Water and Flames

Today I went to the open house for the University of Hawaii’s Institute for Astronomy. There were a lot of cool things there, including devices called Ruben’s Tube and Kelvin’s Water Dropper (the same Lord Kelvin who developed the Kelvin scale for temperature). The Ruben’s Tube is a long pipe with many holes along the top of the pipe. It is sealed with a speaker on one end, and tube connected to a propane gas tank on the other end. The speaker creates sound waves, which are longitudinal waves that have high and low pressure areas, within the pipe. The gas provides fuel for a flame, which responds to the low and high pressure areas created by the sound waves. Higher pressure areas have taller flames because more propane gas is escaping through the hole above it, while lower pressure areas have shorter flames because less gas is escaping through the hole above it. The attendant there told me that with a steady pitch and no wind, the flames will create a sinusoidal wave. Kelvin’s Water dropper features a large water reservoir suspended at the top of the device, which releases drops of water down two separate tubes. Before falling into a metal bucket below the reservoir, the water droplets travel through a tube with a conductive metal ring that is connected to the bucket opposite of it. Because of the ions from minerals that are contained in water, one bucket eventually becomes more electrically positive than the other, creating a voltage difference. This creates a visible spark between metal spheres attached to each bucket. As I walked around looking at other exhibits I noticed that many aspects of astronomy relies on physics as well as chemistry. And I here I thought astronomy was just looking at stars!