Because green light provides better illumination than red light at low levels for the human eye. The problem is that the photoreceptors in human eyes are not well attuned to red light — wavelength around nanometers.
That means it requires more light at that color to give us a certain level of perception than if we were using other colors, especially green. I learned this from an online discussion by Doug Kniffen, a serious amateur astronomer.
Using green light would work better, he says, because you can see the same amount of detail with a dimmer light source than with red light.
He suspects belief in red light is a holdover from the days of developing photographic film. He wrote about Rudolph in a booklet that the store gave away as a lure to Depression-era shoppers. A number of scientists over the years have examined exactly how Rudolph generates all that wattage. Some insects glow, most famously fireflies that mix chemicals together in their abdomen to lure the ladies, and some fish glow, like those scary-looking anglerfish in dark depths that dangle little lights to lure prey into their jaws, and some squids and jellyfish and snails glow.
But no mammals. If the glow is caused by excess blood flow to the surface of the nose that would explain the red color; think of W. The only way to answer this riddle, of course, is to capture Rudolph and do tests.
Dominy points out that Arctic reindeer scientific name Rangifer tarandus tarandus can see ultraviolet light, which is invisible to humans and most mammals--a trait that comes especially handy in mid-winter when the sun is low on the horizon and the high scattered light from the atmosphere is mainly blueish and ultraviolet.
In addition, the reflective tissue tapetum lucidum in reindeer eyes changes from a rich golden color during the summer months to a deep blue color during the winter months. This tissue which causes eye shine at night helps nocturnal animals see in the dark, and a blue one is expected to improve their ability to see blue light. Yet, fog extinguishes blue light more readily than red light, which may make it especially difficult for Santa's reindeer to see blue effectively, never mind fly.
This is where Rudolph's luminescent glowing nose comes into play, as it serves as an excellent fog light for navigating his fellow reindeer. Given that the redness of Rudolph's nose is similar to red holly berries, Dominy was able to estimate the color of light emitted from Rudolph's nose by measuring the color of holly berries.
He found that Rudolph's nose is probably the maximum level of redness that mammals are able to see, which may explain why Rudolph's nose is effective as a fog light. According to Dominy, Rudolph's nose also poses a problem. Reindeer noses are extremely vascular, which causes them to lose body heat through their noses. A glowing nose could cause excessive heat loss for Rudolph, putting him at risk of hypothermia.
As a result of the unique properties of Rudolph, it is no wonder that with a nose so bright, he is able to effectively guide Santa's sleigh. The second part is a thin, enclosed layer of a light-producing organ between the dermis and the epidermis. Inside this layer is luciferin , a light-producing substance, and luciferase , an enzyme that catalyzes the light-producing reaction.
The third part is where the "red-nosed reindeer" part comes in. Most bioluminescent life forms, like fireflies , produce green light. The outermost part of Rudolph's nose, however, would be a red phosphorescent layer -- once the light-producing organ started creating light, the phosphorescent part of his nose would absorb the green light and emit a red light. How would his nose get so bright, though? Bioluminescence often requires another substance, like oxygen, to make light , and Rudolph would breathe lots of oxygen right near the light-producing organs, providing enough reactions for long, intensely shiny bursts of light.
But why is Rudolph the only reindeer with a nose that glows? In the next section, we'll learn about how and why Rudolph has a muzzle like no other. Although Rudolph is what's called a bull -- a male reindeer -- there's a rumor that many of Santa's reindeer might be cows , or female reindeer. Why is this? Have you ever seen pictures of Santa flying in his sleigh with his team of reindeer? If you have, you'll notice that the reindeer have fully grown antlers.
The interesting thing is, though, male reindeer typically shed their antlers by early December, well before Christmas Eve. The antlers grow back in the spring, and the cycle of growth and regrowth continues. Cows keep their antlers all year long, however, so the chances that there are more females than males on Santa's sleigh are a bit higher. This isn't to say that all of the reindeer are female and Rudolph's the only guy out there. Most males shed their antlers, but not all of them, and it's possible that a bull won't lose his antlers until after December.
Accounts of Blitzen, a part of the original team of reindeer, identify him as Rudolph's father, so we know that Santa has both male and female reindeer leading his sleigh.
So we know that Rudolph stands out a bit from other reindeer, but how could something like this have happened? Could Santa be some kind of a mad scientist, tweaking reindeer DNA for his own benefit, or could Rudolph's nose be a biological accident? It's possible that Rudolph's bright honker could be a reindeer atavism. But what's an atavism? An atavism is a trait of distant ancestors that randomly pops up in modern-day organisms -- a whale with legs or a human with a tail are two examples.
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