The Earth’s age is about 4.5 billion years. For most of it the light at it’s surface came from the stars, specifically the Sun. This means that all life on this planet evolved and adapted under that light. One feature that came about, for example, is skin. With the Earth rotating around it’s own axis, it also means there are day and night cycles. Different paths were taken here as well. There are diurnal and nocturnal species, awake during the day and awake during the night, respectively. Our sun has a specific spectrum. Every ray of light that reaches us has a certain frequency. Different frequencies mean different things for organisms. For us humans for example, a frequency of 650 nm corresponds to the visible red light part of the Sun’s spectrum. With the control over fire, there also came control over the light it emits. This change in light technology, however, was rather unimpactful in comparison with what came next. About 130 years ago there was a fair in Chicago, called The World’s Columbian Exposition. Nikola Tesla and Thomas Edison lit up the exposition with light bulbs. From this point on, the control over light changed remarkably, and with it so did the environment. Soon after came compact fluorescent lights (CFL’s) and then light emitting diodes (LED’s). This light isn’t the light from the Sun. This light is vastly different. For many species, life would never be the same again, least of all for humans.
Take a look at the image below, comparing the spectrum of sunlight, LED’s, incandescent lights and compact fluorescent lights.
Notice anything different? Incandescent lights trend upwards toward the red and infrared part of the spectrum. It follows a black body radiation curve (see the image below) and is a thermal source of light. LED’s and CFL’s have spikes, notably in the blue part of the spectrum. They do not follow a black body radiation curve and are cold light sources. In fact, the younger the technology, the more blue it is. If the dose makes the toxin, how toxic are these devices?
Further reading
https://en.wikipedia.org/wiki/Sun
https://en.wikipedia.org/wiki/Earth
https://en.wikipedia.org/wiki/World%27s_Columbian_Exposition