Q--Why are the onset and ending of daylight saving time not symmetrical on either side of the longest day?
A--Because the movement of the Earth around the sun is not symmetrical, that is, not exactly 365 days, and this causes minor variations in time, whether it be the exact minutes of the longest day, or the first day of summer.
Q--Considering the daily variations in the number of daylight hours in different locations, does each location receive the same number of total daylight hours in the course of a year?
A--Yes, the number of hours of daylight are the same, but their intensity varies. In the tropics, where the sun is almost overhead much of the time, light is more intense than at the poles, where the sun shines upon them at a wider angle and thus has to go through more of the Earth`s atmosphere.
Q--Why are yawns contagious? Is it the power of suggestion or something else?
A--Scientists are not sure why one person`s yawn will set off a bout of yawning in others nearby, but one intriguing theory is that oscitation
--yawning--is a vestigial defense mechanism of our distant evolutionary past.
Cats and apes, for example, yawn to signal nonaggression, and the nonthreatening response is to yawn back. This reaction may have become encoded in earliest human behavior.
Another theory is offered by Dr. Perry W. Buffington of the Health Research Corp. in Atlanta, who says boredom is the culprit. In settings conducive to boredom, the rate of breathing slows to 7 or 8 times a minute from the normal 12 to 24, causing carbon dioxide to build up in the bloodstream. Eventually, carbon dioxide-sensitive nerve cells in the brain`s respiration center demand a yawn as a means to restore normal breathing.
The visual signal of seeing another person yawn suggests to the brain that a quick check of its own respiratory system might be in order, Buffington says. Oddly, yawns in babies and animals do not seem to trigger contagious yawning in adults.
Q--How do cellular blankets and thermal underwear work? That is, how do they keep one warm in the winter?
A--These coverings contain pockets, or cells, of air. The air acts as an insulator to help trap body heat close to the skin.