Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (12 page)

Mosquitoes live everywhere on earth except Antarctica and can be so thickly ubiquitous that each member of an Alaskan caribou herd typically loses a pint of blood a day. Despite mosquitoes’ prevalence, males only live a week; females a month at best. Their egg, pupa, and larva stages together last just a couple of weeks. So if and when breeding grounds dry up, mosquitoes vanish a month later.

Frustrated at trying to swat them? Scientists who study insect speeds conclude that they seem faster than they really are. This perception issue harks back to that old business of how many body lengths something moves per second. Mosquitoes most often fly at 2.5 miles an hour, so they can’t even keep pace with a jogger. But since this translates into 170 mosquito body lengths per second, they may seem supersonic.

Bees routinely move at jogger speed—seven miles per hour. Of the emerging springtime insects, flies, which look the fastest, are the fastest, at ten miles per hour. Of these, the horsefly is the champ, as everyone knows who has tried to dodge those creatures from hell. They can fly at 14.8 miles per hour, so only fast sprinters can hope to outrun them. The very quickest insects, however, are the good-guy dragonflies, which appear in 5,680 species and have been clocked at an amazing forty miles per hour. Best of all, they love to eat mosquitoes and have the velocity to catch them effortlessly.

May is when the flower petals of rhododendrons and azaleas add their color, along with crabapple trees and flowering dogwoods, Cornus florida. Also in May, wisteria blooms, accompanied soon thereafter by the magical lilacs—or at least the most cultivated variety of lilacs, Syringa vulgaris. Their heavenly scent, following the magnolias by a couple of weeks, fills the countryside.

Aromas themselves have their own tricky motion, since they can only move with air. Dead calm means that scents scarcely migrate from blossoms. On the other hand, too brisk a wind, and their molecules are diluted and whisked away.

It is still officially spring in early June, when perennials explode almost in unison, along with flowering shrubs such as bridal wreaths and roses and viburnums. The early frenzy is now replaced with the steady rhythms of shrubs, flowers, and trees destined to peak at their own predetermined periods. By the time spring ends, at the June 21 solstice—which is more frequently happening on June 20 as this century progresses, one result of the four-hundred-year Gregorian calendar cycle—the final holdouts, such as hickories and the slowpoke catalpas, have come into leaf even in their northernmost ranges.

This dynamic simultaneous animation of millions of insects, plants, and animals within a hundred yards of your rural home repeats every spring in the same sequence. But now look closer, to the motions hidden behind the curtain.

In 1663, the British philosopher and natural scientist Robert Boyle wrote, “There is in some parts of New England a kind of tree… whose juice that weeps out of its incisions, if it be permitted slowly to exhale away the superfluous moisture, doth congeal into a sweet and saccharin substance.” So indeed, one heralded early-spring marker in the northern states is the tapping of maples for the purpose of collecting sap, which is then boiled down for syrup. Since it takes forty gallons of sap to produce a single gallon of maple syrup, copious fluid is required. Many people imagine that all trees have sap running in them during the spring, but it isn’t true. Very few emit sap when punctured, and the maples do so only under odd conditions—and only before they come into leaf.

Maples produce sap during periods of cold nights and warm days, a situation that occurs most often in March and April. Sap flow stops if the temperature is either continuously above or below freezing and when the nights no longer fall below freezing. It’s very odd behavior. You can tap willow, ash, elm, aspen, oak, and many others and you’ll never collect a drop of sap. We now know that the reason has to do with freezing inside the tree and then the subsequent warming. This releases expanding gases that push the fluid. And yet no one understands why a sweet, sucrose-filled liquid is necessary or what this has to do with living tree cells. So it’s still largely mysterious, though syrup’s gooey, ambrosial presence on pancakes temporarily erases any frustrations we might have with science.

By contrast, other trees have saps running upward through their xylems when they are in leaf, and it is not sweet. Plants and trees transpire, meaning water evaporates from their leaves. This creates a partial vacuum that pulls water up from the roots. You’d think the sap would run fastest on hot afternoons, since plants transpire three times faster at eighty-eight degrees than they do at seventy degrees. But sap speed is fastest in midmorning, even if it continues all day.

Superman’s X-ray vision would observe that sap is no slowpoke. For years, measurements have been attempted by means of injected dyes and radioactive monitoring, but the past decade’s favored method involves thin temperature probes inserted into the tree in various places and the introduction of heat at the trees’ bottoms. These show that the rising sap carries the introduced heat upward at rates as fast as one-third of an inch per second. This may not sound fast, but it translates into ninety feet an hour, letting even the tallest trees quickly deliver water from roots to leaves. Most trees are not so speedy, however, with figures closer to eight feet per hour—still sprightly enough for us to see water motion if we could peer through the bark.

In the deep woods, meanwhile, wildflowers push their shoots above ground to take advantage of the preciously brief period of forest-floor sunlight before tree leaves shade them.

As the thermometer climbs, so does the noise level, for sound is the auditory manifestation of movement. A familiar example of this is the chirping of crickets. Only male crickets stridulate, but what’s obvious in every rural zip code is that the pace changes with the temperature. The chirping sound, which comes from the top of one wing being scraped along the bottom of the other, gets more frenetic on warmer nights.

Once again, it’s the same principle as an old battery failing to start the car on an icy morning. Chemical reactions speed up as temperature increases, as do the metabolic processes in insects, which is why it’s always wisest to dislodge an unwanted hornets’ nest on a frigid night, when they are too cold to respond. Ants, too, walk at a speed that depends on the temperature. All insects rely on myriad chemical reactions in their bodies and have no way to speed them up except to hope for an environmental warm spell. As the temperature rises, they more easily reach the energy threshold necessary for chemical reactions that will let them perform various muscle contractions, a prerequisite for walking, flying, or—in the case of crickets—chirping.

The rate at which crickets chirp depends also on the species, but a good average is about a chirp a second when the night air is fifty-five degrees. If you want to be a show-off at your next scout meeting or Trivial Pursuit game, you can tell everyone that the name for the relationship between temperature and chirping is Dolbear’s law.

Amos Dolbear, born in 1837, was almost the world’s most famous person. And not because of insects. When we think of the invention of the telephone, radio, and electric light, the names Bell, Marconi, and Edison spring to mind. But for a whisker of chance it would have been—some say it should have been—Dolbear alone.

He was no toolshed tinkerer. Amos Dolbear graduated from Ohio Wesleyan University and ultimately became chairman of the physics department at Tufts University. While still in his twenties he created a working telephone that he called a talking telegraph, a device that used his own receiver constructed of a permanent magnet and a metallic diaphragm. This was in 1865, fully eleven years before Alexander Graham Bell patented his version of the telephone. Later, Dolbear tried strenuously to show that he and not Bell was first, and the case went all the way to the United States Supreme Court. The journal Scientific American reported on June 18, 1881: “Had [Dolbear] been observant of patent office formalities, it is possible that the speaking telephone, now so widely credited to Mr. Bell would be garnered among his own laurels.”

Defeated but still energetic, Dolbear turned to wireless communications, and in 1882, while a professor at Tufts, he succeeded in sending signals a quarter mile using radio-wave transmission through the earth. Made wise by his bouts with Bell, he filed for and received a patent for his “wireless telegraph,” improving its transmission capability to a half mile by 1886. This was groundbreaking and beat out the theoretical work of German physicist Heinrich Hertz and, by a full decade, the practical inventions of the Italian Guglielmo Marconi. Dolbear’s patent later prevented Marconi’s company from doing business in the United States and forced the Italian to purchase Dolbear’s patent.

Dolbear even invented a system of incandescent lighting ahead of Thomas Edison, but here, reverting to earlier form, he didn’t pursue it fast enough to edge out Edison’s later monopoly. In short, he was an eyeblink from going down in history as the inventor of all the most important technologies of our time.

It seems that none of these inventors actually stole from the other. Rather, in a strange echo of nature’s predilection for patterns, the same ideas occured to different people at around the same time—a sort of hundredth monkey effect that seems to happen more often than random chance would suggest.3

Out of left field, and bearing no relation to applied physics, Amos Dolbear suddenly submitted an article that was accepted for publication in the November 1897 edition of The American Naturalist. Titled “The Cricket as a Thermometer,” Dolbear’s article spelled out the connection between the night’s temperature and the rate at which crickets chirp. The formula he expressed became known as Dolbear’s law, which still remains widely known in esoteric entomology circles. You simply count the number of chirps that occur in fourteen seconds and add forty. Voilà: You get the current temperature in degrees Fahrenheit. This assumes you’re hearing the snowy tree cricket, the most common variety in the United States.

Fame has fully eluded Amos Dolbear a century after he left this planet. Perhaps we can remedy this, just a little, by announcing the temperature during our next camping trip while grandly invoking Dolbear’s law.

Crickets easily catch our notice because we humans are very aware of repetitions that are roughly in sync with our own heartbeats—and crickets’ stridulation rate rarely diverges by more than 50 percent from this. We especially notice things that repeat between 0.5 and ten times a second. Slower than that and we may regard the individual events—such as the hooting of some owls—as independent and not link them into a single activity. Faster than that and we perceive them as a steady sound, its own sole event rather than an assembly of others.

For example, many mosquitoes give off an annoying drone in the musical note A, the same as a telephone’s dial tone.4

It’s caused by wings flapping at 440 beats per second. But other mosquitoes flap six hundred times a second, producing something like a D or D-sharp. In either case our ears perceive no sensation of separate mosquito beats. Anything more than about fifteen beats a second seems a single tone.

Meanwhile, as bees jerkily dart through the air to pollinate trees and flowers, their low, buzzing pitch comes from wings flapping 230 times a second, the note of A-sharp one full octave below the mosquito drone. But frogs and salamanders are ready for a variety of flying insects, as they quickly arise from their hibernation and start to fill the air with mating songs.

Above all the marshy melodramas, fireflies blink on and off. Their bioluminescence, caused by the enzyme luciferin interacting with oxygen, typically emits a yellow-green light in the same color as an aurora.5 And, like the northern lights, fireflies produce radiance without heat. Also like an aurora, fireflies produce light that is unreliable. The insects are only active for a few weeks in late spring and summer, only when the night is warmer than fifty degrees, and—for reasons that remain mysterious—they almost never turn on their lights west of Kansas.

As spring progresses, the season’s new crop of young mammals becomes obvious to country dwellers. We see bear cubs and fawns staying close to their mothers, but rarely do we observe the more secluded, furtive animals, such as coyotes, who have their pups then, too. None of these large mammals actually breeds in the spring. They mate during the previous fall, instinctively planning for their young to be born during spring’s food festival. Mostly it’s the small mammals who are going out on dates during the spring, and even they time their activities to catch the peak of the season’s abundance. Chipmunks start to be active enough to breed as early as February and are thus among the first mammals we see, even when patches of snow still prevail. They rely on having multiple entrances to their dens to evade predators, and they protect themselves with their jerky speed.

It’s often not enough. Despite some silly claims on the Web that various rodents can whiz along at thirty-five miles per hour, actual laboratory track tests and field measurements show that rodents have a top speed of about ten miles per hour, give or take a couple. They may seem much faster because, once again, they traverse many rodent lengths per second. But a mouse can only dash at eight miles per hour. The common eastern gray squirrel can hit twelve miles per hour on a good day. Unfortunately for them, they cannot outrace their usual predators if the match is held at a straightaway. A house cat can run more than three times faster than any mouse. It’s not a fair contest between Tom and Jerry.

WHO CAN CATCH WHOM

The Chase Is On: Top Speeds of Common Mammals

In Miles per Hour

Chipmunk 7

Mouse 8

Squirrel 12

White-tailed deer 30

Cat 30

Grizzly bear, black bear 30

Rabbit 30

Fox 42

Coyote 43

Fastest dogs 44

The very fastest animals? None races through American forests: it’s a tie between the cheetah and the sailfish. Both can reach sixty-eight miles per hour. The fastest-ever racehorse, at least in the 1.25-mile category, was Secretariat. That day in 1973 when he left all other horses in the distant dust while winning the Kentucky Derby, he posted an average speed of thirty-eight miles per hour.