The fascination with why the sky is blue has captivated thinkers and scientists for centuries. Although Leonardo da Vinci made pioneering observations, it was not until much later that the phenomenon was scientifically explained. Leonardo da Vinci, in his acute observations and detailed notebooks, often questioned natural phenomena. He speculated about the atmosphere and how it scatters light, but his musings did not encompass the detailed scientific explanation we have today.
The precise explanation came from John Tyndall, a 19th-century British physicist, who discovered the scattering of light by small particles, now known as Tyndall effect. It was later, however, through the work of Lord Rayleigh that the specific reason for the sky's blue color was identified. Lord Rayleigh, whose real name was John William Strutt, expanded on Tyndall’s findings, offering the explanation that when sunlight enters the Earth's atmosphere, it collides with molecules in the air. These molecules scatter the shorter blue wavelengths of sunlight much more than they scatter the longer red wavelengths, due to their smaller size relative to the wavelength of visible light.
This phenomenon, called Rayleigh scattering, is why we see a blue sky most of the time. The intensity of the scattering is inversely related to the fourth power of the wavelength; hence, blue light is scattered more than ten times more effectively than red light. During sunrise and sunset, the sun's light passes through a thicker layer of the atmosphere, which scatters blue light out of the line of sight and allows the longer wavelengths of red and orange to dominate, resulting in the beautiful colors of the twilight sky.
Although Leonardo didn't provide the definitive explanation as to why the sky is blue, his curiosity and methodical approach to studying the natural world laid foundational understandings that later scientists like Tyndall and Rayleigh could build upon. His contributions to art and science continue to influence how we observe and interpret our natural world. This historical journey of understanding why the sky is blue illustrates the evolution of scientific thought, from the observational studies of da Vinci to the precise scientific explanations provided by Tyndall and Rayleigh.
