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Cog·i·ta·tion [kojitey'shun] – noun: Concerted thought or
reflection; meditation; contemplation. Kirt [kert] – proper noun: RF Cafe webmaster.
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Rationalizing Pi
While
torturing myself on the elliptical exercise machine in my basement, I often do mental exercises to help pass time
during the utterly boring, albeit beneficial, endeavor. Often the routine is no more complicated than dividing
elapsed calories by time to get a burn rate, then figuring how much longer it will take until my goal is reached
(usually between 1,200 and 1,800 calories), all without the benefit of paper, pencil, or calculator. Of course by
the time I finally come up with a number, I'm way past the point where the calculations began, so I start over.
That reminds me of the old episode of Beverly Hillbillies where Jethro is showing off his new watch to Uncle Jed.
Jed asks what time it is, and Jethro says, "Well, the big hand is on the 2 and little hand is on the 12 and the
second hand is on the 10, so that makes it uh...., shucks, its not that time anymore." He went through the routine
three or four times with no indication that he would ever stop. Finally, Jed asks him, "What's the pertnear
time?," to which Jethro responds, "It's pernear 2:13." ... but I digress.
During my last session on the cursed machine, for some reason I was contemplating
π. Pi has been an enigma in the realm of mathematics and physics since it was first recognized as being
irrational.
The fact that the ratio of a circle's circumference to its diameter is an inexact number has caused enormous
amounts of consternation for dogged investigators of the aforementioned phenomenon. Pythagoras is believed to have
first noticed the irrationality of certain numerical ratios when even something as basic as the cornertocorner
diagonal of a unit square could not be calculated to a finite precision. In some circles even contemplating such
thoughts caused souls to be burned at the stake for daring to assert that such an imperfection could exist in a
perfectly created world. Recall that Galileo was excommunicated for asserting that the earth was not the center of
the universe. I kid you not.
For anyone not familiar with irrational numbers, they are numbers with nonzero decimal places that do not end
and do not have a repeating sequence. The do not end part is what bothers me about pi. Consider that we normally
measure rotation in radians, and that 2π radians is defined as
one full rotation. If we never had to count more than a single rotation, then stopping at something other than an
inexact number is not so bothersome... although it is actually bothersome since the rotation stops exactly at some
angle even if it cannot be measured in terms of pi. It doesn't asymptotically approach a quarter of a turn at
π/2 radians but never actually stops. It can stop at exactly a quarter turn even if pi itself is inexact.
That just doesn't seem right, does it?
To really make the point, progress thorough a full rotation. At some point the first full rotation is exactly
completed and the next rotation ensues. We routinely equate exactly 2π
radians with 360°, which is a rational number. So, how can an irrational number be exactly equal to a rational
number? The concept seems... irrational.
Mathematically, we are comfortable with taking the limit of a function as its variable approaches some value
asymptotically, and declaring that the result can be rational. An example would be ,
exactly. However, we never speak of a limit when using pi to define angles. 2π
radians is precisely one full rotation, π
radians is exactly half a rotation, as are 360° and 180°, respectively. Do you see the logical conflict?
Therefore, not through application of rigorous mathematical manipulations but through elementary application of
reductio ad absurdum I assert that pi must be rational  or at least it cannot be irrational. Maybe it is
pseudorational or pseudoirrational. Either way, I boldly declare quod erat deomonstrandum (QED). Quando omni
flunkus moritati (Red Green, look it up).
This article is written without doing an Internet search to see whether someone else has cogitated similarly.
Surely someone has. I go out on a limb here publically demonstrating either brilliance or idiocy. If it is the
latter, oh well, I've done it before and I'll consider it further confirmation that I'm irrational. If it is the
former, then feel free to nominate me for the Nobel Prize in mathematics for having proved that pi is rational
after all.
Update: I posted this proposition on
LinkedIn and have received a few comments. It's probably not allowed to copy them here, so I'll just post me
reply to the opinions:
**** Thanks again for the comments. My primary point is that it makes no sense to
equate an irrational value like 2 pi radians to a rational number like 360 degrees, which is what we routinely do.
According to Merriam Webster, a radian is “a unit of plane angular measurement that is equal to the angle at the
center of a circle subtended by an arc equal in length to the radius.” A degree is “a 360th part of the
circumference of a circle.” So, you can rotate exactly 360 degrees to complete exactly one full rotation since a
degree is defined as exactly 1/360th of a rotation, thus closing the circle. Can you also rotate exactly 2 pi
radians and complete exactly one full rotation since a radian is defined by what always works out to be an
imprecise, irrational value? For any arbitrarily minute, exact step size you can increment exactly from 360 –
[step size] degrees to a full circle by adding one [step size] degrees. Can you do the same exact sort of
operation using pi and radians? Using pi and radians means you can only close the circle after reaching the last
digit in pi, which if pi is an irrational number, can never be reached. Is there another set of values, not
related to pi, where we exactly equate a rational number to an irrational number?
8/2/2012
Posted 7/21/2012
