Hot Ice

As I write these lines, there is half a metre of snow under the window and it is -10°C. The sunlight is playing nicely on the bruised trees, but the cold is evil. If we have to get out of our gloves, our fingers quickly get cold, our skin starts to burn. The blood circulation to the back of the hand deteriorates rapidly, and the gloves are of no use. It’s better to put your hands under a coat or use a hand warmer.

How to Make Invisible Ink

People have been sending secret messages since ancient times. Countless methods have been devised to protect information—and just as many to uncover it. Nowadays, digital methods are in fashion, and ciphers and chemical inks are more like toys, but there was a time when lives depended on them. Methods for concealing information fall into two … Read more