Qanat, a symbol of science in the ancient world.

The oldest traces of qanats date back to the emergence of the first human civilizations. Traces of ancient Iranian qanats from around the third and second millennia BC still remain in various parts of Iran. The remains of numerous qanats can also be seen from the Achaemenid and Sassanid periods. Qanats are known as a symbol of science and engineering in the ancient world. Qanats demonstrate the ancients' deep understanding of hydrology, geology, and engineering. Recognizing and extracting hidden waters in the depths of the earth and the ability to dig deep and long tunnels and guide water along the slope of the earth required high knowledge and skill. Humans have been able to understand the earth and its limitations for centuries, and by digging qanats in the most complex geological structures several thousand years ago, they became familiar with the science of engineering geology. However, in the 17th and 18th centuries, geology moved out of the realm of speculation and opinion and joined the field of science. Today, the study of underground water resources is carried out with the knowledge of geohydrology, and the exploration of these waters is carried out with surface geophysics. The flow of water in the aqueduct and its transfer from the depths of the earth to the surface is carried out using the principle of hydraulic gradient, while the hydraulic gradient was introduced as a principle by Henry Darcy in 1856. Ancient qanats dug deep into the ground were dug with the law governing soil behavior. The mechanical behavior of soils is studied today under the knowledge of soil mechanics. Qanats are one of the important underground water structures that originated thousands of years ago in the ancient world, and it shows that their builders had a high level of computational knowledge, so that today, with modern tunnel construction technology, they use advanced laser scanners to find the path, while the qanat tunnels in the ancient world were correctly routed.