Commander Chris Hadfield has helped us explain many-a-physics phenomenon over the years, from the ins and outs of space sex, to how to walk in zero-g. But unbeknown to most, between trips to the great-wide forever, the Canadian astronaut paid a visit to an “otherworldly” realm here on Earth: the bottom of the ocean.
Back in 2012, Hadfield ventured to the Aquarius undersea laboratory as part of NASA’s ongoing NEMO mission. Living as an “aquanaut” allowed Hadfield to test equipment that could be used to set up shop on another planet, but as per usual, the YouTuber extraordinare wasted no time before teaching us an important lesson: try as you might, you can’t shake-splode a soda on the seabed.
To understand why, we need to understand why a shaken soda blows its top in the first place. As you probably know already, soda gets its fizz from dissolved carbon dioxide. Before sealing, CO2 is pumped into the can (or bottle) under pressure, forcing the gas to meld with the liquid within it. This is the same process that happens in a Sodastream when you hit that glorious “carbonate me” button. Because the solubility (the amount of a substance that can be dissolved into another substance) of carbon dioxide is higher at high pressure, sealing the can ensures the CO2 molecules stay comfortably combined with the liquid.
When you open the can, you expose its contents to a pressure imbalance: the pressure outside the can is lower than the pressure within it. Like all things, CO2 molecules want to move from an area of high pressure to an area of low pressure, so eventually, all of that gas will escape from the liquid as bubbles. This will happen whether you shake the can or not (it’s why soda goes “flat”), but by putting energy into the system by shaking it, you allow that escape to happen faster by creating tiny spaces (bubbles) between the molecules of liquid. This increases the internal pressure of the can. More internal pressure, more “pssssssthllllllttttthhhhhhhhh” when you pop the top.
OK, fair enough. Now what’s with the underwater anomaly? Aquarius sits about 60 feet (18.2 meters) below the waves, and is pressurized to just over two atmosphere’s (atms). What this means is that anyone, or anything, in the lab experiences twice the pressure they (or it) would experience at sea-level. When Hadfield shakes the can at depth, the same bubbles form within it, but the high-pressure surrounding atmosphere forces those bubbles back into the liquid with near-equal force when the can is opened. So, no explosion. By this logic, soda opened at depth will stay fizzy much longer than soda opened at the surface.
And this experiment works on more than just soda cans. Watch what happens when a diver from the Bermuda Institute of Oceanic Science cracks an egg at 60 ft:
The surrounding water assumes the role of the eggshell itself, exerting enough inward pressure to keep the yolk and white together.
Mhm, Science, we love you.