Tuesday, 27 December 2011

The dangerous unreliability of the human memory

Evaporating Liquid Nitrogen Here's a great story from the Darwin Awards which illustrates how dangerous it is to rely on your memory as a long term knowledge-storage unit.

"My senior year of college opened with the customary research projects, grad school applications, and the like. But that all changed two months ago. Some of you may have heard rumors of some bizarre accident that I was involved in. Here is the truth, unabridged, for those who actually want to know.
"In the second week of school the society of physics students held a roughly annual welcome-back party. As tradition dictates we made our own ice cream with liquid nitrogen, 77 Kelvin, as a refrigerant and aerator. We spilled a little liquid nitrogen onto a table and watched the tiny drops dance around. Someone asked, "Why does it do that?" That may have been the point of no return.
"As is traditionally my role, I answered that the nitrogen evaporates at the surface of the table, which creates a cushion of air for the drop to sit on, and thermally insulates the drop, which minimizes further evaporation. That's why a drop dances around without boiling, without touching the table, and without spreading out like a pool of water. 
"Then I continued. I mentioned that the very same principle makes it possible to dip one's wet hand into molten lead, or drink liquid nitrogen without injury. I had done the latter several years earlier in a cryogenics lab, and remembered the physics of how it worked. 
"Naturally those around me were skeptical. "It will freeze your whole body. Remember Terminator 2?" But I was sure of myself. I had done it before, and I believed in the physics behind it. So I unhesitatingly poured myself a glass and took a shot. Simple. Swallow, blow smoke out my nose, impress everyone.
"Within two seconds I collapsed to the floor, unable to breathe or indeed do anything except feel intense pain. The ambulance arrived. The police arrived. The journey to the hospital. The attempt to explain to baffled ER staff how something like this could happen. Then I passed out. I woke up the next morning connected to beeping machines. It turns out that, in accordance with popular belief, you really should not drink liquid nitrogen.
"I subsequently learned a few things about liquid nitrogen. While you can safely hold it in your mouth and blow neat smoke patterns, you should never, ever swallow. The closed epiglottis prevents the gas from escaping, so expanding gas is forced into your body. And your esophagus naturally constricts around anything inside it, so even though there is a thin protective gas layer, your esophagus will manage to make contact with the liquid nitrogen.
"I also learned that my memory was flawed. When I did the trick six years ago, I put it into my mouth and didn't swallow. Over time, the fine line between parlor trick and fatal accident must have blurred.
"I was badly burned from epiglottis to stomach bottom. The gas expanded to fill my chest cavity, and the pressure collapsed a lung. During a grueling all-night surgery, they removed part of my stomach and ran my entire digestive system on a machine. I was on a breather until my lung was restored. There are a few considerably uglier details which I will spare you. Doctors were impressed with my recuperative skills. I could breathe on my own after a few days. I could sit up in bed after a week, and was walking and eating in two. At eight weeks I'm virtually healed except for a number of unsightly scars.
"And there's good news! I am the first documented medical case of a cryogenic ingestion. Read the New England Journal of Medicine. Three articles are in review now, and will be published soon.
"My little adventure leaves me with a tendency to tell bad physics jokes at department meetings".


oldy said...

don't play with fire....

Nick Milton said...

well, yes, but more importantly, don't think you can rely on your memory of where the safe limits are.

rucsb said...

It was a pure risky behavior . Probably he was too adventurous . Tested principle in all spheres of life, to rely on wisdom of crowds than your own memory.

Nick Milton said...

It was risky behaviour, but he had done it safely before, and thought he remembered how to do it safely again.

People at work are involved in dangerous activities. How do we ensure they do not rely solely on their memory of how to do them safely?

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