In discussions of extraterrestrial intelligences, Enrico Fermi used to ask, if extraterrestrials are so prevalent, “Where are they?”.
He reasoned that, if extraterrestrial civilizations were very common, they must include some star travelers, and must be communicating with each other–and so surely, by this time, we’d at least have HEARD from them?
One attempt to explain why we haven’t is the Drake Equation. Frank Drake, in trying to estimate the number of extraterrestrial civilizations in the Milky Way Galaxy, proposed the following equation (note that, given the massive numbers of other galaxies, there would have to be a multiplier–but the multiplier might not be very large, because though the numbers of galaxies is large, the distances are also very much greater):
N=R* x fE x NE x fl x fi x fc x L
Where:
N = The number of civilizations in our galaxy with which communication may be possible,
R* = The rate of star formation/year in our galaxy,
fE = The fraction of stars with planets,
NE = The average number of planets that can potentially support life (per star with planets);
fl = The number of planets which do develop life;
fi = The fraction of planets that can go on to support intelligent life;
fc = The fraction of civilizations that develop technology which can be detected from space;
And: L = The length of time such civilizations release detectable signs into space.
This equation was first published in 1961, and obviously contains a great many indeterminate variables. For example, the number ‘fE’ (the fraction of stars with planets) is still being determined. Estimates of the fraction of stars with planets are complicated by the fact that people, instead of solving for ‘fE’ insist on solving for ‘NE’. In fact, this is an unnecessary refinement.
Why? The problem is that, well before dependable data about the outer planets in our own star system, theorists were already theorizing about where life could potentially form, And because life on Earth is, so far as we know, an n of 1 (since there is no known life on Mars or Venus), we don’t really know enough to figure out how varied life CAN be. Furthermore, knowledge about life around ‘black smokers’ (hydrothermal vents) hadn’t been analyzed to any degree yet.
indeed, the study of extremophiles in general barely kept pace with studies (mostly flybys until the late 1980s, when orbiters and landers began to be launched) of other solar planets.
In those days, astrobiology was a HIGHLY speculative art, with very little non-terrestrial hard information, and even less understanding of planetary dynamics, and of the less ‘conventional’ forms of life even on Earth. It was in this period that the concept of the ‘Goldilocks Zone’ developed. This theory, basically, argues that there are zones around stars which are too hot to sustain life, and zones which are too cold, but in between is ‘The Goldilocks Zone’ (which, of course, is ‘just right’).
This theory has long been disproven–but too many people still hold to it. For example, Venus, which NOW has no liquid water (really, very little water in any form, because of high sulfur levels, which increase the formation of H2SO4 (sulfuric acid) rather than H2O), may once have had oceans. They may have been very hot oceans, even then–but thermophiles on Earth live and even thrive in very hot water indeed–many of the thermophiles can die if the water temperature around them falls to the boiling temperature of water at sea level.
In addition, there is substantial evidence of huge oceans inside at least three of the Galilean moons of Jupiter, and perhaps even on the surface of Saturn’s moon Titan. Even the very distant Neptunian moon Triton is a possible candidate for liquid water. The reason these bodies have (or could have) liquid water is that tidal forces from the gas giants (and the outer ice giants) compress and expand the much smaller moons, and thus frictionally produce sufficient heating to liquefy ices.
Also, we tend to focus on water as the only possible working fluid, to the point that people searching for extraterrestrial life tend to limit themselves to the mantra ‘follow the water’. But if other working fluids would work, life outside the zone(s) of liquid water might be possible.
So could intelligent life arise outside the ‘Goldilocks Zone’? The short answer is “We don’t know,” Until we get a chance to examine ANY sort of extraterrestrial life, we’re still dealing with an N of 1–albeit a very complex unity.
Note also that the Drake Equation, for all its complexity and variables, may not be the only reason we have yet to encounter unequivocal evidence of extraterrestrial intelligence. Other possibilities include simple distance. Maybe e-t civilizations exist, but are just too far away for messages from them to have arrived at Earth yet.
Another is the possibility that intelligent civilizations are just not likely to be contemporaneous. This is partly addressed in the Drake Equation–that’s what the ‘L’ is about. How long do highly technological civilization survive (meaning civilizations producing electronic signals)? This, so far, is still under litigation–not all districts have reported in yet. And again, it is an n of 1, since, to date, we have only one example of a civilization which sends out electronic signals (with several names, but still one manifestation–so far).
If the present electronic civilization collapses, will others form? We really have no way of knowing. But there’s another possibility, as well. What if other (not-Earth) civilizations have developed other, better ways of communicating?
Whether such other civilizations exist or not, one thing’s for sure: unless some or all of these other civilizations have developed some form of hyperdrive, we really have nothing to fear from them. Whether they’re friendly, hostile, uninterested, or the usual combination of all these, we’re not OBLIGATED to listen to them–we could always switch communications off.
For today’s less obvious question, have you ever wondered why botulism has a name from the Latin word for ‘sausage’? I hadn’t even realized that the ancient Romans HAD sausages, although on reflection it seems obvious they would have. But they didn’t associate the food poisoning we now call botulism with sausage. In fact, the association between the disease and the meat product didn’t develop until the last decade of the nineteenth century, in Germany. Another discovery delayed until microscopes were available? Whether or no, the assignment of a Latin name was, apparently, just a hangover from the times when Latin and Greek were the lingua franca of the sciences.
treraia 