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  1. Thank you, that looks exactly what I need - I'm...

    Thank you, that looks exactly what I need - I'm reading !!!
  2. I think I do understand that, though I don't see...

    I think I do understand that, though I don't see how that applies in all formulations of the paradox.

    I also have a long string of questions now in mind that I want to get to the bottom of - such...
  3. Thank you for this comprehensive post (Edit :...

    Thank you for this comprehensive post (Edit : replying to post #12 from Janus)

    I am now having a go at setting up some example scenarios for accelerating frames/observers. Some of what you have...
  4. OK, sorry it's taken me a while, but I at last...

    OK, sorry it's taken me a while, but I at last have this straight (I think!). What turned it around for me was to take the end event as the origin of the various frames, rather than trying to find a...
  5. Also occurs to me that the nose and the tail of...

    Also occurs to me that the nose and the tail of the ship are both subject to the same acceleration. A remote observer at the end of a ship's journey in this thought experiment is in free fall with...
  6. That notion is completely new to me - though...

    That notion is completely new to me - though there was a reference to it that I didn't pick up on in an earlier post here ! That could explain a lot of my confusion! But it raises an immediate...
  7. Thanks for your reply! I should explain,...

    Thanks for your reply!



    I should explain, before you lose patience with me, that I am not trying to argue that relativity is wrong, or in any way go against the generally accepted view of it. ...
  8. Thank you for your reply. Your points, and those...

    Thank you for your reply. Your points, and those from AndrewC have raised a number of things for me to think about, and to relate to what I think I already understand. I can only spend limited time...
  9. Thank you for your reply, and the subsequent...

    Thank you for your reply, and the subsequent 'edits'. I'm sorry about the slow response - thinking about this has to be a 'background task' for me!

    I am afraid I am still struggling to understand...
  10. Variation on the 'twin paradox' with no change of frame?

    Consider three points in space A,B,F where F is midway between A and B, all in the same inertial frame. Because A,B,F are in the same frame, their clocks can all be synchronised in advance.

    A race...
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    yes - in order to go around a small closed path,...

    yes - in order to go around a small closed path, the car would have to pass through a full rotation (not necessarily 360 degrees on curved surfaces) in direction of travel (though not in...
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    To keep the car aligned, I think you could simply...

    To keep the car aligned, I think you could simply ensure the front and back wheels remain parallel to and rotating at the same speed as each other at all times. Then as the car moves, the...
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    I am new to this so I hope someone else will jump...

    I am new to this so I hope someone else will jump in if I've got it wrong ... but I think the answer is 'yes you can'.

    I don't think you need to move the wheels up and down though - the car can...
  14. thank you :)

    thank you :)
  15. Thanks! That brings a further question to...

    Thanks!

    That brings a further question to mind - how far above the EH might we be talking about? As I understand one of the interpretations, this would depend on the likelihood that tidal...
  16. Thank you for the swift replies :) I think I...

    Thank you for the swift replies :)

    I think I have a problem in principle (highly likely - I am a rookie at this!). I notice that the wiki link you posted quotes an unfamiliar (to me) metric while...
  17. That is part of my point! From what I have...

    That is part of my point! From what I have read, there seems to be an assumption that in principle, Hawking radiation, if it exists, would be detectable, though we'll have a problem detecting it...
  18. Hawking radiation and graviational redshift ... ?

    If Hawking radiation emanates from infinitesimally outside the event horizon, how could it ever be observed, even in principle, since it is coming from infinitesimally close to a 'surface of infinite...
  19. Seems I've answered my own question! ...

    Seems I've answered my own question!

    Stiffening the support cured the problem. For the last four hours, the pendulum has been neatly tracing out 12 degrees per hour, as expected for this latitude....
  20. Well, modelling this as a horizontal spring and...

    Well, modelling this as a horizontal spring and pendulum system, I came up with a prediction of about 36 minutes. If my derivation and arithmetic are correct, this would imply that the original...
  21. Just realised what should have been obvious! ...

    Just realised what should have been obvious! The estimate so far ignores the restoring force from the bar. I think this would result in a prediction of a shorter cycle-time that it should, and...
  22. Analysing behaviour of a wayward Foucault pendulum

    I am attempting to build a desktop scale Foucault problem, just for the challenge since everything I have read says that this is impossible on such a small scale, especially as a ‘home’ DIY project....
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    I was under the impression that weak...

    I was under the impression that weak gravitational lensing had been used successfully to map the distribution of dark matter in some areas, and to correlate its distribution against that of visible...
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    Hi - you sound like you have a similar background...

    Hi - you sound like you have a similar background to me (retired from an IT career and fascinated by science generally and physics in particular). I'm now studying physics and mathematics formally...
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    Thank you - that paper answers many of my...

    Thank you - that paper answers many of my questions, though I'll have to read it six more times for it all to 'sink in'!

    Do you know if that paper is promoting a specific interpretation of just...
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