## Motherhood and Pi

A few weeks ago I had a conversation with a young graduate about useful and useless information. For him, very strongly in the latter category was absolutely everything in mathematics beyond basic arithmetic, and he particularly resented being taught and having to remember the significance of **π**r^{2 }– something he swore he would never ever have to use in what he called ‘real life’. I didn’t bother pursuing this particular line, but I suspect he would not have been able to tell me the value of **π **– i.e. 3.14159 (as readers of this blog will of course know).

Well, for a moment yesterday I thought that help might have arrived for him, as I read a report that a Republican US Congresswoman, Martha Roby, had introduced a Bill in Congress stipulating that from now on **π **will be a much more memorable and manageable value of 3 precisely. This, she was reported as suggesting, would allow American students to be more mathematically competitive in global terms.

Alas, it wasn’t true, or at least apparently not. The internet has been buzzing with this particular item, and yet it took staffers of the conservative Congresswoman (who incidentally prefers to be described as a ‘Congressman’) a few days to state, on her Facebook page and not exactly prominently, that this was all just a joke at her expense. I was hoping that it might be accurate, and that she might follow up this particular second-guessing of Euclid of Alexandria with other radical re-arrangements of mathematical theorems. Unfortunately we are destined to stay wedded to actual reality. Oh dear.

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**Tags:** π, Martha Roby

March 23, 2011 at 3:00 am

Hi Ferdinand,

Stories about attempts to establish the value of pi by legislation have been doing the rounds for a while, especially about various US States declaring pi = 3. It seems that the grain of truth at the bottom of them relates to a bill that was almost passed in Indiana in 1897. An amateur mathematician called Edwin Goodwin attempted to have his (erroneous, of course) solution to the ancient “Squaring the Circle” problem enshrined in State Law. The bill, which can be read here http://www.agecon.purdue.edu/crd/Localgov/Second%20Level%20pages/Indiana_Pi_Story.htm does not make any explicit reference to the value of pi, but a consequence of Goodwin’s contrivances apparently would have been pi=3.2.

Good luck in Scotland!

Rachel.

March 23, 2011 at 7:50 am

First, I should say that 3.14159 is the 5-decimal place approximation to pi. Pi is an irrational number with a non-repeating decimal expansion that continues ad infinitiem starting with

3.1415926535897932384626433832795028841971693…

In primary school we were taught the rational approximation 22/7, which was useful in the days before calculators.

Second, that Congress woman is not the first to try to impose pi=3. In 1897, Representative T.I. Record of Posen county introduced House Bill #246 in the Indiana House of Representatives to the same effect. Some fundamenatlist Christians like this as there is a passage in the Bible: “And he [Hiram] made a molten sea, ten cubits from the one rim to the other it was round all about, and…a line of thirty cubits did compass it round about….And it was an hand breadth thick….” — First Kings, chapter 7, verses 23 and 26

that suggests that the ratio of the circumference to diameter is three.

Third, re that student -where ignorance is bliss….

Tell that student that he obviously has no need for circular objects in his life

March 23, 2011 at 7:53 am

Apologies to Rachel had not read her post re Indiana.

March 23, 2011 at 8:56 am

For me, Pi is important not simply as a value one can plug into formulae, but as a concept. What it shows is an irrational number that can’t be absolutely quantified and therefore one needs to take an approximation when solving ‘real world’ problems. In otherwords it shows the difference between mathematical expressions that describe something precisely and what we can physically measure. This is the basis of all modern science. Secondly, Pi is one of the first examples where students learn that symbols and letters can stand for numbers. Learning to solve equations with Pi is a first step to dealing with algebra. If you simply set Pi to 3 you lose that.

Pi is often seen as dealing with cirlces, but mathematically it’s found in equations dealing with periodic motion, such as pendulums and waves, be they sound, light, etc. It’s also found as a geometric parameter in various equations of forces – anyone remembering Coulomb’s law that describes the force between electrically charged particles will be aware of a 1/4Pi part that describes the sphere over which the force acts. Pi is also found in equations of quantum mechanics, electronic filters, radar systems, etc etc. The value of Pi is not simply 22/7 but the cornerstone of much of our description of reality.

March 23, 2011 at 9:41 pm

Maybe if this student was told that Pi was a transcendental number that might have made it seem more hip.

The final word I think is Homer Simpson’s response to the great number: “Hmmm, pie…”