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How Long is a Piece of String?

The famous question "How long is a piece of string?" is traditionally regarded as rhetorical rather than seeking an answer. It's a question often asked to parallel the unanswerability of another question. For example:

First person: "However long are they going to take to get all this sorted out?"

Second person: "How long's a piece of string?!"

...which means, in effect, "the question is about as answerable as a question about the precise length of pieces of string in general".

It's interesting, because the length of any specific piece of string is directly measurable, whereas in the general case it's indeterminate because of the wide range of non-standard lengths of pieces of string.

This (generality) is a crucial feature of the question "How long is a piece of string?". If it were an enquiry about the specific length of a definite section of twine, then it would be readily answerable. The distance between one end of a string and the other is clearly measurable. The cord has a definite length. However, it's the generality of the question that gives it a subtle mystique.

I am often asked questions of an unusual nature, and I pride myself on my ability to answer and to explain things in ways which people can understand. If I hear someone happen to say in conversation "how high's the moon?", I am tempted to comment that it's about a quarter of a million miles. But occasionally I have heard "How long's a piece of string?", and before noticing the question is rhetorical I am ready to give a brave attempt at answering the question!

Although it may seem initially unanswerable, there are some facts which help to solve the question. For a start, a piece of string can't really be less than a quarter of an inch or it's not "a piece of string" but more of a small sample from some string. Similarly, any string longer than about 100ft isn't usually classed as "a piece" of string, as it's more obviously a reel of string. In fact, for any string to be A PIECE of string, it tends to be a typical length. Pieces of string are typically in their second or subsequent use, and have previously been used in some application such as wrapping up a parcel or tying two things together. As a result, the typical piece of string is in the range of 1ft to 8ft, and if you were going to place a gambling spread-bet of some type, you'd be best to go for a string length of about 3ft 6in or thereabouts.

In a more mathematically factual answer, I'd say that the length of a piece of string has a spread distribution of probability of a continuous function with a graph... well I could imagine the type of thing, with string length along the X axis and likeliness along the Y axis, and a curve which starts low and builds up and then levels off gradually. If someone was so inclined they could put out a request for pieces of string and then measure them and plot the results, which would give a graph somewhat similar to the type of thing I can guess.

It's not easy to express such an answer to the question "how long is a piece of string" as a direct word-based answer, but a good approximation would be: "the length of a piece of string is usually about 4ft +/- 3ft".

Of course it's not a perfect answer, and the distribution would have a characteristic which is spread differentially either side of the most likely length. This type of thing is not as uncommon as you might think, for example electronic components are specified as their nominal value +/- 10% or 20%, and colloquial terms such as "faster than a speeding bullet" have an element of expressiveness which often convey more than the statistical figure.

Anyone care for a thesis? 1. Collect random pieces of string in a university string donations box. 2. produce a statistical survey. 3. profit? (there's a link in it for you, at least. write in)

Meanwhile, question answering here goes quite well. Questions such as how logarithms work, what's the density of mercury, how do you hypnotise a chicken, and how to save money, are answered here. Although I can't promise to answer everyone's questions individually, if you ask a really good question there's a good chance the question and answer will become a page here! To send in a good question, see good question. Hopefully some of the answers should be of help generally.

Now you've discovered this website, it might be a good idea to put it in your favourites as there are a large number of pages of interest like this!

Incidentally, the Horizon programme "How Long is a Piece of String" was not about the length of "a piece of string" where that string is unknown (the classic form of the question), but was instead about the science of measurement, for the purposes of which a specific piece of string was measured using methods of higher and higher accuracy, which involved explaining all kinds of interesting things to do with the science of measurement, and then to do with quantum physics. Interesting stuff.

The science of measurement is known as Metrology.