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The Flicker Fusion Factor By Robert Winkler
Despite the high price of gas, we go everywhere in our cars, and, for most of us, the faster we go the better. Posted speed limits are one of life's great fictions. Virtually no one observes them. Whenever I do I can be sure a tailgater will magically appear in my rearview mirror. Speeding is the norm, the de facto law, and many motorists view anyone who observes speed limits as a de facto lawbreaker or a wimp who deserves to be run off the road. Police enforcement of speed limits is spotty at best. Meanwhile, road improvements, car redesigns, and automaker advertisements are always nudging us to speed up. In our cities and on the highways that feed into them, traffic volume alone keeps speeding in check. In the suburbs, however, it's the Wild West. I frequently observe motorists going 40 miles an hour or faster on winding side streets. Many can't control their cars at such speeds, even those who drive luxury sports cars. As they come around a sharp curve, they go into the lane of oncoming traffic to combat the centrifugal force that threatens to fling them off the road. If they encounter your car coming from the other direction, too bad. You'll just have to move over. Suburban drivers who don't are asking for a head-on collision. Speed has become the driving force in our lives. Everyone is in a hurry—to get to work, to get home, to drop off the kids, to pick them up, to get to the supermarket, the post office, the dump, Wal-Mart. We must go ever faster, and we must build gas-guzzling cars ever bigger and stronger to protect us in the reckless chase for money and status. We pay lip service to the environment, then fill up at the gas station. God help those who get in our way. Man, however, wasn't meant to fly—neither with wings of Icarus nor within our beloved machines that float on a cushion of air. Physiologically, we're designed to locomote on two legs: to walk or to run. When we get behind the wheel of a car, we may think we gain a bird's power of flight, but actually we are poor, pathetic imitators of birds. Thousands of people and millions of wild and domestic animals die every year in this country because motorists lack the perceptual adaptations of birds.1 Motorists cannot avoid accidents because they are incapable of reacting quickly enough when moving at high speed. Their flicker fusion frequency—the point at which an animal sees an increasingly rapid flashing light as a continuous beam—is too slow. Humans have a flicker fusion frequency of 60 Hz (60 cycles per second); in domestic pigeons, flicker fusion frequency rises to 100 Hz. Birds of prey, whose survival hinges on quickness, are thought to have an even higher flicker fusion frequency than pigeons—consider, for example, the northern goshawk, which lives in deep forests and earns its living by chasing down other birds.
Were a goshawk to watch a movie, its high flicker fusion frequency might cause it to see jerky rather than smooth motion, similar to what we see in very old movies, which run at a slower frame rate than modern ones.2 This visual adaptation is thought to give birds greater resolving power while moving. A goshawk flying at high speed can probably perceive an obstacle, and react to it by veering away, in a fraction of the time it would take a motorist to avoid an accident. If the goshawk were subject to the inferior perceptual abilities of humans, it would end up splattered against a tree trunk.3 A road-hugging Porsche may be more responsive than a Ford Focus. But when you’re going 40 and a deer steps right in front of your car, the great equalizer comes into play. If the deer is only a few yards away, both cars will collide with it, because neither driver can escape the physiological limitations of being human. The power we feel when we get into a car or an SUV is illusory. When we become motorists, we actually get weaker. We leave our natural bipedal realm for an airborne one in which we are out of control. Our self-absorption prevents us from accepting our limitations, though every day we see the consequences in untold deaths of humans and non-human animals. Minimizing the ill effects of this hubris is simple enough.4 As Prince observed in “Little Red Corvette”: honey, you got to slow down. It’s the price of being human.Read comments about this essay on Pharyngula, the science blog of PZ Myers. Related articles: Attacked in the Woods I: A female northern goshawk burns her orange eyes into my memory Attacked in the Woods II: The goshawk does not forgive us our trespasses Get Out of My @%^&! Way, an excellent "Rules of Unreality" column by Davin Arul, from The Star (Malaysia) Create a link to this site
A message from Robert Winkler 1 "Speeding is a factor in 30 percent of all fatal crashes. About 1,000 fatalities resulted from speeding-related motor vehicle crashes every month." |
he closest we come to free
flight in our lives is not when we take off in an airplane. It is when
we drive our cars. The speed, altitude, centrifugal forces, and sensations
of flying that we experience in an SUV, a sports car, or, in my case, an
economy box, let us feel what it is like to be a bird. This partly explains
why we love our cars, preferring this mode of locomotion to any other, even
walking and running, for which we are supremely adapted.
Without benefit of road
markings, warning signs, traffic lights, and speed limits, the goshawk zooms
around its wild neighborhood in relative safety. As it hotly pursues a
ruffed grouse or wood duck, the goshawk may fly just above the ground at 40
miles an hour, mirroring the unpredictable twists and turns of its prey.
Although the goshawk’s wingspan approaches four feet, superb vision and
instant reflexes help it avoid collisions with countless branches.