Wolv1's questions about causality and particles

Discussion in 'Physics & Math' started by Wolv1, Aug 25, 2008.

  1. AlphaNumeric Fully ionized Registered Senior Member

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    I think there needs to be a little bit of clarification here.

    In GR, the concept of closed time-like curves is not investigated so people can built a Time Cop machine or for Einstein to go back and kill Hitler, ala 'Red Alert', but because CTC can play a critical role in things like the big bang, the overall properties of the universe and the centres of black holes. For instance, 'Can the universe create itself'. Through the use of CTC, you can construct consistent, self generating universes. Similar things happen when you start talking about paths through the middle of rotating black holes, due to weird properties of the metric near the centre of a ring singularity.

    Considerable amounts of space are devoted to CTC research and discussions in books by Wald, Gibbons and particularly Hawking and Penrose. They are the 'extremal' things in GR, the ones with all the weird and wonderful properties, which (as usual) are also mind bendingly complicated to analyse.

    So I don't think it's correct to call them 'fringe science', because they play a very deep role in relativity. It's just that the depth at which they appear is far beyond what 99.999% of people who even do physics degrees will ever touch upon. You don't need to know about CTC to build the GPS network, but if you're addressing things like 'What would a black hole in CERN appear like?' then CTCs are something you need to really be familiar with.
     
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  3. Stryder Keeper of "good" ideas. Valued Senior Member

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    Just to Clarify I'm not calling CTC's "Fringe", I'm calling the usual topics that escalate in regards to Time Travel fringe (e.g. How to make a time machine in 10 easy steps.). It was Guest254 that seemed to think I was implying that CTC's were "Fringe".
     
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  5. Guest254 Valued Senior Member

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    Closed timelike curves are the general relativity way of saying "time travel". Someone in this very thread asked about them before you moved the thread with the comment:

    Currently any "Theories" in regards to Time Travel are classed as Fringe Science

    You quite clearly state that any theory that involves time-travel is fringe science. This is completely false, as has now been explained to you several times.
     
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  7. Ophiolite Valued Senior Member

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    And i offered this quote of Matt Visser 'for all practical purposes the phrases time machine and closed time-like curve may be used interchangeably.' from Chapter 8, in The Future of Theoretical Physics, a compendium of lectures by leading physicists to mark Hawking's 60th birthday.

    It is up to the admin/mods what goes into the pseudoscience thread, but in my book there is no debate. pseudoscience employs the trappings of science, without the substance. The conept of time travel has been dealt with using sound scientific methodology and it has not been falsified. Therefore it is real science, not pseudoscience.
    If you really want to include fringe topics (and as Guest254 has pointed out time travel is not a fringe topic) then call the sub-forum Strange Ideas, or something like that.
     
  8. Stryder Keeper of "good" ideas. Valued Senior Member

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    I'll tell you what we'll do, this thread has obviously become more of a political stand than actually what the initial OP was referring to. So someone start a Second thread back in the Physics & Maths forum. Just don't blame me if it all goes squew-whiff and ends up here with this thread.
     
  9. Guest254 Valued Senior Member

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    Of course, all this would have been avoided if you'd simply accepted my correction.
     
  10. Myles Registered Senior Member

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    As I've already pointed out, theories require evidence. Where is it ?
     
  11. Ophiolite Valued Senior Member

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    The possibilties of time travel arise out of the equations that describe space-time. These are derived from consideration of relativity theory which has been validated experimentally to many decimal places. That is the evidence.
     
  12. Myles Registered Senior Member

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    Can you provide some referencesplease ?
     
  13. Ophiolite Valued Senior Member

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    I've already given the link to the Hawking memorial book that has a chapter devoted to the subject, including a list of references.

    Go to post 41 in this thread.
     
  14. rpenner Fully Wired Valued Senior Member

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    Thanks. I found the same on arxiv.org in case the Google Books preview expires.

    arxiv.org/abs/gr-qc/0204022
     
  15. Ophiolite Valued Senior Member

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    That's useful. Thank you.
     
  16. (Q) Encephaloid Martini Valued Senior Member

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    Perhaps Oly could explain those equations, and put everyone's skepticism to rest?

    Oly, the floor is yours.
     
  17. Ophiolite Valued Senior Member

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    Please refer to post #41 in this thread, wherein I wrote: Let me point out here that what I know about time travel can be written on a pin head - admitedly by using 0.0003 font.
     
  18. Myles Registered Senior Member

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    I have found nothing but speculation as opposed to evidence. Pseudoscience is the right place for this thread.
     
  19. Guest254 Valued Senior Member

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    It seems there's no telling some people!
     
  20. Ophiolite Valued Senior Member

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    As I have been careful to point out in this thread a couple of times I do not properly understand the maths of relativity. Grasping Lorentz transformations is about as far as I ever get. However, when I read in a variety of sources, over a number of years that time travel appears not to violate any of the equations that we believe explain how aspects of the universe work, when the philosophical objections - which I can understand - are seemingly refuted, and when a distinguished scientists expresses dismay that we haven't been able to rule it out, then I think it is worth taking seriously as a possibility. So, like you, I am bemused that some persons choose to ignore the facts. Discrimantory cicruits oversaturated by the true nuts, perhaps.:shrug:

    Myles, perhaps you would like to tell me why you feel Karl Popper was wrong, or - if you think it is easier - which aspect of time travel fails to meet his definition of a science?
     
  21. Guest254 Valued Senior Member

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    I am lucky enough to work in the academic community, and I can say quite unequivocally that a conversation about "time travel" or "closed timelike curves" in general relativity is certainly not considered fringe science.
     
  22. Myles Registered Senior Member

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    Yesterday I put some ice cubes in a glass. Today they have turned to water, i.e., there has been an increase in entropy in the universe. To reverse this process would violate the laws of thermodynamics.
     
  23. Ophiolite Valued Senior Member

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    1) Today I put water into my freezer. Now I have ice cubes. This did not violate the Second Law, since we are dealing with an open system.
    2) Time travel does not violate any currently known physical laws. Which part of this statement do you not understand. This is not my opinion. It is the view, established through proper methodology, of physicists familiar with the issues.
    3) Please answer my questions re Popper.
     

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