What is a cyanometer?
Horace-Bénédict de Saussure, the inventor of the cyanometer, was an 18th century Swiss scientist and explorer of the Alps. During his expeditions in the Alps, Saussure noticed that the sky appeared bluer at higher elevations. This observation was of great interest to him and strengthened his motivation to understand how the blue of the sky was related to altitude and atmospheric conditions, leading him to develop the cyanometer, a device used to quantitatively measure the blue of the sky in 53 levels of blue.
Although a primitive device that utilized his "eyes" as sensors, he measured the blue of the sky at various locations with this device and observed that the higher the elevation, the bluer the sky appears and the more transparent the atmosphere is. These measurements later led to and proved the discovery of the theory of Rayleigh scattering, which states that the sky appears blue when the amount of particles and water vapor in the atmosphere decreases and light scattering is reduced, and conversely, when the amount of particles and water vapor in the atmosphere increases, the sky appears white.
Thus, by measuring the number and size of particles in the air, we can determine the state of the atmosphere and changes in the environment. Current atmospheric measurements include aerosol sensors and spectrometers. Rayleigh scattering has also contributed to developments not only in atmospheric research but also in optical technology, and today it is applied to a variety of measurement devices, such as particle size distribution measurement devices and nanoparticle characterization devices.
Measuring" the changes we notice every day leads to scientific discoveries in the future. Many changes are occurring around us every day. Temperature changes, plant growth, the movement of the stars, etc., the natural world is constantly moving. The first step in science is to notice these changes and measure them.
Measurement is the key to understanding the laws of nature and acquiring new knowledge. Try Sorayomi Note and discover the joy of "Hakaru".
HORIBA's concept is "Measure to understand, understand to connect. Under the concept of "Hakaru to understand, understand to connect more," HORIBA is co-sponsoring the signature pavilion "Future of Life" at the Osaka-Kansai EXPO 2025. At the pavilion, visitors can experience the fun of "Hakaru" through the "Shores: Edge of Evolution," a light display that expresses the expansion of life woven by "Hakaru" and the AR of water quality measurement 50 years from now, when "Hakaru" will be more familiar to us all.
We look forward to seeing you at the exhibition. For more details, please visit
