18. Let there be planets, forming in orbits around the stars

(continued) Chapter 2. Long Evolution: Universe Emerging



While the sun was evolving, at least eight large clumps spaced out in its debris cloud were also pulling in on themselves, collapsing of their own gravity (and that’s not counting all those other clumps which would become “planetoids” and moons large and small).  As these eight grew denser their increasing gravity pulled in more of the dust and debris surrounding each clump; gradually they all took on roundness. Between any two such rounding clumps the gas and dust separated (separations again, as in Genesis), some going to one clump, more to the clump in the other direction. As the spaces between them grew slowly emptier, all eight grew more dense, more round, more solid. Planets in utero.


The reason these planets-to-be did not get pulled all the way in to become engulfed by the birthing central star/sun was because the entire system, from center to edge, was rotating. The rotational movement imparted centrifugal force to the planets – in effect slinging them “out,” away from the sun. But they could not in fact sling away because another force, Sol’s huge gravity, held them “in.” The solar center had grown so huge and dense that it now had enormous gravity all on its own, and that gravity held all eight new proto-planets firmly in its grip. The two opposing forces – centrifugal outward, gravity inward – held each of the eight in an equilibrium, a sort of stasis, from whence they could venture neither farther out nor closer in. Planetary orbits were born.


Of course the whole story of planetary formation in our solar system is considerably more complex than this simplified version. Recent astronomical research shows how very complicated it is to reconstruct the history of what happened when, millions of years ago and millions of miles away. Newly discovered evidence reveals that the giants Jupiter and Saturn danced a jig, together moving in much closer to the sun, severely discombobulating the small inner planets before they waltzed back out, going farther, farther than they were before, finally settling about where they are today. But these details don’t much matter here – just remember that few things in the long evolution of the heavens have ever been as simple as they might appear to us latecomers.


The whole thing turned, wheels within a wheel. As our birthing sun ignited and began casting forth its enormous new light and heat, it rotated. And each of its newly formed planets orbited in great ellipses around their parent sun, even as they too rotated – all nine bodies slowly spinning on their individual axes. The new star’s entire system moreover moved through the universe in its place at the edge of the Orion spiral arm in its parent Milky Way galaxy. The galaxy itself rotated too – a grand self-organized spectacle of matter and energy in motion. They say the entire universe itself is rotating (though how they might deduce this raises questions as interesting as the obvious question of whether the big bang arrived like a cosmic dreidel flung spinning from the playful hand of God). All this for no apparent reason – devoid of any apparent purpose at all. A gigantic question mark to challenge creatures soon to evolve on the rocky planet third-out from the star to one day be known as Sol.


The relative speeds resulting from all this rotation are interesting in themselves. Relaxing with a toddy in your lawn chair at the equator, you would be traveling roughly a thousand miles per hour with the earth’s rotation. Added to this, the earth is orbiting the sun at 67,000 miles per hour. Plus, add in another 486,000 miles per hour as our solar system keeps pace with the galaxy’s rotation. Plus again, there’s another estimated 1.3 million miles per hour as our galaxy sails through the universe. Add them up. Even when sitting perfectly still, with each sip of your toddy you are traveling through the universe far faster than a puny bullet which speeds along at only 3,000 miles per hour. Pretend you’re Einstein, imagining himself inside an elevator way out in space, figuring out that there’s really no difference between gravity and acceleration. Great minds ponder the simplest questions. Think about that.


Except for their roundness, the eight new planets were but hot balls, hardly recognizable as planets. Major differences among them, however, were already evident. The inner four had surfaces, and those surfaces consisted of roiling magma seething at thousands of degrees. Three were roughly similar in size, but one, nearest the sun, was noticeably smaller. In a distant future they would be called Mercury, Venus, Earth, and Mars.


The other four, the outer planets, were many times larger than the inner four, and they had no surfaces, none at all. They were made of gas – self-formed into spheres surrounding great density at their centers, with gradually decreasing density of the gas correlating with distance from their centers. Where their outermost atmospheres became totally thinned, their planetariness simply ended – and that’s how they still are today.


The innermost of these gas giants, next out from Mars, was a true giant, so vastly more huge than its peers that it has been called a star which never got quite big enough to ignite. Mighty Jupiter, largest planet in our star system, named after the king of the old gods. It was followed next out by almost-as-mighty Saturn, which would one day be encircled by rings of rocky-icy detritus that would seem beautiful as seen from afar. Last-out Uranus and Neptune were smaller, relative to Jupiter, but still gas giants. The immense gravity of these four huge planets would directly affect the orbital motion of each other as well as the motion of all the smaller planets, and would actually make the sun wobble in its location at the center. They still do, and it still does, to this day.


The evolution of the rocky planets is in general more interesting that that of the gas giants, because a rocky planet has a well defined hard surface on which things can happen. It also contains far more heavy elements than a gas giant, and this adds to the interesting things that happen on and in it. From their beginnings as balls of boiling magma, the four rocky planets began cooling and, ever so slowly, their surfaces hardened. The process proceeded a bit differently on each of the four, but noting how it happened on the third planet out will suffice for our purposes.


The earth

Earth had at last formed from a cloud of greatly condensed dust and gas surrounding our young sun a mere hundred million years after gravity had created the sun itself. Spinning on its axis so fast that a day lasted only six hours, the new earth was a lava hell – a turbulent, flowing mass of red hot liquid rock. Pause and consider what this disruption of measurable time must mean for the first six days as described in Genesis. It also means trouble for dividing of the waters, for any water would have boiled away in seconds.


In this roiling maelstrom the earth’s constituent atoms were thoroughly jumbled, but not for long. While lighter elements rose or were pushed to the surface, where they would gradually cool and solidify to become the earth’s crust that we now stand on, gravity pulled most of the heaviest elements in to the center, forming a huge core of molten iron and nickel. It’s still there today, dwarfing by orders of magnitude the pitiful mouse holes we dig to mine teeny slugs of heavy minerals at or near the crust’s outer surface.


The heavy metal core’s churning/turning motion, way down at the center of the molten mantle surrounding it, acts as a planet-sized magneto, creating a magnetic force field that reaches far out into the space surrounding the Earth – a planet-sized manifestation of the electromagnetic force discussed earlier. This invisible field of force makes life on earth possible by deflecting super-charged particles which periodically emanate from sunspots – vast storms on our life-giving sun – and other radiation bursts arriving from faraway quarters of the universe. These so-called “cosmic rays” would be immediately deadly to all life on earth if they were not deflected by our protective magnetic field. Sometimes during intense waves of incoming radiation, we see its deflective action at work and admire it as the aurora borealis – the northern lights. Its force is out there, protecting us. What a lucky accident.


The moon

In our earth’s very early history, while still mostly molten, by chance it was struck not quite fully head-on by a large planetary body thought to have been the size of Mars. A collision of titans, the almighty crash had two immediate results. The invading world disintegrated even while gouging out a massive portion from one earth hemisphere. It left about half of itself in the titanic hole it had dug, becoming a merged part of the earth. The rest of it, along with massive pieces of earth’s displaced crust and mantle, broke free and, by chance, went into orbit around the earth. Luna, earth’s children would someday call it.


Filled with lighter elements gouged from the earth’s crust, the new moon was so big that its considerable gravity gradually reshaped itself into a sphere. Its gravity was never sufficient to hold an atmosphere, and over time it lost most of its internal heat. Any rotation the invader may have arrived with was so undone by the collision that Luna ended up rotating on its axis exactly once per orbit – a curiosity among celestial objects – with the result that we only ever see but one face of our moon, the face it keeps turned toward earth. To see the back side you must become an astronaut.


The oceans

Another hundred million years or two fleeted by. Our planet’s primeval atmosphere had – by various debated possibilities – accumulated copious amounts of water vapor in the form of steam. Initially too hot for liquid water to exist, the earth’s continued cooling eventually allowed the steam to start condensing into rain. Once started, the rain poured down for some millions of years – a real gully washer – enlarging the gullies, filling them, then overflowing them in all directions. Every year for unknown millions of years the daily forecast was for downpouring torrential rain, and more rain, without cease. Every depression on the earth’s crust filled with the new liquid water:  puddles; lakes, streams, rivers, whole seas. At least, that’s the most popular view – as you can imagine, scientists disagree on this too and keep multiple theories and arguments going all the time. In any case, by around 3.8 billion years ago permanent oceans were in place upon the earth – the waters that were “under” heaven.


Notice: the earth now had a moon and worldwide water – both being most helpful for enabling our kind of life to develop. We are familiar with water’s vital role in sustaining life, less familiar with our moon’s unsung role. The moon’s gravitational pull does more than merely create our daily tides and mark menstrual cycles. It also keeps the earth from wobbling – providing a steadiness which tends to ensure (but does not guarantee) that we have no wild climatic swings. The young Earth thus became unusually stable on its axis. Also, Luna’s momentum and gravity oh-so-gradually slowed earth’s rotation, lengthening the initial six-hour day until, a billion or two years later, our familiar 24-hour day eventually was reached. Some slowing still continues, but it is so slight that no one cares.


It is reasonable, though, to wonder about the actual length of each of those first six days cited in Genesis. We could reasonably presume that God can use “magical” gee-whiz powers to make a day last any length He wants. But no, it would be childishly credulous and most unseemly presumptuous to presume anything at all about a God so almighty ingenious that He Knows How to create a whole evolving universe which self generates and self organizes even as it evolves, and out of which ever-higher forms of complexity just “emerge.”  My God! – how indescribably smart God obviously must be! We mere little mortals, ourselves quite obviously an evolved-and-emerged component of God’s Infinite Evolutionary Plan would have to be colossally vain – filled with vile hubris – to think we know very much about how The Infinite God does things. No, that won’t do at all. Better we stop speculating and get back to simply reporting what we think we know of the apparent evidence we’re pretty sure we’ve discovered about how things unfolded.


The seasons

Of great importance for us, the collision which created the moon knocked the earth’s axis permanently into a slight tilt, a few degrees off perpendicular to the plane of planetary orbits around the sun. Because of this minor tilt, our personal planet’s modern climate has an unusual periodicity that we call “seasons.” Great swaths of the earth, lying between the always-hot equatorial zone and always-cold arctic zones, are characterized by four seasons, year after year. These seasons create a constantly evolving environment that is both challenging and highly stimulating to development of thriving life as we know it.


In this telling so far I have tried to emphasize that evolution, starting at the big bang, is a continuous, seamless flow from one happening to the next, each event arising out of one that came before and lending itself inevitably to some future evolutionary change. If perchance you had been standing by somewhere, watching everything evolve from the big bang to formation of planet Earth, watching to see the next significant occurrence in the long evolution of the universe, the stage, as they say, was now set. On a purely chance-driven agenda (the way evolution does), life would emerge next, so as we flow into the next chapter we shall watch to see life emerge on the planet we named Earth.


And, as God so long ago saw that it was good, so shall we.

*          ©          *


…to be continued in one week…


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