Back in 2000 with the coming of the millennium, work began on the island of La Palma in the Canary Islands. It was for the largest optical telescope in the world called the Gran Tecan. This project was sponsored by the Institute of Astrophysics of the Canary Islands and the Spanish Government which took more than seven years to be completed - and two more years to become 100 percent operational.
To build a telescope on a volcanic island, which is almost 2400 meters above sea level is not easy. Especially knowing the components – the primary mirror is 10.4 meters in diameter, segmented into 36 hexagonal, only 8 inches thick but each weighing 450kb! In total, the telescope weighs over 16 tons and the construction material of the mirrors (made in Germany) is the Zerodur, a glass ceramic type that practically does not undergo thermal changes, which is indispensable when working at such altitudes, where difference between day and night are of many degrees Celsius. Furthermore, to avoid imperfections, polished mirrors are coming to have a surface error of only 15 nanometers (0.000015 mm). What that means is that if we could enlarge the mirror to the size of the Iberian peninsula, we would have no more than 1mm mountain high.
But the most impressive of all is that the telescope plus its dome weighs over 500 tons and that whole structure rests on a thin layer of special lubricant that allows a person to turn the entire dome with a single push! It is a spectacular feat of engineering, an example of the creative power of man, which in turn, also helps you learn the secrets of the universe.