Christmas may seem like a time to switch off and suspend disbelief, but there are plenty of ways to bring a little science into the celebrations.
We asked experts to share the best at-home experiments to challenge friends and family.
Sweet science
Matthew Cobb, professor of zoology at the University of Manchester, suggests choosing a sweet, such as marmalade, and closing your eyes and pinching your nose, putting it in your mouth and chewing it, keeping your mouth closed.
“See if you can define what sweet taste is—you'll probably just say 'sweet' and maybe have a vague idea of something else,” says Cobb. “After five seconds, remove your fingers from your nose and you will feel a sudden rush of sensation that will allow you to correctly identify the taste.”
A more extreme version of this experiment, he says, involves grating an onion and an apple separately, then tasting each on a spoon with your eyes closed and your nose pinched tightly. “They should taste the same—until you take your fingers off your nose.”
Cobb says experiments like this show that taste is mostly about smell, not taste. “When we chew, volatile odors emitted by food enter the nose through the back of the mouth, where they stimulate our olfactory neurons,” he says, adding that it is the combination of taste and smell that creates aroma.
“Without smell, things don't have much taste. We all discovered this during the first Covid outbreak when people temporarily lost their sense of smell.”
Laugh
Since crackers are a Christmas staple, Sophie Scott, professor of cognitive neuroscience at University College London, suggests experimenting to see what might influence whether people laugh at a (terrible) joke.
“First, try reading these jokes to yourself and see if you laugh at any of them,” she says. “Second, read the jokes to someone else—perhaps in a room full of people.”
Scott advises seeing if anyone, including you, laughs when you reach your climax, or if they react in some other way, such as moaning. She notes that although we associate laughter with jokes and humor, we laugh mainly for social reasons.
“You're 30 times more likely to laugh if you have someone else with you than if you're alone,” she says. “For joke crackers, this means that a joke read by someone alone is much less likely to make them laugh than the same joke read or heard in a group. And laughter is enhanced by social connections, so the more you know and like the people you're with, the more laughter you'll get.”
Get stuck in the holiday bird
If you have a turkey or other bird for Christmas dinner, take the time to inspect the carcass.
“We had a Thanksgiving dinner a few weeks ago and I took a huge turkey, cooked it for several hours and lovingly basted it every 30 minutes or so,” says Steve Brusatte, professor of paleontology and evolution at the University of Edinburgh. “Mainly to make it tasty, but also to make sure the meat falls off the bones well enough so I can remove the bones and show my wife and six-year-old son the shoulder area.”
This allowed Brusatte to demonstrate how the various bones fit together to move the wing up and down, and how the huge springy wishbone stores energy as the wings flap.
“It’s a simple thing you can do with roast turkey or chicken—look at the bones and understand how they fit together and move, and it gives a better understanding of the biomechanics and movements of flight than I’ve ever seen in any textbook in many years of teaching,” he says. “And then there’s a delicious meal waiting for you.”
Professor Sue Black, a forensic anthropologist, anatomist and academic at the University of Oxford, also recommends dissecting the holiday bird to understand the anatomy of movement.
“Boil the carcass until just the bones remain, and you have a 3D puzzle to reconstruct,” she says.
Chemistry of Christmas
It's common to sprinkle salt on sidewalks during the winter, and there's a simple experiment that can help explain why.
“You'll need 500ml full-fat milk or cream, five egg yolks and 125g sugar. A little vanilla never hurts,” says Andrea Sella, professor of inorganic chemistry at UCL.
“Whip them together, then heat until almost boiling until the mixture begins to thicken. Let it cool to room temperature. Meanwhile, take some ice out of the freezer. Either crush it like an alchemist in a mortar and pestle, or crush it in a blender like a modernist.”
Then, he says, grab two plastic bags—ideally zippered ones. “Throw some crushed ice into one and add a generous amount of salt. In the second, spoon some of the custard mixture, adding sprinkles, nuts or fruit pieces. Seal [second bag] and placed it in the first one.
“Now mash the ice and salt together and the custard in the bag. The temperature will drop to -10C or even lower. In a few seconds you will have ice cream, a soft (and delicious) solid.”
Sella says this happens because the dissolved salt prevents the liquid water molecules formed when the ice melts from freezing back onto the remaining ice.
“So the ice continues to melt and take heat away from the custard (and your fingers),” he says. “It's practical magic, also known as science.”
Holidays pi(e)
“One of the most amazing little science experiments you can do at home is called Buffon's Needle, but for celebratory purposes let's call it Buffon's Pine Needle. It's a way to approximate the value of ϖ,” says Keith Yates, professor of mathematical biology and public affairs at the University of Bath.
First of all, take a bunch of pine needles and select as many pine needles that are about the same length as possible (L). “Suppose you managed to find the sum (T) pine needles of the same size. You will also need a piece of paper with lines marked on it to indicate the distance. W further apart than the length of your needles,” says Yates.
Scatter the pine needles, without aiming, over a sheet of lined paper, then count the number of needles that cross one of the lines. This number WITH.
After counting, you can find the approximation of ϖ by plugging the numbers into this formula: ϖ ≈ 2.LT/CW
“What I like about this is that it shows how ϖ appears in really unusual places,” says Yates. “It looks like magic, but it’s just probability in action on your living room floor.”
