We seem to have accepted in our time the notion that technology always moves forward. But a key factor in the Drake Equation, that long and interesting conjecture that parses the possibilities for extraterrestrial life, is the question of whether technological societies have an average lifetime. Do they invariably survive to reach the stars, or do they destroy themselves before this is possible?
Listen to something Fred Hoyle said back in 1964:
It has often been said, if the human species fails to make a go of it here on Earth, some other species will take over the running. In a sense of developing high intelligence, this is not correct. We have, or will have, exhausted the necessary physical prerequisites so far as this planet is concerned. With coal gone, oil gone, high-grade metallic ores gone, no species however competent can make the long climb from primitive conditions to high-level technology. This is a one-shot affair. If we fail, this planetary system fails so far as intelligence is concerned. The same is true of other planetary systems. On each of them, there will be one chance, and one chance only.
The reference is from Hoyle’s Of Men and Galaxies (Seattle: University of Washington Press), and I ran into it in Andrew Kennedy’s paper on ‘the wait calculation,’ which we’ve been discussing here recently. Hoyle’s take is controversial, to say the least, but it underlines the long-range issues we often focus on in these pages. Do we have the capacity, for example, to solve intractable problems over the course of centuries when this would involve sacrifice on the individual level during our comparatively short lifetimes?
Think long-term about interstellar missions and you see the limitation. In a recent presentation at Princeton, Marc Millis laid out the support levels that might be expected for various human ventures into the cosmos. A mission time of 3-5 years could attract the interest of power brokers in government and industry. A 20-year mission could still capture a significant portion of the populace. But by the time you hit 50 years — and these are the time frames being discussed for Kuiper Belt missions or missions to the gravity focus — your potential audience is reduced largely to the professionals involved.
Millis ponders these things because he is former head of NASA’s Breakthrough Propulsion Physics program and founding architect of the Tau Zero Foundation. And he knows that it has become all but axiomatic that a mission cannot be longer than the lifetime of the scientists who sent it. A 100-year long mission gains virtually no public interest (though still piquing the attention of the scientists most closely involved with the target in question). Mission times over 100 years become problematic in every way, requiring a societal commitment that we haven’t seen since the cathedrals of the Middle Ages or the pyramids of the Egyptian pharaohs. In both those eras, multi-generational projects were undertaken and brought to fruition because of a broader conception of man’s place in history than seems possible today.
On a visit to Marshall Space Flight Center, I once asked NASA’s Les Johnson whether society would ever send a 1000-year mission to another star. I was really asking about the social will to do such a thing, but Johnson took the question more practically. “I’d love a thousand years,” Johnson replied. He meant that we’re nowhere near having the capability of launching even a mission of that length, much less getting those numbers down to a few centuries.
So what are reasonable mission goals? Millis laid out some key numbers at Princeton that serve us well. Get to 6 percent of light speed and Centauri becomes feasible as a 76-year mission, while within 15 light years of Earth (and 265 years of flight time) are five systems that look intriguing from the perspective of habitable planets. Jump to 25 percent of light speed and Centauri is reachable in 22 years (no worse than the Voyagers’ continuing mission), with fully 20 other systems in range in a 100-year time frame.
What throws a wrench into the machinery? Three possibilities, one being the discovery of a nearer target (i.e., a brown dwarf closer than Centauri or something of that nature). Another is a physics breakthrough that dramatically changes mission times (Millis calls this ‘incessant obsolesence’). But the third is the one we seldom discuss: perhaps the pace of technology actually slows, and becomes longer than the actual mission time. At that point, there is no thought of waiting to launch, because no faster mission will get to the target first. In fact, the longer we wait, the worse the chances of ever launching.
If Hoyle is right, a major variable in all this is that technological growth may falter entirely, with terminal exhausion of a planet’s resources. Circle back to Fermi and you get a solution to the question ‘where are they’ that technology optimists like myself don’t like to consider. We don’t see extraterrestrials because technological societies are rare. And they’re rare because most such societies destroy themselves before star missions ever become viable. It’s a bleak assessment but something to ponder as we consider our ability to plan and carry out projects over the lifetimes not just of researchers but civilizations.