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'Information' in computing vs. physical information

  1. Mar 25, 2015 #1
    Hey everyone. I'm sorry if I'm posting something irrelevant here. I really don't know where to ask this question but this hit me while learning Computing Principles (It's my first day in college).

    I'm one who is interested in physics too. Hence, I got a little confused about the term 'information'.

    I'm just going to get straight to the point.

    Is physical information another term for data ?
  2. jcsd
  3. Mar 25, 2015 #2


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    What is the context in which the term "physical information" is used?
  4. Mar 25, 2015 #3
    Data is a numerical representation of something.
    The 'something' may or may not be physical.
    Data could represent the status of a character in a computer game, or it could be your phone bill,
    or it could be the weight of a bag of onions.
    Only the last case is something which is unarguably physical.

    Data doesn't even have to be numerical, it could be a list of sci fi movies.
    Last edited: Mar 25, 2015
  5. Mar 25, 2015 #4
    Physical information could permanently disappear in a black hole. (Black hole information paradox)
    Leonard Susskind said information is indestructible, in which I assume he meant physical information am I right ?

    But what I have learnt in Computing Principles that information can disappear, but data will not. When I think about it, data will change over time. Like conservation of energy, it will only transform but can never be destroyed. Hence, data is also physical information ?

    Please tell me if what I'm asking is two different fields and is non-related because I suddenly feel so. And I sincerely apologize if my question is ridiculous.

    Well according to what I've learnt in Computing Principles, data is something we perceive through our senses, and can never be moved about.

    It sounds somewhat different from your definition of data.

    Does that mean that data has a subjective definition ?
  6. Mar 25, 2015 #5
    In terms of computing, data is values, symbols, signals and so forth.
    It's meaning is defined within the context of the system which processes it.
    It has this defined meaning regardless of who may be perceiving it and what they think about it.
  7. Mar 26, 2015 #6
    Hey, a few things about information.

    Information represents a reduction a space of possibilities. For instance say I rolled a 8 sided die, and tell you its less than 3. I gave you some information because while before all sides were equally likely in your mind for the outcome (1/8 prob of each), now 1 and 2 both have 1/2 probability, the rest are 0 probability. You can quantify this information via probability. Since the probability the outcome was less than 3 was 1/4, the information gained is log2(4/1) = 2 bits of information. If I instead told you it was even, that would be 1 bit, and if I told you the exact number, that would be 3 bits: 2^3 = 8, the number of sides of the die. If there are 2^n possibilities of what can be in a file, than it takes n bits - log(n/1) to represent a version of that file.

    That's a sketch. For more precise calculations Google Shannon Information Entropy. Information is about changes in that entropy of a probability distribution.

    That's classical information. Classical computers (what we use) destroy classical information all the time, and I understand they release it as heat. Quantum information is a different beast. Recent work shows it can be sent non-locally, without physical methods sending it:
    My understanding is the quantum information exists in a way where if you measure it (thus turning it into classic information) its weird magic properties are lost. You can't send classical information without some mechanism. Also, acts on quantum information are reversible, no information is lost. After you learn about logic gates and do a little matrix math, look up Toffoli gates used to model quantum computers, and see how you can always get the input from the output, in effect reversing every computation. This is impossible with gates like OR/AND.
  8. Mar 26, 2015 #7


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    All definitions are subjective to some degree.

    As to whether data can never be moved about, then how can it reach our senses to be perceived in the first place?

    I don't know exactly what you are being taught in Computing Principles class, but your perception and interpretation of it are fundamentally at odds with the real world.
  9. Mar 26, 2015 #8
    Thank you very much. I will look further into this.

    Ah.. That makes sense. It is perceived in the form of information from what I understood.

    Thank you for your answer. I appreciate it. :)
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