In a “Computing Science” column titled “Rumours and Errours,” not quite a year ago, a leading role went to the nondescript number 0.203188. That number emerged from a simulation of how rumors spread through a society; given certain assumptions, 0.203188 is the proportion of the population that never hears the rumor.
A few weeks ago Paul […]

I am the child of a bookkeeper, and I’ve inherited the habit of double-checking receipts and balancing accounts. My friends make fun of me when I carefully note down the dime that I put in a parking meter, but lately I’ve been fretting over even smaller sums—charges that come to less than a penny. It’s […]

Three weeks ago, Duke Helfand of the Los Angeles Times wrote a thoughtful article on high school algebra. A one-semester course in algebra has recently become a requirement for graduation in the Los Angeles unified school district, and many students are having a hard time with it. The Times article tells the story of Gabriela […]

“To those interested in the effective visual communication of quantitative phenomena, William Playfair’s Atlas is like the Bible: an ancient and revered book that is often cited but rarely read.”
—Howard Wainer and Ian Spence
The Commercial and Political Atlas is rarely read simply because it’s rare. Playfair published three versions of the book between 1786 and […]

Casual observers of the mathematical arts might be forgiven for feeling that mathematicians sometimes make rapid progress in the wrong direction.
For example, the concept of a prime number is simple enough to be understood by anyone who knows a little arithmetic. In order to explain the distribution of primes along the number line, however, […]

More on reversible computing.
If all it took to reverse a computation was stepping through a program backwards, there wouldn’t be much to say about the idea. In general, this kind of straightforward reversal doesn’t work. However, I have learned that a computer architecture outlined more than 40 years ago would have allowed such back-and-forth […]

A few weeks ago I reported on two talks about patterns in prime numbers—pairs of primes that lie close together and long sequences of primes in arithmetic progression. Thomas J Engelsma writes to tell me of a closely related undertaking: The search for dense clusters of primes. Although we know that the average density of […]

Still more on reversible and zero-energy computing (see earlier bit-player posts here and here, and the American Scientist column):
M. Maissam Barkeshli of the University of California at Berkeley has a preprint titled “Dissipationless Information Erasure and Landauer’s Principle.” (The paper was first submitted to the arXiv last April, but I missed it then, and noticed […]

This is another loose end from my new column on reversible computing (now available online; also see the earlier bit-player item on swapping).
In the column I mention Henry G. Baker’s idea of reversing Newton’s method for approximating the square root of a number. Undoing the extraction of square roots doesn’t seem like much of a […]

In today’s New York Times (registration required), Gina Kolata writes on rediscoveries and reinventions in the sciences. Her essay is based in part on the experience of Rakesh V. Vohra of Northwestern University, who has discovered that one of his own results has been rediscovered at least 16 times. Kolata also quotes Stephen M. Stigler […]