Big noisy bug, Mount Everest weather, seeing electromagnetic waves
By April Holladay for USA TODAY
Q: Is the loud buzzing sound we hear in the summer due to the heat? Or is it just a big bug in the trees like I always thought?
A: It's a big bug in the trees. With a wingspan of up to eight inches (20 cm), it is a big insect and has the loudest insect voice. At 120 decibels, a cicada rivals a jet engine taking off. It's so loud that the singing male "stops up his ears" (creases his hearing apparatus) so his own song doesn't, literally, deafen him.
Adult cicadas hang around in trees high on trunks or among branches and foliage. For almost all species, the male does the singing. Some species sing in the heat of the day, others at dusk or dawn. The terrible racket has a purpose — to attract females. "Males in these choruses alternate bouts of singing with short flights until they locate receptive females," says John Cooley, entomologist at the University of Connecticut. Females can hear the males' call a quarter of a mile (0.4 km) away.
The cicada sings louder than grasshoppers or crickets, which rub a ridge over a roughened edge like a fiddle bow. The cicada, on the other hand, makes a popping noise like pressing on the top of a bulging tin can. A pair of resonating chambers amplifies the pop, which he repeats 100 to 500 times a second to make a buzzing roar.
His musical sound box lies at his abdomen base. It consists of drum-like membranes held by a stiffly elastic ring, like a tambourine ring with give.
The insect doesn't hit the membrane like a drum. Instead he pulls the membrane down by tightening a muscle attached to it. This presses the membrane down as we might press down on the tin can lid. He relaxes the muscle and the membrane pops back as the lid does.
Each species sings its own unique song. Muscles attached to the ring change the character of the sound: its shape, volume, and quality. Thus, the male produces a signature tune, calling to only his own kind.
•University of Nebraska: Periodical cicada life stages
•University of Michigan: Periodical cicada page
Q: What is the temperature of Mount Everest?
A: It's a cold place. The temperature at the top never rises above freezing. In January, the coldest month, it can drop to -76 degrees F (-60 C) and averages -33 (-36 C). Even in July, the warmest month, it averages -2 (-19 C).
The wind is deadly. Our highest mountain (29,035 feet [8850 m]) thrusts itself almost into space. In the winter, the high-flying jet stream hurtles in from the north and batters Mount Everest with hurricane-force winds exceeding 177 mph (285 km/h).
Climbers venture onto the glacier-carved pyramid only a few weeks of the year. In May and sometimes October winds abate enough for attempts. Mountaineers fear the unexpected. Everest drops ten feet (3 m) of snow in a blink of an eye. Storm-force winds spring alive, carrying sand, small stones, snow, and ice aloft to slash struggling souls.
•The Weather Doctor: The jet stream
•Mt. Everest weather probes
•WonderQuest: Lightning on Mount Everest?
•AdventureWeather.com: Mount Everest weather
Q: Your answer about light got me wondering how we "see" other electromagnetic waves — like ultraviolet light, infrared light, and radio waves. Why can't we see them all?
A: All electromagnetic waves are basically the same. They carry energy through empty space at the speed of light. We can't see all such waves, however, since our eyes evolved on Earth while receiving the Sun's radiation. That's the kind of electromagnetic radiation we see — visible light. In the daytime, we see blue-green light best — the peak energy from the Sun.
Our skin extends the range of electromagnetic waves that we sense beyond visible light. We feel heat (infrared light) and sunburn (ultraviolet light).
To "see" the rest — radio waves through X-rays — we use receivers that are sensitive to those wavelengths. The receivers translate what they "see" into something we can sense. Some chemicals impregnated in film are sensitive to X-rays, for example. We see the X-rays' effects on the film after we develop it. The rays pass through soft body parts and darken the film but are blocked by bones and teeth.
Think of sea waves. The water undulates: peaks and valleys. The distance between two peaks is the wavelength.
Although all electromagnetic waves are the same phenomenon, they differ vastly in their wavelengths. Radio waves on the AM dial are about 3 football fields long. X-rays are a hydrogen-atom long. (Related image:the electromagnetic spectrum
Our eyes can't handle such a range of wavelengths so we supplement their reception with radios, cameras, and the like.
•HyperPhysics: The electromagnetic spectrum
•Cornell University: Quicktime movie of a shockwave 'seen' via an X-ray camera
•WonderQuest: Infrared night-vision
•WonderQuest: Seeing with X-rays
•HyperPhysics: Infrared ear thermometer
(Answered Nov. 21, 2003)