You may not know: Opening a champagne bottle is no different from launching a rocket

Scientists from France and India have employed computer simulation systems to reveal what happens in the first few microseconds when a bottle of champagne is opened. They discovered that during the first thousandth of a second after the cork pops, the gas released forms various shockwave patterns – even reaching supersonic speeds – before the bubbles settle and dissolve into the liquid.

“We have shed light on the surprising and beautiful flow patterns hidden right under our noses every time a champagne bottle is opened,” said Gérard Liger-Belair, co-author of the report from the University of Reims Champagne-Ardenne. “Who could imagine the complex phenomena and aesthetic qualities hidden behind such a common situation that any of us might experience?”

The effervescence of champagne arises from the formation of bubbles on the glass walls of the bottle.

Liger-Belair has studied the physical phenomena of champagne for many years and is the author of the book Uncorked: The Science of Champagne. He has gathered extensive insights into fundamental physics through the process of opening champagne, utilizing techniques such as laser slice imaging, infrared photography, high-speed video recording, mathematical modeling, and other methods.

According to Liger-Belair, the effervescence of champagne originates from the formation of bubbles on the glass walls of the bottle. Once they detach from their nucleation sites, the bubbles grow as they rise to the surface of the liquid, bursting and collapsing. This reaction typically occurs within a few milliseconds, accompanied by the distinctive popping sound produced when the bubbles burst. After the bubbles in the champagne burst, they produce tiny droplets that release aromatic compounds, which are believed to enhance the flavors of the wine.

Additionally, the size of the bubbles plays a crucial role in a glass of champagne. Larger bubbles, with a surface diameter of approximately 1.7 mm, enhance the release of droplets into the air. They also create resonant sounds at specific frequencies depending on their size. Therefore, you can “hear” the distribution of bubble sizes as they rise to the surface in a glass of champagne.

A timeline showing the details of a cork being expelled from a champagne bottle stored at 20 degrees Celsius, captured through high-speed camera.

Champagne is typically made from grapes harvested at the beginning of the season, a time when the fruit has lower sugar content and higher acidity. The grapes are pressed and sealed in containers for fermentation, just like any other type of wine. Carbon dioxide (CO₂) is produced during fermentation, but it is allowed to escape because what is desired at this stage is a base wine. Subsequently, there is a secondary fermentation, during which CO₂ is retained in the bottle, dissolving into the wine.

Creating the right balance is crucial at this point. You need a pressure of about 6 atm and 18 grams of sugar, with just 0.3 grams of yeast. If there is too little, the resulting champagne will be too “young,” while too much will cause the pressure to explode the bottle. The appropriate temperature is also necessary, as this will affect the internal pressure of the bottle. That high-pressure CO₂ will ultimately be released when the cork is popped, releasing a burst of gas mixed with vapor that escapes from the neck of the bottle into the surrounding air.

Previous experiments by Liger-Belair and colleagues used high-speed imaging to demonstrate that shockwaves form when a champagne cork is released. With the current study, “we aim to further describe the surprising phenomenon of gas flow at supersonic speeds that occurs during the opening of a champagne bottle,” said co-author Robert Georges from the University of Rennes 1. The researchers suggest that a typical champagne bottle can be viewed as a miniature laboratory.

Based on these simulations, the research team identified three distinct phases. Initially, when the bottle is first opened, the mixture of gas is partially trapped by the cork, preventing the release from reaching sonic speeds. Once the cork releases, the gas can then escape, moving centripetally and achieving supersonic speeds, creating a series of shockwaves to balance its pressure.

These shockwaves then combine to form patterns known as shock diamonds (also referred to as Mach diamonds, named after Ernst Mach, who first described them). This phenomenon is also commonly observed in rocket exhaust. Eventually, the gas stream will slow down to subsonic speeds as the pressure drops too low to maintain the necessary pressure ratio between the cork and the neck of the bottle.

According to the scientists, this research has implications for a range of applications related to supersonic flow, including ballistic missiles, wind turbines, underwater vehicles, and rocket launch pads.

“The ground beneath the launch pad when a rocket lifts off into the air acts like a champagne cork, where the gas flows that are released will have an impact,” the authors noted. “Similarly, the gas expelled from a gun barrel creates a gas stream at supersonic speeds to the bullet. It can be said that these issues are related to similar physical phenomena and can be addressed using the same approach.”

At the same time, the researcher continues to seek answers as to why bubbles spill from some bottles at the moment the cork is opened, even when they have not been shaken.

“This is an unresolved issue in the sparkling wine industry,” the research group stated.

Therefore, users opening champagne bottles at parties with family or friends need to be cautious to avoid pointing the cork towards areas where people are sitting or towards household items like light bulbs to prevent any unwanted accidents.