People who like to cook are secretly (culinary) scientists. So much so that I think that we should be included in the STEM category, because cooking involves extensive knowledge of all four fields: science, technology, engineering, and math.
Why do you think we call people who make the best cocktails mixologists? Why do you think Mary Berry is so intimidating on The Great British Bake Off, knowing exactly what's wrong with how a contestant made their custard without even seeing them make it? Cooking and crafting drinks involves lots of science-y things, and nowhere is this more evident than in the case of one skilled waiter in India.
On September 9, 2018, BBC Global Correspondent Megha Mohan shared a short but bewildering video of a man at the Chappati Factory in Ponnani, Kerala. In it, the man mixes four full glasses of chai with a literal flick of his wrist.
The video went viral, and in less than three days it garnered more than one-million views, 18,000 retweets, 46,000 likes, and thousands of confused brains, wondering what in the world was happening in the three-second motion he perfected.
This is just amazing— prachi (@ineffable_kai) September 11, 2018
“I’d like a tea, please - swung, not stirred...”— CitizenSRai (@Sushant_Rai) September 10, 2018
I wonder how many motorcyclists were taken out when he was learning— Shauna T (@shauna_t1) September 9, 2018
OMG ... Would love to see live.. how they do this..— Misal Raj (@MisalRaj_) September 10, 2018
Kab bula rahe ho aap ?
When I took a closer look at the video I noticed he actually isn't using his palm to keep the 100% full glass from spilling a single drop — he's using a load of scientific concepts to mix the tea.
To further explain how he's mixing the tea without it spilling everywhere, you first have to know it's really very difficult to do if you aren't an expert like him or a machine, basically. (And if you're planning to try this at home, maybe don't, because I did in my backyard with just chai and milk, and I had to pick broken glass out of the lawn.) He's also making use of three scientific concepts, which explain most of what's happening: immiscibility, centripetal force, and the properties of aqueous foam.
What in the world do those big fancy terms mean?
The reason why some drinks come in layers when you first order them or when you pour them in a particular way is because they're made with an immiscible combination, or the property where two substances are not capable of combining to form a mixture. Oil and water are the most obvious example of this, since oil is hydrophobic (something that repels water) and water is well … water. Since oil is less dense than water, it floats to the top when you mix them.
The Keralan drink in the video is made of chai, which mostly contains water and spices; cream, which contains a little hydrophobic milk protein and is less dense than the tea; and foam, which is mostly made of milk protein and air, is very hydrophobic, and is the least dense of the three. That's why they sit in the order they do, and if the men in the video don't drink them in time, they layers would separate again.
But how is he mixing it without it falling out?
Well, that can be explained by centripetal force. Centripetal force is a force that acts on a body moving in a circular path, directed toward the center around which the body is moving. Think of your car when you take it around a particularly sharp curve while you're driving at speed. When you're in that curve, your body wants to travel in a straight line (because the car is moving, not you), but thanks to the car's doors and seatbelts, you don't. In the case of this drink, the chai and cream want to travel out of the bottom of the glass, but they can't, so they mix while they continuously try to escape.
You may be wondering why, then, the foam doesn't mix too. Well, as I mentioned earlier, milk foam is made of mostly hydrophobic protein and air, which is why when you make a delicious cappuccino, the foam always stays at the top, even when you mix in sugar with a stirrer.
So if you put all three concepts together, there's a lot of tricky science happening, and the conditions have to be just right for this to work. If you play the video again, look closely at when the man picks up the fourth glass. He moves it to an area where he can clearly see those tasty layers, moves his fingers to where the foam and cream meet, and then swings it perfectly for the fourth time. (One wonders how long it took him to perfect this.) It seems like if he held it any lower than that, the conditions wouldn't be ideal for the cream and the chai to mix without also dissolving some of the foam and flying out of the glass when the motion stops.
I don't know about you, but against all my baser instincts, I want to go out and buy a cappuccino machine so I can become my own liquid magician. I'm sorry in advance, backyard.