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geordief last won the day on August 31 2018

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  1. If the x,y and z lines are replaced with lines of test particles is it possible to add to your visualization by predicting how an identical set up and array would play out in time? And how it would differ from an outcome where there was spatial distortion but no temporal distortion? Or are the spatial and the temporal effects so joined at the hip ** that there is no way to distinguish ,in an observational sense one from the other? **they don't "self interact" like gravitational sources do, do they?
  2. Perhaps relevant, I remember one of my teachers some telling us some 50 years ago that it was not so much important what one knew as to know where to find that information. This was of course at a time when the cutting technology was slide rules (a little before pocket calculators) and ,when he referred to accessing the information I imagined he was describing to process of looking through books and their back ends where the subject matter of their innards were catalogued alphabetically. I think if you have to go through the process of tracking down a piece of information ,then a context comes with the furniture.(although one context might be that you look for what you hope justifies your predisposition)
  3. What I was asking (and I feel I have got the answer =yes) was whether they would be able by taking everything ** into account to effectively place themselves behind the eyes of the observer O (at some stage in the past) and so in theory see the physical processes in her vicinity just as if they themselves were then present. Suppose the observer O was looking at an episode of Only Fools and Horses then I expect A and B by applying the Lorentz transformation to the stream of digits arriving from O to be able to view the episode at their leisure. At first it would be gibberish but after the transformation it would be viewing material . ** ie esp their own motion relative to O whether inertial or accelerated
  4. Yes O is a third frame. What I am asking is whether A and B can calculate correctly what O's spatio-temporal measurement of processes occuring in its vicinity would be. Suppose A is based on Earth and B is based on Jupiter can both know exactly what an observer on Mars is measuring by taking account of the correct Lorentz Transformations? (and in similar locations where relative velocities were relativistic) Yes but that is what I was getting at. (my wording was no doubt loose)
  5. They will agree on the timing as seen from an observer at O though won't they ?
  6. Suppose we have two observers ,A and B (who are in inertial motion wrt one another) that are observing a series of events at a third location(O). I understand that both observers will agree on the timing and nature of events playing out at O. Does that mean that both A and B apply Lorentz transformations in spacetime in order to change their own frame of reference to that of the events they are observing at O ? Do they ,as it were "get into and walk in the shoes" of the third observer at O?
  7. https://www.bbc.com/news/world-us-canada-53129524 “Donald Trump: TikTok users and K-pop fans said to be behind poor Tulsa turnout” They done good ....but I wonder how many willing(and harmful) marks would have actually shown up?
  8. Maybe what I am asking is whether ,when calculating the spacetime curvature at any particular point in spacetime,that point itself is in any sense privileged . Let's take an event where the Moon impacts the Earth That event is visible from more or less anywhere in the Solar System and each of those vantage points will (If I have understood correctly) indeed calculate an identical spacetime curvature in the spacetime region around the impact event. So all observers agree on the spacetime curvature but is the assessment of that curvature done by an observer at the site of the event any different (ie in any sense prefetential) in modality from that carried out by any of the myriad of other potential observers? It seems to me that the "in situ" observer has the simplest task Is it not easier as a matter of practicality to calculate the spacetime curvature in a region adjacent to where you are sitting than in a region that is at a remove (possible extremely so) from where you are? And if that observer has the simplest task does that mean he or she has ,in some sense a privileged frame of reference (even though all frames of references do agree ) ?
  9. Yes ,they would be accelerating but would there be a point in space and time where the two bodies would be judged by an observer there to be then moving towards each other at that speed?** And would the observer at that point be at the origin of the frame of reference used to characterise/quantify the spacetime curvature at that point? If GR is a local theory does it mean that any calculation of spacetime curvature uses the location of that curvature as the origin of the frame of reference for the purposes of any calculation? **the observer in this instance would presumably see both bodies moving towards him or her at c/500 at that point in his or her time.
  10. Let's say we have two massive bodies such as two identical black holes ,each with a radius of 1 light second and separated by a distance of 100 light seconds These bodies are not spinning and approach each other directly with a speed of c/1000 Is it possible with that information to say how the curvature of spacetime at a point midway between the two bodies would be characterized or quantified? Would the frame of reference used to calculate this spacetime curvature be that of the point itself,so that it would lie at the origin of the calculation and the two black holes and their motions would be referred to that point?
  11. Well I think I have heard that a gravitational field interacts with itself.** I also have heard that GR is a theory based on locality ańd that a non local frame of reference does not apply. ** perhaps I was ascribing a physicality to the field itself whereas it is perhaps rather a property of matter?
  12. Sorry, I am not certain what you mean by this. By "inputs" I was referring to the two "separate " gravitational sources and their apparently(in my naivety?) independent contribution to the total field. Now I am wondering whether even the field of a symmetric one body system may be seen as an approximation in the extreme analysis when account is taken of the fact that any quantum effects are ignored because they are at present unknown.
  13. Are there setups where this computational approach is 100% faithfull to the separate inputs? So absolutely nothing is lost by combining the separate fields in this way other than the time and effort involved in the process.... I mean ,we are not talking about approximations,no matter how close provided the scenario is simple enough ,are we? (Happy Lockdown Restriction Easing Day!)
  14. Why not leave the statues in place and give them a new or additional plaque that reflects the present view of the person being commemorated? (eg "Notorious and wealthy Slave owner of the 18th century") I remember as a teenager being accommodated by a French family who took me to see the Arc de Triomphe in Paris where are listed all of Napolean's military victories in battle. Totally naively I looked for Waterloo and it was not there. I asked my hosts "Where is Waterloo?" with a very frosty response. I was later informed of my faux pas in as gentle a way as possible.
  15. An extremely small amount of internet research has given me my answer . The photon can have any frequency and corresponding wavelength I think the frequency and wavelength are inversely related via the value of c.
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