Miracles
Page 5
The first variable we may touch upon is simply the size of our planet. Most of us have watched or read enough science fiction that we cannot imagine the size of a planet should make much difference, but from a science nonfiction perspective, this is mistaken. That’s because the size—or really, the mass—of a planet determines how much gravity it has, which determines much else. Though it may come as a surprise to us, if our planet were ever so slightly bigger or smaller, life here couldn’t exist.
If Earth were slightly larger, it would of course have slightly more gravity, which has interesting implications. It’s not just that a person who weighs 150 pounds would weigh more. It’s that if Earth had just a little bit more gravity than it now has, methane and ammonia gas, which have molecular weights of sixteen and seventeen, respectively, would remain close to our surface. Since we cannot breathe methane or ammonia, which are toxic, we would die. More to the point, we would never have come into existence in the first place. If you’re thinking we might have evolved to where we could breathe those gases, that’s more science fiction than reality. Simply put, life cannot coexist with large amounts of methane and ammonia. But if Earth were just a bit larger, these deadly gases would not dissipate into the atmosphere but would stay right down here where we would have to inhale them.
On the other hand, if Earth were a tiny bit smaller and had a bit less gravity, water vapor, which has a molecular weight of eighteen, would not stay down here close to the planet’s surface but would instead dissipate into the atmosphere. Obviously, without water we couldn’t exist. As we’ve all heard, our bodies are 75 percent water. To think that the size of Earth must be almost exactly what it is or we wouldn’t exist is sobering and, frankly, not so easy to believe. But it’s a fact that we need a planet small enough to allow poisonous gases of molecular weights sixteen and seventeen to evaporate, and large enough so that water vapor, with its molecular weight of eighteen, will not evaporate.
Before going further, we should say a word on the unique properties of water. As we all learned in grade school, a gas is less dense than a liquid, which is less dense than a solid. As something moves from one state to the next, the molecules get closer together and it gets denser and, of course, heavier. But if this is true, why does ice float? Shouldn’t it be denser than liquid water, and shouldn’t it sink?
Water does indeed become more dense as it cools toward becoming solid (ice)—until it hits 39.2 degrees Fahrenheit, at which point it begins becoming less dense. So by the time it is actually solid, it is lighter than it is in its liquid state, and it floats. If water did not have this genuinely bizarre quirk, lakes would freeze from the bottom up, killing the fish and other freshwater life, which would have a subsequent deadly effect on other life-forms. The reason water has this vital property is that each water molecule possesses two hydrogen atoms that are connected to the oxygen atom in a V shape whose angle is about 104.5 degrees. Because of this obtuse angle, water solidifies into hexagonal structures that take up a lot of space and are therefore lighter than liquid water. Marveling at this is not inappropriate.
But there are still other properties of water that are dramatically anomalous and make life on Earth possible. Water’s high boiling point is one, and its ability to dissolve a large number of chemical substances is another. Water also retains heat exceptionally well, allowing bodies of water on our planet to help stabilize and moderate temperatures. Once again, if water did not have all of these rare properties, life would be impossible.
Just as most of us don’t think much about how strange a liquid water is, nor rejoice at the perfect size of our planet, who among us can be said to have given much thought to the speed at which our planet rotates? Every time we watch a sunrise or a sunset we see exactly how fast the planet is rotating, but what of it? If it went a bit slower or faster, would it make a significant difference? Wouldn’t life have adapted accordingly? Science says no.
As we suspect the reader knows, our planet rotates once every twenty-four hours. We may all wish there were a few more hours in the day, but it seems that if that were the case and Earth rotated ever so slightly slower, the temperature swings between night and day would be inescapably deadly. If Earth’s nighttime side were dark a few hours longer, the nighttime cold would get dramatically colder and the daytime heat would get dramatically hotter. As a result, life on this planet would simply have been impossible. If our planet rotated a bit more quickly and therefore gave us shorter days, it would produce impossibly high winds. Just how high, we cannot say. Winds on Jupiter are routinely one thousand miles per hour, so if Earth rotated slightly faster than it now does, we may conservatively imagine that it would produce winds sufficient to make impossible a stable environment conducive to life of any kind.
Another critical criterion for life on Earth is the presence of an extremely large planet in our solar system. We are thinking specifically of Jupiter, whose efforts on our behalf most of us have taken for granted. But without the Jovian giant where it is, comets and comet debris would strike us about a thousand times more frequently. Jupiter’s diameter is more than eleven times that of Earth’s; its surface area is 122 times the surface area of Earth, and one could fit 1,320 Earths in a sphere the size of Jupiter. For more perspective on Jupiter’s jumbo dimensions, consider that it has about two and a half times the mass of all the other planets in our solar system combined.
What exactly does this have to do with comets avoiding us here on Earth? Since Jupiter is composed of gas, it’s not nearly as dense as Earth, but it still has 318 times the mass of Earth, and therefore 318 times the gravity. So most of the comets that come anywhere near Jupiter are pulled toward it. It absorbs many of them into its gaseous depths without so much as a hiccup. But in most cases it actually just deflects them away from us and out of our solar system entirely.
THE MIRACLE OF THE MOON
Jupiter’s grand significance to life on Earth, however, must pale in comparison to the significance of our moon.
We may begin with the moon’s size, which is the most insignificant—but nonetheless still tremendously significant—reason for its importance to life on Earth. The moon’s considerable gravity gives our oceans their ebbing and flowing tides. If the moon were slightly bigger, it would cause our tides to be much more extreme, since a larger moon would of course exert that much more gravitational pull. With one-hundred-foot tides, there could be no coastal cities or towns or villages. If the moon were slightly smaller and had less gravitational pull, the tides would be insufficient to cleanse coastal seawater and replenish its nutrients. If the moon were any size other than the size it is, life as we know it wouldn’t exist.
The size of the moon—and its distance from Earth—are also responsible for stabilizing Earth’s rotational axis. If it were not stable or were not at its current optimal angle, we could not be here. Without Earth’s tilt we would not have our seasons, and our temperatures would be much less stable. So if the moon weren’t precisely the right size and distance from Earth, our rotational axis would have changed over the eons, making terrestrial life quite out of the question.
Perhaps the most dramatic of these considerations has to do with the way our moon was formed. Of all the things we will consider, this may be the most difficult to fathom. Most scientists have now concluded that the moon didn’t form at the same time as Earth but about a quarter of a billion years later. There are other theories, but as of now most of them have fallen out of favor. As with much else in this chapter, the consensus around what happened has formed only recently, thanks to our increasing knowledge on this subject, and it’s a consensus that continues to grow.
Here’s what science tells us: Four and a quarter billion years ago, Earth was much smaller than it is now and was still in a molten state. It wasn’t even really the Earth yet at all, so let’s call it “Earth.” Then, out of the infinite reaches of black space, traveling silently on a fixed trajectory for millions and millions (and
millions and millions) of years and light-years, a planetary body larger than Mars homed in on “Earth” and hit it directly amidships. This unfathomably perfect collision of two bodies in the incalculable vastness of outer space made life—and therefore you and me—possible.
The roughly Mars-size mass that hit “Earth” was for the most part absorbed into “Earth,” so that “Earth” went from being “Earth” to actually being Earth. Our size was, via this collision, dramatically increased to what it is today, to the size we have already said is vital to the existence of life. But the remaining chunks produced by this cataclysmic collision began orbiting Earth and eventually coalesced to form what we now know as the moon.
But another thing happened as a result of this collision, without which life could not exist: The head-on collision between these two objects was so perfectly aligned—and therefore so cataclysmic—that it blasted most of Earth’s previous atmosphere into outer space, leaving us with the atmosphere we now have. The previous atmosphere of Earth was forty times as thick as our current atmosphere, so sunlight could not reach our surface. If this collision had not happened precisely as it happened, we would not exist. Our atmosphere and our size were absolutely incapable of supporting life before but perfectly capable of supporting life after.
The addition of the extra mass to our planet also increased Earth’s iron content dramatically, allowing marine algae to flourish, which in turn allowed other marine life to flourish, which in turn allowed life on land to flourish. To say we wouldn’t be here without this collision happening precisely as it did is an impossibly large understatement.
But perhaps what is hardest to understand is that the current, perfect state of Earth is the result of a seemingly random collision 4.25 billion years ago. It is no exaggeration to say that in the infinitude of space, for two bodies to collide as they did is like two bullets being shot from guns on either side of the Grand Canyon and meeting so perfectly head-to-head in midair that they canceled out each other’s momentum and dropped vertically together into the canyon below. For such a thing to occur is essentially an impossibility and yet somehow science tells us that this happened. It can hardly be understood sufficiently, but if this collision had been ever so slightly less than head-on, or if these hurtling giants had missed each other by a hairbreadth, we wouldn’t be here.
Who could deny that to believe this collision happened randomly and “by accident” takes more faith than believing it was somehow “directed” to happen. This is not to say that the collision didn’t happen randomly and accidentally, only that believing that it did is so extremely implausible that the alternative must be at least considered. The human mind longs for meaning and for answers to such extraordinary mysteries: Just how might something so outrageously precise have simply “happened”?
But if that astonishingly perfect collision hadn’t happened precisely as it did, and if the size of Earth or the size of the moon were slightly different, or if the rotation of Earth were slightly faster or slightly slower, or if Jupiter weren’t as big as it is and positioned exactly where it is, life here couldn’t even be dimly possible, much less a reality.
And these are just a small handful of the parameters necessary for life to be possible.
As we said, in the 1960s, when Carl Sagan was trying to calculate how many planets in the universe might potentially support life, there were only two fine-tuned characteristics worth bothering with, which gave him the very hopeful result that about one in every ten thousand planets should support life. Given how many planets there were in the universe, it was clear there must be life out there in abundance. But by 2001 the number of fine-tuned characteristics necessary for life had leapt to 150, and when we do the calculations we discover that the odds of a planet supporting life are less than one in ten to the seventy-third power. That’s a one followed by seventy-three zeroes. In the known universe, the number of planets is only about ten to the twenty-third power. According to these figures, the odds of any planet being able to support life are one in ten to the fiftieth power. To express this more visually and without concern for conserving zeroes, that is one in 100,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000. It doesn’t make any sense at all that Earth should have beat those odds, but we did. Somehow.
This returns us to the further surprising subject of our moon. Since most of us typically don’t think about the moons orbiting other planets in our solar system, we don’t appreciate the particular strangeness of Earth’s moon, which is radically different from the other moons in our star system. To begin with, Earth is the only planet in our solar system that has only one moon. We take this as a matter of course, as though seeing one moon in the sky were the only option. Mercury and Venus are, of course, moonless. Mars has two moons, both so tiny that they almost shouldn’t be called moons. One (Phobos) has a diameter of fourteen miles—the length of Manhattan—while the other (Deimos), has a diameter of less than eight miles. The Brobdingnagian planet Jupiter has nine major moons (although astronomers keep finding new ones, putting the latest real number at fifty and counting), while Saturn has twelve major moons (as with Jupiter, astronomers have found many smaller ones, putting the most recent number at fifty-three and counting). Uranus has twenty-seven known moons, and Neptune has fourteen. These facts put our single moon in some context. In our solar system it’s unique.
When comparing the size of moons to the planets they orbit, Earth’s moon is also anomalous, being far and away the largest. There exist other moons larger than our moon, but they orbit planets like Jupiter and Saturn and Neptune, all dramatically larger than Earth. We’ve already mentioned the size of Jupiter, and Saturn has a diameter 9.5 times that of Earth’s, 764 times the volume, and 83 times the surface area. Relative to the size of its planet, our moon is by far the largest moon in our solar system. The point of this is to say that all that the moon is responsible for, as we’ve said before, is that much more rare when compared to the other moons in our solar system.
We cannot leave the subject of the moon until we touch upon the almost unthinkably amazing subject of eclipses. Most of us haven’t considered that for eclipses to occur as they do, the sun and moon must appear almost precisely the same size in the sky. As with so many things, we take eclipses for granted. They are just a part of the way things are. But when we know the details of the sizes and numbers of the moons throughout our solar system, the idea that the sun and our moon appear almost exactly the same size from our Earth-bound vantage point is essentially preposterous and bizarre. But it is this freakish fact that makes them cover each other so perfectly during a total eclipse. Though it has no bearing on the existence of life as far as we know, like all else we have examined, it gives such startling evidence of design—and therefore a designer—that we can hardly ignore it.
The details are as follows: The moon has a diameter of 2,159 miles. In order for a total eclipse to be possible, it must look the same size as the sun, whose diameter is 864,327 miles. If you divide 864,327 by 2,159, you get 400.337. In other words, the sun is almost exactly four hundred times the size of the moon. So in order for them to look the same size from Earth, the distance from Earth to the sun must be about four hundred times the distance from Earth to the moon. What are the odds that that should be the case? Nonetheless, the average distance of the sun from Earth is almost exactly 93,000,000 miles, and the average distance from the moon to Earth is roughly 238,857 miles. If you divide 93,000,000 by 238,857, you get . . . 389. That number is so close to four hundred that they really do look precisely the same size to us here on Earth. Can we avoid being taken aback by this? If we should be less startled than spooked, who could blame us? Can we avoid at least wondering whether it’s all been somehow arranged?
Is there any escaping the conclusion that the existence of life on planet Earth, or of life of any kind anywhere, is an astonishing, incomprehensible miracle? Can we ever again really take our existence here for granted, knowing h
ow superlatively precarious it is? If God made everything in the vast universe just as it is simply so that we could exist, we must begin to wonder why. What are we to him that he would do all this? Why would he make it all so extravagantly, even so unreasonably perfect? If it was all done just for us, the question arises: Who are we?
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THE MIRACLE OF THE UNIVERSE
Why do we exist?
—ANONYMOUS
In chapter 4 we discussed the statistical impossibility of life on Earth. But what of the existence of the universe itself? Is it possible for us to gain some idea of what the odds might be that it should exist? Most of us probably take the existence of the universe for granted, which is understandable. But let’s consider whether it’s appropriate that we take its existence for granted.
Since the dawn of human consciousness, many people have asked, Why do we exist? But it is usually asked as a philosophical question, meaning What is the meaning of our being here? But Why do we exist? is as much a scientific question as a philosophical question. In other words, why does anything exist? Why is there something rather than nothing? Why is the universe here? If the question is considered carefully enough, it is inescapably dizzying.