Exponential Growth

Linear vs. exponential

The term “exponential growth” strongly implies quick growth. However, something that grows exponentially will seem to grow quite slowly at first. In practice, there is a good chance that you won’t notice it at all until it suddenly “pops into view”. Take the adoption of… read more

Submitted on 26 May 2013

How to Record a Lion in a Concert Hall

Promenadikeskus concert hall [image: Helsinki University of Technology]

I’d like to kick off a series of articles on signal processing with the answer to a very practical question: How to find out how a lion sounds in a concert hall. I’ll deal with more theoretical subjects in later articles. Smuggling an actual lion unseen into a concert hall seems unlikely to succeed, and might… read more

Submitted on 12 May 2013

Earth-Moon System Scale Model

Earth-Moon system scale model

It turns out that the balls in two popular sports, basketball and tennis, are almost exactly the right size for an Earth-Moon system scale model. Take a standard NBA basketball, which has a circumference of 29.5 in (74.9 cm). The diameter of the basketball is then 9.39 in (23.85 cm). If we let this ball represent the Earth… read more


Submitted on 20 April 2013

Earth-Moon System to Scale

Sun, Earth, and Moon, all to scale [Sun photo: Thomas Bresson]

The illustration shows the Earth-Moon system to scale, with the same scale used for size and distance. The diameter of the Earth is 12742 km, while the diameter of the Moon is 3475 km. So, to draw the Earth-Moon system to scale on a screen, each… read more


Submitted on 13 April 2013

Astrology For Teh Win!

Symbol for Spaghittarius, one of the twelve astrological signs

I’ve had it with science and plan to convert this site to be completely about astrology. Astrology (as Wikipedia puts it: “Not to be confused with Astronomy.”) is a shortcut to the truth. After all, if the truth is in the stars (“De Trut Is Uit Daar” as we paraphrase the tagline from The X-Files in Dutch), gathering and analyzing data… read more


Submitted on 1 April 2013

Pi Day 2013

Pi using Hama beads

Today is 3/14 in month/day notation, and \(\pi\approx 3.14\). My daughter Noor (8) and I felt like releasing yet another image of \(\pi\) into the world, in addition to all the existing images. We made this using Hama beads. Today is a good occasion… read more

Submitted on 14 March 2013

The Looming Effect


The animation demonstrates the looming effect that you get when something (a motorbike in this case) approaches you at a constant speed. At first nothing seems to happen, but then the bike suddenly jumps into view. A general explanation of this dangerous effect that often causes motorbikes to be missed by other drivers is… read more


Submitted on 4 March 2013

Valentine Tomography


Happy Valentine’s Day! I might not be very romantic, but I had to do something with it. Imaging the heart is an important application of tomography and other techniques in medical imaging. Since hearts are everywhere on Valentine’s Day, let’s scan one. This article builds on… read more

Submitted on 14 February 2013

Skill Bubbles

Skill Bubbles

This colorful bubble chart is a simple way of freshening up your CV by adding the time dimension to your skill list. A simple list has relatively little value, since it doesn’t indicate the importance of each skill. This can be improved by including an estimate of its strength. To do this, you could simply add the number of years of experience, but I propose to go a bit further… read more


Submitted on 1 February 2013

How to Ensure that Visitors Always See Cached Pages in Drupal 7

All the standard caching options of my Drupal 7 site are enabled. I expected those mechanisms to ensure that the access to a cached page would always be quick, both for human visitors and for web spiders like Googlebot. However, for a small site, this is not so. The Drupal caching mechanism does not work as you might expect. For me, there is a clear difference between… read more


Submitted on 21 January 2013


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