Good day, dear Take in Mind readers! Over the past few weeks, we have been studying together about the “magical” abilities of the ancient Vikings that could determine the sun’s location on a cloudy day. We revealed that behind the seemingly magical abilities one can find very irregular, but explainable physical processes. Today we suggest talking about the Bedouin’s magic.
Let’s remember how the famous Russian writer I. A. Bunin described his visit to the nomadic camp in the novel “In the Spring, in Judea”:
… But meanwhile, outside the tent, refreshments were being prepared for me and the guests. Usually Bedouins eat khibiz – flat maize cakes – and boiled millet with goat’s milk… But the essential refreshment for a guest is kharuf: a sheep which they roast in a hole dug in the sand by heaping layers of smouldering pressed dung upon it. After the sheep they give you coffee, but always without sugar. And so everyone sat and ate as though nothing were out of the ordinary, although in the shade of the felt tent it was hellishly hot and stuffy, and looking out on its wide-open flaps was simply terrifying: the sands in the distance were glittering so, they seemed to be melting before your eyes…
And of course, tea! The symbol of Bedouin hospitality, fragrant and sweet, perfectly quenching thirst. The moment several people gather in the tent, the hosts immediately begin with the preparations. By the way, until very recently, the expenses of tea and sugar were almost the main ones in the budgets of most Bedouin families. The most honored guests are accepted with delicious and beautifully refreshing watermelons. I was once lucky to taste this dessert in a nomad’s tent. The heat of the Arabian desert, peppermint tea, and… a cool watermelon. Really, what could be better on a sultry summer day than pulling a big green berry out of the refrigerator, cutting off a large chunk, and enjoying every bit of sweet juicy red pulp?
There is only one tiny problem: many Bedouin nomads (including our hosting family) still do not use refrigerators. Moreover, the watermelon (the most ordinary one) laid outside, in the open and under the sun until the very last moment. Maybe the nomad used some ancient magic? It was somehow inconvenient to ask our hosts, so for some time I was tormented by this mystery. Until one day, the physics textbook helped me to reveal the simple secret.
So, to cool a watermelon, Bedouin-style, we need:
A) Warm whole (i.e., uncut) watermelon. We held it outside under the sun and thus warmed it up to 37 degrees Celsius.
B) A kettle with boiling water (about 98 degrees Celsius).
C) A sharp knife, and… that’s all! Maybe you can come up with some appropriate magic words (but we personally do not recommend that – you never know what may happen).
Pour boiling water over the watermelon and cut it instantly. For the purity of the experiment, we immediately inserted the sensor, a culinary thermometer, several millimeters deep, and followed the temperature change. Within a few seconds, the temperature dropped by 9 (!) degrees: from 40ᵒ to 31ᵒ. However, the temperature remained high deep inside the watermelon (39 degrees).
Ladies and Gentlemen! We suggest everyone repeat this experiment (but, please, be careful) and validate it with your own experience: the method works!
And finally, a question: how a hot watermelon, drenched with boiled water became fresh almost instantly? Of course, it is not icy (that would be real magic!), but on a sultry day, such a watermelon will seem like a heavenly pleasure.
The answer is very simple: The water from a sliced watermelon evaporates and takes away heat, and, as a result, a chilled surface appears. In preheating uncut watermelon (sun plus the boiled water) the vapor pressure inside the berry increases, which, in turn, accelerates the evaporation process (and chilling) after cutting.
Here we go, now we have a kind of ancient Bedouin magic and a wonderful life-hack for a summer vacation! Enjoy!
Featured image by congerdesign from Pixabay.
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