What is “Life?” Have you ever thought about it (outside of high school biology class)? I’ve been thinking about it lately, and a new concept has occurred to me. I’d like to look at “life” in a slightly different manner.
If you look up the word “life” in a dictionary, you’ll find a rather long and complicated definition having to do with the difference between living and dead organisms, with the ability to grow and reproduce and metabolize, and so on. I looked up the word in two different dictionaries and both definitions were similar. “Life,” it becomes obvious, is not a simple concept to grasp. There’s no real solid definition that’s universally agreed upon, and we’re forced to use vague generalities which may or may not suffice for everyone. Let’s try something else.
Much has been made recently about planets orbiting other stars. Several hundred have been found, though none so far have been shown definitely to be similar enough to Earth for “life” to develop on them. All so far have been either too hot or too cold, or gigantic balls of gas, or hard rocky bodies too close or too far from their sun to allow life to develop, at least the type of life we know here on Earth. But let us suppose, however, that somewhere a planet does exist on which are the proper conditions for life. Temperature, atmosphere, gravity, etc., are similar enough to Earth that we would feel comfortable there, were we to travel to that planet. Would we find “life”? I think we will, though we may not recognize it right away.
Planets orbit stars. Or, if you will, suns. Suns, by virtue of their thermonuclear core, produce light, heat, radiation, cosmic rays, neutrinos, and a whole bunch of other stuff. For the purpose of this essay, we need consider only the heat and light. Our sun produces vast quantities of light and heat, which, if we were able to capture with high-efficiency, would solve the world’s energy problems overnight (pun intended). But that’s another blog and I won’t get into that now. It’s the light and heat from the sun that drives life here on Earth. Without that energy output from the sun, life would never have gotten started and wouldn’t exist at all. Without that light and heat we’d all be feckless wads in the wilderness, as a friend of mine was fond of saying.
It was the sun that started everything, and the sun that kept it going. Thermodynamically, life would be impossible without some sort of energy. There had to be a source of energy to get the phenomenon of life started, and the sun provided it. No one really knows how life got started (it may have even come from outer space), but it is relatively easy to see how small inorganic molecules, readily available on the newly formed Earth could, with energy supplied by the sun, begin to combine and coalesce, forming the first organic molecules which under still more heat and light, could continue the process until some sort of self-replicating molecule is formed, perhaps a protein, perhaps RNA, maybe something we don’t know about. Exact details are not essential here, we need be aware only of the basic concept, driven by the sun. Thermodynamically, that is as likely as that which would happen if you put a pan of water on the stove and turned on the heat. The water will eventually boil; it cannot do otherwise.
The same concept applies to life on another planet. Given that the sun around which that planet whirls is bathing the planet with light and heat, the probability of life developing is high. Granted, the precursor molecules must be present, (carbon dioxide, methane, ammonia, whatever) and some sort of solvent in which those molecules are dissolved must also exist (on Earth that solvent was water but it could be liquid ammonia), but given the influx of heat and light from the sun, something will happen. Just like that pan of water on the stove, it must. Given the right conditions, life must develop. It cannot fail to. It is thermodynamically bound to.
Now, of course, on any given planet, the “life” that develops may not be recognizable to us as Earthlings, and it may take some doing to uncover it and may require some rearrangement of our prejudices to accept it. Therefore, I propose that we re-define “life” as that which arises on any planet under the influence of energy from its sun, over and above the naturally occurring milieu, regardless of what it looks like or how it developed or reproduces, regardless of whether it is capable of metabolism or adaptation to its environment, or any of the other factors we insist on for “life” here on Earth. Our definition of “life” is based on what we find on Earth; it does not necessarily fit that which we may find on other planets, and with our sophistication about the presence of life on other planets increasing at an almost exponential rate, we need a definition which will encompass all forms of “life” everywhere. Where’s Noah Webster when you really need him?