May 8, 2013 7:20:26 AM
It is surprising how living things cram themselves into every possible corner of our world; a natural space that is completely sterile is, well, unnatural. Some of those living things are truly weird. Just think of how alien to us are spiders, for instance, or the fungi that help our soils keep going. It hasn't been long that humans have known about microorganisms, and just a few decades ago we never would have thought that hydrothermal vents on the ocean floor were teeming with life, as were rocks deep beneath our soil or inside the Antarctic ice cap. So, yes, such life is weird, but it all comes from some common ancestor billions of years ago, and it all uses the same key molecule of DNA and the same amino acids which the DNA codes into proteins. These cousins of ours are covered briefly in Weird Life: The Search for Life That Is Very, Very Different from Our Own (W. W. Norton) by David Toomey. But as weird as "life as we know it" might be, it isn't as weird as life that uses different amino acids, or uses ammonia for its solvent rather than water, or uses silicon rather than carbon for "organic" molecules, or even inhabits alternative universes with vastly different physics. Toomey is an English teacher, but he has written before on scientific subjects, and his explanations here are playful and amusing. There is plenty of science in the book, but the weird life forms are theoretical, which is part of the fun. Sure, there is no evidence right now that such life exists, but it is a big universe out there.
A huge question right off the bat is, "What is life?" These three simple words hide amazing and perplexing complexity. Sure, we know life when we see it. That cute bunny or the rosebushes in the garden, well, that's life. What about viruses, though? They have DNA (or the alternative RNA), and they evolve, but they cannot exist without relying on actual cells. It used to be that people figured that there was some immeasurable, invisible "vital force" or spirit that conveys life; it was imbued somehow when an organism was born (or was conceived) and given up when the organism died. The problem is that there is no such thing, and as far as we know, a living organism is just a fantastically complicated chemical factory. The reactions of life are chemical reactions, so the materialists told us, but which chemicals? It would be handy if certain chemicals or reactions were always seen in living things and never seen in non-living ones, but things are not so simple. Perhaps it is best to define processes; living things grow, consume, maintain themselves though chemical activity, and die. But a candle flame does these things. A candle flame cannot reproduce itself, so perhaps we should latch onto that. Until we realize that worker ants can't reproduce themselves, and seem to be very much alive. Perhaps knowing life when we see it is going to be better than any definition in words.
The trouble is that we don't really know what we will be seeing. The speculation on many of these pages isn't extreme. We (and the other strange creatures of our planet, including the ones living almost invisibly in extreme environments) use water as the foundation for the interactions that go on in our cells, but maybe that's just because water happened to be handy. Astrobiologists, who are interested in hypothesizing about life on other spheres, think about alternatives. On Saturn's moon Titan, for instance, all water is ice, since the temperature doesn't go much above -179 degrees centigrade. It cannot provide a medium for all the jostling molecules in a cell, but methane could. On Earth, methane is a gas, but it is liquid at such cold temperatures, and there isn't any reason that enzymes and cells might not do very well in it. There is also a slush of water and ammonia, which might also work. We will be investigating Titan someday, and it may well be that a probe looking for life will need to be broadminded enough to take in these possibilities and not blinkered into looking for the life we are accustomed to on Earth (as has been the bias in Martian probes, for instance).
Toomey explores many stranger possibilities for life not-as-we-know-it. What if there are creatures that use mirror-image molecules of the ones we ourselves use? The chemistry would be essentially the same, but such creatures would live in an independent world unconnected chemically to our own. In fact, some biochemists have looked for mirror-image microbes; nothing has turned up yet, but maybe next sample. There are other speculations here about other forms of weird life that live right alongside of us, but most, of course, have to do with those out in our vast universe. There has been a search for extraterrestrial life, SETI, now for over fifty years, and Toomey summarizes much of that here. There have been "more than a few honest mistakes, one hoax, and one possible signal, the last never repeated but still unexplained." Carl Sagan loved the idea of listening in to interstellar broadcasts, but he also knew how weird life out there might be. Taking into account the ecology of the atmosphere on Jupiter, he speculated that there could be enormous hydrogen-filled floater organisms, all the better to mate with other floaters (as part of a life cycle that included sinkers back on the lower levels). There are, after all, microbial species floating within the earthly clouds, so this might not be too far-fetched. There is a theme to this book, though: "If that's not weird enough for you, let's get even weirder." Perhaps there are organisms (maybe this is the wrong word) that are interstellar dust clouds communicating by electromagnetic signals. Maybe matter interacts in a living way around black holes. Maybe there is life in those other universes, if the multiverse model is true. In fact, if there are all those universes, then in total, they have to contain every form of life possible that the physics allows.
If that isn't a deep enough plunge into murky cosmological and philosophical waters, consider that while millions of us enjoy making simulations of cities and nations by computer models, such simulations someday might be detailed enough that the simulated creatures may have characteristics of life. In fact, try proving that our current world is not some fantastically detailed simulation created by superior beings whose capacities are so far above ours we will never comprehend them. If this sounds just too weird, remember that it is very close to religious conceptions that many people hold, and they don't consider them weird at all. Weird Life swoops in and out of biology, chemistry, astrophysics, cosmology, philosophy, and more, a wild tour of possibilities that are, right now, speculative fiction. We have an abiding interest in seeing if life is "out there" somewhere, and if we do find it, count on it to be at least as weird as the life forms described here.