something when you don't understand the basic ideas.
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    Quote Originally Posted by Aristarchus in Exile View Post
    Quote Originally Posted by Janus View Post
    Nothing. The earth in this example just a "marker" for a reference frame, the reference frame still exists without the Earth being there, its just easier to keep track of the reference frame when you assign a physical object to it.
    Okay .. so we eliminate external references. We initiate a light beam. Within this beam we send information which either does not rely on light as a carrier, or in which the light quanta actually push the information ahead as we slip in between the light quanta in by corkscrewing the information similar to how polarized light is said to corkscrew. As the information moves through the beam, relativity says the light ahead of it is still travelling at the speed of light, so that no matter how fast the information moves the light ahead of it is still travelling at C. The infomation can then travel at infinite speed without breaking C. This could be how Non-Locality works .. as light appears to be everywhere in the known universe the beams are already there. I wonder, did I just come up with an original idea?
    No, it can't work like that. For one, you can't use light as frame of reference as already mentioned. Secondly, you are still trying to treat things as if it is the light that is special rather than the speed c. Thirdly, you cannot add velocities in the way that you are thinking. Velocities add by the rule of:



    Note that even if both v1 and v2 were equal to c, the answer only equals c. You cannot get around this.



    (Please remembre that at one time the sound barrier was considered a physical barrier though which an aircraft could not pass.)
    There is no similarity between the "sound barrier" and the universal speed limit of c. Even before the "sound barrier" was "broken", there were plenty of examples of objects that traveled faster than the speed of sound. Projectiles from guns and even the tip of a bullwhip traveled faster than sound.

    What the "sound barrier" represented was the aerodynamic problem caused for the control surfaces of planes as they neared the speed of sound. It wasn't that the planes couldn't reach those speeds (for example, if pushed into steep dive.), But that the pilots lost control of their planes when they got close to them. It was an engineering problem.

    The speed of c is a completely different animal. It represents a limit that is built into the very rules that determine how the universe works. It is not something that can be engineered around, because it is an integral part of reality itself. Once you establish that a speed (c) is invariant (is measured as the same by everyone), the automatic and unavoidable result is that the speed becomes the natural speed limit of the universe.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Quote Originally Posted by scinerd View Post
    Yes light does slow down as it propagates through different transparentmaterials…hence the reason we have the ‘refractive index’ (i.e. n = c /v).
    For all the confusionon what happens to matter as it approaches the speed of light I give you theLorentz transforms straight out of Einstein’s original papers.
    lorentz03.gif


    These equations represent the idea that astationary observer measuring Einstein’s good old fashion measuring rod, as it approachesthe speed of light, would observe a decrease in length along the x axis with an increase in velocity. Nowimagine, if you will, a clock sitting on the measuring rod, the stationaryobserver would read the time on the clock as shortening (slowing down in termsof time t) with an increase invelocity as well… so what happens if you are ridding the measuring rod as ithits a velocity of c and I’m watchingyou go by? Let’s just say that’s the first and only time I’ll see someone flyup their own ass hole
    Lastly the debate about catching a beamof light. Let us not forget that relativity is all about reference point. So theidea is that an observer standing in a stationary system of co-ordinates wouldobserve the same c as an observerstanding in a moving system of co-ordinates, however the observers would vieweach other as changing throughout the motion. Hence the first postulate ofSpecial Relativity “Observers can never detect their uniform motion exceptrelative to other objects. The laws of physics are the same for all observers,no matter what their motion.”
    Thanks for the explanation .. but I don't understand your reference to going up the butthole ... does he sneak up on himself from behind through a time warp?

    Okay .. here's a thought fresh to me .. slingshotting photons in the way spacecraft slingshot planets to pick up speed. Just a picture for now.
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    Haha I apologize for butt hole comment; I also apologies for not re spacing my script after converting it (I’m a noob on the cite) I hope you were still able to decipher it ok. Anyways if you work out the Lorentz transform for x’ (the change of x near relativist speeds) you may notice that as you hit v = c you are dividing by zero which cause the equation to be undefined. When I first saw this as a sophomore in my high school astronomy class, I asked my teacher what this event would look like to a stationary observer. Of course my teacher being a PhD. had the witty remark of “it’s just like the English (something bird, I forget). It flies round and round in circles going faster and faster, until it flies up its own butt hole out of existence!”. That was his way of saying it can’t happen anyways so don’t worry yourself, since then that description has stuck with me. So that’s the story of the butt hole description, I apologize for it but it still makes me laugh!

    And on your slingshot idea… that makes me think of the Large HadronCollider (LHC) which is a large circular pipe line used to contain atomic and subatomic particles as they are slingshoted to relativistic speeds by superconducting magnets. Then they crash those bad boys into each other like a 670,616,629 miles per hour car crash on a one way road! So if you want to find ought what happens to particles at that speed all you have to do is search the latest news about the LHC. [/FONT]

    Good luck with your ideas
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    I would also like to make a comment to Janus and Strange… excellent simplified explanations of Special Relativity. However, in your scorn you were all too hasty to forget that nothing in this field is set in stone. So in the spirit of science being driven by hopes and dreams I would like to remind you both that there is still room for the next big idea. Don’t forget, that yes, even the field equations from General Relativity “theory” have a percent error and even Special theory has its paradoxical entities. For example the edges of the very fabric of spacetime are considered to be expanding faster than the speed of light (i.e. to allow us to not to have reflections bouncing all over the place, a house of mirrors effect if you will). And not to mention we are all too far away from bridging the gap between the physics that govern the quantum world and those that exist in classical spacetime. That’s why Iwould encourage reading books such as Terence Witt’s Our Undiscovered Universe, even though rejected by main stream cosmology. It’s women/gentlemen like that, who inspire different thought processes that keep the knowledge pool from becoming stagnant. My point is that just because we haven’t or don’t possess the ability to observer ultra-luminescent particles, doesn’t mean we can rule them out just yet (sorry I took offence to the part about “c… becomes the natural speed limit of theuniverse”). I know such motion would unravel the theory of Relativity… but perhaps Einstein just gave us a good starting place.

    I shared some links for you to broaden your knowledge, or just touch up on the complex mathematics. Oh and it will also give you something to dream about

    http://www.olduniverse.com/1,6 Einstein Eq. Limits.pdf

    Einstein's Special Relativity - For Dummies

    Particles found to break speed of light | Reuters
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    Quote Originally Posted by scinerd View Post
    I would also like to make a comment to Janus and Strange… excellent simplified explanations of Special Relativity. However, in your scorn you were all too hasty to forget that nothing in this field is set in stone.
    Indeed. Maybe I should create a signature saying that everything I write should be prefixed with "According to our best theories..." and ended with "... as far as we know".
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    Quote Originally Posted by scinerd View Post
    Haha I apologize for butt hole comment; I also apologies for not re spacing my script after converting it (I’m a noob on the cite) I hope you were still able to decipher it ok. Anyways if you work out the Lorentz transform for x’ (the change of x near relativist speeds) you may notice that as you hit v = c you are dividing by zero which cause the equation to be undefined. When I first saw this as a sophomore in my high school astronomy class, I asked my teacher what this event would look like to a stationary observer. Of course my teacher being a PhD. had the witty remark of “it’s just like the English (something bird, I forget). It flies round and round in circles going faster and faster, until it flies up its own butt hole out of existence!”. That was his way of saying it can’t happen anyways so don’t worry yourself, since then that description has stuck with me. So that’s the story of the butt hole description, I apologize for it but it still makes me laugh!

    And on your slingshot idea… that makes me think of the Large HadronCollider (LHC) which is a large circular pipe line used to contain atomic and subatomic particles as they are slingshoted to relativistic speeds by superconducting magnets. Then they crash those bad boys into each other like a 670,616,629 miles per hour car crash on a one way road! So if you want to find ought what happens to particles at that speed all you have to do is search the latest news about the LHC. [/FONT]

    Good luck with your ideas
    The LHC cost billions to build, I think a collider could be built using one glass fibre if photon slingshotting could be made to happen.
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    Quote Originally Posted by scinerd View Post
    For example the edges of the very fabric of spacetime are considered to be expanding faster than the speed of light (i.e. to allow us to not to have reflections bouncing all over the place, a house of mirrors effect if you will).
    There has been thought given that the universe is a house of mirrors, with parts of it statling close in resemblance to other parts. I don't have any backup on this, but I have read it. Of course, the mirroring could be just part of growth. I used to raise rabbits, skinned perhaps a hundred, and the insides of their hides were same-patterned left side and right side.
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    ok. nice to se al the comments and realy. there are some excellent mind at work here. first of all, I like the idea of changing 'light' by a numerical information system, that has exactly the same propreties of light but applied with the old fashion science, comming back to my first idea like like bij Janus his animations. now the second great idea is that of considering that we talk about 'almost the speed of light'. but, even if considered impossible, what happens if we do take the speed of light? I mean, let's just imagine taking it as an idea, just like trying to take light as a frame... and then the third thing I liked was that equation put down by scinerd. let's take v=c. now you would say it's impossible because our calculators would say that it's impossible to deide by 0... and what if we changed squareroot of 0 by something else... just like we all thought you couldn't have square root of a negative number but found a practical way bij changing squareroot of -1 bij i. actualy I'm just trying to break open my mind, get my thoughts out of a cage.
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    this is more or less how I came up with the idea (just read the top comments. it realy looks like Einstein opened the door. but that there is still much to be discovered. and there are some anomaly's we try to find a way around without really dealing with the probleme.
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    and there we have a next question. let's consider A and B travelling at almost the speed of light so that every frame is possible. let A and B collide in opposite directions but let us take A (or B) as a frame... now tell me, what is the speed of B? shouldn't it be twice the speed of 'alomost the speed of light'?
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    Quote Originally Posted by Raymond van Hemert View Post
    let's take v=c. now you would say it's impossible because our calculators would say that it's impossible to deide by 0...
    The problem is not with our calculators (after all, they can't calculate factorial 1000, either). It is simply undefined in standard mathematics.
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    Quote Originally Posted by Raymond van Hemert View Post
    and there we have a next question. let's consider A and B travelling at almost the speed of light so that every frame is possible. let A and B collide in opposite directions but let us take A (or B) as a frame... now tell me, what is the speed of B? shouldn't it be twice the speed of 'alomost the speed of light'?
    The speeds do not add linearly. The speed that A will see B travelling at is given by the equation provided earlier:


    Even if v1 and v2 are 99.999% of c the result is still less than c.
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    found kind of the answer that I was looking for
    How Can Galaxies Travel Faster Than Light? - YouTube
    however there are no formulas
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    Ahh, well galaxies travelling faster than light is a different issue to the one you outlined above.

    Simply put, here we are not talking about objects travelling through space faster than light, we are talking about the expansion of the universe - a common analogy is to say that rather than the galaxies moving through space, it is the space between them that is "expanding".

    The article below was published in Scientific American and describes, in layman's terms, how this concept works:
    http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf
    (Note: Page 1 is blank, don't get confused and think the download has failed!)

    And here is the paper on which the above article was based, by the same authors. It includes all the formulas required:
    [astro-ph/0310808] Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe
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    ok, now we all know that neutrino's travel faster than speed of light, I ask another question: "imagine A moving away from B (neutrino's) at the speed of light (or now even faster) could they still see each other?
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    Quote Originally Posted by Raymond van Hemert View Post
    ok, now we all know that neutrino's travel faster than speed of light
    Actually we don't know that. And if they are, we don't yet know why and so we can't say what t means for physics.
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    ^^^^ What he said ^^^^
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