How a Game of Billiards Solved a Queueing Problem

“Please hold the line, your call is important to us.” It’s a sentence we’re all frustratingly familiar with. Just as familiar as we are with standing in line at the supermarket or post office, with the other queues seeming to move much faster than the one we happen to be in. Thankfully, mathematics can help. Queueing theory studies such situations mathematically, and tries to find solutions that minimise the average customer waiting time while also limiting the average time a queue server remains idle. This double constraint makes the problem a difficult one. An additional source of difficulty is the randomness involved. Customers usually do not arrive at regular intervals, but their arrival times are what is called a stochastic process. Coming up with a general formula that provides a solution for such stochastic problems is generally difficult, and sometimes even impossible. Recently my uncle Arie Hordijk and I studied such a queueing problem, and came up with a solution based on the movements of a ball on a billiard table…

Read the full story on Plus magazine.

Life: It’s Chemistry!

What is life? This question is still much debated in science. After the discovery of the structure of DNA by Watson and Crick in 1953, and the more recent advances in DNA sequencing technology, living organisms have become primarily viewed as being defined by their genes. However, there is more to life than genetics alone. In fact, a more “holistic” view is emerging in which the essence of life is considered to reside in the complex collection of chemical reactions that enable an organism to grow, repair, and reproduce itself. In other words, life as a network of self-sustaining chemical reactions. This alternative view could have important consequences for many areas of science, for example the way we might treat diseases like cancer, search for possible life on other planets or grow artificial donor organs. And now there is mathematical evidence that at least one particular living organism (the well-studied bacterium E. coli) is indeed such a self-sustaining reaction network, thus formally supporting this alternative view of life.

Read the full article on The Naked Scientists.

A Recent Increase in Earth Activity? The Data Provides Little Support.

The internet is buzzing with claims that there has been a significant recent increase in seismic, volcanic, and atmospheric activity on our planet, and there seems to be a specific emphasis on the years 2012 and beyond. Suggested causes for such an increase include global warming having an effect on these earth activities, deliberate geo-engineering, changes in solar activity and/or cosmic radiation, and an as yet unknown or undisclosed disturbance within our solar system. However, a simple analysis of relevant and publicly available data provides surprisingly little support for such claims.  [Last update: 29 Dec 2015]

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Sunset in Santiago

I’m in Santiago, Chile, for two weeks to provide some computing support for a colleague. Unfortunately this city is often covered in a blanket of smog (especially during the summer). As a consequence the Andes mountains, which are pretty much right next to the city, are rarely visible in their full glory. But occasionally the smog lifts, revealing beautiful mountain views, especially during sunset. Here are some impressions (click on any pic for a full-sized view).

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