The wooden crate arrived via air freight from Geneva. Fifteen bottles of champagne and a simple handwritten note with the words "I concede" and the name of the sender.
A few branches of physics have a curious way of dealing with a class of disputes. People make conjectures that are impossible to test at the time. When strongly held disagreements flare. The tradition, dating back at least to 19th century Cambridge is the gentleman's wager. A statement is made by one of the conjecture holders in writing and witnessed. Often these are of the nature "in ten years such-and-thus will have been found." In this case it was fifteen years and was the sort of thing Paul would be committing the next ten or so years of his life chasing. Paul's hunch was right. In this case the quality of the champaign wasn't specified. I'm told two of the bottles were excellent and the rest average.
There were four of us from the old group and we couldn't let the booty go to waste. We wanted to learn something about the physics of popping the cork and immediately began asking questions. Where does the pressure that pops the cork come from, how strong is it, how fast does the cork fly, what happens in the liquid when the cork comes off, what happens to the gas above the liquid and so on... The only thing we had to make was the mechanical cork popper.
We read what was available - literature on champagne told us about ten grams of carbon dioxide is produced by yeast fermentation in the standard 750ml sized bottle. Outside the bottle it would occupy about six liters, so the pressure inside the bottle was fairly high - nearly 90psi (or over 600 kPa) , or roughly what you have in a bicycle tire. It jus sits in equilibrium waiting...
When the cork is released the pressure gives it a fine sendoff. Our fastest cork cocked in at a shade over 11 meters per second - about 25 miles per hour. Our release mechanism wasn't that good and one high speed photograph showed a hand released cork moving a bit faster. The speed depends on the temperature of the liquid. CO2 is less soluble at high temperatures, so warm champagne will give you a faster cork. This, of course, is offensive to the French, so we tried to stay below 10° C.
There's an immediate drop of pressure in the neck of the bottle with the temperature falling to about -60°C for a few milliseconds. Water and alcohol vapor condense in a short lived cloud that your eye might catch. (We used photography and scattered laser light to get a sense of droplet size)
Inside the liquid a fizz starts as the carbon dioxide comes out of solution. There is some disagreement on how to properly pour the liquid and what kind of glass should be used. These questions and others are addressed by a number of papers that came about a decade after our little investigation. The dynamics of the bubbles near and above the surface of the liquid are very important. Ideally the fizz throws bits of wine into a diffuse cloud that hangs over the surface. People say this greatly enhances the drinking experience. The bottom line is a flute shaped glass does the best job of concentrating the cloud, but high carbon dioxide concentrations are acidic in the nose and mouth. The trick, apparently, is a tulip shaped glass. The trick for pouring is to tilt the glass at an angle and pour down the side. Anything else leads to turbulence that liberates too much carbon dioxide.
Bubbles are historically important in particle physics. You've probably see photographs of particle decays. From the mid 1950s up until about 1970 most of those images really were photographs. A high speed particle would collide with a particle in a target and the collision products would head towards a bubble chamber. These were tanks fulled with a clear liquid (usually liquid hydrogen) under pressure and a dissolved gas (hydrogen in this case). Just before the collision the pressure in the chamber was lowered by quickly pulling a piston out a bit. This sensitized the liquid just before particles from the collision flew through at a fraction of the speed of light. They were long gone when the exposure was made, but they disturbed the liquid enough to form tiny strings of bubbles along their paths. At just the right time a flash went off and three exposures - one for each axis - were made. Timing and lighting were issues and the optics were mind boggling, but miles and miles of special film was exposed in the day. An The results were measured by hand by "girls" (sexism of the day) on digitizing screens and then sent to a computer for pattern recognition. Later computer programs digitized the images directly from the film eliminating a very tedious job. To my knowledge this was the first use of a computer to make sense of an image and possibly the first example of big data. Certainly one of the most exotic types of camera every made and they led to over a dozen Nobel Prizes.
(cork popping image by Niels Noordhoek [CC BY-SA 3.0], from Wikimedia Commons
Comments