![nature knows no color line isbn nature knows no color line isbn](https://d28hgpri8am2if.cloudfront.net/book_images/onix/cvr9781501196256/horse-crazy-9781501196256_xlg-back.jpg)
This has helped to make science, and optics, a global preoccupation. The last era started with the dawn of twentieth century that opened not only with new and revolutionary theories of Physics but also with a revolution in communication technology. The crusades (1095–1272) and the conquest of Islamic Spain made the Muslim scholarship and the Greek traditions accessible to the Europeans, helping to initiate the glorious era of scientific revolution in the West. The third era started in Europe around the fourteenth century when medieval Europe that had slipped into a dark age after the fall of Roman Empire started to emerge out of it.
![nature knows no color line isbn nature knows no color line isbn](https://i.gr-assets.com/images/S/compressed.photo.goodreads.com/books/1348791406l/818924._SX98_.jpg)
It had its golden age till around middle to late thirteenth century when Mongol invasion destroyed the eastern center in Baghdad in 1258 and the decay set in the Western Center of Cordoba. The second era belongs to the Islamic civilization, with its centers in Baghdad and Cordoba. It seems that hardly anything of significance in our understanding of light was contributed between 200 AD till around 750 AD when Muslims burst onto the scene.
![nature knows no color line isbn nature knows no color line isbn](https://washingtonpress-us.imgix.net/covers/9780295993294.jpg)
This era extended from about 800 BC till around 200 AD. The first era, with its center initially in Athens and then Alexandria, belonged to the Greeks. We can divide the history of light into four distinct eras. While tracing the history of ideas that shaped our understanding of nature and the properties of light, it is quite remarkable to see how one can almost neatly divide the geographical regions where human thoughts progressed during a certain time period followed by a decay and setting of the dark ages.