QR Codes

QR code structure

You have probably already encountered a few QR codes. These codes are becoming more and more common, and can be found on business cards, ads, historical buildings, T-shirts, etc. You're meant to scan them using your smartphone. They can contain all sorts of information, the most common being plain text, URLs, and contact information. The information is… [This article contains a demo in which you can create your own QR codes!] read more


Submitted on 25 October 2011

Beware of Silently Assuming Linear Intensity in Astronomical Images

Demo of the effect of screen gamma

This article points out the danger of assuming that astronomical images are encoded using linear intensity. It is meant for the many people that are performing astronomical observations using regular cameras. Not because there’s something wrong with that, but because those cameras are optimized for “normal” photography and video, not for numerical calculations on their images. The illustration below… read more

Submitted on 17 September 2011

What's in a Distance

The distance between two points is a concept that is, in every day use, clear and unambiguous. Mathematically, the normal (every day) distance between two points is called the Euclidean distance, but mathematicians generalize this definition. I show how, and I try to make you think by showing how circles look using some of these alternative definitions… read more

Submitted on 6 July 2011

WheelPhoto Page


Still on the theme of bicycles, this is the front wheel of one, securely locked to an immovable object. The wall is the bank of one of the canals in Amsterdam, The Netherlands. read more

The Harmonic Series

If you would have to guess the value of the infinite sum 1 + 1/2 + 1/3 + 1/4 + 1/5 + …, what would you do? The value of the individual terms clearly goes to zero. But does that mean that the total sum will be finite? Well, it doesn’t. This was already proven by Nicole Oresme in about 1350. The proof is actually… read more

Submitted on 24 May 2011

The Greatest Physics Experiment Ever, Live in Your Browser

LHC dashboard when adjusting beams [image: CERN]

The Large Hadron Collider (LHC) must surely be the greatest physics experiment ever. Remarkably, you can follow the day-to-day operations of this experiment on the web, through the online dashboard. Have a look! The fascinating thing is that such a large machine is needed to study the smallest of things, elementary particles. The LHC is a particle collider that… read more


Submitted on 18 April 2011

Bicycle and DuckPhoto Page

Bicycle and Duck

This old bicycle caught my eye. It was lying in the water at Lake Geneva (Lac Léman), Switzerland. read more

Formulas Ahead!

Showing mathematical formulas on the web is not straightforward, as HTML (Hypertext Markup Language) does not contain built-in commands to typeset mathematics. Although MathML (Mathematical Markup Language) was designed to be an extension of the standard markup language for mathematics, it is not yet supported by all browsers, so it’s not quite ready for prime time! So we are stuck with… read more

Submitted on 6 April 2011

Pinhole Photography

Pinhole photography is arguably the most simple form of photography. Instead of using an actual lens, a simple hole is all that is needed. All rays of light from the scene pass through this hole, forming an inverted image inside of the camera. Pinhole photos are blurry, but this is somewhat compensated by their depth of field being practically unlimited. I use... read more

Submitted on 30 March 2011

Miffed Entrance LightPhoto Page

Miffed Entrance Light

This is the green entrance light of the harbour of Emmeloord, The Netherlands. The harbour, part of the Schokland UNESCO World Heritage site, is actually surrounded by meadows since the draining of the Zuiderzee. read more


Subscribe to TomRoelandts.com RSS