The Hesitation of Light – a concert performance in the historic Spiral Ramp

On the shortest day of the year, when daylight reaches its minimum, experience the hesitation of light interpreted in a musical performance by artists Sonja Strange and Barbara Skovmand.

Until the 1670s, it was widely believed that light travelled instantaneously, at infinite speed. However, when the Italian astronomer Giovanni Cassini and the Danish astronomer Ole Rømer observed irregularities in the orbit of Jupiter’s moon Io, this assumption came into question. Rømer maintained that the variations must be caused by the finite speed of light. He demonstrated that the shifts in the times at which Io disappeared behind Jupiter and re-emerged could be explained by the time light takes to travel through space.

This very transition — from the instantaneous to the delayed, from the constant to the hesitant — is the central theme of the musical work The Hesitation of Light.

An Otherworldly Experience

The work is performed by two artists: Sonja Strange and Barbara Skovmand. In the Round Tower’s iconic Spiral Ramp, they translate this scientific discovery into a physical and acoustic experience.

Visitors can experience Sonja Strange singing as she moves upwards through the tower in a continuous spiral, her melodies responding to the music produced by Barbara Skovmand’s après-Baschet sound sculpture, in which glass rods are rubbed with wet fingers. The vibrations are transmitted to steel plate resonators, which amplify and distort the sound, giving it an almost otherworldly quality. Between voice and resonance, an echo emerges — a delay, a hesitation.

The composition, created by composer Toke Odin, weaves the two sound sources together, allowing space, body and music to express the same idea.

Sound and light gradually fade on the shortest day of the year, as the stillness of the solstice becomes a counterpoint to the movement of light. The work thus brings Round Tower’s LIGHT YEAR 2026 to a close — a year of exhibitions and events marking the 350th anniversary of Ole Rømer’s discovery.

This is an immersive experience rather than a traditional seated concert. The audience should therefore expect to stand in the cool surroundings of the tower’s Spiral Ramp and experience the sun being played down upon the unique sound sculpture.

The performance takes place at 4:30 pm and again at 5:30 pm. There is no need to purchase tickets in advance — simply arrive on the day and pay the standard admission fee.

Admission also includes access to the Round Tower’s permanent exhibition on Ole Rømer and His Great Discovery, as well as the special exhibition Light Echoes. You are also welcome to explore the tower or make your way to the top to enjoy the view across the city.

The performance is part of the LIGHT YEAR 2026 programme at the Round Tower—a full year dedicated to celebrating light and the 350th anniversary of Ole Rømer’s groundbreaking discovery of the speed of light.