Blond
boy whose light, almost white hair color will probably darken. Photo courtesy of
Nino Barbieri and Wikipedia.
Blond
boy whose light, almost white hair color will probably darken. Photo courtesy of
Nino Barbieri and Wikipedia.A: "Light hair, as a rule, has a tendency to darken during childhood, says geneticist Rick Sturm, principal research fellow at the University of Queensland in Australia.
Hair darkens because genes that control hair color switch on.
The more pigment produced in the hair follicle, the darker the hair. Much pigment results in dark brown hair; little pigment causes blond hair.
Sometime during your childhood, the genes* controlling hair color changed, and told the pigment protein to produce much pigment. Your hair consequently gradually turned to dark brown. It's an 'on' / 'off' order, like switching on a light.
We don't, however, have a clue why the genes changed. They just do for many children.
We strongly suspect genes control the timing of the change. In 1975, two pediatricians (Adam P. Matheny Jr. and Anne Brown Dolan of the University of Louisville School of Medicine) examined the hair color of identical twins (169 female twins and 161 male) routinely from the time the twins were six months old until they were six years old.
They found marked changes in the hair color for both sexes. Moreover, they discovered a "high rate" of agreement at every age "in spite of the general change in hair color." Both twins' hair color changed, beginning at about the same age and continuing at nearly the same rate. They, therefore, concluded that genes influenced the timing of color changes.
In addition to hair darkening during childhood, "there are changes [causing hair to darken] also apparent at puberty that would likely be hormone related," says Sturm. The darkening can continue past puberty into the 30's and 40's.
By the way, the hair of some herd animals (for example, giraffes) darkens, but not with age. "The top male's hair darkens when he takes the alpha position," says Sturm, who suspects hormonal changes (maybe testosterone). "The specific example I have seen was a group of giraffes where the alpha male had noticeably darker spots. The keepers told me that this changed over time as the alpha male position was handed on. And it happens in other animals."
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*Genes controlling hair color include: tyrosinase,TYRP1, MATP, SLC24A5, SILV etcS and OCA2
Sex and genetic differences in hair color changes during early childhood, University of Louisville School of Medicine, 1975.
Hair color, Wikipedia
Understanding genetics, hair color, Stanford University
Color makes no difference how fast a candle burns. "Black candles burn no faster than white," says chandler Stefan Phillips of the Island Candle Company.
Wick size is the primary factor determining candle-burning rate. "A larger wick is like stepping on the gas pedal," says Phillips. The big wick delivers more fuel to the burning flame.
By the way, a candle is a cylinder of solid fuel — paraffin wax — that surrounds a wick. How does it burn? Bringing a lit match to a wick melts and then vaporizes the wax coating the wick. The wax vapor combines with oxygen, and burns.
Wax is the most important ingredient that makes a candle burn faster. Soft wax has a higher oil content and lower melt temperature; therefore, it burns faster. Typically, candles in jars have soft wax, and pillar candles have hard wax. The longest burning candles are pillar candles made of a blend of beeswax and paraffin.
Why a candle flame goes up, WonderQuest
Tips for taking care of candles: a burning guide, Island Candle Company
Candle burning, Newton ask a scientist
Why
do people only snore when they are asleep? You breathe all the time, but
it's noisier when you are fast asleep. Why?
I'll publish the best answers, and you get credit. Click here:
Answer-the-question
to give me your answer.
(Answered April 30, 2007)