Degenerate Era plate tectonics
Reporters were calling me last week about a paper that turned up on astro-ph, Dark Matter and the Habitability of Planets, by Hooper and Steffan.
Their thesis is that in regions where the density of non-baryonic dark matter is high, an abundance of dark matter particles scatter off the nuclei in the planetary interiors, and get trapped inside a planet, where they wheel on rapidly precessing orbits through the near-transparency of the rocky firmament. Weakly interacting dark matter likely constitutes its own anti-particle, and so when trapped WIMPS encounter each other, they annihilate, producing heat. In The Five Ages, we drew on this process to keep the white dwarfs and the neutron stars shining weakly through the dark expanses of the Degenerate Era.
In Hooper and Steffan’s picture, WIMP annihilation isn’t wimpy at all. In fact, they lean on the process to produce enough heat to keep the water liquid and the planetary surfaces habitable, even in the absence of a parent star.
Sounds like a long-shot to me, but where the WIMP annihilation mechanism might be quite useful is in powering geological activity for the duration. There are plenty of potentially habitable planets orbiting low-mass M-dwarf stars which have staggeringly long main-sequence lifetimes. The long-term habitability hitch for the planets orbiting these stars is not the loss of stellar radiation, but rather cooling of the planetary interior and the attendant shut-down of mantle convection. A cold planet like Mars doesn’t maintain a dynamo, it has no magnetic field to speak of, and its atmosphere is therefore subject to the ravages of solar coronal mass ejections. It’d really be quite nice if WIMP annihilation could keep things ticking long after the heat of formation and the heat of radioactive decay have e-folded into oblivion.
Cosmology in the middle-stelliferous era
The discovery that the expansion of the universe is accelerating came just about the time that my book with Fred Adams, The Five Ages of the Universe, was going to press. So we were significantly out-of-date right from the start. Some of the bigger-picture details in our narrative, such as gravitationally-based computation, almost certainly won’t occur if all of the other galaxies are all accelerated out beyond our causal horizon, but all the events dealing with stars and planets are unaffected by the presence of dark energy.
A recent paper by Avi Loeb (arXiv:1102.0007) shows that astronomers of the extremely distant future will be able to unravel large-scale cosmological insights by making careful velocitiy measurements of the faint escaping halo of red dwarf stars that will surround Milkomeda, the merger remnant of upcoming Milky Way-Andromeda collision.
One might reasonably wonder whether they might have an easier time by simply reading the old issues of Astrophysical Journal. Given, however, my general inability to curate the computer files that I generated in the 1990s, its a good bet that in a trillion years it’ll be considerably easier to just go out and do the observations.
Ancien Régime
I don’t like AdSense-style ads, and I’m contemplating shelling out $29.95 so that readers of Molybdos and The Five Ages won’t have to see them. If you’re seeing an ad related to this post, it’s courtesy of WordPress.com, not yours truly.
It’s not that I’m against advertising. I like looking through the ads in the New York Times Style Magazine — ads that impart a vicarious aspirational buzz, I especially approve of. This past summer, when I was in Paris, I saw the whole machinery of the advertising industry in full swing. At mid-morning, in the midst of my seminar on Gliese 876, the tranquility of the Paris Observatory grounds was abruptly shattered by the diesel roar of generators and the clangorous shouts of workmen.
The tree-lined promenade along the Paris Meridian leading up to south-facing exposure of the grand Seventeenth-century observatory had been rented out to Lacoste in order to stage a runway show. The interior of the observatory was, additionally, off-limits to astronomers, as there was a champagne reception in the Cassini Room in association with the show.
Having seen the writing on the wall first hand, I spent some more time looking into Demand Media’s business model. It seems almost alarmingly feasible to set up a content farm sourced with NLG-generated articles. In fact — and here’s the tie in to The Five Ages — I think the entire universe could very well be a content farm…
The Future: Empty of Content
I learned yesterday (in the course of a conversation with Philip regarding stocks with potentially perilous valuations resembling that of CRM) about the concept of content farming, and the business model underlying Demand Media. I have to say, I found this article from Wired to be absolutely fascinating.
At the moment, it appears that Demand Media is relying on humans to generate their content. Their code parses frequent search-engine queries, and commissions endless “how to” and “top ten” pieces. While the writers of their articles appear to be real humans, the article assignments are done on a completely automated, completely algorithmic basis.
Clearly, the next step is to dispense with the actual human writers and commission computers to write the content. Based on our work with automated planet discovery and article generation using BAM, it’s pretty clear that NLG algorithms are not too far from being able to slip past Demand Media’s copy editors and quality control. Given that a lot of the necessary tools are open source, It looks like there might be a window of opportunity to outsource their article writing to computers before they get wise and start doing it themselves.
Once NLG is capable of generating something on order of the News of the World, I think that a Google-killer will be spawned.
clouds
This morning, flying over the Basin and Range Province, a few of the higher peaks floated likely snowcapped islands in a sea of white.
Astronomy would have had a very different progression had our world been perpetually covered by clouds.
Dark Energy
It occurs to me that the redshift at which the Dark Energy starts to dominate is similar to the redshift at which the first technological civilizations might reasonably have emerged (assuming that the Earth is at least a reasonable baseline example of a “standard” trajectory.)
Might there be a connection?
Live transmission
Fifty years on, with the commisioning of the Allen Telescope Array, the seti enterprise continues to be long radio.
From an unscientific perspective, though, radio seems to be on the way out. I do listen to NPR all the time while I’m driving around, but the KUSP transmitter is, I believe, rather low-power. The pledge drives generally seem to fall short of their goals. Certainly, KUSP is less powerful than the 140-mile distant WLS transmitter that I tuned into with my clock radio every night in 7th grade while doing my homework.
When I moved away from Illinois, I didn’t take my clock radio.
By 1800, the mathematical sophistication evident in Laplace’s Mécanique Céleste was more than sufficient to support a profound understanding of Maxwell’s equations. The equations themselves, however, came more than fifty years later, and what might qualify as the first radio broadcasts came in the 1890s. Nearly seventy years then elapsed before the advent of interstellar seti.
Speculation of the day: we’ve got the mathematical sophistication to understand the actual mechanism of communication, but we don’t yet know the physics, and we certainly don’t have the technology.
Nothing on the airwaves
It’s hard to post regularly to a blog that nobody reads. Sending communications out to an audience that might not exist, or might not be interested, and which will take years to get an answer is similar to writing an unlinked weblog. An initial flurry of activity followed by long stretches of nothing.
Unless you have an agenda.
S.E.T.I. (Suggested Dosage: 1 per day)
American Scientist asked me to review a new SETI book, The Eerie Silence, by Paul Davies.
The premise is effectively the Fermi Paradox 50 years on. Certainly, the lack of any success with SETI must be telling us something.
A low traffic weblog seems like the right environment to collate thoughts along these lines…
It’s said that the highest-level programming language is a graduate student. As one settles further into the academic environment, ideas, direction, come easily, but responsibilities and busy schedules conspire to keep you away from the front line. There’s less time to debug code, less time to spend truly immersed in one topic. I have a suspicion that very few members of the National Academy actually write their own code.
A model, then, or rather the social dynamic for SETI contact when it finally occurs, would be us, humanity, as the eager, energetic, naive graduate student, and them as the jaded bemedaled advisor.
Seven subjects
Over the past decade, I’ve resided on the swampy verge of being a public intellectual. This generates an intermittent stream of inquiries from producers of television documentaries dealing with futuristic global catastrophes. Of late, the frequency of these inquiries has increased. A trailing (and leading) indicator, perhaps, of the zeitgeist. Last Thursday, I got an email which read in part:
“We are in early development of a big one-off special for Discovery Channel. The narrative is simple – seven great scientific miracles of the Earth, how they’ve gone wrong in the past, and what would happen if they went wrong again now. Our subjects are:
1. The spinning Earth suddenly stopping
2. The Earth’s core becoming unstable
3. The collapse of the Earth’s magnetic core
4. How gravity might go wrong
5. When is the next ice age?
6. Does life come from outer space?
7. Are humans indestructable?”
Point one is clearly of no concern. There’s no viable mechanism of any consequence whatever that could induce gross worldwide violation of angular momentum conservation. The Dow will go to zero. Earth will continue to spin. In the growing clamor of anxieties, we have confidence that the Sun will continue to rise.
Maybe point two alludes to concern over a near-term episode of trap volcanism? Catastrophically large eruptions associated with mantle plumes, which with a significant stretch of colloquial license might be described as “the Earth’s core going unstable”, have wreaked havoc in the past. Last September, queued seven-deep on the hot asphalt at a traffic light, I heard an NPR segment that linked the formation of the Siberian traps at the Permian-Triassic boundary to the Great Dying, the Permian extinction. The parallels — catastrophic global warming, ozone depletion, massive buring of coal, anoxic oceans, paving 7 million square kilometers of land area — all seemed to have a certain currency.
Point three must be referring to a reversal of Earth’s magnetic field. No big deal. A declining global dipole field prior to a reversal would wreak havoc on satellite electronics, and there is a possibility of environmental consequences (see here), but field reversals have occurred thousands of times in Earth’s history, and we’re here.
Point four. There’s no immediate problem with gravity (that I know of). It would be very weird if it “went wrong”. Perhaps decay of the false vacuum would change G? Orbital instability mediated by gravity, however, is an entirely different and much more clear-cut matter: one percent chance in the next 5 billion years. Laskar’s upcoming Nature paper will be the definitive reference on this issue.
Point five. Possibly later rather than sooner, but as of this writing, I’m currently out of my depth. Here’s a peer-reviewed article (Berger & Loutre, Science 2002) arguing that the present pulse of greenhouse gasses will act to delay the onset of the next ice age. It’ll be interesting to return to this question.
Point six seems a little out of place. Does he refer to an Andromedae Strain-style extraterrestrial virus? To the space refugium hypothesis? It seems clear that there’s very little transfer of material between mature solar systems in our galaxy, making it a real stretch that extrasolar microorganisms seeded Earth via an impact vector. Aliens arriving in space ships likely pose a higher risk.
A recent paper in the Astrophysical Journal argues that it’s possible that Earth has seeded several extrasolar planets with microbes. That would indeed be quite an accomplishment.
Point seven: no.
