The Human Condition:

Unique or Ubiquitous? – October 30, 2016


It’s the age-old question: Is life—that curious reversal of entropy—unique to the Earth or ubiquitous in the solar system, the galaxy, and/or the universe? We don’t have an answer for that yet—although a more thorough examination of the surfaces of Mars, Jupiter’s moon Europa, and the planets circling other stars at distances which permit liquid water to flow may soon provide more solid evidence, yea or nay.

Right now, the only hard evidence—and not counting teasing suggestions of ancient water courses on the surface of Mars, microbe-like bubbles in rocks on from that planet, vast oceans and icy geysers on Europa, and so on—is that life seems to be ubiquitous on our home planet, Earth. It exists everywhere and adapts seamlessly to the harshest conditions. Life thrives in hot springs that would sterilize surgical instruments. It metabolizes sulfur particles in the volcanic heat of deep-ocean vents. It lives in Antarctic lakes so far beneath the ice that they never see daylight, and in deep caverns under the Earth’s surface that harbor eternal darkness. Life in the form of single-celled microbes has existed on this planet since the crust was cool enough to walk on and mineralized water first collected in puddles among the rocks. Life exploded half a billion years ago into multi-celled organisms that, through the wandering adaptations of evolution, have since then populated the oceans, crawled up on land, and then flopped back into the oceans. In many forms, and many times, life has invented complex structures for eyes, lungs, wings, and brains. Life has invented tools, and now those tool-users are inventing even more complex tools that emulate life in both its motions and its mind. Life has invented dreams, self-knowledge, and a personal sense of purpose.

But whether our kind of life originated here, through the accidental bonding of one atom to another in a chemical-rich tidal pool, or blew in from interstellar space as a microbial spore, or was deposited here intentionally by alien astronauts on a seeding expedition, or was simply left as an alien microbe inside an astronaut’s dropped glove—any proof one way or the other is lost in the Earth’s earliest history. The only clue we have is that all our forms of life—from ocean vents to deepest caves and all across the planet’s surface—use the same chemicals in the same recording system. All the life that we know uses just four DNA bases in a three-pair reading frame, coding sixty-four possible combinations calling out just twenty different amino acids, to make all the proteins that comprise this planet’s viruses, bacteria, fungi, plants, animals, and human beings. If there ever were competing coding systems, evolutionary rivals to the DNA/RNA/protein domain on Earth—say, with different kinds of nucleic acids,1 or more or fewer possible base-pair combinations, or calling on other amino acids, of which there are many, or creating novel proteins—they all lost out long ago in competition with our kind of DNA coding. And then, in short order, atmospheric weathering and the predations of our kind of life wiped all trace of these competing systems from the face of the Earth.2

But if life is ubiquitous elsewhere in our galaxy and throughout the universe, where is it? That’s the question originally posed by physicist Enrico Fermi. If billions of stars in our galaxy are similar to our Sun, and if a large fraction of them have Earth-like planets, and if life is as simple to create and ubiquitous as we believe—that is, not a divine act by a deity with a particular interest in this one planet—and if many of those stars and planets and ecosystems are far older than Earth, so that ancient spacefaring civilizations should by now have grown up, spread out to other star systems, started exploring their neighborhood and sending radio and other electromagnetic transmissions back and forth … then where is everybody?

I’ve already given one answer.3 If the Sol System, at four billion years old, is one-third of the estimated age of the universe, and if just one of the planets in our system has taken this long, first to develop life itself, and then for that life to become intelligent enough to conduct something so complex as a civilization, and if we’ve only just sent our first probes to other planets and out among the stars … then perhaps ancient, spacefaring cultures are not as common as one might expect. And it’s a big galaxy. The farthest stars we can see with our naked eyes are only about 15,000 light-years away, and the galaxy itself is six times that, or 100,000 light-years in diameter, with a lot of it hidden by interstellar dust. So an active star-based civilization might lie on the other side of the great spiral, and we would never know it. And they would likely never come visiting.

A second answer to the question of where is everybody lies in the imponderable distances between stars. We imagine that humanity will one day form its own interstellar trading empire, composed of colonies sent out from Earth. We imagine that other intelligent species from other star systems have already established their own empires and will one day come visit us, either as explorers, inquisitive academics, and benevolent diplomats or as resource-hungry conquerors.

Both of these imaginings require the existence of ships and interstellar drives that will bridge the distances between the stars in a reasonable amount of time. Right now, these ships and drives are the products of fantasy, created either by writers who want to place their dramas out among the stars among alien peoples, or by mathematicians and scientists who believe that a twist in the physics we know will let these drives and ships one day become reality. But for now, they are fantasy.

Traveling faster than light is prohibited by the persuasive theories and mathematical conclusions of Albert Einstein. Any object with a mass greater than a photon’s cannot attain even the speed of light—let alone exceed it—because then its mass becomes infinite and its passengers’ perception of time stops. Perhaps this limit itself is a mathematical chimera, a fantasy, and ships can zoom past 299,792 kilometers per second (186,282 miles per second) with no ill effects. Perhaps the speed of light as a physical limit has no more standing than the speed of sound did back in the early days of jet aircraft. But for now, that’s not the way to bet.

Of course, any motion by a ship in space requires some gain in acceleration, and this is only achieved by ejecting mass in a direction opposite to the direction of travel. The formula for this is F=ma, force equals mass times acceleration, Newton’s Second Law of Motion. If you’re going to travel fast you have to carry fuel with you. Every rocket escaping Earth’s gravity burns some fuel and oxidizer to create thrust. And early in the flight, you must carry great quantities of fuel and oxidizer—far more than your payload. Notions of other propulsion systems, like “gravity polarizers” or “impulse drives,” are just that—fanciful notions.

Perhaps you can get to the stars by collecting interstellar dust and hydrogen from the region ahead of the ship with a magnetic sweep, compressing it inside a fusion drive, and blasting it out the back—the principle behind the Bussard ramjet. But that sweep has to catch an awful lot of dust and gas for a hard burn. At those densities, the impact of the gas coming at you and being slowed and captured by your magnetic field becomes a serious factor. Perhaps, instead, you can rig huge, reflective sails that catch the emitted sunlight and solar wind of ejected particles from your own star, which lies behind you, and let them drive you outward. But that force becomes exponentially weaker the farther you go. Certainly, you can blast free of your own planet’s gravity and then from your star’s gravity with a rocket or a ramjet or a solar sail and then coast the rest of the way to the nearest star. But that’s the slow way, the really slow way. Coasting outward would require your passengers to enter “suspended animation” or “hyper sleep”—another unproven technology—for hundreds or thousands of years on the voyage. Or, instead, they might pass their genes down through succeeding generations, creating their own mini-civilization, while humanity travels to Proxima Centauri, our nearest neighbor with a possibly habitable planet.4

Writers and scientists imagine ways to get around these limits. One way is to punch a hole through the fabric of spacetime itself, assuming that fabric is wadded up like a crumpled piece of paper or twisted piece of laundry, so that entering the hole at one set of temporospatial coordinates takes you effortlessly and timelessly—without violating the law about light speed—to another set of coordinates which may lie any imaginable distance away. Another trans-light transport system would collapse the fabric of space ahead of a vehicle which itself is moving at sub-light speeds—and stretch out that fabric behind the ship—so that the ship rides the “warp” at any imaginable speed faster than a beam of light but without the ship actually going faster than light in physical spacetime. Aside from the epistemological trickery of moving faster than light through space by manipulating space itself, either of these methods assume that space has some kind of structure or substance rather than being empty nothingness inhabited by random molecules of gas and dust. The notion that space has more than three physical dimensions—x, y, and z, or sideways, up-and-down, and forward-and-back—and one dimension of time, is the subject of mathematical speculation. Physicists can play with these dimensions in their minds and write formulas about them. But no one has ever gone into them, pushed an object through them, or managed to tweak them using any amount of force.

Right now, putting aside all the fantastical drives and all the ways the universe might operate through speculative mathematics, the only method we have for traveling to another star—the only way that we know works—is the blast-free-and-coast method. It’s the way the Voyager probes have left the Sun’s immediate environment … and they’ve been traveling for almost forty years now.5 Maybe alien intelligences will have access to different mathematics, greater energy resources, and different conceptions of space and time. Maybe one day we humans will discover or create these things for ourselves, so that the limits imposed on interstellar travel by our current physical laws will disappear, just like the barrier once represented by “the speed of sound.”

But even with a really solid push, the trip to Proxima Centauri and its newly discovered, possibly habitable planet is going to take much longer than the four years at light speed. Even if we could travel almost that fast and establish a colony that wanted to communicate, trade, or even remain in touch with Earth, the distance makes those interactions problematic. A phone call with a time lag of 4.24 years becomes impossibly frustrating. A shipment of goods that takes huge energies and decades of transit time to deliver becomes impossibly impractical. Encyclopedic knowledge and new scientific discoveries might be worth encoding and sending by tight beam to the colony world, but you would never know how much got garbled in transmission or was misunderstood and misapplied on receipt by people who barely speak your language anymore and no longer share your culture.

If your children or business partners or planetary administrators embark for a life among the stars—even as close a star as Proxima—then you must kiss them goodbye and go on about your Earthly business. If you embark on the journey yourself, then your new family, your trading partners, and your social structure are all sleeping the pods next to yours.

Travel to the stars—by any system that we can say for sure works—will be a one-way migration. The colonists are no more going off to create a trading or political empire than the first bands of Homo sapiens who wandered out of Africa some 65,000 years ago, making their way on foot and by dugout canoe, and eventually pitching their tents in Arabia, Eastern Asia, and the Americas, were intent on trading with or expanding the political sphere of the people they left behind, half a world away, in Africa.

Perhaps life exists across the universe. I certainly believe it does—that our curious reversal of entropy is not unique to Earth but ubiquitous throughout the stars. But unless other intelligences have access to a different and greater understanding of space, time, matter, and energy, they will live as they started: isolated pools on planets separated by imponderable distances. And whether they arrived in each place in their current form by traveling in blast-and-coast ships, or their distantly ancestral DNA blew in as a sporulated microbe riding a chunk of dust and then evolved into uniquely adapted species—this matters not much at all. The travelers will forget about the “home world.” Their children will not know it except in ever more fancifully embroidered stories and legends. And no one will ever go back—only outward in blind migration.

And that’s where everyone is.

1. Of course, deoxy-ribose nucleic acid (DNA) in the cells of microbes and in the cellular nuclei of multi-celled organisms is transcribed into a messenger ribose nucleic acid (mRNA) during the production of proteins. This simpler molecule—missing a hydroxyl group on the ribose ring’s second prime carbon atom—substitutes the base Uracil for Thymine among the four bases of the code. These differences suggest that RNA is an earlier and possibly competing form of the pattern-encoding molecule, or that DNA is an evolutionary development out of RNA. But both are still part of the same coding system.

2. For more on this theme, see DNA is Everywhere from September 5, 2010.

3. See Where Are They? from July 6, 2014.

4. See “Potentially Habitable Planet Found Orbiting Star Closest to Sun” in National Geographic News, August 24, 2016.

5. See Voyager: The Interstellar Mission by NASA’s Jet Propulsion Laboratory.