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 https://cosmosmagazine.com/physics/in-lager-veritas-the-physics-of-beer

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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.

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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 Smithsonian.com.

“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.

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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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Rivers of Hope

IMG_0613Biologist Dr Chris Fulton and Masters student Mae Noble sat around the campfire as the sun rose, looking at their frozen wetsuits.

Soon they would have to struggle into them ready for a day of snorkelling in freezing high country streams, looking for glimpses of the Murray Crayfish, the world’s second largest.

It had been a long hike the day before up into the high country west of Canberra, laden with underwater cameras and snorkelling gear. It had a confronting end as they reached their destination, the Goobarragandra River.

Dr Fulton had described to the American student the shady trees hanging over the idyllic stream of clear water gurgling over boulders he visited six years earlier.

But when they arrived, the trees had gone and only a muddy creek remained.

“It was hard to believe it was the same stream, it was pretty brutal,” says Fulton, GradCertHE ’09, a biologist from the ANU Research School of Biology.

Huge floods in 2012 had devastated the Goobarragandra, eroding the banks and choking it with silt.

As the pair began searching for the iconic crayfish with its distinctive white claws, their fears were confirmed. The population had plunged by 95 per cent.

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Duck sex is so wrong

For Patricia Brennan, duck penis researcher from University of Massachusetts..

Give thanks for the birth of Duck minor
Mother duck has a corkscrew vagina
But daddy’s erection
curls in the other direction
Proof God’s no intelligent designer

Duck love making’s no simple deed
what’s more god has deceed
that the knob of this stud
will drop off in the mud
as soon as he’s planted his seed

If you think this seems a sad song
the drake will regrow his dong
this new percy I’ve heard
measures a third of the bird
a behemoth that’s 8 inches long!

Things then get wronger and wronger
Sir Drake scares his mates with his donger
If he thinks he’s the king
it shows up in his thing
which grows to be 20 % longer

So you think your love life’s out of luck
Be thankful you are not a duck.
your bits stay attached
and your organs are matched
when you’re both in the mood for a ….. cuddle.

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