Archive for the ‘worlds’ Category

The IAU Exoplanet Names

December 15th, 2015 Comments off


If nothing else, the extrasolar planets comprise a thoroughly alien cohort, albeit one that is hitched awkwardly to a naming scheme of utilitarian expedience: Tres-4b, Gliese 876e, HD 149026b, and so forth.

When it comes to exoplanets, I’m somewhat chagrined to realize that I fall into the old timer category, and so predictably, back in the old days, I stuck up for the conservative, default naming convention. In this post on exoplanet names back in 2008, I wrote:

A sequence of letters and numbers carries no preconception, underscoring the fact that these worlds are distant, alien, and almost wholly unknown — K2 is colder and more inaccessible than Mt. McKinley, Vinson Massif or Everest.

The International Astronomical Union, however, just issued official crowdsourced names for 31 exoplanets.

Some of them might take a some getting used to. Fortitudo, Orbitrar, Intercrus. “Son, that’s not 51 Peg b, that’s Dimidium.”

So will the names come into general use? I’ve set up a prediction market at our new website Metaculus to determine whether or not it’s likely:

What do you think? Sign up and make your prediction count…

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How did they get there?

November 30th, 2015 Comments off


There are of order 500 million hot Jupiters in the Milky Way. Swollen and massive, with blisteringly short periods, they crowd the tables and the diagrams showing extrasolar planets. The first of their number were career-cementing front page news, trophies of planet roving planet hunters. Two decades on, they slip into the census with little fanfare and less notice.

Conventional wisdom holds that hot Jupiters form at large, Jupiter-like distances, where water ice is stable and where the orbital clock runs slowly. Then they migrate radially inward, either gradually, by interacting with the disk that produced them, or, even more gradually, via the Kozai process, or perhaps, violently, as a consequence of dynamical instabilities that toss giant planets to and fro.

When the first hot Jupiters were discovered, their presence was so strange, so unpredicted and so uncomfortable that there was a certain need for a point of contact with the familiar. It seems more sensible that a planet should form in the right environment and then go astray, rather than defy odds and logic to emerge spontaneously in a location where it obviously shouldn’t be. It’s a short leap from the Copernican principle to the idea that the Solar System has no special distinction. We have nothing orbiting at forty days, not to speak of four.


Yet there is a tantalizing gap in the mass-period diagram that hints that short-period super-Earths that reach fifteen or more Earth masses might engage in rapid gas accretion. Such promotions need happen less than once in a hundred tries. In the spirit of trying to go against the grain, in the perverse hope of eliciting a paradigm shift, Konstantin, Peter B. and I have been working to make the case that many hot Jupiters might just form where they’re found.

The details are all in a paper that we just posted on arXiv.

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Self Portrait

July 14th, 2015 Comments off


Image Source

The New Horizons probe just flew through its closest approach to Pluto, and is executing its minutely detailed plan. Fingers on keys and its robotic spirochetes are spacelike-separated events.

The detail in the most recent photograph of Pluto — radioed as an assurance of success in the event that something hit the spacecraft during the last few hours — leaves the impression of a world that has been painted. Eons of weak geysers, subtle rarefied winds, and the sepia tones of photochemistry have combined to produce the illusion of shadow, oil pigments and diffuse lighting that eerily evoke this newly discovered portrait by Rembrandt.


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July 9th, 2015 Comments off


First thing every morning, I check the raw images from New Horizons. Today there is a fresh set. The Independence Day glitch has been left millions of miles behind, and only days remain until arrival.

Pluto’s current remove seems to lie at a point of heightened mystery. Mottled patches and curiously regular features are starting to fill the frame.


The detail seems reminiscent of Mars seen through a refracting telescope, and brings to mind Percival Lowell’s drawings that combined real features and artifacts in a tantalizing juxtoposition.


Lowell’s drawing is from 1894. It was still a lifetime — seventy years — before Mariner 4 rushed past Mars and radioed cratered, disappointing close-ups of of the Martian surface. Undaunted, I rode my paper route during the early summer of 1976, concocting vivid premonitions that the first pictures from the Viking I lander would provide some shocking, irrefutable vista of fossils, sandblasted ruins and crashed saucers.

A more quantitative, but effectively similar vein of speculation informed this article by Loeb and Turner from a few years ago:


We need wait only another hundred hours or so if there is to be a view of Pluto’s lit-up cities of the night.

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June 21st, 2015 Comments off


This morning, June 21, 2015, a Google image search for Pluto brings forth inane cartoon dogs, blurry, best-effort HST images, over-the-top space-art landscapes, and a selection of shiny photo-realistic globes, clearly influenced by Ganymede, Io, and Triton.


The New Horizons spacecraft, on its ballistic pinpoint trajectory, is just 22 days, 16 hours, 14 minutes from arrival at Pluto, devouring its ever-shrinking gap at 30,800 MPH. A remarkable recent movie posted by the Mission Controllers imparts enough detail to see by eye that the system is tidally despun. And with the targets still effectively at infinity, the scale of the bodies and the orbit is perfectly illuminated. Perspectives during the encounter will use foreshortening and narrow field of view to optimal effect, obscuring the fact that any system with an orbital time scale of order a week is, when taken as a whole, of order dozens of times less dense than air. Effectively just empty space.

In less than a month, the same Google search will be dominated by a small handful of thousand-fold improved images, possibly even by a single best photograph impressed in the camera’s eye during the dramatic needle-threaded moment of urgency.

Pluto’s cultural status made the mission possible. Perhaps the spacecraft will reciprocate with image that will become a touchstone, a visual shorthand for distance, isolation, frigidity and exile.

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March 10th, 2015 Comments off


I was struck by the image that NASA released several days ago, just before the Dawn Spacecraft braided itself into orbit around Ceres.

From a graphic standpoint, the photograph is perfect. The black expanse relays that the asteroid belt, and by extension the solar system, are mostly empty. Even more subtle is the message telegraphed by the crescent phase. We arrive to our first clear view of this world as outsiders, from a distance further from the Sun than Ceres itself. A consequence of the energetics and the constraints of the trajectory design to be sure, but metaphoric nonetheless.

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February 22nd, 2015 3 comments

Have you noticed that the Internet can seem slow? Sometimes it takes a long time for web pages to load. It would really be better if they would just snap up instantly on the screen.

In practice, “instant” response occurs if the latency is less than ~1/30th of a second, or ~30 msec. Animation at thirty frames per second looks smooth. Only a small minority of the population has the retinal read-out frequency required to see that the Crab pulsar is flashing at 33.5 msec intervals.

Coincidently, the speed-of-light travel time along the (almost entirely overland) great circle route between Tokyo and New York is (to within a millisecond) the same as the Crab Pulsar’s current spin period. In theory, it should possible to load Japanese-sourced web pages with barely perceptible latency, as the service of a request involves a round-trip.


The fastest communication between Japan and the West Coast of the United States is via NTT’s PC-1 cable, which runs between cable landings at Ajigaura (near Tokyo) and Harbour Pointe (near Seattle). Round-trip communication on the cable takes 80 msec, which, given that the speed of light in optical fiber is ~1.44x slower than the speed of light in vacuum, indicates that cable must adhere fairly closely to the great circle route beneath the Pacific.

Here’s an interesting paper by Ankit Singla and his collaborators which explores the various drag terms that keep the Internet from actually running at the speed of light. As part of their research, they report on 20+ million measurements of 28,000 web urls served from 120+ countries. The cumulative distribution function of all that pinging points to a median latency for loading html that is ~40x slower than if the message was covering the inferred great circle distance at the speed of light in vacuum.


Singla et al. argue that the speed doesn’t have to be so slow:

A parallel low-latency infrastructure: Most flows on the Internet are small in size, with most of the bytes being carried in a small fraction of flows. Thus, it is conceivable that we could improve latency for the large fraction of small-sized flows by building a separate low-latency low-bandwidth infrastructure to support them. Such a network could connect major cities along the shortest paths on the Earth’s surface (at least within the continents) using a c-speed medium, such as either microwave or potentially hollow fiber. Such a vision may not be far-fetched on the time horizon of a decade or two.

Even a decade might be an overestimate. As readers know, during the past several years, a secretive fleet of microwave networks have sprung up to transfer information between the Chicago and New York metro areas at as close to the speed of light as possible. The fastest of these networks now transmit within ~2% of the physical minimum. Tremendous efforts have gone into squeezing out every last source of delay.

It’s thus interesting to look at what a national low-latency microwave backbone might look like. To optimize on costs, and to minimize connection times, one wishes to connect a number of nodes (metropolitan areas) with the minimal complement of route segments. This task, known as the Steiner tree problem has an interesting history, and computationally, is non-deterministic polynomial-time (NP) hard. One can get analog solutions by placing a board with pegs representing the nodes into soapy water. The connective soap bubble films are physical representations of the Steiner trees:


I coded up a Steiner tree finder using an incremental optimization algorithm, and ran it on the top 20 metro areas in the US by populations, which (ranked according to distance from their centroid) are:

10 PHX
11 TPA
12 PHL
13 NYC
14 MIA
15 SAN
16 LAX
17 BOS
18 SFO
19 PDX
20 SEA

The algorithm, which employs the Vicenty distance formula between points on the Earth’s surface, and which is not guaranteed to find the absolute shortest route, links the 20 cities with a total path length of 9,814km, about 10x the length of a NYC-CHI route:


The added interconnecting nodes on the tree are the Steiner points. A prominent example on the map above connects Dallas and Denver with the Minneapolis-Chicago interconnect point, and lies in an obscure field a few miles south of Haven, Kansas.
Remarkably, when one zooms in on the exact spot, and settles into street view, there’s a red and white microwave tower a hundred meters or so from the actual Steiner point.
Rather fittingly, the tower has three dishes, indeed, pre-aligned and pointing in what appears to be the requisite directions…
The Gaia hypothesis, was introduced by James Lovelock in the 1970s and “proposes that organisms interact with their inorganic surroundings on Earth to form a self-regulating, complex system that contributes to maintaining the conditions for life on the planet.”

As the planet wires itself and its computers ever more tightly together in an ever-lower latency web of radio links and optical fiber, it no longer seems like a particular stretch to float an Electra hypothesis in which computational nodes and their interconnections assume a global role comparable to that now filled by the biological organisms.

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The Machine Epoch

February 14th, 2015 Comments off


In looking through oklo’s activity logs, it is evident that many of the visitors are not from the audience that I have in mind as I write the posts. The site is continually accessed from every corner of the planet by robots, harvesters, spamdexing scripts, and viral entities that attempt to lodge links into the blog.

A common strategy consists of attempts to ingratiate with generically vague comments of praise:


The Turing test was envisioned as a text-only conversation with a machine. The machine passes the test if it can’t be distinguished from a real person. In Alan Turning’s Computing Machinery and Intelligence, he asks, “Are there imaginable digital computers which could do well in the imitation game?”

For now, the general consensus seems to be no. Machines can’t consistently pass the test (and the test itself seems increasingly dated), but their moment is approaching fast. Judith Newman’s recent NYT article about interaction with the iPhone’s Siri telegraphs the stirrings of the current zeitgeist.

The economics of comment spam must be relatively minor. Were serious money was at stake, a Nice Post! robot armed with state-of-the-art-2015 natural language processing skills and tuned to the universe of text strings and facts could almost certainly pull the wool over my eyes.


In early 2001, I was working at NASA Ames Research Center. The first Internet Bubble hadn’t quite ended. Highway 101 was a near-continual traffic jam. Narrow billboard trucks advertising this or that dot com were still cycling aimlessly up and down the Peninsula. We had just published our plan to move the Earth in response to the gradually brightening Sun.

I got an e-mail with a address from someone named John McCarthy, who asked if he could come to NASA Ames to talk with us about astronomical engineering. This was before the Wikipedia, and for me, at least, before the ingrained reflex to turn to the web for information about someone one doesn’t know. I just wrote back, “Sure!”

I recall McCarthy in person as a rather singular character, with a bushy white beard surrounding thick black glasses. He had a rattletrap car with a bulky computer-like device somehow attached next to the steering wheel. My co-author, Don Korycansky, was there. I remember that the conversation was completely focused on the details of the orbits and the energy budgets that would be required. We didn’t engage in any of the far-out speculations or wide-eyed ramifications that thrust us, as a result of my ill-advised conversation with a reporter a few weeks later, into a terrifying worldwide media farce.

Only later did I realize that John McCarthy was one of the founding giants of computer science. He coined the term Artificial Intelligence, invented Lisp, and was famous for his Usenet .sig, “He who refuses to do arithmetic is doomed to talk nonsense.”

McCarthy’s Progress and Sustainability web pages (online at are dedicated to the thesis of optimism — that human progress is desirable and sustainable. He wrote, “There are no apparent obstacles even to billion year sustainability.” In essence, the argument is that the Anthropocene epoch, which began at 05:29:21 MWT on July 16, 1945, will stretch to become an eon on par in duration with the Archean or the Proterozoic.

Optimistic is definitely the operative word. It’s also possible that the computational innovations that McCarthy had a hand in ushering in will consign the Anthropocene epoch to be the shortest — rather than one of the longest — periods in Earth’s geological history. Hazarding a guess, the Anthropocene might end not with the bang with which it began, but rather with the seemingly far more mundane moment when it is no longer possible to draw a distinction between the real visitors and the machine visitors to a web site.

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February 8th, 2015 Comments off


Vladimir Arnold, he of the A in KAM Theory, wrote a classic graduate text entitled Mathematical Methods of Celestial Mechanics. This, as one might imagine, is a book that is not exactly a storehouse of easy homework assignments. There are, however, a scattering of problems that offer insights while, at the same time, not actually requiring the tough-guy methods that are the text’s primary focus.

During his walk in outer space [as part of the Voskhod 2 Mission on 18 March 1965], the cosmonaut Alexey Arkhipovich Leonov threw the lens cap of his movie camera toward the Earth. Describe the motion of the lens cap with respect to the spacecraft, taking the velocity of the throw as 10 m/s. Neglect the asphericity of the Earth.

(Ria Novosti/Science Photo Library)

Leonov’s space walk tipped off a hair-rising adventure which began with his being nearly unable to re-enter the spacecraft, and ended with a frigid way-off-course landing in the Siberian Tiaga, all of which is covered in a recent BBC documentary.

One can hand-crank the problem by noting that the radially directed, \({\bf v}_{i}=10\,{\rm m\,s^{-1}}\), launch of the lens cap exerts no torque, so that \({\bf r}\times{\bf v}_{i}=0\), whereas the total specific energy of the lens cap’s initial orbit, \(-GM_{\oplus}/2a\) is augmented by \(\frac{1}{2}v_{i}^{2}\). Given the new semi-major axis, \(a_{\rm new}\) and the before-and-after conservation of \(h=(GM_{\oplus}a_{\rm new}(1-e^2))^{1/2}\), one can solve for \(e\), and then proceed to all four orbital elements by noting that \(r=a(1-e\cos E)\) and \(M=E-e\sin E\), and then working out the longitude of pericenter, \(\varpi\), relative to the reference direction defined by the radius vector from the Earth’s center to the point where the lens cap was thrown. Clumsy.

The guiding center approximation revives the old idea of epicycles to describe the motion of a particle (in this case, the lens cap) on a low eccentricity orbit. For modest \(e\), the true Keplerian motion is approximated as a compound of the circular motion of a “guiding center” and the counter-directed motion about the guiding center on a 2:1 ellipse, where the semi-minor axis is oriented radially, and has length \(ae\). Both motions complete once per orbital period. Here’s the basic idea, drawn for an orbit with \(e=0.3\), which is actually quite a substantial eccentricity:


For the lens cap problem, the guiding center materializes at a distance \(2ae\) ahead of the launch point. The motion associated with the guiding center is the superposition of two simple harmonic motions. For the radial oscillation, \(\frac{1}{2}v_{i}^{2}=\frac{1}{2}n^{2}x^{2}\rightarrow v_{i}=nae\), which works out to \(e=0.0013\). To first (and very good) approximation, the lens cap arrives back 88 minutes later in the close vicinity of the spacecraft, after inward and outward radial excursions of 8.4 km, and after leading the spacecraft by as much as \(4ae=34\) km. The small total gain in orbital energy lengthens the lens cap’s orbital period slightly, which means that the cap fails to catch up by a few tens of meters at the end of a full one-orbit epicyclic oscillation.

In Michael Rowan-Robinson’s Cosmology (3rd ed.) Oxford University Press. pp. 62–63, one finds, “It is evident that in the post-Copernican era of human history, no well-informed and rational person can imagine that Earth occupies a unique position in the universe.”

If one insists on a strictly inertial frame, I guess that’s true, but non-inertial frames often have more value. Thousands of extrasolar planets have been found, and not one of them is remotely habitable. Many lines of evidence are beginning to point toward an Earth that is unique, probably in the galaxy, and perhaps, even, in the accessible universe. In the post-post Copernican era, epicycles (2:1, rather than 1:1) have a certain appeal. And indeed, there’s nothing inherently wrong about the Tychonic model of the solar system, it simply subscribes to an Earth-centered point of view. Don’t we all?

On the topic of epicycles, I have to say I wasn’t a fan of the article on “retrograde beliefs” that appeared a few weeks ago in the New York Times Magazine. Obviously, astrology is a bunch of bunk. It’s known to be wrong. One can make the argument that taking it down in the genteel and informed confines of the NYT magazine amounts to shooting fish in a barrel. Satire is probably the best approach. Aside from this stylistic quibble, the writing in the NYT piece seems incoherent, somehow second-hand and artless. An intricate 1756 diagram by James Ferguson (who is no longer around to defend his work) is given a rather underhanded misrepresentation:


The full title of Ferguson’s book is Astronomy Explained Upon Sir Isaac Newton’s Principles, And Made Easy to Those who Have Not Studied Mathematics. The diagram reproduced in the NYT is not the product of some recalcitrant Ptolemaic view as implied in the caption, but rather appears in a chapter entitled “The Phenomena of the Heavens as seen from Different Parts of the Solar System”. It shows the intricate motions of the inferior planets in a co-rotating Earth-centered frame, and Ferguson gives a fascinating description of the analog-computational method he used to create the diagram:


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Exhaustive new review article on exoplanets.

January 25th, 2015 1 comment


One tends to roll one’s eyes when the topic turns to Georges-Louis Leclerc, Comte de Buffon, the French encyclopedist and pre-revolutionary intellectual luminary.

Buffon sounds regrettably similar to Buffoon, especially considering that The Comte is best-known for some memorable blunders. For example, Georges-Louis came out on the losing side of a tussle with Thomas Jefferson regarding the general valor of the New World fauna. From the wikipedia article:

At one point, Buffon propounded a theory that nature in the New World was inferior to that of Eurasia. He argued that the Americas were lacking in large and powerful creatures, and that even the people were less virile than their European counterparts. He ascribed this inferiority to the marsh odors and dense forests of the American continent. These remarks so incensed Thomas Jefferson that he dispatched twenty soldiers to the New Hampshire woods to find a bull moose for Buffon as proof of the “stature and majesty of American quadrupeds”

Buffon also speculated, in 1778, that the solar system’s planets were the result of a collision between a comet and the Sun, a hypothesis that is completely incorrect. Even in the 1750s, perturbation analyses (such as those carried out by Alexis Claude Clairaut in connection with the successful predictions of the return ephemeris for Halley’s Comet) had made it clearly evident that cometary masses are far smaller than planetary masses.

Buffon, however, was definitively not a buffoon. He came remarkably close to having a full command of all the scientific disciplines, and some of his efforts still sparkle. He calculated that the chance of the Sun rising tomorrow is \(1-(1/2)^x\), where \(x\) is the number of consecutive days that it has risen to date. In his treatment of probability theory, he also stated that one chance in 10,000 is the lowest practical probability — an enormously useful bon mot, on par, say, with Andy Warhol’s remark that “when you think about it, Department Stores are kind of like Museums.”

Buffon’s Histoire Naturelle, which aimed to exhaustively cover all of the natural sciences, ran to 44 quarto volumes, eight of which were written and which appeared after he died, and all of which were out of date the moment they were printed. Even in the 1700s, scientific knowledge was accumulating so rapidly that it was impossible to keep up.

It has been recently hammered home to me that the same situation also now holds true for extrasolar planets. Jack Lissauer and I just finished a review article on exoplanets for the forthcoming second edition of Elsevier’s Treatise on Geophysics. A pre-print is up on today’s arXiv listing. In writing the article, it was painfully clear just how large the literature is, and how fast it is growing…

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