Reading: Sipser Chapter 3

Your reading assignment for this week (and for PS4) is Sipser’s Chapter 3, The Church-Turing Thesis. This chapter contains what I think is perhaps the most bogus sentence in the entire book. If you can find it, there will be at least a token reward for the first correct answer. Post your guesses and explanations (why you think its bogus) as comments here.

5 comments to Reading: Sipser Chapter 3

  • aml9j

    “A Turning machine can do everything a real computer can do.”

    This is bogus because there are many ways to use a computer outside of performing computations. It has physical applications. For example, a computer can act as a paperweight.

  • Nathan

    “A turing machine can do everything a real computer can do. Things real computers can do: Generate heat, stop a door, provide an adequate habitat for fish”

    –David Evans

  • Kevin Leach

    As mentioned above, the sentence is “A Turing machine can do everything a real computer can do.”

    Don’t forget that a desktop can also make a reasonable footrest, and the monitor can provide a good nightlight.

  • Yes, that’s the sentence I had in mind – well done. No need for more people to post the same sentence, but there are several other bogus, but not quite so bogus, sentences in this chapter. If you identify others, post them here for “consolation prizes”.

  • jcf4r

    This is maybe not a bogus sentence…but slightly misleading and/or unclear. On the same page (first sentence) Sipser states:

    We turn now to a much more powerful model, first proposed by Alan Turing in 1936, called the Turing Machine.

    However, according to my sources (a wikipedia article, quoted word for word):

    The idea came to him in mid-1935 after a question posed by M. H. A. Newman in his lectures — “Was there a definite method, or as Newman put it, a mechanical process which could be applied to a mathematical statement, and which would come up with the answer as to whether it was provable” (Hodges 1983:93). Turing submitted his paper on 31 May 1936 to the London Mathematical Society for its Proceedings (cf Hodges 1983:112), but it was published in early 1937. ”

    And since sources are generally quoted by their publication date, 1937 would be the more “appropriate” year to use.

    Also, at the time he called it an A-Machine (for automatic machine)…and in 1948 in an essay explaining the machine further, he called it the Logical Computing Machine. It wasn’t until the 50s when people began referring to it as a Turing Machine.

    I guess the book isn’t exactly inaccurate…it just ignores a lot of the history that went into developing it.

    The book the wikipedia page sights for this information was:
    Andrew Hodges, Alan Turing: The Enigma, Simon and Schuster, New York. Cf Chapter “The Spirit of Truth” for a history leading to, and a discussion of, his proof.