Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Past Uncertainty

  1. Apr 7, 2009 #1
    In a current thread the book
    http://www-thphys.physics.ox.ac.uk/p...ney/QBhome.htm [Broken]

    is recommended...
    I skimmed the first chapter and like the explanation and style...I'm printing and reading more carefully now...
    but I already have a "burning" question (perhaps 2 ) maybe someone can address.

    The first sentence of the book is this:

    How do we know that's ALWAYS true??
    (Ever since I found out Einstein discovered time and distance are NOT fixed I'm suspicious of all obvious assumptions...)

    Is the past absolutely certain?? How do we know that??
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Apr 7, 2009 #2

    alxm

    User Avatar
    Science Advisor

    The first sentence of the book is just a lead in to a paragraph which relates your ordinary, every-day perception of life. It's obviously not intended as an absolute statement of some eternal physical truth.

    Being skeptical isn't the same as being excessively literal in your reading.
    Oh, and here's a http://www-thphys.physics.ox.ac.uk/people/JamesBinney/QBhome.htm" [Broken].
     
    Last edited by a moderator: May 4, 2017
  4. Apr 7, 2009 #3
    alxm...thanks, but unhelpful.

    I finally found a brief reference I was seeking: I had hoped, here, to possibly receive some interpretations of Fay Dowker/James Hartle/Murray Gell Mann's "consistent histories formulation" of quantum cosmology, a formulation based on decoherence.......or even better, some more recent work of others or updates....

    Different histories apparently CAN be elicited via different inquiries...The reference dates to a Quantum Gravity conference, Durham England, 1995....and I have not seen anything else since...It's a brief passage in Lee Smolin's THREE ROADS TO QUANTUM GRAVITY, pAGE 43-45, 2001...

    and I also wondered if any subsequent quantum theories have looked forward instead of backward....
     
  5. Apr 7, 2009 #4
    "The future is always uncertain."

    That sentence is obviously false. Assume it were true. Then you would be certain that it is not possible to be certain about the future. However, you would also have to acknowledge that you would find yourself in the same situation later, with absolute certainty (truths are always true). Ergo, you are certain about some situation in the future. This contradicts the assumption that it is impossible to be certain about the future, ergo, it is not the case that it is impossible to be certain about some situations in the future. One can therefore say that the future is sometimes certain.

    Seriously, though, that sentence isn't meant to be technically correct, it's just a little bit of showboating to get your interest up.
     
  6. Apr 7, 2009 #5
    There is a short explanation of consistent histories in Wikipedia at:

    http://en.wikipedia.org/wiki/Consistent_histories

    excerpts:
    Better than nothing, but hardly inspirational!!!! And nothing about the future, so that might imply there is not much theory in that direction ....
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Past Uncertainty
  1. Quantum Past (Replies: 6)

  2. The uncertainty (Replies: 9)

  3. Past Particles (Replies: 1)

Loading...