Universiteit Leiden

nl en

Opening event wall formulas Snellius and Lorentz

On Thursday 3 November Leiden University will celebrate the official opening of two wall formulas in the city centre. As of now, Snell’s law and the Lorentz force formula shine on two walls in the heart of Leiden. They are part of a project to display at least ten groundbreaking formulas with a Leiden origin.

Wall poems

Pedestrians in Leiden city centre often catch sight of a poem painted in giant letters on a wall. This poetry is mostly written in a foreign language that few Leiden citizens understand. Still, this doesn’t pose a problem. We see the beauty in a verse without exactly knowing what it says. We feel it is art, we read the name and the time in which the poet lived and play the story in our heads.


Physicists Sense Jan van der Molen and Ivo van Vulpen realized that this principle goes just as much for physics formulas. Not everyone understands all mathematical symbols or gets the meaning of the letters, but we do feel the intrinsic beauty of the formula as a whole. A universal law, remaining undiscovered for billions of years, is now embodied in a short, simple line. A complex natural phenomenon, like the refraction of light in a glass of water, lies wonderfully captured in only a few symbols.


Leiden has a particularly grand history in physical discoveries. That is what inspired Van der Molen and Van Vulpen to set up a project together with Stichting Tegenbeeld to paint formulas originating in Leiden on walls in its historic centre. They assembled a collection of over ten groundbreaking formulas, all with a Leiden connection. The first formula was painted last year on Museum Boerhaave: the Einstein field equation.


Now, the second and third wall formulas have also been realized. People can admire the formula for the Lorentz force from Hendrik Lorentz’ old residence on the Hooigracht and Snell’s law of refraction is flaunted further down the same street. On Thursday 3 November we will celebrate the official opening with a festive event in the Kamerlingh Onnes building in Leiden. Everyone is welcome.


Lorentz room (A1.44), Kamerlingh Onnes building, Steenschuur 25, Leiden

15:00     Walk-in (coffee)
15:15      Introduction (Sense Jan v/d Molen & Ivo van Vulpen)
15:20     Snellius (Eric Eliel, LION)
15:30     Lorentz (Carlo Beenakker, Instituut Lorentz)
15:45     Walking tour wall formulas
16:15     Drinks in Eetcafé de Hooykist

The formula for the Lorentz force on the wall of Eetcafé de Hooykist on the Hooigracht. Hendrik Lorentz lived right across the street from here. The formula describes how a charged particle, for example an electron, is deflected in a magnetic field.


Snell’s law on a wall on the Hooigracht. The law describes the refraction of light when it crosses into a different medium. A straw in a glass of water seems to bend because water has a different refractive index compared to air.​
This website uses cookies.  More information.