The Science of a Rubens' Tube

Can you think of a time you have “seen sound?" Sound waves are invisible vibrations that travel through the air, but we can see how these vibrations affect other objects.

For example, when music is played loudly next to water, we can observe the vibrations ripple across the surface of the water. Sound waves are longitudinal waves and when they travel through a medium (like water, air, or sand), they also include compressions (high pressure) and rarefactions (low pressure).

In 1905, a German physicist named Heinrich Rubens displayed his flaming tube for his students to observe acoustic standing waves. He pumped his brass tube full of coal gas, waited two minutes, and then ignited the gas that was escaping through 100 2mm holes on top of the tube. Rubens’ students gazed with delight as the little flames flickered each time Rubens struck a tuning fork at the end of the tube.

As sound waves travel from one end of the tube to the other, the pressure changes and affects the height of the flames. Where there is oscillating pressure, less gas will escape, and the flame will be lower. At the points where there is constant pressure, the flames are higher.

Adventure Science Center’s Rubens’ Tube will be debuted at Camp Way Late on Friday, June 9, 2023. Visitors will be able to roast marshmallows over the three-foot-long flaming aluminum tube. Guests will be able to change the shape of the fire by toggling between different frequencies on an iPad.

Which frequency will make the longest wave? Which frequency will make the shortest wave? Learn the answer to these questions and so much more at Camp Way Late!

Heinrich Rubens’ original tube:

• 13ft long (4 meters)
• Brass
• 100 holes
• Coal gas

Adventure Science Center’s tube:

• 3ft long (0.91 meters)
• Aluminum
• 35 holes
• Propane gas

*Image above sourced from Wikipedia