light propagates at c + v?

Discussion in 'Alternative Theories' started by BdS, Nov 21, 2015.

  1. James R Just this guy, you know? Staff Member

    Messages:
    39,397
    Hi expletives deleted,

    Welcome to sciforums.

    Students of the theory of relativity need to take care at all times to avoid falling into traps that can appear when certain assumptions are made that in everyday experience would be called "common sense".

    In our everyday lives, for most practical purposes we can regard the speed of light as essentially infinite. That is, when we look at something in the distance we see it practically instantly. Any time delay between light coming from the side of the object closest to the observer and light coming from the side furthest from the observer is negligible. In part this is because most objects we see move very slowly compared to the speed of light.

    If we try to extrapolate from our everyday experience what we would expect to "see" when a relativistic object flies past us at a reasonable fraction of the speed of light, then we risk making serious mistakes if we don't take the travel time of the light into account. This is essentially what Terrell rotation is about.

    When students first learn about the special theory of relativity, they learn about things such as length contraction. To make things simple, this is usually handled in one dimension only. We consider the lengths of objects parallel to the direction of motion. This can lead to various incorrect assumptions about how solid objects might "look" when travelling at high speeds. For example, one might assume that because Special Relativity tells us that a relativistic sphere contracts in the direction of its motion (but not in directions perpendicular to that), such a sphere would look "squashed" into a football-like shape as it flew past. This is not the case. To know what it looks like, we need to consider how light travels from different parts of the sphere to an observer, with light from different parts taking slightly different amounts of time to reach the observer.

    Naive students of relativity often confuse how things look with how things are. The Lorentz transformations of special relativity, for example, translate the coordinates of events in spacetime from one reference frame to another. That is, they can tell us exactly where at particular point on an object is at a particular time, in a particular reference frame. They do not, without more work, describe the particular sets of points in space that emit light that reaches a certain point in space at the same time, thus creating what is seen at that point at a particular instant.

    Many introductory textbooks gloss over to a greater or lesser extent the difference between what is seen and how things are at a given instant (in a particular frame of reference).

    Another issue is with the word "observer" itself. That term is used to mean an entire reference frame in some instances, while in other instances it is used to mean a particular object or detector or person located at just one point in space(time) in a reference frame.

    I'm not sure how relevant any of this is to the current thread, although it does seem to me that danshawen, for one, doesn't really understand that distinction.
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. expletives deleted Registered Senior Member

    Messages:
    410
    Thanks for your kind welcome, James R.
    That wiki article correcting misconceptions in the scientific literature and in textbook illustrative analogies, both of which have been depended on for teaching and training the thought processes and understandings of new students of relativity for a long time before being corrected, implies that professional physicists may have been explaining things incorrectly for some time now when attempting to defend the official line regarding actuality versus imagery, doesn't it? If that is the case, shouldn't everyone go back to scratch to re-examine their own understandings of the maths and the physics used to defend relativity claims and assertions which may have been subject to the long prevailing misconceptions now acknowledged in that wiki article?

    I am not yet informed enough to have made any judgement regarding whether danshawen has or hasn't missed the distinction. Can you or some other kind member elaborate on what the distinction is in actuality and how that wiki article correcting long held misconceptions may impact on re-examination of all rotations concepts and conclusions historically embedded in maths and physical assumptions, analysis and theoretical interpretations?
     
    Last edited: Jan 20, 2016
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. paddoboy Valued Senior Member

    Messages:
    27,543
    Science progresses continually, and physicists and scientists certainly need to move with the new data and revelations.
    In saying that, let's also understand that lay people such as yourself and I, are really not going to change anything, or even able to change anything. We do not have the expertise, simple as that.
    WIKI also, although OK for explanations etc, probably ranks just behind links and such from learning institutions and Universities, I'm sure you'll agree.
    In essence, Jame's article makes perfect sense.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. expletives deleted Registered Senior Member

    Messages:
    410
    I didn't need telling that, I had worked that out for myself, thanks just the same. But the wiki subject matter was not in that vein; it was not in regard to "new data and revelations", but in regard to correcting long held misconceptions of "existing data and revelations" which adversely affected both professional physics and layman education and explanations for quite some time and intercourse in the past (and still in the present) between opposing camps in the past who based their respective positions on such misconceptions now corrected as per that wiki.
    Please speak for yourself and don't include me in your generalizations or prejudiced opinions about other members capabilities. And I am not here to "change anything", but to read interesting discussions in science and sometimes to post on-topic if I choose to, without any guidance needed or asked for, especially not from self-appointed would be helpers who themselves are laymen not qualified to set the tone for others participation in science threads.
    I reserve my opinion; and would be obliged to you if you also reserved yours in future and left me alone to determine for myself with what I will or will not agree.
    Please leave me to work out for myself, from James R's kind and learned on-topic responses and content, what makes sense or not as the case may be given the science and logic in his replies.

    You are not involved nor wanted in my conversations with others, paddoboy. And since I am already of the opinion that it would be counterproductive to respond to you further, you would be assisting me greatly in my efforts to maintain my blood pressure to within medically acceptable levels if you no longer responded to my posts addressed to other members who I choose to engage because, unlike you, they don't seem to be trying at every opportunity to drag exchanges off-topic according to off-topic agendas I am not interested in, now or ever. Thanks for your kind cooperation in future and so helping me keep my blood pressure at safe levels, paddoboy.
     
  8. paddoboy Valued Senior Member

    Messages:
    27,543
    My dear friend, I'll weigh things up as they eventuate: Sorry about your condition, but this is a science forum and if I believe rubbish is posted under the guise of science, I'll respond with whatever knowledge and data I have.
     
  9. paddoboy Valued Senior Member

    Messages:
    27,543

    Please Register or Log in to view the hidden image!

    Hmmmm, Interesting, quite Interesting.
    [1]It will be interesting to see what your opinion is on cosmology and how it lines up with some on this forum.
    [2]I'm sure you have already determined with what you agree or don't agree with, the point is, this is a science forum and does not constitute academia and mainstream cosmology, as it is open to all, including you and me.
    [3]Do you disagree that James' post makes sense or not?
    Involvement in your conversations is open to all and sundry when you post here...you know that, so please do not disgrace your persona by asking me not to take part, OK?
     
    Last edited: Jan 21, 2016
  10. expletives deleted Registered Senior Member

    Messages:
    410
    Thanks for your commiserations for my blood pressure condition, paddoboy; but please in future do not presume to take such a familiar tone with me, since I don't know you and, frankly, am already of the opinion that I don't want to know you or engage with you at any level of familiarity. If you are a layman unqualified to determine what is or isn't "rubbish" when it comes to scientific ideas and discussions posted by other members, then your "beliefs" will more than likely be misleading, especially if your own understandings are essentially not informed to the levels necessary to avoid your own misconception of both old and new data and revelations in the scientific fields which are beyond your pay grade to assess properly.

    So if you will excuse me, I will look to more open minded and learned members for scientific enlightenment and discussion, and not to opinionated laymen who seem to treat science discussions as somehow appropriate to take off-topic and personal on whatever pretext. No thanks, paddoboy; please do your thing, whatever it is, with those who may appreciate your off-topic attentions and intrusions into their exchanges with more science learned and on-topic members.
     
  11. rpenner Fully Wired Valued Senior Member

    Messages:
    4,833
    So...
    • Is this your first time on the Internet?
    • Do you brush off your mother's attempts to be sociable with that mouth?
    • Where upthread was your résumé, curriculum vitae, or verifiable instrument of peerage posted so that we might have had fair warning of your intent to dictate appropriate posting behavior? In short, how may we distinguish you from the opinionated laymen?
     
    paddoboy likes this.
  12. paddoboy Valued Senior Member

    Messages:
    27,543
    Yet we have this long rant directed at me.

    Please Register or Log in to view the hidden image!



    My ideas and knowledge, in the main, align with accepted cosmology: I certainly do not pretend to be somebody else of which I'm not

    Please Register or Log in to view the hidden image!


    If your own views stray from mainstream, then please supply a link supporting them, and of course your credentials, when you are ready of course.

    Please Register or Log in to view the hidden image!


    Otherwise you'll be confronted with it just as "the god" was and failed in all areas miserably.
    As yet we do not have your credentials.

    Please Register or Log in to view the hidden image!

    Please Register or Log in to view the hidden image!

    Any problem with that?
    Oh, and we certainly have other learned people about: I know who they are and they do to:
    Your stay here should prove interesting....It already has.

    Please Register or Log in to view the hidden image!

     
  13. expletives deleted Registered Senior Member

    Messages:
    410
    Whatever my opinions are, they will be based on more than just vacuous uninformed layman misconceptions of the science involved. You could try to emulate that in future.
    It's open for on-topic discussion of the science not off-topic discussions which you keep intruding every opportunity you get. Your very first post to me was filled with personal opinions and prejudicial gratuitous advice to me about how I should interact with certain other members which seem to be the targets of your personal agenda and off-topic intrusions.
    That's for me to know and your curiosity is prurient; and most likely waiting to latch on something from me which you can use for turning into a personal off-topic insult fest or uninformed blather because you as a layman have not understood what or why.
    Surely there must be (or should be) some kind of filter on this site for forestalling counterproductive intrusions by scientifically misinformed and trolling laymen who, even from their very first post to me, demonstrate they have no interest in science but in their own personal agendas and blatherings against members who are trying to discuss science and not interested in scientifically unprofitable personal byplay.

    If there is no such filter here, then I ask that you take the hint and take your off-topic and personal byplay to those who have more tolerance for such aggravation than I have due to my blood pressure condition. Thanks for your cooperation, paddoboy; maybe put me on ignore if that is all the filtering capability that's available here.
     
    Last edited: Jan 21, 2016
  14. paddoboy Valued Senior Member

    Messages:
    27,543
    • Please do not troll or goad other members, especially when you have been told that your attentions are not welcome.
    Whatever your opinions are, it doesn't matter a rat's arse. Standard cosmology has come a long way and although still much more to be done, are doing OK, without lay people and their rantings on science forums such as this.
    Not in the least...Just informing a newbie that this forum being open to all, has its fair share of cranks and nut balls. You can see how there threads in the main, are moved to alternative sections and/or pseudoscience, and cesspool.
    I could give you a pointer to a couple of really humdingers there if you like?

    Please Register or Log in to view the hidden image!


    But you probably wouldn't like that.
    And what are your credentials? Is that for you to know also? [Sounds like another [the god] that posts nonsense on this forum]
    And yet you continue......I do have two excellent tutorials on this forum though, that was only ever opposed by one pretentious fraud.
    http://www.sciforums.com/threads/black-holes-tutorial-based-on-observations-and-gr.152589/
    and
    http://www.sciforums.com/threads/the-story-of-the-universe-tutorial.152814/
    You may learn something from either or both.
    Just out to help!

    Please Register or Log in to view the hidden image!


    Oh stop it! I'm laughing so hard I have a pain in the gut!

    Please Register or Log in to view the hidden image!

     
  15. expletives deleted Registered Senior Member

    Messages:
    410
    By your condescending tone I gather you are an old hand on the internet forums. Regardless, and with respect, rpenner, you do me an injustice by putting it on me like that. I don't know you and I hope you are not one of those people who prefer personal byplay over science discussion. I cannot see what is wrong in a new member trying to avoid getting caught up with opinionated laymen with personal agendas they made abundantly clear from their very first post to a new member. It was that opinionated layman who immediately and without ceremony tried to insidiously influence and effectively dictate what my opinion and interacting behavior was to be regarding certain members against whom that layman obviously has a personal grudge or whatever it is. Please try to get the facts straight before again presuming to correct me when it is the other party that deserved your correction. Please do not prolong this off-topic issue introduced by the layman in question in his very first post to me, a new member.
     
  16. paddoboy Valued Senior Member

    Messages:
    27,543
    There's so much more to this that meets the eye my friend.
    The first question is asking is all what you say true?
    Time will reveal more I'm sure.

    Please Register or Log in to view the hidden image!

     
  17. expletives deleted Registered Senior Member

    Messages:
    410
    Why keep introducing sinister undertones into straightforward exchanges? You started doing that with your very first post to me, a new member, while me and James R were discussing on-topic science he raised to danshawen. What possible use is your introducing all this personal sinister agendas and insinuations when you could just kindly stop trying to impose your agendas and feuds on a new member who wants not a bar of it? Please leave me out of it. Thanks, paddoboy.
     
  18. paddoboy Valued Senior Member

    Messages:
    27,543
    Here's a couple of papers on the Terrell effect.......
    http://arxiv.org/pdf/physics/0512054.pdf

    GAMOW’S BICYCLE: THE APPEARANCE OF BODIES AT RELATIVISTIC SPEEDS AND APPARENT SUPERLUMINAL VELOCITIES ANDRZEJ NOWOJEWSKI
    Abstract.
    A human creates an image basing on the information delivered by photons that arrived at his retina simultaneously. Due to finite and constant velocity of light these photons left the moving body at different times, since not all points of the body are equidistant. In other words its image represents the body as it was in several different times i.e. it is distorted and does not correspond to its real appearance. The useful experimental arrangement is set and then used to derive the general expression that transforms two-dimensional stationary shapes to their apparent forms, which could be photographed once they are set in motion. It is then used to simulate the so-called Gamow’s bicycle combined out of circles and straight lines. The simulation outlines two important aspects of bike’s motion: apparent distance of two points and apparent velocity which are then discussed thoroughly. It is found that the approaching body is elongated and its apparent speed is greater than its real one (under certain conditions can exceed the speed of light), whereas the receding one is contracted (but not in a matter of Lorentz contraction) with the speed smaller than the real one. Both the apparent length and speed tends to a certain limit when time tends to ±∞. The change of both parameters takes place in the vicinity of the nearest approach to the observer and is more rapid when the velocity greater and the distance is smaller. When the moving vertical rod is seen at right angle, its total apparent length is Lorentz contracted, however its interior is still distorted. At the same conditions apparent velocity of a point equals its real one. Finally it is proven that not only the apparent geometrical shape changes as the body moves but also its color according to Doppler shift.
    :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
    http://arxiv.org/ftp/physics/papers/0106/0106049.pdf
    The "optical" version of the barn-pole problem Eric Baird (eric_baird@compuserve.com) We present diagrams and simple calculations for the apparent (i.e. photographable) length of a moving ruler skimming the observer’s position, under three different classes of model. Special relativity’s predictions in this particular situation are the root-product average of the two more basic first-order predictions generated by simple “propagation timelag" arguments. We find that special relativity can legally predict either a photographable Lorentz contraction or a photographable Lorentz expansion in the "centred" ruler, depending on whether our camera is at the ruler’s “apparent” or “official” centre
    ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
    http://arxiv.org/pdf/physics/0412040.pdf
    Projection of relativistically moving objects on a two-dimensional plane, the ‘train’ paradox and the visibility of the Lorentz contraction∗
    Abstract:
    Although many papers have appeared on the theory of photographing relativistically moving objects, pioneered by the classic work of Penrose and Terrell, three problems remain outstanding. 1. There does not seem to exist a general formula which gives the projection of a relativistically moving object, applicable to any object no matter how complicated, on a two-dimensional plane in conformity with Terrell’s observation. 2. No resolution seems to have been provided for the associated so-called ‘train’ paradox. 3. No analytical demonstration seems to have been offered on how the Lorentz contraction may be actually detected on a photograph. This paper addresses all of these three problems. The analysis does not require any more than trigonometry and elementary differentiation.

    5 Conclusions
    That there is contraction on the right-hand side of the houses (figure 3) and relative elongation on their left-hand sides is clear when referring to figure 5 and is due to the fact that light ‘emitted’ from the houses from different parts must be ‘emitted’ at different times to reach the observation point O simultaneously. We have also seen that all the lines that are parallel to the x ′ -axis remain straight lines in the U-V plane for all β, and this is the content of the resolution of the ‘train’ paradox given in section 3. It is readily checked from (9) and (10), that any lines parallel to the y ′

    All of the above observations and deductions follow from our general formulae obtained, which are easily accessible to students and sufficiently precise to illustrate faithfully the main features of the Terrell effect. The next programme in this fundamental problem of relativity is how to generalize the observation site from a pointlike to a non-pointlike one. This is a formidable problem which will not be attempted here and remains to be tackled.
     
  19. paddoboy Valued Senior Member

    Messages:
    27,543
    You seem very touchy shall we say?
    You seem to see the need to want to cast doubt on relativity on some aspect you presumably had not heard of before?
    Your lengthy replies seem to contradict what you claim in them.
    My first post to you in post 328:
    Hiya expletives deleted, and welcome also.
    I have only contributed a few posts to this thread, but beery's problem as I told him, is that he simply is taking the philosophical issue of BH existence to its extreme and total logical reasoning based on what we know with regards to GR.
    BH's exist: as simple as that, And for anyone to claim they do not, need to come up with a realistic model as to what is causing the conditions observed in spacetime and matter/energy that we observe.
    We had another who calls himself the god, quite egotistical and fully enveloped by self gratuitous opinions of himself and his dreams of rewriting cosmology. That's the first number one point any newcomer should realise....That is not, nor ever will happen. It's the height of stupidity to believe it will. Sadly, he seems to have missed his regular evening rants at this time.

    Please Register or Log in to view the hidden image!


    Standard accepted cosmology today has plenty going for it, particularly with regards to the state of the art probes and equipment they have at their disposal, plus of course the brain matter to interpret that data.
    Still a long way to go but we are doing OK, thanks to Einstein, GR/SR and other aspects of cosmology that has arisen from GR like gravitational lensing.
    I'm sure you'll be in agreement after reviewing all the evidence, reputable links and scientific papers.

    """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
    Why the angst? Really, it appears you are hiding something.What are you hiding?
    Any way back onto cosmology. What don't you accept with today's standard cosmology?
    Why?
    What credentials do you have? after all you know mine.
     
  20. paddoboy Valued Senior Member

    Messages:
    27,543
    But are you not also a lay person?
    Nothing wrong with that anyway, so come out and show you have nothing to hide.
     
  21. expletives deleted Registered Senior Member

    Messages:
    410
    In the body of that first post from you to me, a new member, you tried to drag me into personal agendas of your own making claims about other members and trying to influence and prejudice my opinions about other members based on your own uninformed and likely misconceived opinions as a layman who is not sufficiently critically learned and competent enough to make such judgements about others scientific presentations, alternative or mainstream. I ask you again to stop dragging me into your off-topic personal byplays. Thanks.
    And when I am ready to discuss cosmology or anything else involving the science rather than the byplays, I will do so with whomever I feel is competent and learned enough to know what they're talking about and not just opinions based on lay misunderstandings which is what you seem to offer so far. And please stop insinuating I have any claims or opinions to offer, as what I may or not "accept with today's standard cosmology" is not important to anyone but myself. I am here to learn what others may or not accept and why; which I hope to find out in due course from pertinent discussions by learned and competent members, if they can be left alone to get on with it without people intruding personal byplays that may cause me to miss something important that I may have wanted to know. Is this off-topic episode over now? If so, thanks.
     
  22. paddoboy Valued Senior Member

    Messages:
    27,543
    Ignoring your ranting and usual byplays, what lay misunderstandings are you on about.....
    That GR BH's exist and will be the fore runner theory until someone can explain the observations we see in another model that stands up to scrutiny?
    Or that spacetime is real according to the evidence and as lead by GP-B?
    Or that GR predicts compulsory collapse once the Schwarzchild radius is reached?
    Or that GR is a classical theory?
    Pray tell me, which one is a lay person's interpretation as distinct from a professional interpretation.
    And of course as rpenner has already asked you, [and myself] what are your credentials to question any mainstream cosmology, if you are indeed questioning mainstream cosmology.
    Or are you going to keep remaining silent on that issue?
     
  23. James R Just this guy, you know? Staff Member

    Messages:
    39,397
    expletives deleted:

    There is an "ignore" function which you can use if you wish to make posts from people you'd rather not interact with invisible to you. You should be able to access this from your user settings, under "People you ignore".
     

Share This Page