02/14/2007
Black, White and Red
I’ve been walking the beach here on Marco Island for two weeks and I must say those walks have been the least colorful and least interesting in all the years I’ve been coming here. I haven’t seen a single conch shell, sand dollar, jellyfish, scallop shell of any significant size, dolphin or even any dead fish even though there’s reportedly a hint of red tide in the area. Also, not a single sea urchin, subject of last week’s column.
There was some color, or lack of it, associated with one of our stocksandnews.com crew. I must join the ranks of the many who have congratulated our Lamb creator and award-winning cartoonist Harry Trumbore on his 55th birthday last week. More impressive than reaching this milestone was his winning of his black belt in karate the night before his birthday. This required him to fight seven individuals, most of them much younger. The fights are no holds barred with punching, kicking, etc. Aside from the black belt, Harry is also garnered a black eye in one of those fights! At 55, his parents are relieved that he survived the combat.
Our editor, Brian Trumbore, reports that Harry’s eye is a relatively mild degree of blackness. An object is black when it absorbs most or all of the light that hits it. Both blackness and whiteness are the subjects of two very different recent scientific investigations. Chunlei Guo of the University of Rochester and his research team have been working on blackness. Specifically, they’ve found a way to make almost any metal black – no black paint involved. An article on their work in the November 26, 2006 Toronto Star is reprinted on the university’s Web site. What Guo and his team did was to focus extremely short pulses of an intense laser beam on tiny spots on the surface of various metals. By extremely short, I mean a few quadrillionths of a second! By tiny spot, think the size of the spot to be about the area of the point of a needle.
It’s hard to believe but the article says that the ultrashort laser burst unleashes as much power as the entire power grid of North America onto the tiny spot. This is somewhat akin to what we did as kids when we took a magnifying glass and focused the sun’s rays on a small spot on a piece of paper or wood and made it burn. The ultrashort bursts of laser power on such tiny spots results in the formation of nanosize pits, globs, and strands of metal that increase the surface area tremendously. When the laser pulses are scanned over a sizeable area, the irregularities in the surface make it difficult for light to get back out once it hits the surface. Virtually no light is reflected. Almost all of it gets absorbed and the surface is pitch black.
Why should anyone care about making black surfaces? If you’re in the game of detecting light, say in astronomy, a black surface will capture those photons very efficiently. A silicon solar cell captures photons to make electricity. Guo and his team have also made silicon black. Silicon is pretty good at capturing photons as it is but the black silicon might improve the efficiency of solar cells by about 30 percent. Black trim on cars could be another possible application. The laser-pulsed surface should be more resistant to scratches or other wear and tear than a painted surface. Another possible application is in fuel cells, which depend heavily on platinum or other catalysts for their operation. Catalysts are more effective the higher the surface area, which is enhanced by the laser pulsing.
Admittedly, the laser process used by the Rochester team is not yet ready for prime time. To blacken an area on the surface of a piece of metal the size of a fingernail may take over half an hour and the researchers are studying how to speed up the process. Don’t try this at home – these short pulses of laser light can burn through your skin if it gets in the way!
Blackness is the absence of reflected light; whiteness is the opposite, when light of all colors is scattered and reflected. The January 19 issue of Science contains an article by Pete Vukusic, Benny Hallam and Joe Noyes of Exeter University and Imerys Minerals Ltd. in the UK titled “Brilliant Whiteness in Ultrathin Beetle Scales”. I hadn’t realized that really striking whiteness is relatively uncommon in animals. The article reports an uncommonly white whiteness in the Cyphochilus spp. beetle.
The article in Science seems to expect the reader to know what a Cyphochilus spp. beetle is. I had to turn to an article on the BBC Web site sent down here by Brian Trumbore to find it’s a “finger tip sized” beetle that lives in Southeast Asia. The beetle is brighter and whiter than milk or the average human tooth, measuring 60 on a whiteness scale in which human milk teeth rank about 40. What surprises the scientists is that the beetle has scales that are only 5 microns thick; a human hair is typically around 50 microns or so. The scales are also in a haphazard random arrangement that scatters and reflects light of all colors.
Why is the beetle so white? Speculation is that it evolved to be so white as a camouflage ploy to avoid predators since it lives in an environment of white fungi. In the world of color, it’s possible to make white just as bright and white as the beetle but it takes materials around a hundred times thicker than the beetle scale to accomplish the whiteness. There’s the possibility that whiter plastics or paints could result from these studies on the Asian beetle. Maybe someone will marry the black metals with the white plastics to create unique black-white contrasts in products that people will want to buy.
I’m posting this column on Valentine’s Day and, appropriately, Brian Trumbore also sent me an article by Natalie Angier in the February 6 New York Times titled “How Do We See Red? Count the Ways”. Angier points out that red is the premier signaling color in the natural world and not just on Valentine’s Day. Take the attraction of the redness of a ripe apple or the avoidance of a red poisonous ladybug by a female bird that, on the other hand, will be attracted by a male’s scarlet feathers. Red is a color of passion and danger and apparently the first color we learn to identify as babies.
The light-sensing cone cells in our retinas are the cells that provide us with color information. We and our great ape cousins are supplied with more red- and yellow-sensing cone cells than cells sensitive to bluish light. Reds and yellows are the colors most prevalent in fruit and the speculation is that we evolved to better detect the ripeness and condition of desirable fruits by concentrating on the reds and yellows. Natalie jokes in her article that she has 40 (red) lipsticks she never wears compared to only three blue eye shadows. She also cites research by Russell Hill and colleagues at the University of Durham in the UK. They found that in Olympic sports such as boxing and tae kwan do, where red or blue shorts are randomly assigned to the combatants, the red-shorted competitors won more often than expected from chance. The reasons for this finding are not apparent.
Speaking of red, I misspoke when I described my walks as colorless. The beach has been consistently covered with what I had thought to be unusually large amounts of seaweed. However, a news item on the local TV news dealt with a problem that apparently extends over a wide area of Southwest Florida apparently. It’s not reddish brown seaweed. It’s red algae. So, color my walks red. Happy Valentine’s Day!
Allen F. Bortrum
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