Scrubs used to be white — the color of cleanliness. Then in the early 20th century, one influential doctor switched to green because he thought it would be easier on a surgeon’s eyes, according to an article in a 1998 issue of Today’s Surgical Nurse. Although it is hard to confirm whether green scrubs became popular for this reason, green may be especially well-suited to help doctors see better in the operating room because it is the opposite of red on the color wheel.
Green could help physicians see better for two reasons. First, looking at blue or green can refresh a doctor’s vision of red things, including the bloody innards of a patient during surgery. The brain interprets colors relative to each other. If a surgeon stares at something that’s red and pink, he becomes desensitized to it. The red signal in the brain actually fades, which could make it harder to see the nuances of the human body. Looking at something green from time to time can keep someone’s eyes more sensitive to variations in red, according to John Werner, a psychologist who studies vision at the University of California, Davis.
Second, such deep focus on red, red, red can lead to distracting green illusions on white surfaces. These funky green ghosts could appear if a doctor shifts his gaze from reddish body tissue to something white, like a surgical drape or an anesthesiologist’s alabaster outfit. A green illusion of the patient’s red insides may appear on the white background. (You can try out this “after effect” illusion yourself.) The distracting image would follow the surgeon’s gaze wherever he looks, similar to the floating spots we see after a camera flash.
The phenomenon occurs because white light contains all the colors of the rainbow, including both red and green. But the red pathway is still tired out, so the red versus green pathway in the brain signals “green.”
However, if a doctor looks at green or blue scrubs instead of white ones, these disturbing ghosts will blend right in and not become a distraction, according to Paola Bressan, who researches visual illusions at the University of Padova in Italy.
So, although doctors trot down the street these days in a rainbow of patterned and colored scrubs, green may be a doctor’s best bet.
Source: Live Science
From red to blue to violet, all the colors of the rainbow appear regularly in urine tests conducted at hospital labs.
The prismatic pee collection seen in this stunning photo took only a week to assemble for medical laboratory scientists at Tacoma General Hospital in Tacoma, Wash. Heather West, the laboratory scientist who snapped the picture at the hospital, said she and her colleagues collected the urine colors to highlight their fascinating behind-the-scenes work.
“My picture was intended to illustrate both the incredible and unexpected things the human body is capable of, the curiosity in science, and also the beauty that can be found in unexpected places,” West said. “A mix between art and science.”
None of the urine samples were treated with chemicals in the lab to change their hue, West said. “When I posted the picture [on Flickr], people thought that we did something magical to it. They did not believe it was actually urine,” she said.
Hospital labs are often tucked away in a windowless basement, but they play a critical role in patient health. West, 26, who works the night shift, said a love of science and a wish to work in the medical field drew her to the career. “We are impacting every patient that comes into the hospital in multiple ways,” she said.
While the chromatic colors of pee are amazing, doctors are usually more interested in the contents of urine. Only a few colors, such as red or dark brown, warn that something is wrong with a patient’s health.
“I wouldn’t generally just monitor the color of someone’s urine,” said Kirsten Greene, an assistant professor of urology at the University of California, San Francisco. “But if it’s red or bloody, that’s a really strong cue that there’s infection or cancer, and that’s the one I would worry about the most.”
Here are some of the reasons for the pee shades.
Blood is the most common cause of red urine, and is a definite health warning signal. “As a urologist, I’m always worried when people have red urine,” Greene said. Bladder cancer, infections and kidney stones can all cause bleeding that shows up in urine, and all are worth a trip to the doctor.
More benignly, eating a lot of beets can turn your pee pink.
Dark-colored urine also points to health problems. Liver cancer can cause dark brown urine, containing excess bilirubin, a brownish pigment produced by the liver.
A drug called phenazopyridine (Pyridium) created the bright orange urine seen in West’s photograph. It’s a painkiller given to people with urinary tract infections, and converts pee into a Gatorade-like color.
“Antibiotics often alter urine color to orange,”Green said. “People who eat enough carrots to turn their skin orange can have orange pee, too,” she added.
Many people have seen the effects of dehydration on pee — a dark yellow- colored urine. Without enough water, a pigment called urochrome becomes more concentrated in urine.
On the other hand, in hospitals, some patients on intravenous fluids are so hydrated they produce nearly colorless urine, West said. The cloudy, yellow urine in West’s picture was caused by an infection.
Green urine usually flows from dilution of blue urine, as in West’s image. Occasionally, a urinary tract infection may trigger green pee.
The rarest of all on the pee rainbow, blue urine often comes from chemicals and drugs given to patients. The No. 1 offender is a drug called methylene blue, used to treat carbon monoxide poisoning, and as a dye during surgery. It makes the blue and green urine seen in West’s photograph.
Methylene blue was also a malaria treatment during World War II. Other medications that make blue urine include Viagra, indomethacin and propofol — the anesthetic drug infamously linked with Michael Jackson’s death.
Genetic conditions that affect the breakdown of dietary nutrients can also cause blue urine. Even blue food dyes sometimes passes into pee.
Indigo and Violet
In this photo, the deep purple urine comes from a patient with kidney failure. “The dark black one is something that you usually see in kidney failure,” West said. “Your kidneys should be filtering your blood and getting rid of your waste, and when you damage the kidneys, there’s a lot more blood [in the urine],” she said.
Another violet venue: Patients with catheters can develop a rare complication called “purple urine bag syndrome,” linked to a urinary tract infection and highly alkaline urine. A genetic condition called porphyria may also trigger deep purple pee.
The earliest life on Earth might have been just as purple as it is green today, a scientist claims.
Ancient microbes might have used a molecule other than chlorophyll to harness the Sun’s rays, one that gave the organisms a violet hue.
Chlorophyll, the main photosynthetic pigment of plants, absorbs mainly blue and red wavelengths from the Sun and reflects green ones, and it is this reflected light that gives plants their leafy color. This fact puzzles some biologists because the sun transmits most of its energy in the green part of the visible spectrum.
“Why would chlorophyll have this dip in the area that has the most energy?” said Shil DasSarma, a microbial geneticist at the University of Maryland.
After all, evolution has tweaked the human eye to be most sensitive to green light (which is why images from night-vision goggles are tinted green). So why is photosynthesis not fine-tuned the same way?
DasSarma thinks it is because chlorophyll appeared after another light-sensitive molecule called retinal was already present on early Earth. Retinal, today found in the plum-colored membrane of a photosynthetic microbe called halobacteria, absorbs green light and reflects back red and violet light, the combination of which appears purple.
Primitive microbes that used retinal to harness the sun’s energy might have dominated early Earth, DasSarma said, thus tinting some of the first biological hotspots on the planet a distinctive purple color.
Being latecomers, microbes that used chlorophyll could not compete directly with those utilizing retinal, but they survived by evolving the ability to absorb the very wavelengths retinal did not use, DasSarma said.
“Chlorophyll was forced to make use of the blue and red light, since all the green light was absorbed by the purple membrane-containing organisms,” said William Sparks, an astronomer at the Space Telescope Science Institute in Maryland, who helped DasSarma develop his idea.
Chlorophyll more efficient
The researchers speculate that chlorophyll- and retinal-based organisms coexisted for a time. “You can imagine a situation where photosynthesis is going on just beneath a layer of purple membrane-containing organisms,” DasSarma told LiveScience.
But after a while, the researchers say, the balance tipped in favor of chlorophyll because it is more efficient than retinal.
“Chlorophyll may not sample the peak of the solar spectrum, but it makes better use of the light that it does absorb,” Sparks explained.
DasSarma admits his ideas are currently little more than speculation, but says they fit with other things scientists know about retinal and early Earth.
For example, retinal has a simpler structure than chlorophyll, and would have been easier to produce in the low-oxygen environment of early Earth, DasSarma said.
Also, the process for making retinal is very similar to that of a fatty acid, which many scientists think was one of the key-ingredients for the development of cells.
“Fatty acids were likely needed to form the membranes in the earliest cells,” DasSarma said.
Lastly, halobacteria, a microbe alive today that uses retinal, is not a bacterium at all. It belongs to a group of organisms called archaea, whose lineage stretches back to a time before Earth had an oxygen atmosphere.
Taken together, these different lines of evidence suggest retinal formed earlier than chlorophyll, DasSarma said.
The team presented its so-called “purple Earth” hypothesis earlier this year at the annual meeting of the American Astronomical Society, and it is also detailed in the latest issue of the magazine American Scientist. The team also plans to submit the work to a peer-reviewed science journal later this year.
David Des Marais, a geochemist at NASA’s Ames Research Center in California, calls the purple Earth hypothesis “interesting,” but cautions against making too much of one observation.
“I’m a little cautious about looking at who’s using which wavelengths of light and making conclusions about how things were like 3 or 4 billion years ago,” said Des Marais, who was not involved in the research.
Des Marais said an alternative explanation for why chlorophyll doesn’t absorb green light is that doing so might actually harm plants.
“That energy comes screaming in. It’s a two-edged sword,” Des Marais said in a telephone interview. “Yes, you get energy from it, but it’s like people getting 100 percent oxygen and getting poisoned. You can get too much of a good thing.”
Des Marais points to cyanobacteria, a photosynthesizing microbe with an ancient history, which lives just beneath the ocean surface in order to avoid the full brunt of the Sun.
“We see a lot of evidence of adaptation to get light levels down a bit,” Des Marais said. “I don’t know that there’s necessarily an evolutionary downside to not being at the peak of the solar spectrum.”
Implications for astrobiology
If future research validates the purple Earth hypothesis, it would have implications for scientists searching for life on distant worlds, the researchers say.
“We should make sure we don’t lock into ideas that are entirely centered on what we see on Earth,” said DasSarma’s colleague, Neil Reid, also of the STScI.
For example, one biomarker of special interest in astrobiology is the “red edge” produced by plants on Earth. Terrestrial vegetation absorbs most, but not all, of the red light in the visible spectrum. Many scientists have proposed using the small portion of reflected red light as an indicator of life on other planets.
“I think when most people think about remote sensing, they’re focused on chlorophyll-based life,” DasSarma said. “It may be that is the more prominent one, but if you happen to see a planet that is at this early stage of evolution, and you’re looking for chlorophyll, you might miss it because you’re looking at the wrong wavelength.”
“Light is a nutrient much like food,and like food,
the wrong kind can make us ill, and the right kind can keep us well.”
Humans need light of specific intensity and color range to regulate their internal biological clock. Without it, our daily, monthly and annual rhythms become disrupted. A lack of sunlight can lead to ill health with a variety of mental, emotional, and physical symptoms.
How does “light starvation” or “Malillumination” happen?
Working and living indoors: Poorly illuminated environments with inappropriate artificial lighting could have serious health implications. For example, most artificial indoor lighting lacks ultraviolet light (UV), which at the proper intensity is essential to the production of vitamin D and the metabolism of calcium.
Unhealthy artificial light: Most indoor lighting lacks the requisite full-range color distribution and the proper intensity to sustain health and certain functions, such as vitamin D and hormone production. Light’s effect on human mind body health has, until recently, been ignored in architecture, design, and engineering. Both fluorescent and incandescent lights have lots of Red, but are lacking in Green, Blue and Violet. Furthermore, indoor lighting is generally not bright enough, amounting to only 1/20th the intensity of outdoor light in the shade on a sunny day. The amount of light that we receive from 16 hours indoors is dramatically less than the amount we receive from a single hour outdoors.
Negative lifestyle habits: Even in sunny California and Florida, the average individual receives little sunlight in a 24-hour period. The additional interferences we have, such as tinted sunglasses and contact lenses, tinted car windshields, and tinted windows, don’t allow in the health-giving properties of the entire spectrum of light.
Seasons/low light conditions: In winter in the northern hemisphere, the onset of winter depression and seasonal affective disorder (S.A.D.) occurs in late fall and peaks in February. (These symptoms usually wane in early spring, as the days get longer.)
The Symptoms of Light Starvation:
- Fatigue Increased illness – due to lowered immune function
- Hypersomnia – sleeping too much
- Vitamin D deficiency
- Calcium deficiency
- A disturbance of bodily rhythms such as SAD, winter depression and other phase shift disorders.
What Light Nourishes:
Light enables us to see, and it plays several vital roles as it enters our eyes and our skin. Light enters the pineal gland (the body’s light meter) via the retina. Its neurotransmitter, melatonin, influences the hypothalamus, which is responsible for controlling many of the endocrine functions that are disturbed in depressed individuals such as sleep and wakefulness, reproductive physiology, mood, and the timing of the biological clock.
Sunlight shining on the skin triggers the production of melanin, a dark pigment that protects the surface of the body. As UV rays from the sun penetrate the skin’s surface layer of melanin, the body’s supply of vitamin D is replenished. Vitamin D is known as the “sunshine vitamin”, and although vitamin D can be obtained from milk and fish, this form is not as biologically effective as the vitamin D produced by sunlight.
Vitamin D3 is a skin hormone called solitrol, which works in conjunction with the pineal hormone, melatonin, to control the body’s response to light and darkness. Solitrol works antagonistically with the melatonin to produce changes in mood and our 24 hour bodily rhythms, as well as affecting our immune system.
Vitamin D enters the blood stream and goes to the kidneys and liver where it plays a key role in the absorption of calcium from foods, as well as the utilization of the mineral phosphorus. Nutritionally oriented physician Dr. Elson Haas states that since vitamin D is intimately related to the metabolism of calcium and phosphorus, it is important to the growth and development of bones and teeth in children. Dr. Haas adds that D3, because of its effect on calcium levels, is important in the maintenance of the nervous system, heart functioning, and blood clotting.
The learned compute that seven hundred and seven millions of millions of vibrations have penetrated the eye before the eye can distinguish the tints of a violet. ~Lytton
The word violet is from the Middle English and old French violette, and from the Latin viola, the names of the violet flower. The first recorded use of violet as a color name in English was in 1370.
Violet can also refer to the first violas which were originally painted a similar color.
In Arabic language Violet color is called Nile and the dye Nilege made from Viola flower (of the violet color) which was dominant on the shores of the Nile River, giving the Nile color as the name of the Nile river. The Violet shade of Blue is called Nili in Contemporary Arabic.
In Chinese painting, the color violet represents the harmony of the universe because it is a combination of red and blue (Yin and yang respectively). In Hinduism and Buddhism violet is associated with the Crown Chakra.
Violet is one of the oldest colors used by man. Traces of very dark violet, made by grinding the mineral manganese, mixed with water or animal fat and then brushed on the cave wall or applied with the fingers, are found in the prehistoric cave art in Pech Merle, in France, dating back about twenty-five thousand years.
More recently, the earliest dates on cave paintings have been pushed back farther than 35,000 years. Hand paintings on rock walls in Australia may be even older, dating back as far as 50,000 years.
It has also been found in the cave of Altamira and Lascaux. It was sometimes used an alternative to black charcoal. Sticks of manganese, used for drawing, have been found at sites occupied by Neanderthal man in France and Israel. From the grinding tools at various sites, it appears it may also have been used to color the body and to decorate animal skins.
Berries of the genus rubus, such as blackberries, were a common source of dyes in antiquity. The ancient Egyptians made a kind of violet dye by combining the juice of the mulberry with crushed green grapes. The Roman historian Pliny the Elder reported that the Gauls used a violet dye made from bilberry to color the clothing of slaves. These dyes faded quickly in sunlight and when washed.
During the Middle Ages violet was worn by bishops and university professors and was often used in art as the color of the robes of the Virgin Mary. Violet and purple retained their status as the color of emperors and princes of the church throughout the long rule of the Byzantine Empire.
While violet was worn less frequently by Medieval and Renaissance kings and princes, it was worn by the professors of many of Europe’s new universities. Their robes were modeled after those of the clergy, and they often square violet caps and violet robes, or black robes with violet trim.
Violet also played an important part in the religious paintings of the Renaissance. Angels and the Virgin Mary were often portrayed wearing violet robes. The 15th-century Florentine painter Cennino Cennini advised artists: “If you want to make a lovely violet colour, take fine lacca, ultramarine blue (the same amount of the one as of the other)…” For fresco painters, he advised a less-expensive version, made of a mixture of blue indigo and red hematite.
The violet or purple necktie became very popular at the end of the first decade of the 21st century, particularly among political and business leaders. It combined the assertiveness and confidence of a red necktie with the sense of peace and cooperation of a blue necktie, and it went well with the blue business suit worn by most national and corporate leaders.
Violet is at one end of the spectrum of visible light, between blue and the invisible ultraviolet. It has the shortest wavelength of all the visible colors. Violet is a spectral, or real color – it occupies its own place at the end of the spectrum of light. Violet is the color the eye sees looking at light with a wavelength of between 380 and 450 nanometers. It was one of the colors of the spectrum first identified by Isaac Newton in 1672.
In the traditional color wheel used by painters, violet and purple lie between red and blue. Violet is inclined toward blue, while purple is inclined toward red.
Symbolic meanings of violet:
- Knowledge and intelligence
- Wavelength: 380-450 nm
- Frequency: 800-715 THz
- Hex triplet: #8F00FF
- sRGBB: (143, 0, 255)
- CMYKH: (44, 100, 0, 0)
- HSV: (274°, 100%, 100%)
Note: This post was compiled by Shirley Twofeathers for Color Therapy, you may repost and share without karmic repercussions, but only if you give me credit and a link back to this website. Blessed be.
In the traditional color wheel used by painters, violet and purple are both placed between red and blue. Purple occupies the space closer to red, between crimson and violet. Violet is closer to blue, and is usually less intense and bright than purple. While the two colors do look similar, from the point of view of optics there are important differences.
Violet is a spectral, or real color – it occupies its own place at the end of the spectrum of light, and it has its own wavelength (approximately 380-420 nm). It was one of the colors of the spectrum first identified by Isaac Newton in 1672, whereas purple is simply a combination of two colors, red and blue. There is no such thing as the “wavelength of purple light”; it only exists as a combination.
I have had good success eliminating a migraine prodrome aura. I cured it by using a special eye exercise. The procedure was intended to work the eyes and the visual centers of the brain harder than usual by forcing them to do a cross-eye fusion procedure. The speculation behind the possible success using this method was based upon a reported brain scan done during migraine attacks which showed an abnormal blood flow to the visual cortex located in the back of the brain. These cross-eye procedures force the brains visual centers to do far more work than is usually required of them and that forces the brain to allocate the blood flow in a different way from what they were doing to create the migraine aura.
This is an experimental procedure which I performed upon myself. I am only reporting what appeared to work for me and I do not necessarily suggesting that you try the experiment so any results you may have, good, bad or inconclusive are strictly upon your own recognizance. However, below are the cross-eye charts which I used successfully to eliminate my visual hallucinations in about three minutes. Usually it takes about 30 to 50 minutes in a dark room with a hot or cold bag on the back of my head to clear up the aura. I have tried both the hot and cold treatments but found that tapping the back of the head worked better. But this cross-eye treatment worked best of all.
What works for me is to look cross-eyed at my finger tip held between the flags about half way to the screen and then to slowly move it towards and away from my face while looking at my finger tip and thinking about the dot. At some point the central dots from the opposite fields fuse into one. When they fuse I slowly lower my finger out of sight while watching the dot. And then in about twenty seconds the light show begins. With Red-green target #36 I like to move my stare between the various smaller dots around the center and to slowly read the numbers and letters. If my eyes uncross I return my finger to the position where fusion took place and can usually get the fusion back in a few seconds.
I created these pictures for the cross-eye fusion experiments but I discovered that they confused my visual centers so much that the effort of fusion soon forced my brain to abandon migraine auras and give its attention to the fusion. Even under normal non-aura brain functioning these pictures created highly volatile liable images which will shift quickly through a variety of colors and golden blends.
For more detail on these cross-eye fusion experiments go to the previous mind fuzing experiments. Here is a group of similar eye experiments with more instructions on how to cross your eyes: Eye Experiments.
Please remember these are experiments and you are totally responsible for any strange effects or results. I intended them for learning how your perception works and how it sometimes does very strange and unexpected things.
Try to imagine reddish green — not the dull brown you get when you mix the two pigments together, but rather a color that is somewhat like red and somewhat like green. Or, instead, try to picture yellowish blue — not green, but a hue similar to both yellow and blue.
Is your mind drawing a blank? That’s because, even though those colors exist, you’ve probably never seen them. Red-green and yellow-blue are the so-called “forbidden colors.” Composed of pairs of hues whose light frequencies automatically cancel each other out in the human eye, they’re supposed to be impossible to see simultaneously.
The limitation results from the way we perceive color in the first place. Cells in the retina called “opponent neurons” fire when stimulated by incoming red light, and this flurry of activity tells the brain we’re looking at something red. Those same opponent neurons are inhibited by green light, and the absence of activity tells the brain we’re seeing green. Similarly, yellow light excites another set of opponent neurons, but blue light damps them. While most colors induce a mixture of effects in both sets of neurons, which our brains can decode to identify the component parts, red light exactly cancels the effect of green light (and yellow exactly cancels blue), so we can never perceive those colors coming from the same place.
Almost never, that is. Scientists are finding out that these colors can be seen — you just need to know how to look for them.
Colors without a name:
The color revolution started in 1983, when a startling paper by Hewitt Crane, a leading visual scientist, and his colleague Thomas Piantanida appeared in the journal Science. Titled “On Seeing Reddish Green and Yellowish Blue,” it argued that forbidden colors can be perceived. The researchers had created images in which red and green stripes (and, in separate images, blue and yellow stripes) ran adjacent to each other. They showed the images to dozens of volunteers, using an eye tracker to hold the images fixed relative to the viewers’ eyes. This ensured that light from each color stripe always entered the same retinal cells; for example, some cells always received yellow light, while other cells simultaneously received only blue light.
The observers of this unusual visual stimulus reported seeing the borders between the stripes gradually disappear, and the colors seem to flood into each other. Amazingly, the image seemed to override their eyes’ opponency mechanism, and they said they perceived colors they’d never seen before.
Wherever in the image of red and green stripes the observers looked, the color they saw was “simultaneously red and green,” Crane and Piantanida wrote in their paper. Furthermore, “some observers indicated that although they were aware that what they were viewing was a color (that is, the field was not achromatic), they were unable to name or describe the color. One of these observers was an artist with a large color vocabulary.”
Similarly, when the experiment was repeated with the image of blue and yellow stripes, “observers reported seeing the field as simultaneously blue and yellow, regardless of where in the field they turned their attention.”
It seemed that forbidden colors were realizable — and glorious to behold!
Crane’s and Piantanida’s paper raised eyebrows in the visual science world, but few people addressed its findings. “It was treated like the crazy old aunt in the attic of vision, the one no one talks about,” said Vince Billock, a vision scientist. Gradually though, variations of the experiment conducted by Billock and others confirmed the initial findings, suggesting that, if you look for them in just the right way, forbidden colors can be seen.
Then, in 2006, Po-Jang Hsieh, then at Dartmouth College, and his colleagues conducted a variation of the 1983 experiment. This time, though, they provided study participants with a color map on a computer screen, and told them to use it to find a match for the color they saw when shown the image of alternating stripes — the color that, in Crane’s and Piantanida’s study, was indescribable.
“Instead of asking participants to report verbally (and hence subjectively), we asked our participants to report their perceptions in a more objective way by adjusting the color of a patch to match their perceived color during color mixing. In this way, we discovered that the perceived color during color mixing (e.g., red versus green) is actually a mixture of the two colors, but not a forbidden color,”
When shown the alternating stripes of red and green, the border between the stripes faded and the colors flowed into each other — an as-yet-unexplained visual process known as “perceptual filling in,” or “image fading.” But when asked to pick out the filled-in color on a color map, study participants had no trouble zeroing in on muddy brown. “The results show that their perceived color during color mixing is just an intermediate color,” Hsieh wrote in an email.
So if the color’s name is mud, why couldn’t viewers describe it back in 1983? “There are infinite intermediate colors … It is therefore not surprising that we do not have enough color vocabulary to describe [them all],” he wrote. “However, just because a color cannot be named, doesn’t mean it is a forbidden color that’s not in the color space.”
Fortunately for all those rooting for forbidden colors, these scientists’ careers didn’t end in 2006. Billock, now a National Research Council senior associate at the U.S. Air Force Research Laboratory, has led several experiments over the past decade that he and his colleagues believe prove the existence of forbidden colors. Billock argues that Hsieh’s study failed to generate the colors because it left out a key component of the setup: eye trackers. Hsieh merely had volunteers fix their gaze on striped images; he didn’t use retinal stabilization.
“I don’t think that Hsieh’s colors are the same ones we saw. I’ve tried image fading under steady fixation … and I don’t see the same colors that I saw using artificial retinal stabilization,” Billock said. In general, he explained, steady eye fixation never gives as powerful an effect as retinal stabilization, failing to generate other visual effects that have been observed when images are stabilized. “Hseih et al.’s experiment is valid for their stimuli, but says nothing about colors achieved via more powerful methods.”
Recent research by Billock and others has continued to confirm the existence of forbidden colors in situations where striped images are retinally stabilized, and when the stripes of opponent colors are equally bright. When one is brighter than the other, Billock said, “we got pattern formation and other effects, including muddy and olive-like mixture colors that are probably closer to what Hseih saw.”
When the experiment is done correctly, he said, the perceived color was not muddy at all, but surprisingly vivid: “It was like seeing purple for the first time and calling it bluish red.”
The scientists are still trying to identify the exact mechanism that allows people to perceive forbidden colors, but Billock thinks the basic idea is that the colors’ canceling effect is being overridden.
When an image of red and green (or blue and yellow) stripes is stabilized relative to the retina, each opponent neuron only receives one color of light. Imagine two such neurons: one flooded with blue light and another, yellow. “I think what stabilization does (and what [equal brightness] enhances) is to abolish the competitive interaction between the two neurons so that both are free to respond at the same time and the result would be experienced as bluish yellow,” he said.
You may never experience such a color in nature, or on the color wheel — a schematic diagram designed to accommodate the colors we normally perceive — but perhaps, someday, someone will invent a handheld forbidden color viewer with a built-in eye tracker. And when you peek in, it will be like seeing purple for the first time.
NASA wasn’t trying to make a fashion statement when it picked bright orange for the spacesuits astronauts wear when they launch and land on the space shuttle.
In fact, that bright hue called International Orange was chosen for safety, because it stands out so well against a landscape.
“It’s highly visible for search and rescue,” said Brian Daniel, shuttle crew escape subsystem manager at NASA’s Johnson Space Center in Houston. “It’s one of the most visible colors, especially for sea rescue.”
The same shade of orange coats San Francisco’s Golden Gate Bridge and Japan’s 1,090-foot (333-meter) tall Tokyo Tower.
The shuttle ascent and entry suit, called the Advanced Crew Escape Suit (ACES), is a pressurized shell designed to help an astronaut survive if an accident occurred during liftoff or landing. The suit contains a supply of air and water, along with a parachute and survival gear such as radios, flares and medicine.
The current version of the suit was adopted in 1994, though the previous version, called the Launch Entry Suit (LES), was the same color. [Graphic: Cosmic Apparel Over the Years]
Before the space shuttle, U.S. astronauts wore white or silver suits.
And today’s NASA astronauts wear a completely different suit for spacewalks, or extravehicular activities (EVAs). These suits are designed for a different purpose survival in the near-vacuum of space, rather than survival on Earth.
Thus EVA suits are white, which reflects the strong heat of the sun and stands out against the black expanse of space. These suits are called Extravehicular Mobility Units (EMUs), and are even bulkier than the ACES. They include temperature control, breathable air and drinkable water, and a tough shell to prevent small pieces of space junk, called micrometeoroids, from harming the astronauts.
Russia has its own spacesuits the Sokol suit for launch and landing, and the Orlan suit for spacewalks for those flying aboard Soyuz spacecraft. Both of these suits are white, and function similarly to their U.S. counterparts, with some differences.
China the third nation to independently launch humans into space has its own custom-designed spacesuits for spacewalking called Feitian suits, modeled on Orlan suits. Chinese astronauts have worn suits that closely resemble Sokol suits for launch and landing.
Why is the color red so impressive? The answer lies in our tree-living past.
In the back of the vertebrate eyeball are two kinds of cells called rods and cones that respond to light. Cones take in a wide range of light, which means they recognize colors, and they are stimulated best during daylight. Rods respond to a narrower range of light (meaning only white light) but notice that light from far away and at night.
Isaac Newton was the first person to hold up a prism and refract white light into a rainbow of colors and realize that their might be variation in what the eye can see. Color comes at us in electromagnetic waves. When the wavelength of light is short we perceive purple or blue. Medium wavelengths of lights tickle the cones in an other way and we think green. Short light wavelengths make those cones stand up and dance as bright spots of yellow, orange and red.
Various animals distinguish only parts of that rainbow because their cones respond in different ways. Butterflies, for example, see into the ultraviolet end of the rainbow which allows them to see their own complex markings better than we can. Foxes and owls are basically color blind and it doesn’t matter because they are awake at night when the light spectrum is limited anyway.
Humans are lucky enough to be primates, animals with decent color vision, and we can thank monkeys for this special ability.
Long ago, primitive primates that resemble today’s lemurs and lorises saw only green and blue, the longer wavelengths of color. But when moneys evolved, around 34 million years ago, their cones became sensitive to even shorter wavelengths of color and they saw red.
And what a difference. With red, the forest comes alive. Instead of a blanket of bluish-green leaves, the world is suddenly accented with ripe red, yellow, and orange fruits, and even the leaves look different.
For a monkey leaping through the forest canopy, color vision would be an essential advantage. Unripe fruit doesn’t have enough carbs to sustain a hungry primate and they taste really sour. Unripe leaves not only taste bad, they are toxic and indigestible.
For the first humans foraging about the forest and savannah around 5 million years ago, it would have been be much more efficient to spot a ripe fruit or tuber than bite into a zillion just to get the right one. And so humans ended up with color vision even though we no longer live in trees.
But color is more than wavelengths, more than an indicator of ripeness, to us. Color has become symbolic, meaning it has meaning, and that meaning is highly cultural.
Chinese athletes and Chinese brides wear red because red is considered lucky. The U.S. athletes also wear red because that bright color is in the U.S. flag, and because designers of athletic wear, as well as scientists, know that red gets you noticed.
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