“A sense of wonder,” Richard Fortey said, “cannot be purchased over the counter at the superstore. Nor can it be wheeled out of the corner cupboard at the behest of some curriculum or other. Instead,” he wrote, “it steals up on the child unexpectedly.”

Wonder might arise from a beautiful demonstration of a complex piece of equipment. Or it might steal up from the perfection of a starry sky. This particular piece of wonder falls somewhere in between.

Place a nickel on the back of your hand. Hold your arm straight out, with the nickel toward the ceiling. Now jump.

What happens to the nickel? For just a moment, when you reach the highest point of your jump and then fall back down, the nickel floats! Why? Because as things fall, they are weightless! Weight isn’t gravity pulling down. Instead, weight is the ground (or your chair, or your hand on the nickel) pushing back up!

This simple fact leads to so many places. Why do heavy and light objects fall at the same rate? Because when they’re falling, they’re not heavy or light! They have no weight, and so a heavy object falls at just the same rate as a light object.

 

Why do astronauts float in the space shuttle? Almost everyone thinks it’s because there’s “no gravity in space.” But that can’t be true, otherwise why would the shuttle orbit the Earth at all? In fact, astronauts float because they and their shuttle are falling. And because they are falling, they have no weight.

Why, on the other hand, do you feel your weight on an airplane? Because, unlike the space shuttle, an airplane isn’t falling. Instead, the airplane is pushing down on the air, and the air is pushing back up on the airplane.

Finally, what is gravity, anyway? Albert Einstein was asking himself this same question when he realized that if he fell out a window, he wouldn’t feel his weight on the way down. This realization, what Einstein called his “happiest thought,” led to the General Theory of Relativity, which is, without a hint of hyperbole, one of the greatest accomplishments of our species.

We think of gravity as this pervasive thing, everywhere, impossible to avoid, constantly dragging us down. Yet you yourself (and your nickel) can overcome the entire force of the Earth just by jumping up. Wonder is as close as the soles of your shoes.

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