I had a marvelous image: a synthetic planet in the Kuiper Belt–deep deep space, far beyond the orbit of Neptune–made solely from water. We let buoyant fusion reactors drift in its depths, fusing deuterium extracted from all that water to provide the light and heat needed to keep the planet liquid. (All that water makes a great neutron absorber). With a large enough volume, it would have a surface gravity close to Earth’s, or at least, strong enough to keep an oxygenated atmosphere from escaping to deep space. Imagine cities floating on the surface, with permanent night above and deeply lit ocean below, with enough cheap energy to fuel a civilization of a billion people, ten times richer than the modern day US, for ten million years….by
Autumn is the season to sit near the fire with a good book. To help you do that, now through November 11, every ebook edition of all my stories and novels are on sale at over 50% off list price. That’s right, for less than the price of a latte, you can buy a novel or three short stories, from most major ebook retailers in countries around the world, including Amazon, Barnes & Noble, Kobo, iTunes, and more!
But remember, this sale ends November 11. Don’t miss out!
Thanks to Asher Pembroke and Victoria Astley, a while ago I was on a panel with “Analog MAFIA” member Alexis Glynn Latner, and Chad Wilson of the University of Houston to the Rice Physics and Astronomy Graduate Student Association about “The Interplay of Science and Science Fiction.” There’s about an hour of great video that barely scratches the surface of this topic. Check it out!by
Charles Chase of Lockheed Martin’s Skunk Works (the folks who designed the U-2 and SR-71 reconnaisance planes and the F-22 Raptor, among other aircraft) recently gave a talk suggesting his group’s work could lead to commercially available nuclear fusion reactors within 15 years.
Here are some quick thoughts:
He’s talking about deuterium-tritium fusion. Deuterium is a plentiful, easily enrichable isotope of hydrogen. Tritium is another isotope of hydrogen, but very uncommon and has a short half-life (hint, those two facts are related). To produce tritium, you either need a breeder reactor working with lithium-6, or a fission reactor using heavy water for cooling. Neither route is cheap. (Even if the Skunk Works’ fusion reactor is the breeder working with lithium-6, lithium is relatively rare and lithium-6 requires enrichment). Plus, regarding transportation, tritium has the same chemical and physical profile as hydrogen, i.e., it’s very flammable and can relatively easily leak out of containers. The radioactivity of tritium isn’t much of a risk (don’t breathe it and you’ll be fine), but in our litigious age, that risk still has to be mitigated. Still, guys with high school degrees drive tanker trucks of hydrocarbons around without any major problems, so tritium transport is solvable.
Take the 15 year time frame with a grain of salt. Fusion has been 20 years in the future since the 1950s. (I remember my youthful indignation in 1990 when a physicist at Los Alamos made a comment like that). I also remember Pons and Fleischmann, and even if you don’t, you’ve probably heard the term “cold fusion” used to dismiss something as a pseudotechnology. On top of that, as the Pournelle-Anderson law of big engineering goes, “Everything takes longer and costs more.” Given Lockheed Martin’s recent track record with the F-35, well, yep.
One striking thing about comments on the Youtube video (or at Walter Jon Williams’ site) is the large amount of conspiracy theorizing, that Big Oil (and/or Big Banking) will suppress commercially workable fusion. My Midwestern, middle-class upbringing makes me want to dismiss this as paranoia, but I’m a lot more cynical than I used to be. Cynical enough to see the backroom deals that would foil Big Oil and bring fusion to the market. Note that Charles Chase gave his talk at Solve for X, a forum sponsored by Google. A 100 mW power plant would be useful to a company with a massive server farm, such as, say, Google. And while Big Oil can pay for one congressman, senator, or senior bureaucrat’s hookers and cocaine, Google can call up another and say, “We noticed someone used your computer to contact a gay escort service. Sure would be a shame if that hit the WaPo or NY Times.” (And check out the money quote from this link, “The Chairman of Google’s girlfriend was being used as a back channel for Hillary Clinton“). If there’s a power struggle between Big Oil and Big Data, Big Data is already winning: consider, anti-fracking is a mainstream position, while being anti-Google puts one in tinfoil hat territory.
If it’s technically feasible, then it will happen. Imagine a fusion reactor in every small city on Earth that wants one, providing enough cheap electricity to give everyone who wants it a First World lifestyle. All without any carbon emissions or any need to handle fissile isotopes, if you’re worried about those things. It won’t be utopia, of course — no society involving human beings ever will be — but energy supplies won’t be one of its problems. Nor will drinking water (fusion powered desalinization plants at the seashore), overpopulation (wealthy societies have fewer children, because children are only an asset in labor-intensive agriculture, and are a liability in high-tech agriculture and city life), and a host of other issues that techno-pessimists hand-wring over.by
Uncertainty in calculating the Drake Equation has led us to a broad range, with N = [0.84-16.03] * f_i * f_c * L. Despite the uncertainty, we concluded that relatively high values of f_i (the fraction of life-bearing worlds that give rise to intelligence), f_c (the fraction of intelligent species that develop technology detectable across interstellar distances), and L (the lifespan of that high-technology phase of that species’ civilization) would lead to scores, if not hundreds or even thousands, of intelligent species producing detectable signals in the Milky Way galaxy right now.
The radio silence we observe from other intelligent life suggests at least one of f_i, f_c, or L is very low. Today we’ll examine part of f_i, from the origins of life to the cusp of intelligence, from self-replication to genus Homo.
Here are some factors tending to lower f_i:
* It took roughly 4 billion years to go from the formation of Earth to something we would recognize as an animal or plant. (Assumption: only animals or plants can evolve intelligence). If Earth is normal, then we know from the maximum stellar lifespan data that all O, B, A, and the largest and hottest F type stars cannot live long enough. That knocks out about two-thirds of all stellar systems. So f_i is instantly no greater than 0.33.
* Intelligent life requires a lot of energy. (More on this in the next post). Assuming that free oxygen is required for life to generate enough energy, oxygenic photosynthesis has to evolve. (If it doesn’t, all the free oxygen in an atmosphere would rapidly react with carbon, iron, etc. It’s that high reactivity that makes free oxygen so potent in energy generation). If Earth is normal, oxygenic photosynthesis will evolve on any life-bearing planet. The first tranche of free oxygen liberated by photosynthesis will be consumed by metals in a planet’s oceans and surface. (That’s where most of Earth’s commercially relevant iron ore deposits are from). The second tranche of free oxygen will be consumed by gases in the planet’s atmosphere. If Earth is normal, then methane will be one of those gases. Methane would, in effect, burn, yielding carbon dioxide and water.
Methane is a greenhouse gas far more potent than carbon dioxide and water. What happens if most of the methane in a planet’s atmosphere is lost? In Earth’s case, the planet froze over for up to 400 million years. It was only continued volcanic activity, spewing more methane and other greenhouse gases into the atmosphere, that allowed Earth to heat up again enough for the global ice cover to at least partially melt.
Without unglaciated land to colonize, intelligence wouldn’t have appeared on Earth. (Even if dolphins and whales are intelligent, they are mammals adapted to return from land to the sea). So with little or no volcanic activity, a planet after the evolution of oxygenic photosynthesis could freeze over and remain frozen for billions of years, i.e., until its primary star leaves the main sequence. On average, planets smaller than Earth would be more likely to have cold cores and little or no volcanic activity. Let’s say a third of all planets would be too small to have significant volcanic activity, and thus, couldn’t recover from a freeze over. That drops f_i to 0.22.
* “Without photosynthesis, no free oxygen; without free oxygen, no intelligence” also means that intelligent life could not evolve in an atmosphere without sunlight, because photosynthesis would never arise. Good-bye, intelligent Europans, in your ocean encased by 15 miles of ice. If about a third of all planets on which life arises are moons of gas giants, f_i is now 0.15.
* It’s easy to assume there is an inevitability to evolution. (We’ll talk more about this in the next post). But to get to the cusp of intelligence, life on Earth went through a lot of contingent events. The evolution of photosynthesis. The symbiosis of the first eukaryotic cells. The evolution of sex. The evolution of multicellularity. The formation of the ozone layer, to make land habitable against excessive UV. The emergence of animals. Delay any one of these–at least from photosynthesis to multicellularity–on a planet, and you increase the chances of its primary star running out the main sequence clock.
Why assume any of those could be delayed? Why not? There’s no purpose to evolution: it’s simply the blind pursuit of local optima. In light of that, we’ll lower f_i by another two-thirds, to 0.05.
* One last point. Sporadic waves of mass extinction are a good thing, at least as far as we’re concerned, because they cleared the way for the species that gave rise to us. It may be that Jupiter’s size is in a sweet spot to propel the optimal number of large, dinosaur-killing impacts our way. A smaller gas giant would send too many impacts our way, thus interrupting the rise of the successors; one much larger than Jupiter would not send enough. Even if Earth is normal, there are reasons (hot Jupiters, super Jupiters) to conclude Jupiter is not. So f_i ratchets down again, to the arbitary value of 0.02.
We’re now at N, the number of detectable civilizations in the galaxy, at [0.02-0.32] * f_c * L. And that’s assuming intelligence is inevitable when sufficiently complex multicellular life on land has arisen. Is it inevitable? Find out in the next post.by
Here’s my update:
As a huge fan of Niven growing up, it pains me to write that. As a fan of Delany’s core sf of the ’60s into the early ’70s, the reasons why I write that pain me.
What are those reasons? Delany wrote some great core sf, didn’t he? Oh yes. Even a book I think of as a failure, Triton, fails in a thought-provoking manner. (Though my sense of that book as a failure is evolving). The first 15 years of his career are both necessary and sufficient to name Delany a SFWA Grand Master.by
This has been the toughest post in the series to write, because the question of how life arose is the most open. A look at the linked article will show a lot of different conjectures. Which one(s) explain how life actually arose on Earth and/or would arise on other planets are still unknown.
Let’s make some guesses about the upper and lower limits on f_l.
The upper limit is, of course, 1. In other words, it might be the case that life arises on every planet where the ingredients are present for a sufficient length of time (estimating from the early Earth, life needs 500-750 million years). This fits with the mediocrity principle, that there’s nothing special about Earth, and so since life arose here, it would arise anywhere.
Even so, let’s bear in mind Clarke’s comment that “the universe is stranger than we can suppose,” and step back from the max. For our purposes, we’ll say the upper limit on f_l is 0.95.
The lower limit depends on which conjecture for the origin of life you subscribe to.
Does the origin of life require sunlight and tidal pools? Then a large moon (for a terrestrial planet) or a large primary (like Jupiter for Europa) would be very important, if not mandatory. (The sun drives only about half of Earth’s tides). For a terrestrial planet to have a large moon probably requires an impact with a [planetary-embryo-sized] body at a particular speed and angle to form that large moon. Though impacts are common in young stellar systems, large moons are not. (See Venus).
Does the origin of life require a step of nucleic acid solutions absorbing UV radiation? Then stars that generate little UV (e.g., the highly numerous stellar class M) are less likely to meet that requirement.
Does the origin of life require deep sea hydrothermal vents? Those vents would be driven by hot planetary cores, which generally would result from the heat of planetary formation and/or radioactive materials. The upshot: small planets (cooling too quickly) or planets around metal-poor stars (not radioactive enough) are unlikely to support life. However, note the moons of gas giants have a third route to core heating—tidal forces from the gas giant and other moons. (That’s the source of Io’s volcanoes and whatever liquid ocean might exist under Europa’s ice.)
(Aside: The further we go in this series, the more I conclude the moons of gas giants would be the most common homeworlds for life).
What, then, is the lower limit for f_l? Who knows. Out of intellectual laziness, we’ll say the lower limit is 0.05 and be done.
Plugging into the Drake equation, we get:
N_upper = 16.03 * f_i * f_c * L
N_lower = 0.84 * f_i * f_c * L
We’re close enough to end of the series to see that, even at the lower limit, if the values of f_i, f_c, and L are relatively high (the first two > 0.90, the last > 100 years), then scores of intelligent civilizations are sending out signals of their existence at all times. If we go closer to the upper limit, and bump up L to 1000 years, then the number of intelligent civilizations is north of 10,000.
Is the explanation for the Fermi Paradox simply that we’re oblivious to their signals? Or is one or more of f_i, f_c, and L very close to 0? My answer is coming up.by
As we discussed in the series so far (1 2 3), the Drake Equation gives an estimate of the number of civilizations in our galaxy with which communication might be possible, N. After entering the first two values, we have:
N = 5.625 * n_e * f_l * f_i * f_c * L
Today, we’ll talk about the third term, n_e = the average number of planets potentially supporting life per star that has planets.
(Credit: NASA / Jenny Mottar)
What does a planet need to potentially support life? Three things:
Elements capable of forming a wide variety of chemical bonds
A solvent for those elements
An energy source to drive otherwise unfavorable bonds formations
On Earth, those requirements are primarily met by:
Carbon, hydrogen, oxygen, nitrogen, sulfur, and traces of other elements
Let’s be carbon- and water-chauvinists and assume we need the same elements and solvents to potentially support life off-Earth. After all, while silicon can form the same number of bonds as carbon, silicon is about 900-fold more prevalent in Earth’s crust, yet life is built with carbon. As for water, it has a huge advantage over other plausible solvents for biochemistry: its solid form is less dense than its liquid.
Regarding an energy source, though, sunlight isn’t the only game in town. Geothermal energy can support life, and all planets have molten cores early in their existence.
The question then becomes, on average, how many planets per star have carbon, water, and sunlight or geothermal energy? Answer: probably several. In the early years of our solar system, Venus, Earth, Mars, and probably Europa had all three requirements for life. It’s also possible Mercury, Io, and Ganymede did as well. Is our solar system typical? Tough to say, until we know a lot more about extrasolar planets.
Based on all that, we’ll write on the back of our envelope a value for n_e of 3. With n_e = 3, our current value for the Drake equation is:
N = 16.875 * f_l * f_i * f_c * L
So far, we’ve given values to the terms that are favorable to a hypothesis of a galaxy full of high-technology alien civilizations. We’ll see if the fractions of planets that develop life (f_l), particularly intelligent life (f_i), and particularly high-technology civilizations (f_c), will further support that hypothesis in future posts.by
As reported elsewhere, Gene Wolfe, author of the Fifth Head of Cerebus, the four-volume Book of the New Sun, and numerous other works of complex, erudite science fiction and fantasy, was named this year’s recipient of the Damon Knight Memorial Grand Master Award by SFWA. This is seriously cool news for a number of reasons:
1. A knowledgeable and sophisticated observer of science fiction predicted this about a year ago.
2. I live within a mile of his childhood home. Honest, he grew up in Houston. It’s possible he walked or biked by my house en route to the drugstore where he read pulp sf mags on the racks.
3. To other sf writers, he represents an aspirational archetype. The nearest metaphor is what an old *nix beard, full of command-line- and regex-fu, represents to a computer geek. Wolfe’s vocabulary is immense, and even better, not flashy. He doesn’t call Severian’s cloak “fuligin” because it has three syllables to the one of “black,” but because it’s darker than black and has connotations of sootiness, which metaphorically fits Severian’s starting position as an apprentice torturer. Wolfe is very adept at not explaining his sf props, and instead, providing enough context for the reader to figure them out. (E.g., the arquebusers and destriers.) And Wolfe is the master of using unreliable narration: the first and third novellas in Fifth Head of Cerebus, Severian throughout the New Sun books, head-injured Latro in the Soldier of the Mist series. Again, he doesn’t wield these as tricks, but to enrich the story–consider Severian’s eidetic memory, his response to the note regarding “Master Gurloes and the other masters” early in Claw of the Conciliator, and what that says about Severian that he never puts into his own words.
In sum, a well deserved recognition of the man Neil Gaiman called “our greatest living writer.”by