The Physics of Beer

It’s a common pub prank to tap the top of a friend’s beer, to make it suddenly erupt in froth. Funny to some people, annoying to others; but to Spanish physicist Javier Rodríguez-Rodríguez, intriguing.

Rodríguez-Rodríguez, from the University Carlos III of Madrid, decided to investigate the strange phenomenon, and in the process has discovered a host of complex physics in a glass of beer, which could help scientists understand all kinds of processes, from volcanic eruptions to the formation of asteroids.

“There are many different physical phenomena going on in a beer glass, and every time you drink a beer, all this physics is right before your eyes,” Rodríguez-Rodríguez says.

His thirst for knowledge has even led him to convince his PhD students to drop beer off a 100-metre high tower to study bubble formation in the micro-gravity environment of free-fall.

“Carbonated beverages are portable laboratories that can be used to demonstrate in an amusing way the working of many flows also found in nature and industry,” he and co-author Robert Zenit write in a review of the beer facts they have discovered, published in the magazine Physics Today.

The key to many of the processes in beer is that it is carbonated – a colloquial term for it being a super-saturated carbon dioxide solution. As the beer brews, fermentation by yeast emits micro-farts of carbon dioxide, building up pressure in the bottle.

Some of the carbon dioxide gas dissolves into the beer: the fraction is determined by Henry’s law, which holds that the higher the pressure, the more gas is dissolved.

When the bottle is opened, the pressure is released, meaning that amount of gas the liquid can hold is lower: suddenly the solution is super-saturated. But it takes a while for the solution to catch up. Over a few hours the carbon dioxide seeps out until it reaches its new equilibrium point, termed by beer lovers as “flat”.

The rate at which the gas departs, and the dynamics it sets off, forms the basis for much of beer’s intriguing behaviour – such as in the beer-tapping prank.

Rodríguez-Rodríguez’s study of it was first published in the journal Physical Review Letters and revealed that the trigger for the beer volcano is a pressure wave sweeping upward through the liquid.

The sudden jolt leaves the beer behind momentarily. At the sides of the bottle, the effect is minimal as the glass slides past the beer.

However, the downward shift of the base of the bottle has much greater ramifications, and creates a sudden drop in pressure in the liquid at the bottom. This low-pressure region propagates upward, triggering the dissolved carbon dioxide in the beer to suddenly form bubbles.

The beer then catches up with the bottle and the pressure rebounds. This sudden high pressure fragments the bubbles that have only just formed. Rodríguez-Rodríguez found each one breaks into as many as a million smaller bubbles.

These, now in a cloud formation, begin to rise, growing as they suck in more carbon dioxide. It takes a second or two before they reach the top and froth up.

The rise of the cloud is due to the buoyancy of the bubbles, which set Rodríguez-Rodríguez and his team thinking about what would happen in zero gravity.

Rather than sending beer into space, they decided to drop some off the 100-metre high drop tower of the Centre of Applied Space Technology and Microgravity (ZARM) in Bremen, Germany.

For the actual experiment they had to find a substitute liquid. “We cannot use beer,” says Rodríguez-Rodríguez. “It’s too dirty.”

Using carbonated water, the team could observe the evolution of the bubble cloud as it hovered within the liquid, capturing high-speed video of the process.

As well as being of relevance to the formation of bodies such as asteroids and meteorites in low gravity environments, Rodríguez-Rodríguez’s research addresses the potentially important issue of astronauts drinking beer.

The buoyancy of the bubbles is what enables the gas from the carbonated drink to rise from the stomach and be expelled, but Rodríguez-Rodríguez points out that in zero gravity, they would not be buoyant.

“The bubbles would not be able to escape the liquid within the digestive system, leading to painful bloating in the stomach and intestines. So, sorry, no bubbly drinks for space people!” he and Zenit write in their review article.

Rodríguez-Rodríguez admits to enjoying drinking his experimental apparatus sometimes, but is careful to point out he is not doing so with government research funds. He says the guidelines for research preclude expenditure on alcohol, so he buys all beer for experiments from his own money.

“I consider it the Rodríguez-Rodríguez Foundation for the Advancement of Science,” he adds.

Results from the microgravity experiments are in preparation, and will be submitted to a journal soon.

Original published 29/5/19

Continue Reading The Physics of Beer

The hard questions

The easy part’s the answer

The resolution to the cadence, the final pose of the dancer

The hard work’s dynamic tension

build the elegant clash, the clarity in a question


World shaking shift of continental drift

Earthquaking violence from a pace so placid

The twist in dioxy-ribonucleic acid


Einstein astride a soaring light beam

Nothing’s as absolute as it seemed

The revelation comes at the speed of light

A universe of relative wrongs and rights

No more can you trust the rules you revere

Time stops, space shrinks as it all becomes clear.


by Phil Dooley, written for The Poet’s Guide to Science play.

First performed at Smiths Alternative in Canberra, August 24, 2018, as part of National Science Week.

Continue Reading The hard questions

Bubbles! The Physics of Champagne

Phil plus bubbles
Bubbles – the physics is surprisingly complex.

Original published in Cosmos Magazine, 6 November 2018. This has attracted media attention – check my Phil Up On Science Live page for radio interview times.

Opening a bottle of champagne not only signifies the start of a celebration, but also uncorks a swathe of sophisticated physics phenomena that contribute to the special appeal of bubbly.

Just as the pop of a cork marks a change in mood, it also marks a sudden change for the champagne. Pressure that has been building for months during the fermentation process is quickly released and suddenly things are out of equilibrium. What makes champagne fun are the dynamic processes that bring the system back into balance – pops, bubbles and fizz.

But where did the pressure come from in the first place? The answer is micro-farts. The yeast introduced by the winemaker feeds on sugar in the wine, using its energy to power its life, and then ejects its waste: carbon dioxide.

In each bottle of sparkling wine, yeast microbes produce more than 10 grams of this gas. That equates, in the confines of the sealed bottle, to a pressure about three times that found inside a car tyre. Under these conditions most of the carbon dioxide dissolves in the wine.

As the cork is loosened the pressure of the gas in the bottle pushes it out. Cork speeds can reach more than 50 kilometres per hour, says Gérard Liger-Belair from University of Reims Champagne-Ardenne in France.

Liger-Belair has made a career of studying the physics of bubbly; for him a glass of champagne is “a fantastic playground”, although he insists he does not drink his experimental samples.

Instead, he enjoys a glass of champagne with laser tomography, infrared imaging, high-speed cameras and mathematical models.

His measurements show the speed of the cork depends on the temperature of the wine. The carbon dioxide is much less soluble at higher temperatures, which leads to a higher pressure inside the bottle and thus a faster launch speed.

At the perfect drinking temperature of eight to 10 degrees Celsius the corks pops out at around 40 kilometres per hour. His experiments extend only to 20 degrees Celsius, at which the speed is in the low fifties. Presumably, champagne warmer than that is inconceivable in France.

In the moments after the it pops, fleeting wisps of fog appear – another dynamic phenomenon. The sudden five-fold drop in the pressure of the gas in the neck of the bottle causes a temperature decrease of around 80 degrees Celsius. As it momentarily dips below minus-70, traces of water and alcohol in the gas condense into an evanescent mist that quickly evaporates as the gas approaches room temperature.

Next the fizz begins, as the carbon dioxide dissolved in the wine starts to escape. If one were to let the contents of the bottle go absolutely flat, it would take more than 10 hours and involve the release of more than six litres of gas.

A bad pour can let the fizz out too quickly, says Liger-Belair. He recommends a gentle stream into a tilted glass to preserve bubbles. Pouring into the middle of a vertical flute will stir up the wine and release too much carbon dioxide immediately.

Even with such precautions, there is an initial rush of bubbles. University of Tokyo physicist Hiroshi Watanabe was part of a team that used supercomputers to model how quickly bubbles of different sizes form in liquids, and how the different sizes interact.

“After many bubbles appear at the moment of uncorking a champagne [bottle], the population of bubbles starts to decrease,” Watanabe said in an interview with

“Larger bubbles become larger by eating smaller bubbles, and finally only one bubble will survive.”

Bubbles are a vital part of the taste of champagne, say researchers from the Sorbonne University in Paris, France. As they burst, they throw droplets of wine into the air above the surface and enhance the drinking experience.

The scientists identified two mechanisms that produce droplets. First, as the surface of the bubble ruptures, it throws up dollops 50 times smaller than the radius of a hair. Then as the rounded bubble shape collapses, it sends up a jet of up to 10 slightly larger droplets.

“The tiny droplets ejected during bursting are crucial for champagne tasting as their evaporation highly contribute to the diffusion of wine aroma in air,” said Elisabeth Ghabache and her colleagues in a paper in the journal Physics of Fluids.

There’s been much debate about how champagne should be served. Some insist on a narrow flute, while others prefer a wide coupe.

Liger-Belair does not recommend the coupe, despite its claim to fame as being modelled on the left breast of French queen Marie Antoinette (or Napoleon’s wife Josephine, or model Kate Moss).

His gas chromatography and infrared images showed that flutes funnelled the aroma-carrying carbon dioxide more effectively into the headspace above the glass where the drinker can inhale it. But carbon dioxide’s acidic nature is actually an irritant if the concentration is too high, so Liger-Belair recommends the middle ground, a tulip shaped wine glass.

Exactly how the flavours interact with the nose and taste buds is a very individual thing. So the scientific thing to do – even if you don’t have infrared cameras and a gas chromatography set up – is to emulate Liger-Belair at your next celebration and perform your own experiments, one glass at a time.

Continue Reading Bubbles! The Physics of Champagne

Quantum pancake reveals clues to better electronics

First published on Cosmos Magazine site, 25/9/18

An experiment with a cloud of ultracold atoms squashed into a quantum pancake has revealed never-before seen quantum effects that could lead to more efficient electronics, including high temperature superconductors.

A team at Swinburne University in Australia observed a quantum anomaly in lithium-6 gas cooled to a few billionths of a degree above absolute zero and squashed between two laser beams.

“We’re seeing quantum mechanics that’s visible on a macroscopic scale – a large collection of tens of thousands of atoms all behaving quantum mechanically,” says project leader Chris Vale, a researcher at Swinburne’s Centre of Excellence in Future Low-Energy Electronics Technologies.

The team’s work is published in the journal Physical Review Letters, concurrently with that of a team from Heidelberg in Germany which reported similar results.

The Australian team used laser beams focused into a flat plane to create a pancake of lithium-6 gas with a radius of 200 microns and the thickness of a single atom – around 500 nanometers. Then the researchers compressed the gas slightly with a magnetic field, to set it vibrating. Shining another laser from below, they measured the vibration frequency of the gas cloud by watching the shadow of the cloud on a camera.

The frequency of this radial vibration, known as a breathing mode, gave the telltale sign of a quantum anomaly: it vibrated 2.5% faster than the classical model predicted.

Symmetry in the classical model dictates that gas properties such as pressure and density should scale in a straightforward way as the size of the gas cloud oscillates. But the full quantum analysis predicts a higher frequency: the classical theory breaks down because of strong interactions between the gas particles.

To further test the model, the scientists jammed more atoms between the laser beams, and turned the pancake from a two-dimensional crepe into a fatter flapjack. Its three-dimensional nature conformed to the classical model.

Vale says the interactions between the gas particles in the quantum crepe was mid-way between two well-known states of matter: Bose-Einstein condensates, in which atoms in a gas interact strongly and exhibit uniform quantum behaviour, and low temperature superconductivity, in which electrons in a material form weakly-bound pairs known as Cooper pairs that can carry electricity through a material with no energy loss.

“There’s a continuous crossover between these two limits, what happens in the middle is not well understood,” he says

“There’s a lot of interesting physics there. For example, this is where we find the highest superfluid transition temperatures, in the intermediate zone where the binding energy of the fermion pairs is similar to the natural energy scale for the system, the Fermi energy.”

By studying a two-dimensional system, Vale hopes to spark developments of new materials for the electronics industry, for example topological insulators or high-temperature superconductors.

In the current highest-temperature superconductors, ceramics based on copper oxide, the superconducting current is carried in two-dimensional layers within the material – although exactly how the electrons pair up is not fully understood.

The power of the experiments at Swinburne is their simplicity, says Vale – the microscopic properties of the lithium atoms and their interactions are precisely known, which is not always possible in more complex materials such as solids.

“In a sense, our cold atoms are acting as a quantum simulator, where we can test models of many-body physics with precisely known inputs that can be difficult to pin down in other materials,” he says.

Continue Reading Quantum pancake reveals clues to better electronics

Wave of the Century

Originally published in ANU Reporter:

The discovery of gravitational waves is the culmination of a search by a generation of ANU physicists, reports DR PHIL DOOLEY, BSc (Hons) ’90, PhD ’99.

An excited hush fell over the briefing room at Parliament House as Professor David McClelland stepped up to the microphone.

“I’m pretty sure you all know by now but I want to say it. We’ve done it,” he said as his voice quavered.

Spontaneous applause broke out, as McClelland allowed himself a smile. Camera flashes popped and TV cameras zoomed in.

“We detected a wave that was generated 1.3 billion years ago when two black holes crashed into each another… the most violent event ever witnessed.”

The announcement was sweet reward for McClelland, an ANU laser physicist who has spent his career working towards this moment.

Albert Einstein predicted the existence of gravitational waves but thought they were too small for humans to ever detect.

To prove Einstein wrong and right in a single stroke is rare treat for a scientist.

“This is a moment that will be remembered for a thousand years,” McClelland said.

Gravitational waves are vibrations of space and time themselves, one of the most outlandish predictions of Einstein’s 1916 General Theory of Relativity. Yet, they appeared exactly as predicted and join the long list of successes of Einstein’s theory over the last century.

The first success of Relativity came three years after Einstein’s publication, when a solar eclipse allowed astronomers to pick out the tiny deflection of distant starlight by the sun’s gravity.

Continue Reading Wave of the Century

Space technology for a world of problems

The benefits of satellites are far-reaching and versatile. They can improve productivity on farms, locate people stranded in disaster zones, and even track sports performance.

Naohiko Kohtake’s research area of space once seemed among the least practical realms. But his work solves real-world problems for everyday people working on the land, looking for safety, or scoring their next try.

Kohtake is a system design scientist at Keio University, who thinks big about how satellites can collect, analyze, and even send out data. “The key is a holistic view,” says Kohtake, who is also an adjunct associate professor at the School of Engineering, Asian Institute of Technology. “Many people focus on specific areas, but we focus on optimization, system thinking, and modeling to design a sophisticated, merged system.”

A striking example of this is Kohtake’s disaster management systems. He has used location data collected from mobile phones and taxi GPS to analyze how people behave during disasters across Asia, such as the 2011 Tohoku earthquake and resulting tsunami. “Data is useful for finding social issues,” he says. “We can understand the program underneath — the human mind.”

While developing these systems, Kohtake realized that satellites could also help with communication in the confusion of a natural catastrophe. “After a disaster it is difficult to maintain contact and communicate messages to people,” he says.

Taking advantage of the fact that Japanese navigation satellites can broadcast messages directly to the GPS receiver built into mobile phones, Kohtake and students designed an app to get location information about designated meeting points or safe routes to people in disaster zones. Already, the system has been successfully trialed for bushfires in Australia and for tsunami warnings in several Asian countries.

This example, like many of Kohtake’s diverse research areas, grew out of his passion to broaden the uses of satellite data.

“Nearly every university has a program on how to build rockets and satellites, but few have courses on how to use satellite technology,” he says. To address this, Kohtake leads the Geospatial and Space Technology Consortium for Innovative Social Services (GESTISS), a collaboration set up in 2012 between several universities in Asia, including Keio University’s Graduate School of System Design and Management. Every year, GESTISS organizes tutorials, seminars and summer camps for 100 students across Asia and inspires them to think about how to employ satellites for social good.

Kohtake’s GESTISS students, in collaboration with Malaysian researchers, traveled to palm plantations in Malaysia, where they revolutionized the labor-intensive planting practices. Using satellite and drone data to create three-dimensional maps, they developed an app that enables a single person to calculate the optimal planting position — far more efficient than the traditional team method using long wires.

A team of students trained by Naohiko Kohtake have used satellite and drone data to improve the productivity of palm farmers in Malaysia.

 A team of students trained by Naohiko Kohtake have used satellite and drone data to improve the productivity of palm farmers in Malaysia.

© Naohiko Kohtake, Keio University

As well as rural settings, Kohtake is working in the most densely populated areas of the world. The obstacle of tall buildings can cause errors in navigation systems of several meters, which could lead to disaster for driverless cars. Kohtake’s solution is to develop a navigation app that uses data from multiple satellite networks — the Japanese Quasi-Zenith Satellite System, the Chinese BeiDou and the United States Global Positioning System (GPS) — and is accurate to within a meter.

Kohtake’s positioning system is so precise that he is now using it to benefit his favorite pastime, rugby. Each player is equipped with a small tracking device, enabling them to download a record of their every movement on the field, to analyze and improve their performance.

Wearable sensor technology (black vests) can be used to track a player's movement on the field.

Wearable sensor technology (black vests) can be used to track a player’s movement on the field.

© Keio University Rugby Football Club

This revolution in sport science, believes Kohtake, who is an adviser at the Japan Sport Council, will also give professionals a career path when they retire from sport.

“Top athletes interested in their performance data develop analytical skills, which are good not only for sport but also can help them move to other domains.”


  1. Choy, S. et al. Application of satellite navigation system for emergency warning and alerting. Computers, Environment and Urban Systems. 58, 12–18 (2016). | article
  2. Okami, S. & Kohtake, N. Fine-scale mapping by spatial risk distribution modeling for regional malaria endemicity and its implications under the low-to-moderate transmission setting in western Cambodia. 11, PLOS ONE e0158737 (2016). | article
Continue Reading Space technology for a world of problems

A new spin on data storage

Seems physicists are inventing particles faster’n I can write about em. Who ever knew you could call a twisted magnetic field a particle?

First published here:, 8 May 2017.

Magnetic field patterns in two types of skyrmions (Wikimedia)

Study into spirals of magnetic spin showcases potential of layered materials for future data storage

Tiny spirals of magnetism called skyrmions could be used as ultrahigh density energy-efficient data carriers.

Jarvis Loh, Gan Chee Kwan and Khoo Khoong Hong from the A*STAR Institute of High Performance Computing have modeled these minute spin spirals in nanoscopic crystal layers. They found that alternating layers of manganese silicide (MnSi) and cobalt silicide (CoSi) forms a promising material architecture.

“Skyrmions are nanosized entities, only tens of nanometers, so they hold the promise of higher storage density than the current technology,” said Gan.

Storage based on skyrmions would represent binary data such as ‘1’s and ‘0’s as clockwise and anticlockwise spin spirals, respectively. Skyrmions can improve energy efficiency as they can be created and manipulated with currents significantly smaller than those required for conventional magnetic hard disk technology.

Skyrmions had been experimentally observed in manganese silicide, prompting the team to explore simulations of manganese silicide in its pristine form and in combination with similar materials.

The team selected cobalt silicide because cobalt sits close to manganese in the periodic table, and its similar lattice characteristics mean it should combine well with manganese silicide. Cobalt also has strong magnetic properties — it is ferromagnetic.

The team’s simulations showed that coupling cobalt silicide to manganese silicide enables the spin spirals in manganese silicide to be engineered. “What’s interesting is that we can now vary the size of skyrmions in an easy and elegant way,” Loh said.

In the skyrmion’s center the magnetic spin of the atoms is flipped 180 degrees relative to the spin on its outside edge; between the edge and the center the spins progressively tilt between the two extremes. Critical in the size of skyrmions is the ability of the material to support high relative tilt between neighboring atoms in the lattice, which enables the skyrmion to be packed into a smaller spiral.

The team found that adding cobalt silicide layers to the manganese silicide layers increased the possible relative tilt. However there is an upper limit — for cobalt silicide layers double the thickness of the manganese silicide, the material ceased to support skyrmions and transitioned to a more conventional ferromagnetic behavior.

One of the attractions of skyrmions as a data storage medium is their robustness, says Loh. “Unlike current magnetic storage, skyrmions are resistant to defects in the lattice. They are topologically protected.”

The team plans to apply their successful approach to other potential architectures, such as nanowires.

The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing.


  1. Loh, G. C., Khoo, K. H. & Gan, C. K. Helimagnetic order in bulk MnSi and CoSi/MnSi superlattices Journal of Magnetism and Magnetic Materials 421, 31–38 (2017). | Article
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