Wheels within wheels within wheels.
the wondrous wizardry of a puny weakling

With the International Year of Astronomy at our very doorsteps I felt it appropriate to philosophize just a little about the best-known of nature's forces - gravity. The universally-active force of gravity is responsible for a truly paradoxical situation. Gravity is oh so pathetically weak, yet this puny force works sheer magic in the heavens, governing the intricate paths of all celestial objects from the tiniest speck of space dust to super clusters of galaxies.

Just how puny is gravity? Really puny! As you probably know, the gravitational force exerted by any object depends entirely upon its mass. The bigger the object, the more force it exerts. Now stop and think. It takes an object the size of our earth to hold a brick down. And the brick is anything but riveted to the ground. You - yes you - can defy the force of gravity exerted by this massive planet. You can pick up the brick! Let Wikipedia elaborate:

The gravitational force is extremely weak compared with other fundamental forces. For example, the gravitational force between an electron and proton 1 meter apart is approximately 10^-67 newton, while the electromagnetic force between the same two particles is approximately 10^-28 newton. Both these forces are weak when compared with the forces we are able to experience directly, but the electromagnetic force in this example is some 39 orders of magnitude (i.e. 10³⁹ ) greater than the force of gravity - roughly the same ratio as the mass of the Sun compared to a microgram mass.

Yet, in spite of its impotence, the weakling keeps the universe a-dancing in a remarkably-choreographed, complex and intricate heavenly reel. Well now, that statement doesn't tell the full story. Credit for the remarkable suite of gravitationally-mediated, intricate movements found throughout the universe, from the parabolic trajectory of a pirate's cannon ball to the "real" tracks made by a galaxy as it moves around in response to pulls from other galaxies and clusters of galaxies, has to be shared with another remarkable phenomenon - momentum, or, more simply put, movement. The cannon ball won't carve out any path under gravity's influence unless some Blackbeard fires it. In the beginning, God not only assigned a precise value to the force of gravity He also imparted motion to all the universe's denizens. Some He sent this way and others He sent that way; from that moment on gravity has constrained their movements.

Unlike a primordial explosion, which would produce haphazard, random, ugly and potentially hazardous motions, God planned the waltz of the heavens to ensure that no cosmic pileups would ever occur. Beauty and harmony are the order of the day. But He did choreograph some spectacular collisions - between comets and planets, between galaxy and galaxy, and even, as recently discovered, between clusters of galaxies (see photo at top). All to the glory of the One who assigned their motions all the way to the end of the dance, a dance which continues to increase in complexity as it unfolds. Moons around planets around stars around galaxies around galactic clusters - nobody knows what paths heavenly objects actually carve out. Wheels within wheels within wheels.

In our own solar system millions of dancers - comets, asteroids, planets, and moons - orbit the local waltz's lead dancer, the sun. In addition, they sometimes weave complex paths around and (occasionally) between each other as they also fall under the influence of one another's gravitational attraction. Constant movement means that forces of attraction between flying objects will wax and wane as they approach each other or move apart. Some encounters are sufficient to nudge a smaller body into a new trajectory, sometimes temporarily and sometimes permanently. Occasionally a comet's orbital path is perturbed in such a way as to bring it close enough to giant Jupiter to fall under its gravitational spell and receive a "fatal" slingshot impetus, kicking it right out of our solar system and forcing it to trespass in foreign territory. Or, as happened to Comet Shoemaker Levy, it might smash into the planet.

Calculating the trajectories of two moving bodies under mutual gravitational attraction is easy-peasy. But add a third body into the equation, and you stump the cleverest of mathematicians. To this very day, the "three body problem" has not been solved by mathematicians. They cannot come up with formulae that enable you to predict exactly where all three will be in fifty or a hundred years from now. I jest not. Yet God had to work out a multi-billion-body problem. Now that's one brain! That's a Being worthy of fervent, ever-lasting worship.

In spite of the weakness of the gravitational constant, it's just right. Absolutely, precisely spot on. Change it ever so slightly and chaos would ensue. The Holy One of Israel, the father of Jesus Christ, makes no mistakes. He knows exactly what He is doing.