Monday, August 3, 2015

Extraordinary Near-Earth Asteroids II: 2010 TK7


 
Another denizen of the zoo of Near Earth Asteroids is a little rock called 2010 TK7.  The first clue to its unusual nature comes from its orbital period: 1.00039 Earth years.  The second clue is the orbit it pursues to permit it to avoid collision with Earth.  This 300-meter NEA follows the L4 Lagrange point on Earth’s orbit, 60 degrees ahead of Earth.  Its behavior is similar to that of the Trojan asteroids on Jupiter's orbit, 60 degrees ahead of and 60 degrees behind Jupiter: we can call it an "Earth Trojan". It circulates slowly around the exact L4 point because its orbit is quite eccentric (eccentricity 0.1908) and inclined (20.882 degrees).  As it ranges from perihelion, 0.8094 AU from the Sun (closer to Venus’ orbit than to Earth’s), out to aphelion at 1.1911 AU, its orbital velocity constantly changes

There have been numerous suggestions that this asteroid would be a very easy target for spacecraft missions from Earth.  The usual rationale is that, unlike most NEAs, it is always close to Earth and therefore easy to reach.  But this argument is simplistic and requires scrutiny.  Suppose the spacecraft departs from the Earth-Moon system with a relative velocity of 2 km per second.  The mean distance between Earth and the L4 point is 150,000,000 kilometers; to get there would then require 75 million seconds (about two and a half years), after which the spacecraft would fly by the asteroid at a relative speed of 2 kilometers per second, traversing the diameter of the asteroid in 1/7 of a second.   To reduce the flyby speed to the point at which the spacecraft could rendezvous with, orbit around, or land on the asteroid requires a velocity change (“delta V” to rocketeers) even larger than that required to take off from the Moon and get into orbit. 

The size of 2010 TK is poorly known.  Its apparent brightness and distance, measured at the time of discovery, permit us to calculate an absolute magnitude of 25.3, which is about 30 meters in diameter if the asteroid has “average” composition and reflectivity; probably 20 to 50 meters within the uncertainties of our data.

In case you haven’t seen the concept of “absolute magnitude” explained, it is the apparent magnitude a body would have if observed at a distance of 1 AU form Earth and 1 AU from the Sun.  The scale for measuring magnitude is an adaptation of the ancient naked-eye system: a bright star is “of the first magnitude”, a noticeably fainter star is 2nd magnitude, and so on down to the practical limit of naked-eye observation, 6th magnitude.  Every interval of 5 magnitudes corresponds to a factor of 100 ratio in the intensity of visible light.  Thus Vega is about magnitude 1, the faintest star your naked eye can see, about magnitude 6, provides 100 times less light, and a body of magnitude 26 is 25 magnitudes fainter than Vega, or five factors of 100 (10 billion times) fainter.

Is there anything about this rock that would attract the attention of explorers or miners?  Because of its orbit, it can never approach Earth closely enough to make it a practical target for spectroscopy or for radar observations.  If we needed to know what it is made of, its chemistry, mineralogy, and physical structure, we would have to go there.  In other words, to find out whether it would make sense to send a spacecraft there we would have to send a spacecraft.  This is not a compelling argument for planning a mission.

"The Day after Tomorrow" is no Closer


 
High on the list of things that Everybody Knows is the claim that the Gulf Stream is slowing down, delivering ever less heat to the Northeastern US and Western Europe and inevitably triggering a new Ice Age.  The “evidence” comes from proxy data and computer climate predictions; the reality of the problem was attested by the 2004 eco-porn movie “The Day after Tomorrow”, in which New York is eaten by a glacier.

There are just a few little problems with this story.  First, there is the use of the word “evidence” to describe the predictions of models and proxy estimates.  Let’s be clear about this: the way science progresses is to 1) collect data, 2) propose one or more ideas, called hypotheses, that might explain the data, 3) use quantitative models of these hypotheses to generate predictions of future observations, and 4) carry out a new round of experiments designed to test (and discriminate between) the competing hypotheses.  Steps 1 and 4 deal with evidence (data); step 3 is not evidence; it is informed conjecture, as-yet untested speculation, whose sole purpose is to motivate a search for critical new data, NOT to predict the future. 

Second, the role of disaster movies is not to teach science; it is to sell tickets.  Anyone who derives his understanding of climatology from disaster movies is a fool.  This judgement includes those whose knowledge of asteroids comes from Bruce Willis.

Third, (a most inconvenient truth): we actually have direct observational data on the flow of the Gulf Stream covering some 23 years of recent history.  Shock, horror: we don’t need to rely on hypothetical speculation!  A research team headed by an eminent expert on oceanic circulation, Prof. H. Thomas Rossby of the Graduate School of Oceanography of the University of Rhode Island and his team, have been measuring the speed of the Gulf Stream since 1992.  Their study was based on observations made on the Bermuda Container Lines’ ship Oleander, which makes weekly crossings from Elizabeth NJ to Bermuda.  The Oleander carries a Doppler current meter that directly measures currents to a depth of about 600 m.  And what are the results of their research?  They find no evidence whatsoever that the speed of the Gulf Stream has decreased over the time of their study. 

Why do we get so much bad science in the press? Because untested conjectures are often much more interesting than the truth. Which sells more papers (or movies), the "news" that we are on the verge of a new Ice Age, or the demonstrated fact that everything is going on normally? By ignoring the distinction between untested hypotheses and replicated fact, they mislead the public, misrepresent the science, and sell their undigested pap as news. 

Sherlock’s Debt to Giordano Bruno


 
             Followers of the excellent BBC Sherlock series (yes, you—it’s OK to admit it) have surely noticed the remarkable antipathy Sherlock holds against the “Napoleon of blackmail”, the reptilian Charles Augustus Magnussen.  But they also have perhaps been intrigued by the “memory palace” process of memorization that Sherlock and Magnussen have in common. 

            The revival of this ancient memory technology traces back to Giordano Bruno’s “Art of Memory”, in which ideas, people, and images are inserted into the context of a house or palace with many rooms.  This process was described and elaborated in Frances A. Yates’ wonderful book, “Giordano Bruno and the Hermetic Tradition”.

            But the technique is of far more ancient origin.  Cicero and Aristotle wrote of this technique, as did the famous Jesuit Matteo Ricci.  They in turn provided the inspiration to Bruno, whose ideas were again brought to current awareness by Yates’ scholarly writings.  And, as so often happens, these ideas were again “invented” by the writers of Sherlock, who surely were familiar with Bruno’s contribution, but who, in proof if their freedom from stuffy academic conventions, passed them on to us free of scholarly attribution.

            This oversight is perhaps made more understandable when we realize that the inscrutable Mycroft Holmes, in his assumed persona of Mark Gatiss, is the producer and one of the writers of Sherlock.  Surely he has some game afoot, if only we knew what it was…

            Perhaps all will become clear in Season 4, if it ever materializes.

The Alinda Family of Asteroids


The asteroid 887 Alinda has long been known to follow an orbit that is nearly resonant with the orbital periods of both Jupiter and Earth: its orbital period of 3.915 years is close to the 1:4 Earth resonance and close to the 3:1 resonance with Jupiter.  In recent years the rate of discovery of previously unknown asteroids has been enormous, with thousands of new asteroid discoveries each year, so it is not surprising that a number of other Alindas have been found.  Membership in this family requires an orbital period very close to 4 Earth years, which in turn requires that the mean distance from the Sun (the orbital semi-major axis) must be close to 2.54 AU.  That places these bodies in the inner asteroid belt—except for the excursions brought about by the eccentricities of their orbits. 
Orbits close to a Jupiter resonance are not only subjected to the gravitational perturbations exerted by Jupiter on all asteroids, but experience repeated perturbations with the same approximate geometry.  This allows, like the resonant pumping of a child on a swing, a constant buildup of self-reinforcing disturbances, which cause a constant growth in the eccentricity of the asteroid’s orbit, making an ever more elongated ellipse. Eventually, this growth in eccentricity imperils the asteroid by extending its orbit inward to perihelion distances ever closer to the Sun, crossing the orbits of one or more of the terrestrial planets, while also stretching the orbit outward so that its aphelion distance can approach Jupiter.  Close encounters with any planet can seriously disturb an asteroid’s orbit; the closest encounters, resulting in collisions, are fatal to the asteroid and may be seriously disruptive to the target planet.
The 23 Alindas now known include eleven in low-eccentricity orbits (e ranging from about 0.30 to 0.34).  These bodies roam the reaches of the Solar System from about 1.7 to 3.4 AU from the Sun, spending most of their time in the asteroid belt and never approaching any planet closely. They are the "young" Alindas, recently nudged into resonant orbits.  In such orbits their resonant relationship to Jupiter causes their orbits over time to gradually become more eccentric.  They are not in immediate danger except for the small probability of colliding with other asteroids, but they are in for serious trouble in the long run.
Three of the known Alindas (6318 Cronkite, 8709 Kadlu, and 6322 1991 CQ) have orbital eccentricities between 0.465 and 0.475, sufficient to have them cross the orbit of Mars.  These three Alinda Mars-crossers do not cross the orbit of any other planet; Mars has a small mass and cross-section area, and cannot remove these bodies as rapidly as Jupiter can replenish them and move them on to even more eccentric orbits.
Then there is the namesake of the family, 887 Alinda itself, with an eccentricity of 0.564.  Its perihelion distance (q) of 1.084 AU qualifies it as a near-Earth asteroid (NEAs by definition have q < 1.300 AU).  It grazes but does not cross Earth’s orbit, making it an Amor asteroid as well as an Alinda family member.
Even more pumped-up Alinda clan members include eight (with eccentricities between 0.57 and 0.75) that cross Earth’s orbit: at perihelion they are closer to the Sun than Earth is at aphelion, 1.017 AU.  They are therefore Apollo-family NEAs as well as Alindas.  Since all Alindas are Earth-resonant, they may fly by Earth repeatedly at close range at 4-year intervals for decades at a time, affording radar observation and spacecraft launch opportunities—and collision opportunities—over that time period.  One such asteroid is 4179 Toutatis, which was the target of a close flyby by the Chinese Chang-e 2 spacecraft in 2013.  Two members of this group, 7092 Cadmus and 8201 1994 AH2, could be termed Venus-grazers, having perihelia inside 0.76 AU.  The most eccentric of the Alindas is 3360 Syrinx, a Venus-crosser with e = 0.743.  Its orbit makes six crossings of planetary orbits every four years (twice each for Mars, Earth, and Venus), a highly unstable situation that suggests a short life expectancy.  Interestingly, all three of these most-eccentric Alindas have aphelia close to 4.3 AU.  None of the Alindas approach Jupiter closely, a wise precaution.  A close encounter with Jupiter could swallow the asteroid whole, kick it out of the Solar System permanently, or wreak other orbital havoc.
The Alindas serve as a reminder of the role Jupiter plays in sending hazardous bodies toward us; a fringe benefit is the opportunity to have many repeated launch opportunities to a given asteroid.  The Alindas are loose cannons, subject to disturbance by Jupiter, Mars, Earth, and Venus.  These asteroids are both carrot and stick, guaranteeing that we will hear a lot more about them in the future--such as when Toutatis comes by again in 2016! 

Thursday, July 30, 2015

The Wrong Stuff on the Wright Brothers


April 2015

Research is hard work; copying the work of others is a lazy man’s vice.  In the world of family history, as in many other areas of research, there is a vast gulf between the uncritical copying of undocumented allegations and the critical evaluation of primary sources. 

I recently stumbled across a classic example of the victory of credulity over real research.  While reviewing the family history of Wilbur and Orville Wright I was amused (though not especially surprised) to find multiple undocumented reports of the marriage and descendancy of Orville Wright, including proud claims of living persons to be his direct descendant.  Having already researched the Wrights, with whom I share as common ancestors the 17th century Dutch immigrants Gerrit Wolfertse van Couwenhoven and Aeltje Cornelise Cool, I knew that Orville Wright never married.  Then why do so many family trees posted on Ancestry.com report a wife, children, and even several generations of descendants for Orville?  This question can only be answered by careful research. 

Warning: on Ancestry, many family trees cite no primary sources at all; many others list sources, but the sources they cite actually contradict the information they claim to have found in them.  Citing a reference is no substitute for reading, understanding, and using it!  And remember that the family trees on Ancestry.com are contributed by any interested party, whether they know the rudiments of research or not, and are neither produced nor vetted by Ancestry.

A good place to start is the 1930 United States Census.  In it we find two people named Orville Wright of about the right age and location.  Orville #1, a single male, was born in Ohio in 1871 and lived in Van Buren, Montgomery County, Ohio.  His father was born in Indiana and his mother in Virginia.  Also in his home were his housekeeper Carrie Grumbach and her husband Charles.  At the same date, Orville #2, who was born in Illinois in 1881, was living in Canton, Fulton County, Illinois.  According to the 1930 Census, his father and mother were both born in Illinois.  He was married, and gives his occupation as “farmer”.  His wife, Hattie, was in the same household. 

Which Orville is the “Wright stuff”?  It should be pretty obvious that the Ohio Orville is the better candidate, but let’s go back a decade to the 1920 U. S. Census and check up on them.  In 1920, we find “Orvill Wright”, born in Ohio in 1871, living in Van Buren, Montgomery County, Ohio, with his sister “Catheryn” and the Grumbachs.  His father’s and mother’s birthplaces agree with the 1930 data.  Once again he is listed as a single male.  He reports his profession as “aeronautical research and engineer”.  In 1920 we find Orville #2 living in Illinois with his wife Hattie, occupied as a farmer. 

Pushing back to the 1910 U. S. Census, we find Orville #1 living in Dayton, Montgomery County, Ohio with his sister Katherine, brother Wilbur, and their father Milton, an 81 year old widower.  Lest there be any doubt, the brothers give their occupation as “inventor, aeroplane”: not a married Illinois farmer. Family trees that conflate the two Orvilles are, sadly, quite common: Orville #1 ends up with Orville #2’s wife.

Now that we have seen that the Illinois Orville Wright is really Wrong, let us look at his family and descendants.  Several family trees on Ancestry.com give his wife’s maiden name as Hattie McLoren or Hattie V. (or N.) McLaren; the 1910 U. S. Census says Orville and Hattie married 2 years earlier (1908), when Orville was 27, and other trees say that his wife was Bessie F. Haffner, whom he married at age 59 in 1941.  There is no conflict if Orville #2 remarried after the death of his first wife in 1936.

More interesting are the numerous trees that report that Orville and Hattie had a daughter named Buckingham, born in 1890 to Orville in Montgomery County, Ohio.  Now of course the problem is that Hattie married Orville #2 in Illinois, not Orville #1 in Ohio.  In 1890 Orville #2 was not only unmarried; he was 9 years old.  Other trees allege that Orville #1 had two children with Hattie, Viola Ann (born 1890) and Buckingham (born 1890 or 1894).  But Orville #1 was still single and living at home with his parents in Ohio in 1900.

If you think you are descended from either Buckingham or Viola Ann (born 1890), you need to come to grips with several facts.  First, Hattie reports in the 1910 Census that she had never had a child.  There are no children in their household in any Census.  Second, there are no Census, birth, marriage or death records for the alleged daughters Buckingham and Viola Ann.  What sources are cited in the Ancestry family trees that contain these names?  The only sources are references to other trees.  There are absolutely no primary sources cited because there are none.  There is nothing but unsubstantiated rumor to support the claims that Orville Wright #1 (the aeronaut) was married, that he had children, or that he is anyone’s ancestor.  Some of the enthusiasts have conflated Orville #1 with Orville #2, despite overwhelming evidence that they were different people, apparently in order to prove their descent from a famous man.  But even this ploy fails because neither Orville had descendants.  And, by the way, neither did Wilbur.

The bottom line: do your research in primary sources.  Issues of fact are not to be settled by vote or consensus.  Three and a half centuries ago the Royal Society in London took as its motto the epigram “nullius in verbum”.  That means “take nothing on someone’s word”: check the facts for yourself in primary sources.  Do you believe the Apollo program was a fake?  Do you believe in the “hockey stick” temperature graph?  Cold fusion?  Better check it out…

Extraordinary Near-Earth Asteroids I: 2014 PP69


April 2015

 We presently know of about 13,000 Near-Earth Asteroids, including nearly 1000 that are larger than 1 kilometer in diameter.  Typical NEAs range from Earth’s general vicinity out to the heart of the Asteroid Belt on each orbit around the Sun.  Their orbits typically have inclinations (relative to the plane of the Solar System) of 10 to 30 degrees, eccentricities of 0.2 to 0.6, and orbital periods of about 2 to 4 years.  The mean distance of any NEA from the Sun is usually near 2 AU.  But the NEAs are a wildly diverse collection of bodies that originated at widely separated locations in the Solar System.  The outliers of this population include some truly remarkable nonconformists.  One such asteroid is 2014 PP69. 

You will recall that the first five characters in an asteroid’s name tell us when it was discovered, in this case in 2014 in the second half of July.  This provisional name will be used until there is a long enough history of accurate tracking (usually at least one full synodic period, the time needed to “lap” Earth in its orbit around the Sun), to certify a precise, accurately predictable, orbit.  The synodic period is about 2 years for most NEAs.  At that time the asteroid will be given a catalog number such as 155629, at which point it will be referred to as 155629 2014 PP69.  Once an asteroid has been cataloged the discoverer may propose a name for it, such as Eros or Ceres; let’s call this one Egbert.  Then it will be called 155629 Egbert; just plain Egbert to its friends.  But the object of this post is just plain 2014 PP69: in the nine months since its discovery there has been no opportunity for it to pass by Earth again, and therefore no chance to assign it a very precise orbit and enter it into the catalog of numbered asteroids.  Once the refined orbit is determined, the discoverer of the asteroid gets to give it a name.

So here’s what’s unusual about 2014 PP69: its perihelion distance of 1.25 AU, which qualifies it as an Amor asteroid, contrasts sharply with its aphelion distance of 41.79 AU, well outside the orbits of Neptune and Pluto and well into the Kuiper Belt.  Its orbital period is an incredible 99.84 years, longer than that of Halley’s Comet.  But that’s not all: the inclination of its orbit is 93.63 degrees, meaning that it orbits almost at right angles to the plane of the Solar System—in fact, the orbit is slightly retrograde, moving around the Sun in a direction opposite to that followed by the planets.  The eccentricity of its orbit is 0.942, higher than that of the typical short-period comet.  At perihelion, closer to Mars’ orbit than to Earth’s, it is traveling at a whopping 40 kilometers per second.

What do we know about the asteroid itself?  Almost nothing.  The discovery images show that it has a visual (H) magnitude of 20.17, which, by the crude “rule of thumb” used for newly discovered NEAs (an assumed average albedo of 0.14; 14% reflectivity in visible light) corresponds to a diameter of about 330 meters.  However, the orbit is cometary, suggesting that a more realistic albedo would about 0.035.  If it’s that bright and that black, then its cross-section area must be four times as large, and its diameter twice as large, as this crude guess would suggest.  That implies eight times the volume and about eight times the mass, raising the question of its impact hazard.  The good news is that, despite its large size and kinetic energy, the point at which it crosses the plane of Earth’s orbit is far outside our neighborhood. 

The body is almost certainly of cometary composition, similar to the Centaurs and the Kuiper Belt bodies and to short-period comets.  A reasonable guess would be that it is about 60% by mass ices and about 40% rock, which in turn contains perhaps 5-10% of organic matter, mostly complex polymers.

Sending a spacecraft to visit 2014 PP69 would be extremely difficult because of its very high relative velocity.  And then there is the problem that the next optimal launch opportunity is a century off.

How soon will 2014 PP69 qualify for a catalog number?  On its next pass through the inner Solar System we will have an opportunity to track it again with such a long span of observations (a century!) that a very accurate orbit can be calculated.  That will be in the year 2114.  The bad news is that the discoverer will no longer be alive to exercise the option of naming his baby!

The Hyperloop Supersonic Train: the Hot New Idea of 1909


May 2015

Some people are just way ahead of their time.  Leonardo drew plans of helicopters and submarines in 1515; Konstantin Tsiolkovskii wrote of exploiting asteroid resources in 1904.  Now another visionary, Elon Musk, has proposed a supersonic train operating inside an evacuated tunnel, serving the San Francisco-Los Angeles corridor.  This technically demanding scheme seems fated for development many years in the future.

But let us turn to the November 1909 issue of Scientific American.  (No, not 2009!)  In that issue we find an editorial, “The Limits of Rapid Transit”, based on an essay written in 1904 by an undergraduate at Worcester Polytechnic Institute and submitted to Scientific American earlier in 1909, advocating the building of a supersonic rail system serving the Boston-New York-Philadelphia-Baltimore-Washington corridor.  High speeds are achieved by running the hermetically sealed train inside an evacuated tunnel.  Sound familiar?  If Musk is a certified visionary for proposing this concept in 2012, what would we call the lad who advocated the same idea in 1909?

The precocious lad in question was none other than Robert Hutchings Goddard, father of American rocketry, the first in the world to build and fly liquid fuel rockets.  He was also the first to discuss putting astronauts in suspended animation for prolonged space voyages, and the first to propose the use of gyroscopes to stabilize aircraft—and all of these visionary ideas originated while he was still an undergraduate.

One other coda to append to this story: the website “Russia beyond the Headlines” attributes the origin of the supersonic train idea to one Boris Weinberg of Tomsk, who published the idea in an article entitled “Motion without Friction” in 1914.  The website reports that Weinberg carried out tests of his device in which speeds of 6 km per hour were achieved.  (Six km per hour is 3.6 miles per hour, the speed of a brisk walk.)  Only in Russia is 1914 earlier than 1909, and only in Russia is walking speed supersonic.  Oh, by the way, in 1914 it wasn’t Russia, and certainly not the Soviet Union: it was the Russian Empire.  For your amusement, the puff piece can be read at:
 http://rbth.com/news/2013/08/19/russian_ideas_inspire_californias_hyperloop_plan_29029.html