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

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Smells like Tauon Spirit

Tom Lehrer’s Elements Song is 150 years out of date – the science and the music (The Major General’s Song from Gilbert and Sullivan’s Pirates of Penzance) are both from late 1800s.

So it’s time for an update, to the tune of Nirvana’s Smells Like Teen Spirit. Video coming soon… email me if you want to hear it live!


A memory for elements, I’ll leave that for the elephants
A 4×4 explains it all, matter, forces, light as well.

hydrogen , helium, lithium, they’re all done
Atom, proton, neutron they’re all gone.
Hello boson, hello lepton, Hello quarks in 3 rows-


Drop the table, Mr Lehrer, Standard model it’s much clearer
The colliders smash up atoms, matter’s only quarks and leptons,
like neutrinoes yeah neutrinoes ….

Quarks in threes are nucleons, But you can’t get a quark alone
The quarks in me are downs and ups, electrons, small, can’t break em up,

Quark charge, one third and sometimes two
Baryon three quarks, meson only two
Electrons’re leptons, neutrinos too, and there are two more rows-


There’s an up quark and a down one,
strange and charm quarks, Top and butt quarks.
Tau & muons are fat electrons, and neutrinos come in three rows

Yeah neutrinos, mu neutrinos, tau neutrinos,

Antimatter, it’s no sin,  just flip the charge and quantum spin
A photon’s light, waves of course, & carries electromagnetic force
Magnetic fields’re no magic trick, it’s just a boson swapping quick.
They’re virtual, too short to see. They bind the quarks in me-


Interactions, they’re all bosons, ‘lectromagnets are just photons,
there’s a strong one, it’s a gluon, weak force W and Z bosons.

In Geneva, found a big one, It’s not special, God’s no boson

Higgs boson, a higgs boson, a higgs boson …

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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.

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Would you let me put drugs in your brain?

The amazing Dr Kiara Bruggeman gets all Dr Seuss with her rhyme about her PhD research to develop a bandaid for the brain. Previously she won FameLab people’s choice award with this piece.


Filmed at Health and Medical in the Pub at Smiths Alternative in Canberra. Supported by National Science Week ACT, ANU Medical School, Australian Society for Medical Research.

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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.

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