Monday, June 27, 2016

Why sidewalk cracks can seem like the Grand Canyon.

A Science Guy’s Almanac #27. Year 2. June 27, 2016
Why sidewalk cracks can seem like the Grand Canyon.

We’ve all walked on sidewalks.

Normally, there’s no problem with walking on a sidewalk. The name sidewalk describes the function of the strip of concrete.

Every now and then, there is a problem. You’re walking along, minding your own business, when
You trip and have to fight gravity to avoid face-planting right then. Embarrassed and upset with the situation, you begin to search for the offending area in the sidewalk. You expect

When you find nothing as obvious as the photo above, you alter your search parameters.

Finding nothing even remotely as obvious as even that photo, you continue your search. If you’re lucky you might find a minor variation in the sidewalk's topography.

“I don’t understand,” you mutter. “I thought for sure that there would be a hole the size of the Grand Canyon that tripped me. How can I trip on maybe a half and inch difference in height?”

The answer to that question is this.
Brains hate to waste energy. 

Your brain is very efficient. It does all it can to reduce the amount of energy you use in any task you undertake.

Watch a child learning to walk. Go ahead, click the link. It's my granddaughter. Each step is a journey into unexplored territory. Knees, when they bend, rise high as the brain ensures the foot clears the confines of the ground beneath it.

After walking for a few months, the height of the child’s knee-lifts lesson. The brain learns that most surfaces upon which we walk are not littered with tall obstacles. Expending energy to clear a non-existent object in the pathway is a waste of energy. Brains hate to waste energy.

After many years of walking, mostly on smooth surfaces, your brain has your stride down to a science. Without you requesting it, your brain determined the absolute minimum amount of clearance your toes need as they move forward in a stride. You use that stride all the time. Everything’s fine with that stride—until some slight imperfection lies in your pathway.

In general, toes have less than one-half inch clearance from the ground on each stride.

Most of you knew this without knowing you knew about this. If you’ve purchased a pair of shoes with soles thicker than your last pair, there’s a good chance you’ve experienced the above.

If you want to see the truth in that clearance height value, find a sidewalk where people are walking. This works best if there’s a curb. Lay down in the gutter with your eyes even with the sidewalk. Watch people’s feet as the walk past you. The people you observe will think you’re a derelict or feeble-minded, but you’ll see that what I’ve written here is true.

Question: How much ground clearance do most toes have?
Answer: Less than one-half an inch!
Why? Brains hate to waste energy.

The next time you trip on the sidewalk, try not to look back and see what chasm attacked you. If you find such a crater, put up a historic marker. Chances are good that you’ll never have that happen again.

Next Almanac post: It’s summer. Here’s an Almanac re-run!

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