I’m warning you ahead of time, this is going to be long, as evidenced by the “Part One” bit above, but hopefully it’ll be interesting as well. I’ll do my best.
One of the staple topics of all-night bull sessions, and not just in college dorm rooms, is the concept of intelligent life elsewhere in the universe, or to keep it simpler, elsewhere merely in our own Milky Way Galaxy. And you can’t discuss the topic properly without bringing up two “key” factors: Drake’s Equation, and Fermi’s Paradox. Both of them, however, do more to bring up questions than provide any answers. I’ll state right off the bat that this was actually the intention of both, though they typically are used exactly the opposite way. I’ll be brief, though.
Drake’s Equation is a string of values run together to determine the probability of intelligent life in the Milky Way Galaxy, though potentially this could be applied to the universe as well. I won’t go into it here, because it’s somewhat long, but that link will give you all you need to know. Multiply the number of new stars, times the number of ones that have planets, times the number that have conditions to support life as we know it, times the time to develop intelligence, and so on. Eventually you get a figure that tells you how many forms of intelligent life should be out there.
There are a lot of problems with this, though. First off, we have no firm answers for most of the values you would need to plug in to get the solution. We can speculate, but that tends to fall all over the place, and scientists that are exceptionally knowledgeable in the fields get wildly varying solutions. This is because we really can’t determine much info about other star systems, and don’t even know if our own should be considered typical (and thus give us a baseline to work from.) We also don’t know how life started on our own planet, and there’s even theories that it was introduced from elsewhere by comets, which throws calculations for a loop (the equation says nothing about comet passes.) We can’t say if life developing on this planet happened quicker than average, or much slower. There’s even the factor that, if it weren’t for a (probable) asteroid impact 65 million years ago, mammals might never have taken over as dominant life forms because the sauropods had that title, or at least it might have taken a lot longer.
Time is another key point: how long can a species be expected to last? The dinosaurs occupied about 175 million years, just under 4% of the planet’s history, while we, as Homo sapiens, have occupied just over .002%, and the amount of that spent as intelligent enough to indicate our presence with radio signals is an impressive .000002%. Presuming, perhaps rashly, that we last as long as the dinosaurs and that this can be considered a working average, this means that we’d have to overlap our 4% with some other species’ 4%. Otherwise, we would have radio signals reaching the ears of the “dinosaurs” on other planets and all the good that will do.
Now, Frank Drake knew all of this, and never intended the equation to be accurate. He actually created it to demonstrate the amount of information that we needed to know in order to even approach accuracy. He also knew about Fermi’s Paradox. Enrico Fermi, apparently in a flash of idle thought, came up with a key question: If intelligent life is likely to occur, how come we see no evidence of it? I’ll discuss UFOs in a later post – for now we’ll go with the evidence that isn’t vague and possible to misinterpret, which is… none. While the Galaxy might be brimming with life, we have seen no indication of this. How come?
Again, there’s no firm answer for this, and so we can only speculate. It might be put down to the timeline factor above, which means that life is out there but we haven’t intersected yet. Or it might be that some of the factors are a lot smaller than we think, because we really don’t know anything much about planetary system formation, and a lot of what we think we know about our own immediate neighbors (Jupiter, Uranus, Pluto, etc.) is just guesswork. As we start to find evidence of planets around other stars, we’re seeing some interesting things. Some astronomers think that a gas giant like Jupiter is necessary for a rocky body like Earth to form at the right distance from the star, a belt called the Habitable Zone, where water can be a liquid and chemical catalyzing can take place. The gas giant attracts and shields the smaller, closer bodies from debris impacts that are likely to occur early in the planet formation stages. But now there are thoughts that Saturn was responsible for locking Jupiter where it is now – otherwise it would have drawn closer to the Sun through mutual gravitational pull and totally wiped out all the planets in between, Earth included. We see evidence of this right now in the information we’re getting from other stars. And there’s more. Uranus is sloped way the hell over on its side, its pole facing counter to the way it should based on current planet formation theories, which might indicate a close, disruptive pass of another massive body in the solar system. And our own moon is thought to be debris from the collision of a Mars-sized object with our own planet, early in the formative years. It’s safe to say that not only would such a collision totally eradicate everything on the surface of the planet, it delayed the process of life forming in the first place. And we can’t forget the asteroid impact that probably wiped out the dinosaurs – it would likely do the same for us humans, too, and it occurred, in galactic terms, ten minutes ago. If Jupiter is shielding Earth from impacts, an awful lot of them still got through, and the satellite that was formed from one of them is absolutely covered in its own impact scars. You start to get the impression that it’s a bit hostile around here.
This raises an interesting question as to whether the span of life on this planet, roughly 3.5 billion years, might be abnormally long, a lucky accident, and most planets suffer catastrophic impacts, solar radiation, or other ills before intelligence can arise, or too soon after it does. We believe that debris impacts occur mostly early in the development of a planetary system and taper off over time, cleaned out by the formation of the planets, but does this mean “dustier” star systems take a lot longer to sweep up, or that fewer planets means more catastrophic impacts? We actually have a belt of asteroids between Mars and Jupiter, held there by the balance between Jupiter’s and the sun’s gravities – is that a handy condition for us (as opposed to them wandering into semi-routine orbital intersections and impacts throughout a system’s lifespan?)
There’s one other question that is solely mine, at this point (meaning that, to my knowledge, this is not a factor routinely considered in cosmology.) Our entire solar system contains certain percentages of key elements for our life as we know it, and to get these elements out of the original cosmic expansion known as the “Big Bang” (it was not an explosion,) they had to have passed through several different suns first. And yes, I said, “through” – the fusion taking place in a star’s core is responsible for creating the heavier elements, and the death of the star then sends them away in an expanding cloud of loose matter, later to be captured by another star, either within the star itself, or in our own case, in a cloud of orbiting dust that slowly coalesces into planets. And by heavier elements, I mean iron, carbon, oxygen, nitrogen, silicon, and so on. As Carl Sagan said, we are literally made of star stuff – the atoms in our own bodies passed through several stars on their way here (and will again, too.)
But this takes a certain amount of time, because stars have a lifespan. The universe is 13.7 billion years old, but our own system is 4.5 billion – that means that the elements we see right now gathered together when the universe was 9.2 billion years old, roughly two-thirds its current age. If the elements are made in stages within stars, how many stars and how old do they have to be in order to create the percentages we now have, that pave the way for the chemical reactions that we call life? And how much time is spent traveling between stars when the last host blows off these elements as its life ends? Is it possible that we’re not seeing life because it really only just started? Is a lot more time needed for the evidence to filter across the really vast distances of the Galaxy? Let’s face it – our radio signals are barely traveling outside our own solar system, and will need a lot more power and time to get anyplace serious (or Sirius.) If we’re, relatively speaking, early to the party, we simply won’t see evidence until their signals have time to get here.
There’s a lot of questions and virtually no answers. We’re trying, really hard, to find some of them, and our latest efforts to pin down more information is progressing by an astonishing amount – I’m impressed with the idea that very little about out universe that I learned in my youth is even vaguely accurate anymore, and even stuff from ten years ago has been supplanted by more accurate information. We’re not likely to have the answer to my original question anytime soon, but we’re working on it. And what we’re finding in the meantime is fascinating.
[Illustrating image comes from an experiment I was performing to show how “orbs” occur in photographs, and is simply mist against a black background, out-of-focus and illuminated by a flash. For artistic effect, I tweaked the colors into what you see here.]