Irrational Birthday Celebrations

Dave Richeson from Dickenson College has a nice blog at his Division by Zero blog that is good news (of a sort) for anyone born in 1980 (if you live long enough).

"De Morgan was always interested in odd numerical facts and writing in 1864 he noted that he had the distinction of being {x} years old in the year {x^{2}} (He was 43 in 1849). Anyone born in 1980 can claim the same distinction."

If you live to your 45th birthday in that year, you too can say you are x years old in the year x^2. Overcome by curiosity, he searched out and found the last few times this has happened

Here are a few other people who could have made De Morgan’s claim (listed by year of birth). 1892: J.R.R. Tolkein was 44 in 1936 1806: John Stuart Mill was 43 in 1849 1722: Samuel Adams was 42 in 1764 1640: Bernard Lamy, the mathematician, was 41 in 1681 1560: Annibale Carracci, Italian painter was 40 in 1600 1482: Maria of Aragon and Castile, queen of Portugal would have been 39 in the year 1521 (she died in 1517) 1122: Eleanor of Aquitaine was 34 in the year 1156

Dave's list of notables was a little "unimaginative" for a mathematician (sorry Dave) so I would alter his list to : 1892: Stefan Banach was 44 in 1936 1806: Isambard Kingdom Brunel was 43 in 1849 (and amazingly, the Brooklyn Bridge Engineer, John Roebling was also(good year for Engineers?) 1722: Samuel Adams was 42 in 1764 *(OK, I like Adams, and I could not find one mathematician on the St Andrews Math History site who was born in 1722... my closest choice for a math related person would be French astronomer Abbé Jean Chappe d'Auteroche. 1640: Bernard Lamy, the mathematician, was 41 in 1681*** wonderful, especially right before Pi Day...Nice one Dave. 1560: Thomas Harriot (Solving equations by factoring is Still called "Harriot's method by some (me)", 40 in 1600, and he turned a telescope to the stars before Gallileo. 1482: The first printed version of Euclids Elements, printed in Venice, was 39 in the year 1521 1122: Ok, by this time I have developed a new appreciation for the difficulty Dave had coming up with names...You would think some mathematician/scientist/engineer would have been 34 in the year 1156, but they are hard to come up with... Ok, submit your list.. who would be the best "square" for each year. In exchange, I propose that we do not allow people who were integrally blessed to steal all the glory...If you were born anytime after 1936, you can share this property sometime during your 44th year. For instance, in 1910,  if the 302nd day of your 45th year (you would have been 44.83302354.. years old) you qualify.. and if you are too young, in 2011 on the 308th day you turn 44.844... years old, you can join this illustrious group...   alas, my time has passed, but I can say with DeMorgan, that I turned x years old in the year x, it just was an irrational x, but heck, it was an irrational year when it happened. .

The Mathematics of Rivers

Dave Richeson, who writes the Division by Zero blog is an Associate Professor of Mathematics at Dickinson College and also the author of a really good math book, " Euler's Gem: The polyhedron formula and the birth of topology" from Princeton University Press.


He also just introduced me to a word I didn't know, potamology, from the Greek ποταμός, river. The word is the technical name for the study of Rivers. Incredibly, there is some really cool math and statistics involved in the study of rivers. For one thing, they are sort of fractal, or as Dave explained it, " the size of a river cannot be determined by its shape on a map. In particular, if you looked at an aerial snapshot of a meandering river, you would not be able to tell whether it is the Amazon or a small neighborhood stream!"

Dave goes on to relate how a the distance between two meanders in a river are related to its width. If we let the width be w, and lamda be the distance between the beginning and ending of one not-quite-sinusoidal period of the meander, then lamda = 11w.
For stats kids, he also posts a regression plot of the actual ratio between meander length and channel width....stats in action baby.

Go to Dave's site and read the whole thing.... he has cool pictures for examples also, including the one above.