Whenever you see a video of an astronaut drinking water, they do it like they’re playing a game of orbital Hungry Hungry Hippos, picking off drops floating in mid air. Off-camera, they have better ways of drinking than doing it drop-by-drop, but astronauts are showoffs. And come on, wouldn’t you eat dropletized liquid if you got the chance?
Turns out, you actually can---while staying comfortably on Earth. You just have to use a little chemistry.
Liquids spilled on a table don’t spread into a single layer. They clump into mounds of countless trillions of molecules called, of course, droplets. The droplets form because the molecules in the liquid all attract one another and try to get as many neighbors as possible. Molecules on the edge get pulled in toward the center, preventing the edges from spreading out.
This tendency to form a droplet is called surface tension. You can play with it by letting a faucet sloooowly drip onto the surface of a penny, making as big of a droplet as you can. Eventually, no matter how careful you are, your drop will get too big and it’ll collapse under its own weight. Water molecules only attract each other with so much force, and at a certain point they’re just not strong enough to hold the droplet up against gravity any more.
That’s why a better way to play with surface tension is to go to space. In orbit, your motion cancels out Earth’s gravity, so water droplets just keep growing, floating amorphously before your eyes like bubbles.
Even those space-based drops aren’t ideal, though. If a water droplet smacks into another, the two combine. It would be really cool to have a droplet down here on Earth that both kept its shape without having to sit on top of something and didn’t combine with other drops.
To do that, you need to ramp up the surface tension of a droplet and coat it with a stabilizing layer. This process, demonstrated in this video with our friends over at ChefSteps, is called reverse spherification, and you can use it to eat your drinks just like the astronauts do. Watch to see how it’s done. And to see why it’s called reverse spherification, go check out their website.
