2. The Parallax Problem

Fatal Miscalculations

In 2008, as Hurricane Ike approached Houston, Texas, local officials ordered evacuations from coastal counties before the storm. All the electronic news media had gone to 24-hour coverage of the storm in advance of its landfall. Many weather services had predicted a storm surge up to 24 feet high. In fact, when the surge finally came onshore, it swept homes off their foundations and left seaweed lodged high on telephone wires more than ten miles inland.

Despite the warnings, many residents of coastal communities refused to evacuate. Worse, curious onlookers were drawn to the storm like moths to a flame. As a consequence, at least 74 people died.[1] Why did all these people ignore the warnings designed to save them? Why did so many  make fatal miscalculations when they had days to save their lives? We can only conjecture that they must have believed the storm would not be as devastating as the predictions.

Exactly why they believed that, we will never know. We can say with a high degree of certainty, however, it was not because the warnings were unclear or unheard. Sheriff’s department personnel went door to door ordering people to leave.

Obviously, people were conflicted. Something, or someone, even if it was just an inner voice, told them they had a good chance of riding out the storm by sheltering in place.

Parallax Defined

A phenomenon called parallax might explain some of that conflict. Parallax is an inherent issue in any system or organism that looks at the world from more than one point of view. Parallax is a form of perceptual distortion in which the position or orientation of an object appears to differ when viewed from different perspectives.

Humans, for instance, have two eyes. To experience parallax, try this simple experiment. Hold a pencil about six inches in front of your nose with the writing facing to one side. Now close one eye at a time. You should see two things. The position of the pencil will appear to shift relative to the background even though it has not, and the writing will be visible with one eye but not the other.

You can also experience parallax with any camera that uses different lenses for composing and taking pictures. Called rangefinder cameras, as opposed to single-lens reflex cameras, these typically contain optical systems offset from each other by several inches.

This offset makes no observable difference in photographs taken at a distance. However, parallax distortion makes a huge difference in close-up photos. Imagine photographing a flower from several inches away with such a camera. When you center the flower in the viewfinder, it may not fit within the angle of view of the picture-taking lens.

Try another simple experiment. Close your left eye and hold a finger two inches in front of your right eye. Now, without moving the finger, close your right eye and open the left. You probably can no longer even see the finger.

Photographers and astronomers encounter this problem frequently. An astronomer in the southern hemisphere may not even be able to see stars that a colleague in the northern hemisphere could. Different observation points limit their range of vision.

Parallax Among Mediums

Likewise, someone receiving information through two different mediums will process information from two different points of view, introducing a kind of parallax effect that can distort perception.

On a simplistic level, when viewed through one medium, the alligator may signal “threat.” When viewed through another, the alligator may appear to be unreal, unbelievable, a hoax, a joke, or even humorous.  What accounts for these differences?

In the case of the East End Park alligator, people who experienced the danger firsthand drew different conclusions than those who read the story in a newspaper or saw it on TV.

Hurricane Ike victims may have experienced this same parallax effect. Imagine this scenario:

You own a beachfront home high on stilts on the Bolivar Peninsula, east of Galveston Bay. In the previous two months, two tropical storms and one hurricane threatened you. For days before each storm, you watched TV, read the papers, listened to radio, and scoured the Internet for every piece of information you could find about the storms’ trajectories, intensities and threat levels so that you could prepare appropriately.

In each case, officials called for the evacuation of coastal communities. You heeded their warnings during the first two storms. You took off work, bought plywood, and boarded up your windows. Then you packed up your family and pets, evacuated, sat in traffic jams for hours while you crawled 100 miles or more inland, and fought with hundreds of thousands of other people for scarce hotel rooms. In the end, the first storm, Dolly, veered far southwest of you before landfall and caused no damage in your area. The second, Tropical Storm Edouard, dumped less rain on your home than a big thunderstorm even though it passed directly over your property. You breathed a sigh of relief.

After Edouard, you returned from three days on the road. You discovered that someone had looted your home. Fatigued and angry, you took down the plywood covering your windows. No sooner had you filed the insurance report than a third storm, Gustav approached.

Exhausted from the first two storms, you again watch TV and listen to the official calls for evacuation. This time, however, you decide to take your chances with the storm. It veers slightly east as it approaches leaving you on the dry side with the winds pushing water back out to sea. You sleep through the storm. The next morning, coffee in hand, you walk outside to inspect the damage. With the exception of some missing shingles, there is none.

Less than two weeks later, a fourth storm approaches. Officials warn against “hurricane fatigue” and urge everyone to take this one, named Ike, seriously. As it approaches, you keep a wary eye on the Gulf, mindful that the storm killed several hundred people as it crossed the Caribbean.

The storm intensifies as it nears land, but is only a Category Two. Officials call for evacuations again. Your neighbors, who have ridden out several previous Category Two storms, decide to stay. After listening to their stories, you decide to stay also.

The storm approaches in the early evening. Just before you lose power, you hear that the eye of the storm is headed directly toward you and that the National Weather Service predicts a storm surge up to 24 feet high in your area.

You start to panic. Your house is only elevated 18 feet. You gather your family and pets, grab a flashlight and run down to your car to try to evacuate at the last minute. Less than a block away, you discover that the waves are already covering the road that represents your only way out. With no choice, you turn around and climb the stairs to your home, praying that the forecasters will be wrong again. They will not be.

This is a likely scenario experienced by many of those who perished in Ike. It was not simply a case of stupidity, bravado or excess testosterone that kept people in the storm’s path. Conflicting reports, experiences and advice caused people to make bad decisions. Parallax distorted their perceptions.

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