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What is (physical) information?

  1. Feb 7, 2012 #1
    Hello PF!

    (Not sure this is in the right section.)

    I've learned very little about maths/physics in school, but went back to uni last year to do maths. Physics is still a bit of an alien territory, but nevertheless I like exploring it in my own amateur way.
    One of the things that started to bother me is that the word "information" seems to be used in a slightly different way in the context of physics, a way that I am not sure I understand. For example I have seen a documentary which mentioned the holographic principle and the black hole information paradox, and I also started reading essays on the FQXi website with explore the question "is reality digital or analog?".

    I understand information as a representation of a relation or state, encoded in a physical object, which can be "read" by another system that can meaningfully interpret the data and implement it in another physical system.
    Now, this may be a wrong way of looking at this, but in this context the following sentence from the wikipedia entry on the black hole information paradox makes sense to me: " A postulate of quantum mechanics is that complete information about a system is encoded in its wave function, an abstract concept not present in classical physics".
    But this does not explain what is meant by physical information when we don't talk about quantum mechanics (is there such a way?).
    Where and how is it stored? How is it represented in a particle? How is it encoded/decoded?
    The only way I can make sense of this is to think of this information as being stored outside of individual particles themselves, but instead as vibrations in their environments.
    Did I understand something back to front?

    Any pointers to more...uhm "information" will be welcome :)

    Thank you.

  2. jcsd
  3. Feb 7, 2012 #2


    Staff: Mentor

    the information revolution came with Claude Shannon's paper

    wikipedia has a discussion on it:


    basically the Shannon information eqn looks an awful lot like the Thermo eqn for entropy and the leap was made that they are one and the same.

    It was then applied to conditions at the event horizon of a black hole noting that its surface area corresponds to the amount of mass in the BH and could be used to describe the entropy of the BH.

    And from there physicists speculated that maybe we ourselves live in a holographic universe.
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