There is an elite group, hidden in the shadows, that secretly determines the fate of scientific research, as well as how humans interact with and understand the world as a whole. This isn’t the Illuminati, this is the International System of Units (SI); a group of measurements that shapes how humanity sees reality and defines the nature of the known universe.
There are seven core SI units from which all other forms of measurement derive.These include the meter for length, kilogram for mass, second for time, Ampere for electric current, Kelvin for temperature, mole for substance, and Candela for luminous intensity. Each unit measures a basic aspect of the quantifiable universe, allowing scientists to conduct complex dimensional analyses, even on bodies that are light years away.
What is a Candela?
One of the most under-appreciated of these units is the Candela. Its operational definition is luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz, and that has a radiant intensity of 1/683 watts per steradian. A common candle emits a brightness of approximately one Candela in any given unobstructed direction. This is different from lumens, which is the measurement used by companies like C and J Lighting Inc., to explain the amount of visible light.
This definition is important because it places the frequency of light used in determining one candela at 555 nanometers, where the human eye is most sensitive. Before the candela, different countries depended on a variety of measures that were subject to the quality of the light sources. The different measures made it difficult for scientists to compare notes and collaborate on research.
The Candela is the one of the most confusing SI units because it’s a flexible variable that changes drastically with slight variations of the light source. For example, a twenty-five watt bulb will emit an estimated 135 cd in all directions. If scientists focus that same power in a 20° beam, the intensity will jump to around 18000 cd.
Why Does it Exist?
Measuring luminous intensity is important, especially in space technology as it plays an integral part in measuring distance between Earth and other heavenly bodies. In addition, fluctuations in luminous intensity let scientists estimate the size of a planet even if they can’t see it. Measuring luminous intensity also allowed early scientists to accurately measure distance, even without a fixed reference point of known dimensions.
Studying light is one of the most exciting and confusing parts of science because of its dual nature and flexible properties. But, understanding it may be the best bet humanity has in unlocking the physical secrets of the cosmos, and finally answering questions that have been boggling people for centuries.