I am fascinated by the fact that an extended series of extremely unlikely conditions allowed life as we know it to exist on earth. For starters, each of the known four forces at work in the universe -- gravity, the electromagnetic force (e.g. light, etc.), and the less familiar but essential weak and strong forces determining the behavior of subatomic particles -– have to be what pretty much exactly they are. If any of them were significantly different, there would be no stars, planets, air, water, trees, Broadway musicals, or essentially anything we might enjoy.
Leaping ahead, there are other improbable but essential accidents. For example, the earth was born without a moon, but one came along only a few tens of millions of years after the earth was formed. At that time there were many more planetary objects in the solar system and many collisions. One important collision kicked a piece of earth off into nearby space sending plenty of stuff into orbit around the earth, finally coalescing into the moon.
The moon is spiraling away from earth at the rate of 1.5 inches a year. Calculating backwards, which I have just done, it appears that three billion years ago, when life first came about on earth, the moon, receding at its current pace, was roughly 75,000 miles closer than it now is – 165,000 miles rather than the present average distance of 239,000 miles, and it would have been spinning around, appearing larger by half and played hell with the tides. (The moon’s orbit is eliptical and its distance from the earth varies by up to 25,000 miles.)
Fortunately, during our time here the moon is perfectly placed to preserve our existence by stabilizing the earth, giving us predictable seasons and the right tides for the success of life. By remarkable coincidence it is also the right size and distance away to block all but the outer edge of the sun when seen from the narrow path of a total eclipse, allowing us to learn much about the universe that we would otherwise not know. Think how little we would know if the sky were perpetually cloudy.
Yours From The Field,