# π

3.
1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679 8214808651 3282306647 0938446095 5058223172 5359408128 4811174502 8410270193 8521105559 6446229489 5493038196 4428810975 6659334461 2847564823 3786783165 2712019091 4564856692 3460348610 4543266482 1339360726 0249141273 7245870066 0631558817 4881520920 9628292540 9171536436 7892590360 0113305305 4882046652 1384146951 9415116094 3305727036 5759591953 0921861173 8193261179 3105118548 0744623799 6274956735 1885752724 8912279381 8301194912 ......

Happy π Day!

# Dijkstra's algorithm

Dijkstra's algorithm for finding the shortest paths in a graph is a classical one that most students of computer science get to learn about, although I suspect few have actually read the original paper. Published in the very first volume of the journal Numerische Mathematik in 1959, an official copy of the three-page paper A Note on Two Problems in Connexion with Graphs is available from SpringerLink, although you would have to be at an academic institution with a subscription or have a personal subscription to SpringerLink to download the paper.

# Blog carnivals

With the elections on November 4th in the United States being over, the special election edition of the Carnival of the Liberals is up at The Lay Scientist. It includes articles that focus on the election, organized by whether an article was written before or after. My punditry as to what went wrong with McCain's presidential campaign is included in the latter category.

In the same vein, the 43rd edition of the Carnival of Mathematics is up at The Number Warrior, which has a preponderance of puzzles this time around. Among them is my explanation of a puzzle of chance presented at the Shores of the Dirac Sea.

# The probability of a probability

The Shores of the Dirac Sea has a somewhat head-scratching puzzle about probabilities:

Let us say that someone gives you a lopsided bet. Say that with probability $r$ one gets heads, and with probability $1-r$ one gets tails, and you have to pick heads or tails. You only know the outcome of the first event. Let's say after the first toss it came out heads. What is the probability that $r > \frac{1}{2}$?