Bar room science: What beer can teach us about volcanoes
The physics of tapping a beer bottle sheds light on fundamental science principles
Scientists in Spain have used the principle behind a common bar trick to better understand the physics of volcanic eruptions and the release of deadly gasses from the Earth. It's a wonderful demonstration of seeing basic scientific principles at work in everyday life.
The trick, observed by Javier Rodriguez-Rodriguez, a fluid mechanician at Carlos III University of Madrid, and his colleagues, involved tapping the top of a newly opened bottle of beer with another bottle. It triggers a rapid release of foam. (If you try this, step back from the table; it can make quite a mess ...)
To understand the physics of bubble formation, the scientists conducted controlled experiments in the lab. They discovered that the dissolved carbon dioxide in the beer, which normally comes out of solution in bubbles, is accelerated by shock waves from the tapping.
Beer bubbles are usually somewhat large, but when they are hit by compression waves passing through the liquid, they break into many smaller ones. The larger number of small bubbles increases the surface area of the liquid, making it available for more carbon dioxide to come out of solution.
A sort of bubble chain reaction takes place until a buoyant foam is produced, which quickly rises to the top and out the restricted opening of the bottle's neck. This can often be in the form of a fountain that could end up on the lap of an unsuspecting beer drinker.
Now, it might seem like a waste of expensive scientific equipment and laboratory time (and beer) on such a frivolous bar prank, but understanding the dynamics of gasses trapped in liquids relates to the same processes - on a much larger scale - taking place within the Earth.
Magma welling up from within the Earth's crust can contain a lot of compressed gasses within the molten liquid. When a volcano erupts, those gasses are released, sometimes intensifying the force of the eruption, such as the explosive destruction of Mt. St. Helens or Mt. Vesuvius. Understanding the physics of the gas can explain how shock waves from an earthquake can trigger an eruption.
The next time you pour cream in coffee, take a look at the white swirls spinning across the surface. Those spiral shapes, known as vortices, are found in everything, from hurricanes to the Great Red Spot of Jupiter, and all the way out to the spiral shape of our Milky Way galaxy. They spin off the wingtips of airliners, give tornadoes their shape and even get our waste down a toilet bowl.
Discovering the science of everyday things is one of the most powerful teaching tools for young people, because it puts the scientific principle right in their own hands, using objects they are familiar with. A little baking soda and vinegar can go a long way to explain volcanoes, or the properties of carbon dioxide, which is heavier than air. The clicking sounds of static electricity when taking off a sweater, along with the flashes of light if you do it in the dark, are a great introduction to the principles of lightning.
Science is more than people in white coats working in laboratories; it's all around us. And we need to see it in action in our everyday lives because it affects just about everything we do.
If we are to make intelligent decisions about the future of energy, the protection of the environment, or whether we should go to Mars, we need to understand the basics. And a good place to start learning about them could be right in the palm of your hand.