Why are things green? Why are the flowers so colourful, and the moths fluttering to the fire? What is the phototaxis of organisms? Why do birds crash into buildings? Why do whales kill themselves?
These seemingly simple questions, but few people in the world really know the fascinating biophysical principles behind these phenomena. To answer these questions, allow me to start from the earliest days of life on Earth.

So life only use the only constant light energy, from infrared ~ ultraviolet, life use the infrared ray to provide heat energy for themselves, use ultraviolet ray to help reproduce, this is because ultraviolet ray energy is higher, the vibration caused by their irradiation can promote cell division. So after trial and error, smart plants finally decided to their own color green, so in the spectrum, red, orange, yellow, green, cyan, blue, violet, green from the red line and uv are equal distance, in the middle! Able to fully absorb light energy equilibrium of such plants, but also reflect the green light to see the animals, so animals eat plants by pulling at the same time help plant the seeds of spreading everywhere, this is the social harmonious cooperation, dedication is to help yourself, if not reflected light plant will be black, it will die alone in the dark, quiet die, eventually the entire race. We humans have evolved by natural selection to feel comfortable looking at green, and we wouldn't have evolved if we didn't feel good looking at green.

As the earth's early plant growth process emissions increase in the number of oxygen, oxygen from the atmosphere has increased dramatically in nearly 1.5 billion years, oxygen react with high-energy photons in the air once again the sun to generate ozone O3, along with the increase in ozone, formed the ozone in the atmosphere, the ozone layer has a characteristic, is the reflection ultraviolet light, and ultraviolet (uv) is the important condition of plant breeding. As the ozone layer thickened and the ultraviolet rays were greatly reduced, plants died in large Numbers. The plants that survived began to think, and they came up with an ingenious solution, which was a major event in the evolution of life. This event is called a plant flowering event.