I remember that, in my childhood, when there was no air conditioning, people used evaporative cooling by simply hanging wet cloths and curtains in doorways and windows. Due to the wind that blew across the wet products the air in the house was cooler. I thought it was awesome. And it really helped. I considered their idea a very ingenious one. But it seems that it wasn’t theirs at all. On the contrary! The Ancient Egyptians are credited as being the first to have used it!

There is more. Another mystery is the temperature inside the Great Pyramids of Giza, which is constant, 20 degrees Celsius, despite the fact that the temperature around it reaches 50 degrees.

The mystery does not end here. The temperature in the pyramid is equal to the internal temperature of the Earth.

Is this a coincidence, or did the Egyptians really have both the knowledge and the technical possibility to create and maintain this temperature in an artificial structure?