Gravity. No, seriously.

Ask yourself this important question:

Where would we be without gravity?

Think about it. Do you realize how difficult it is to clean up spilled beer uh, milk if there is no gravity? Or to sit in a recliner? Or make a left-hand turn at a busy intersection? Or flush a toilet? Or eat pistachios? Or just hang out?

See what I mean? There is—literally—no telling where we’d be without gravity. Because gravity is what keeps us and everything else pinned to the earth, and that everything else includes items like the water we drink and the air we breathe and the burger on the grill.

Gravity is the earth-bound name for a basic natural force called gravitation, the attraction between bodies of mass. The more mass, the more gravitation. Planets, stars, moons, all exert gravitation. So does a baseball, though not enough to have an effect. So do you and me, but again, not so’s you’d notice.

The gravitational force of the moon, and the sun, are what cause the tides in our seas and oceans. Their gravity tugs at our whole planet, but it is the liquid sea that responds in the most obvious fashion.

Gravity is one of the four natural forces that control our physical universe. Besides gravitation, the others are the electromagnetic force, the strong force and the weak force.

Still, despite the best minds being applied to it—and I mean folks like Aristotle, Galileo Galilei, Isaac Newton and Albert Einstein—we’re still not sure exactly what causes gravitation. Einstein’s theory of general relativity suggests that gravitation is a warping of spacetime, an actual inward flux of the fabric of the universe caused by the mass of objects. The moon, therefore, orbits the earth because it is caught in this four-dimensional gravitational dimple, like a marble spiraling around the inside of a serving bowl with the earth at the center.

A simplified diagram of the spacetime warp caused by gravitation.

In real terms, spacetime is drawn in from all directions. In the case

of our moon, its velocity prevents it from falling to earth; actually,

the moon is very gradually moving away from earth.
CLICK THE IMAGE FOR ANIMATION (Image NASA)

Oh-oh. This reminds me of a joke. Hey, it’s a gravity joke, okay?

A tourist, wandering around the charter boat docks in Key West, sees the captain of a dive boat cleaning scuba gear and he shouts out, “Hey, Captain, why is it that divers always fall backward off a boat?”

At which the captain snarls, “’Cause if they fell forward, they’d still be in the blasted boat!”

There’s a ton of minutiae about gravity, lots of esoterica and other tidbits, but I think there is one significant concept that is, perhaps, most important to keep in mind. It seems that gravitation is the main problem between classical physics and quantum physics. Gravitation doesn’t have much of an effect on the sub-atomic particles that are the basic bits and pieces of all matter. That is why the strong nuclear force and the weak nuclear force were proposed, as a way of explaining the structure and behavior of atomic particles.

I still think they could have come up with better names for them.

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Answer to last week's quiz, what is the sun's stellar name? Sol