Friday, July 03, 2015

The Deadly Thing at 2.4 Kiloparsecs: Are we sharing the galaxy with something large, dangerous and periodic?

Never before online, this highly speculative piece was published in Analog Magazine way back in May of 1984. It won the Analog Award for Best Fact Article for the year. Some of the research may be dated...but the concepts still intrigue...

Note: This article mentions  the work of NYU's Michael Rampino who later on realized that Earth's major extinctions appeared to recur in cycles of roughly 26 to 35 million years.  He has an improved theory for that!  Indeed, despite involving Dark Matter, it is likely better and more plausible than the one I raised in this old Analog piece. Still, my hypothesis was unprecedented and certainly fits the observed facts... a deadly thing may indeed, still be out there, lapping us every... 200 million... or even thirty million or so! Certainly the concept deserves to be posted somewhere and available on the Inter-Tube.

Okay, then. To the way-back machine!

======  Dialing back to 1984... and here we go... =======

Mass extinctions are much in the news these days. Like a scandal long buried and only just being uncovered, the demise of the dinosaurs now seems to be only the uppermost layer of something far more regular – and deadly.

Several recent events have spurred this renewed interest in the ecological holocausts of the past. The most significant of these has been progress in the arcane art of reading the fossil records in ancient sedimentary rocks.

Paleontologists such as Dr. James Valentine of the University of California at Santa Barbara have been reconstructing the family tree of Earth’s living organisms, sorting which orders or phyla ended in extinction, and which branches evolved into new, competitive forms.

Some of the pieces of the puzzle seem, at last, to be falling into place. We now know, for instance, that the fall of the great reptiles – and the associated extinction of many marine forms – was not a unique event. Valentine and others report that there have been at least four, and as many as ten suspected mass dieoffs, in which large portions of the Earth’s biota – whole families, orders, and phyla – declined and then dropped completely from sight. In three of these cases, the evidence is statistically indisputable. These extinctions were indeed catastrophes which enveloped the entire Earthly ecosystem when they occurred.
  • At the end of the Cretaceous Period, approximately 65 million years ago
  •  At the conclusion of the Permian Period, about 185 million years before that
  •  And at the terminus of the Ordovician Period, approximately 210 million years further back in time.

The Great Die-offs

The Earth was far different in appearance each time it happened. Where the Cretaceous featured great reptiles and pre-placental mammals, the Permian was a time of tremendous fern forests and advanced amphibian forms. The Ordovician, on the other hand, featured hardly any life on land at all. But in each case the die-off was sharp and easily distinguished in the geological record. Suddenly, a large fraction of all the species at the time were wiped out.

Now (1984) Andrew Knoll of Harvard and Gonzalo Vidal of Lund University in Sweden report a fourth great extinction, at a time, 650 million years ago, when the highest forms of life were colonies of algae. This is about 200 million years before the Devonian event.
(Take note of the intervals between these major occurrences: 185, 210, and 200 million years. We’ll come back to them shortly.)

The paleontologists aren’t the only ones working on the problem of the past extinctions. A second discovery has received a lot of attention lately, adding another piece to our puzzle.
Led by Louis Alvarez of the University of California at Berkeley, a number of scientists have pointed out that some of the mass deaths are associated with unusual layers of clay – and that the layer representing the catastrophic end of the Cretaceous Period features astonishingly high abundances of certain rare isotopes.

Their conjecture is that a great meteorite struck the Earth, kicking up huge dark clouds and cutting off the sunlight. This supposedly then led to the ecological disaster observed in the fossil layers. Dust contributed by the vaporized meteorite supplied the unusual isotopes Alvarez and his team found in the Cretaceous-Tertiary boundary layer.

But the clay layer by itself is weak evidence for the falling rock conjecture. There are other ways to account for it. The abnormal isotope profile within that narrow layer is what the impact proponents rely upon most heavily.
But there may be another way to explain it.

Theories for Cycles

Veron 2008
Let’s go back to Fact One, the episodic occurrence of ecological disasters in Earth’s history. Would it not be interesting if there were some periodicity to these mass extinctions? If there were some pattern, then we might be able once and for all to assign a culprit … and incidentally know what to watch out for.

Recently two University of Chicago researchers, David Raup and John Sepkowski, have claimed that the four major and six lesser extinctions observed in the sediments seem to be part of a larger pattern that repeats at a rough average interval of 26 million years. They draw the implication that there is some repetitive process which puts the ecosystem of the Earth under stress in a regular pattern.

But even if the pattern they see is real, what sort of process could operate over such vast time scales, repeating reliably at 20 to 30 million year intervals?
Raup and Sepowski are not sure. Along with England’s Martin Whyte, they guess that the culprit may have to do with the interval workings of the Earth itself – with cyclic changes in the planet’s moment of inertia, its magnetic field, or the rate of transfer of heat to the mantle and crust.

It is an intriguing proposal, and it merits further investigation. However, there is a problem. No one can assign a clear-cut mechanism. Nor can anyone explain the dramatic difference between the six lesser and the four great extinctions.

One other potential periodic mechanism, that I discussed in the May 1983 issue of Analog, is the possibility that waves of settlement by starfaring civilizations might be responsible for episodes of extinction, followed by long periods in which the galaxy is empty of intelligent life. The theoretical time scales – 10 to 100 million years – seem to put this idea in the right range to be considered as a candidate, however it still remains pretty vague and hard to pin down. All we can do is catalog the hypothesis and move on.

The Major Extinctions

For the sake of argument, let us look at the four great die-offs alone … the four for which there is no dispute. Remember – 65, 185, 210, and 200 million years? Recall that these are fairly rough numbers. Nonetheless, one quickly sees the outlines of a pattern. If we assume we’re 65 million years into the latest phase of a repeating cycle, we might be tempted to guess that the greater die-offs occur at intervals of approximately –
197 Myr ± 12 Myr. (Myr = one million years.)

The uncertainty of 12 Myr is soft, but it is small enough to leave us encouraged that we may be onto something. It certainly looks like a pattern.

Could something periodic be causing this?
Not many natural processes occur with such regularity at such vast intervals. Only one cycle comes to mind with a periodicity similar to this. It is the revolution of the sun around the center of the galaxy … an orbit that astronomers now estimate to take approximately 238 million years.

 Might we be sharing the Milky Way with something deadly? Something that reaches out to “touch” our planet as we pass near it, roughly every galactic year?

Let’s pause and think about galaxies for a moment.
A spiral galaxy like the Milky Way does not rotate like a solid disk. Instead it is composed of many parts.
The galactic “halo,” like the core, consists of older, metal-poor, possibly planet-less stars of the first generation. In the halo the long, lazy orbits of solitary stars and globular clusters take them far out into the nearly empty territory above and below the spiral plane.

At the opposite extreme, in the galactic core, the crowded stars jostle and occasionally collide. They may even merge into super-compact bodies, giving rise to strange happenings. We shall speak more of these later.

Still, most of the really interesting things seem to be going on in the great, complicated disk of the galactic plane. Here the stars and gas and dust clouds rotate in their nearly circular paths, the inner zones finishing their orbits more quickly than those further out. This “differential rotation” is one of the things that drives the spiral design of our type of galaxy, helping to create the shock fronts where new stars are formed.

The shock fronts, along the concave faces of the spiral arms, are where clouds of gas and dust are compressed into new stellar systems. Some believe that life could not exist without these alternating zones of compression and release around the galactic rim. The sun’s orbit appears to meet one of the galaxy’s great spiral arms about every 110 million years or so. It takes about 10 million years to pass through one, about a million years alone to pass the shock front at the leading edge. We’re emerging from an encounter with the shock front of the galaxy’s Orion Arm right now.

Can one use these spiral fronts to explain the cyclical pattern of the mass extinctions? There are several theories which do make the attempt.
Source: NASA
W.H. McCrea contends that when the solar system moves into a shock region a sudden influx of gas and dust is absorbed by the sun, causing a dramatic increase in luminosity. That, according to the English astronomers Hoyle and Littleton, should increase precipitation on Earth, lowering sea levels and setting off a series of ice ages. 

The history of the last million years – featuring a series of ice ages only recently ended – lends the hypothesis some support. A related idea, by Napier and Clube, is that the galactic shock fronts are crowded with “planetesimals” like asteroids and comets, and that the sun regularly picks up a swarm of these every hundred million years or so, causing the Earth to regularly get “pasted.”

Or maybe the abundance of young, hot stars in the shock-front regions creates an area with a high incidence of supernovae (which would certainly wreak havoc on the Earth if one occurred close enough!)

All three mechanisms sound plausible, at least. Could the solar system’s periodic encounters with the spiral arm shock fronts then explain the major extinctions that have befallen life on Earth?

(2015 aside: Back in 1984 we didn't know the galaxy is "pleated" and that our solar system would rise and then dip through these pleats, several times during every 240 million year galactic orbit.)

Alas, the timing is all wrong.

Our encounter with the Orion Arm may indeed have triggered the ice ages of the ice ages of the Pleistocene, but the cycle of entering and leaving spiral arms clearly doesn’t fit the truly great die-offs of the Pre-Cambrian, Ordovician, Permian, and Cretaceous. The hundred and ten million year interval is over forty percent below the figure we calculated earlier – apparently way too low to apply to the major ecological holocausts of the past.

The Deadly Thing

If we re-examine the numbers just one more time, there does appear to be one more possibility – one more periodicity that no one seems to have covered yet. Our galactic orbital period.

We seem to be hit by something deadly every 195 million years or so. That’s similar to the 230 Myr solar orbit around the galactic center, but it’s clearly not the same. The 15% difference is enough to bother even the most impulsive pop theorist.

Until one realizes that anything truly dangerous floating about in our galaxy would itself have to be in orbit around the galactic center! With differential rotation, every distance from the center has its own unique orbital period, the sun’s happening to be 230 to 250 million years. There may be some “thing” co-orbiting with us – a little further out or closer in – the inner object “catching up” with the outer one at a period a little more rapid than one solar-galactic “year.”

It’s a problem that can be solved – roughly --  using the back of an envelope and a book of astronomical tables.

If the sun has, say, a period of 230 Myr, and we encounter “a thing” about every 197 Myr, then “Its” orbital period is solved by taking the difference of the two reciprocals (orbital frequencies) and dividing one more time.

If we do this, “It” turns out to have an orbital period of about 107 Myr.

We then go to the some of the tables of galactic rotation rates (laboriously collected by diligent astronomers, and published for the benefit of sleuths such as ourselves). The angular frequency versus radial function given in the literature is a little complicated, but when used carefully it gives a pretty clear result.

“It” has to orbit the center of the galaxy at a distance of approximately 2.4 kilo-parsecs, or seven point seven thousand light years. Our system, orbiting at about 10 kilo-parsecs, then has its nearest passage to the thing every 197 million years, as expected.

(2015 aside: note that if the extinctions cycle around 30 million years, that only shifts the orbit of the deadly thing inward, closer to the center of the Galaxy.)

Geological Astronomy

This is “geological astronomy” with a vengeance. We have just used the Earth as a great observatory, reading the sedimentary rocks like ancient photographic plates. Have we deciphered the clues correctly? Is there a Thing out there, which periodically catches up to use and does deadly mischief on our ecosystem with each near passage?

(Like many scientific discoveries or conjectures, this one has a haunting premonition in science fiction. In Poul Anderson’s Brain Wave, the die-off of the dinosaurs was caused by a beam which suppressed brain activity in the entire sector of the galaxy.)

If our Thing exists, it has to be pretty powerful, for according to our calculations we never pass closer to it than seven thousand parsecs. This means that it must somehow be selective, or act over a narrow angle.

The strongest possibility among known or modeled phenomena seems to be a rotating black hole which is emitting a powerful jet of sub-atomic particles.

The central cores of some spiral galaxies are extremely busy places, emitting awesome, energetic beams. SF author Gregory Benford (who is also professor of high-energy physics at the University of California at Irvine) has studied cases in which narrow, self-focused streamers of charged particles seem to be shooting narrowly across tens of thousands of parsecs, carrying as much energy as is being emitted from all the rest of the galaxy!

Clearly nothing like these monsters exists in the Milky Way today. But recent radio surveys have discovered an intriguing object, albeit much, much smaller – perhaps a fair to moderate black hole – very close to our galactic center. Radio-maps indicate a pair of jets several light years in length, spurting outward from the object.

(2015 note: this object has been confirmed to be our galaxy's central black hole, containing more than a million solar masses, and yet quiescent, at present, having long ago sucked in those objects whose orbits might bring them within grasp.)

In terms of modern galactic astronomy, this is small potatoes. But there may be others in the Milky Way, somewhere in between the sizes we’ve mentioned above. And one of these may be our culprit, now hidden behind the dust lanes of the galactic lens.
Source: Popular Science
Benford thinks the best candidate might be a condensed source projecting a beam of positrons and electrons, precessing and sweeping out a disk-like portion of the galactic lens.

An energy source like that would, indeed, be a deadly thing. An interstellar jet, even one barely grazing by the solar system, could explain a lot, such as the anomalous isotopes in those clay layers – if the particle fluxes were high enough to cause elemental transmutation. And it might be no problem for such a beam to overwhelm the ozone layer, causing collapse of the Earthly ecosystem.

Even if the beam passed nearby for only a brief time, it would probably be enough to do great harm. 

(2015 note: Rampino now sees the pattern as being roughly 30 million years.  This would be consistent with an object even closer to galactic center than my earlier hypothesized beast at 2.4 kiloparsecs.  Still, the basic idea here is not disproved.  It belongs on our shelf of possibilities.)

There you have it, still another explanation for a set of mysteries exhumed from under the dust of our ancestors. All the witnesses are long dead, of course. But that doesn’t keep us from sifting through the clues, looking for culprits.

Over the years we’ve heard conjectures of nearby supernovae, wobbling planets, and even colonization from the stars, in order to explain the demise of the dinosaurs and other mass-extinction victims. Though noe of them have rhythmic periodicity.

If the giant-meteorite proponents are right, we might be wise to take some precautions, to keep track of those bits of rock tumbling about the solar system. The other “periodic” solutions, too, each seem to offer their own bogey men to watch out for as well.

Now there’s this new “thing” to worry about, possibly orbiting out there roughly 2.4 kilo-parsecs from the center of the galaxy … just waiting, it would seem, to reach out one more time and get us.

It’s a little unnerving.

Still, one shouldn’t lose too much sleep over it. Dangerous and nasty as the little bugger may be, we probably have another 130 million years to get ready for it. If any money is going to go to chicken little preparations, at this point I think I’d rather spend it on asteroids.

Author’s final (1984) note: Remember where we mentioned TEN recorded ecological holocausts? This paper only dealt with the four greater die-offs, whose apparent regular intervals lead to an interesting conjecture.

But there are six much smaller events in the record as well. Of these, two are “intermediate” in magnitude – one about 80 Myr after the Ordovician disaster, and the other approximately 30 Myr after the Permian.

You can’t do much with two data points, of course. Certainly there’s no way we can imply that each major even is followed by a secondary die-off an average of 55 Myr later, is there?
It is now 65 Myr since the major holocaust of the Cretaceous…

No. The author steadfastly refuses to state that we seem overdue for one of those littler extinctions. That would be stretching things too far.

He hopes.

== ... back to 2015! ==

And there you have it.  A clever -- if somewhat unlikely -- rumination from my younger self.  The article was discussed on the Weird Astronomy page of the Atomic Rockets website: "...just because the assumptions are questionable does not mean that they are wrong."  This "lapping" mechanism has some appeal, whether applied to the thirty or 190 million year cycles.  Still, if wagering, I'd give stronger odds to some version of Mike Rampino's orbital "dipping" process... with or without the recent Dark Matter gloss.

And yet, aren't these marvelous times, as we sift for evidence and plumb the past for mysteries?  Our ancestors, if told of this quest, would be puzzled!

But the best of them -- I think -- would also be proud of us.

You should be too!  Try to get your fellow citizens to realize it, as well.


Jumper said...

Three-body problem.
Not to mention bogus pattern recognition.

Alex Tolley said...

Richard Muller thought it was a 62 my cycle. Galactic Drift and Mass Extinction. His hypothesis was the sun emerging from the galactic plane and being exposed.

More recent findings suggest that the extinctions are triggered by impacts that also cause massive lava eruptions. Eroded craters have been identified as matching more of these extinction events.

The problem with the "Thing at 2.4 kiloparsecs" is that the galactic rotation curve is not the one expected by Newtonian gravity, but rather more like a solid disc, possibly due to dark matter. Therefore there is no overlapping. If there is an object, it must be in the center of the galaxy where rotation is slow and the sun passing it every galactic rotation. To get the needed extinction rate, the central source is either in a slow orbit, or rotating, or there are more than one objects, e.g. 4 "beams" radiating outwards so that the cycle is approximately 230 my/4 = 57 my.

But whatever the cause, we need to account for the coincidence of impacts and lava fields with major extinction events. It certainly cannot be "Nemesis" as we would now have seen it with our telescopes, like WISE.

Then again, it could be random, as Raup originally thought. Extinction: Bad Genes or Bad Luck?

David Brin said...

Alex sorry you are wrong about all that and need to re-examine your sources.

Alex Tolley said...

Which one[s] is wrong and why?

David Brin said...

The galaxy rotating like a solid disk? Oh lord.

Dwight Williams said...

Indeed. More like a collection of warped plates spinning through one another's "molecules". And I know that's a rotten analogy!

Paul SB said...

Dr. Brin, I'm not very up on the astrophysics, so I thought you might be able to help me here. I have often wondered if some of the missing matter issue could relate to black dwarfs, which are very hard to detect. Given the long age of the Universe, which would presumably allow for several generations of stars, many of which would end up as black dwarfs, is it possible that these could account for some of the gravity anomalies that lead people like Jan Oort and Vera Rubin to propose dark matter? Also, is there any process that would destroy and/or recycle all that carbon, or would they just be floating around their home galaxies in approximately the same orbits they had when they were "live" stars?

David Brin said...

Alex & Paul and Dwight, the differential rotation of the galaxy is well established. As is our own orbital period around galactic center, roughly 240 million years. But Fritz Zwicky long ago realized that if you tabulated all the stars and dust and gass in an estimated mass, the objects orbited faster than could be explained by all that visible matter alone. The two biggest theories for Dark Matter were MACHOs (massive Compact Halo Objects) and WIMPS (weakly interacting massive particles. MACHOS would be normal matter... LOTS of black suns and brown dwarves... and though we've found some, it's orders of magnitude too little.

WIMPS would be particles that interact via gravity but not at all (or much) via Electromgnetism or the strong force. That's the current top theory and the one Rampino adapted for his latest model of the sun passing thru the galactic disk every 30 M years, causing BOTH heating of the magma and infall of comets.

Paul SB said...

Okay, so even if our estimates for the numbers of non-luminous dwarf stars are off by an order of magnitude, it still wouldn't be enough to account for a very sizable portion of the missing mass. MaCHOs and WIMPS? The alphabet soup makes you wonder if there is something Freudian going on here.

Happy ID7/04!

locumranch said...

Monty Python Universe Song:

Alex Tolley said...

The galaxy rotating like a solid disk? Oh lord.

"rather more like" DOES NOT EQUAL "like". OK, maybe poor analogy. But hey, I'm calling squirrel pointing.

Let's do the math.

Dr. Brin's claim is that there is a "Thing" co-orbiting our galaxy with a period of 107 my, situated at a radius from the galactic center of 2.4 kpc. Every 197 my the "Thing" closes in on our sun and somehow causes extinctions.

Let's look at their velocities in arbitrary units (orbital distance/period):

Sun = 2*PI*10/230 = 0.27
Thing = 2*PI*2.4/107 = 0.14

This means that the "Thing" has an absolute velocity of 1/2 that of our sun.
What does the observable data show?

Wikipedia ref
MIT education class experiment

Both references show that the absolute velocity of an object at 2.4 kpc is quite close to that of one at 10 kpc, certainly not even close to 1/2 the velocity.

"Thing at 2.4 kpc" hypothesis is false. QED.

[A reference showing that the galactic rotation curve that shows a relative velocity for the "Thing" that fits the required relative velocities would be sufficient to rescue the hypothesis as stated, or a recalculation of its distance using the observed grc for our galaxy].

Other evidence, e.g. Muller's 62 my extinction frequency, and the more frequent Rampino estimate of 30 my can only be accounted for by an object much closer to the galactic center (much closer than 1 kpc where the velocity drops rapidly allowing a 107 year period). However this hypothesis also does not account for the impact cratering and extreme lava flows associated with major extinction events that implies a different mechanism than a distant object sending out hypothetical beams. I rate this theory as having a very low probability of being explanatory, supported only by a BoE calculation that doesn't reflect observational data of extinction frequencies, terrestrial geological evidence and observed galactic orbital velocities.

David said...

Yes, searches for gravitational lensing in the 90's by Alcock and friends showed that MACHOs cannot be the main component of dark matter. Far fewer lensing events were seen than what would been required if they were dominant source of dark matter. Most of dark matter is likely to be in the form of WIMPs.

Paul451 said...

Paul SB,
"MaCHOs and WIMPS? The alphabet soup makes you wonder if there is something Freudian going on here."

WIMPs were named first, IIRC, and was a play on the "weakly interacting" part of their identity. MACHOs were then named as a play on WIMPs, given that it was a rival theory. Whimsical, not Freudian.

Aside: From the last thread,
"males who have been castrated do not completely lose their sex drive, but have no way whatsoever to alleviate it."

Castration is the removal of the testes, not the penis. Castrated men are capable of erections and sex. Indeed, ancient eunuchs (although presumably not "ancient eunuchs") were prized as lovers by the harem-wives; the inability to ejaculate leads to prolonged erections. The harem's lords were concerned with not being cuckolded, not with physical "cheating" itself. The association of "eunuchs" with "sexless" is fairly modern, and probably comes from confusing eunuchs with Castrati (who were castrated before puberty, precisely to prevent sexual (and thus vocal) maturity.)

Paul SB said...

Paul451, I'm good with whimsical! The Freudian paradigm has some major flaws, anyway. A question on the eunuchs, though, is if 2/3rds of their testosterone came from the missing organs, would they be capable of reaching orgasm, or would they be mere sex toys for their partners, forever frustrated themselves. Why else would Voltaire's character have been so upset? Irresponsible males who want 100% birth control would have an easy and permanent solution.

An older colleague of mine told me that when Richard Francis Burton went abroad, he was informed by his English peers that it is expected of a gentleman in foreign parts to write essays so the people at home would come to know the world better. Burton obliged by writing an essay on the relative merits of eunuchs verses young boys as prostitutes, concluding that young boys were better as they had more to hold onto. He was not asked to write such essays again. I haven't confirmed the veracity of this story...

Jumper said...

Lincoln's thoughts on Jefferson.
Have a good 4th, those who participate!

Jumper said...
Au contraire, amis.

Laurent Weppe said...

"Why else would Voltaire's character have been so upset? Irresponsible males who want 100% birth control would have an easy and permanent solution."

Remember that in Voltaire's days, Irresponsible males already had a 100% certain birth control method: refusal to acknowledge the children as one's offsprings. I'm not even kidding: until very recently* irresponsible dudes could have sex, and then stomp their foot and say "I refuse to acknowledge the child as mine" when presented with the living, breathing consequences of their carousing and be freed of all paternal responsibilities. Sure, the offsprings existed, but their male progenitors could pretty much let them starve to death in the gutter without having to face any legal repercussion.

* In France, the law that requires biological fathers to admit that they are their own offsprings' progenitors was voted in 2006: before that, 19% of children (approximately 80.000 annually) born outside marriage's fathers refused to acknowledge their paternity. Let it sink: it took until Year Two-God-Fucking-Thousand-and-Six for this type of callous irresponsibility to finally become illegal in Voltaire's country.

Paul SB said...

Hello Laurent,

I was aware of this barbaric practice from history classes and period literature, though I haven't taken a history class since around 1998. I had no idea it took France that long to get a law on the books. This was common all over the Western world, in the US as well, until the 20th Century. Unfortunately the 19th Century Romantic Era set back many of the gains made in the century of Voltaire. That's humans for you - they tend to swing between extremes. The Romantic Era produced some wonderful music, but on human rights it was a mixed bag. Emancipation from slavery on the plus side. Suffrage movements got started but made little progress until a century later. Some centuries take two steps forward and one step back the next.

Jumper, I looked at the wikipedia article you linked to, but saw nothing in it that answered the question. It just seemed to be some basic anatomy. Would you mind explaining what you meant here?

Dr. Brin, it occurred to me that there must be many physics nerds around the world who would rejoice to know that the WIMPS have overpowered the MaCHOs.

Jumper said...

As a major component of semen is made in the vesicles, eunuchs could ejaculate. Of course one assumes a notable lack of desire to do so.

Paul SB said...

Jumper, another major component is made in the prostate gland as well, but the presence of fluid and the hormonal signal needed to trigger its release are not the same thing, like a gun that has bullets but no firing pin However, I did a quick Googoo search and multiple sites said that they could still climax, which would make the custom slightly less barbaric.

However, this brings to mind a more interesting discussion that came up in an anthropology class I had ages ago. What Paul451 wrote about men being more concerned with being cuckolded than by unfaithfulness per se gets to the actual reason behind the sorts of sexual morals we see in state-level societies. Ultimately they, and the double standard that goes with them, come down to property rights, specifically inheritance. Before the discovery of mini satellite DNA which led to DNA fingerprinting, the maternity of a child has always been easy to determine but paternity was shrouded in mystery. This means that after a property-owning father dies, men could show up to claim the right to inherit who might not actually be offspring of the deceased though they were offspring of the deceased's wife. This could be a thorny problem, but one that reaches a level of wide-scale destruction when the inheritance in question is a whole kingdom. By creating a faithfulness taboo and sanctifying it through religious proscription, found in all of the world's major religions (not just the Abrahamic ones), it helps to solve the problem of dangerous succession struggles. The history of monarchies is rife with succession crises anyway, but without such taboos it would have been much worse, making feudalism even less stable. But since most nations are more or less democratic these days, the old ways might not be as adaptive as they once were.

We're getting a little off the astronomy subject we started with...

LarryHart said...


MaCHOs and WIMPS? The alphabet soup makes you wonder if there is something Freudian going on here.

As someone familiar with Dave Sim, you must realize that pattern-recognition is often in the eye of the beholder, and reading too much into the mere existence of a pattern often leads to insanity.

For anyone who might have read Vonnegut's "Hocus Pocus", I like to use his character's line that was repeated any time a pattern of that sort was noticed. "How much longer can I go on being an atheist?"

LarryHart said...

Paul SB:

Before the discovery of mini satellite DNA which led to DNA fingerprinting, the maternity of a child has always been easy to determine but paternity was shrouded in mystery. This means that after a property-owning father dies, men could show up to claim the right to inherit who might not actually be offspring of the deceased though they were offspring of the deceased's wife.

I feel I must be missing something obvious.

I understand the concept of a stranger showing up claiming to be the man's illegitimate son, whether true or not. But how does "offspring of the deceased's wife" affect the claim one way or another? If you mean the property-owning man had been cuckolded, wouldn't the "son" have already been raised within the family? How would a son of the wife (but not the husband) be out there ready to pounce on a claim after the husband's death?

Unknown said...

IRONIC that David's cosmic discussion on mass extinctions devolved to this.
My only concern was wheather we are about to meet the deadly thing soon (within the next million years or so) or if we have another 100+ million years. I am sure whatever it is does correspond to the earth taking some hits while catacylsmic volcanic activity is triggered.
The timing of the next encounter might change my approach to my plant breeding and introductions.

Paul SB said...

Larry, you're right here. I think I should wait until I have been adequately caffeinated before coming here. I can do that during the summer, but not during the school year. It would be the illegitimate offspring of different women by the deceased that seems to cause most of the problems, although one could always challenge the legitimacy of a purportedly legitimate inheritor (an episode of the original Black Adder is swirling around in my neural pathways).

On overactive pattern recognition, it's just so much fun to mess with - drives grad students crazy!

Eric, I think many of us would love to hear about your plant breeding experiments. What kinds of characteristics would you breed for to survive a crust-busting meteoric catastrophe? High tolerance to both sulfuric and carbonic acid, I would guess. But if we are looking at a scale of millions of years, we couldn't be sure that any selected genes would not be removed from the pool by mutation and replacement, unless you have come up with much more effective repair enzymes. Am I in the ballpark?

Laurent Weppe said...

* "The history of monarchies is rife with succession crises anyway, but without such taboos it would have been much worse, making feudalism even less stable"

which ignores the elephant in the room: that the most stable pre-DNA-sequencing form of succession is the matrilineal one.


* "If you mean the property-owning man had been cuckolded, wouldn't the "son" have already been raised within the family? How would a son of the wife (but not the husband) be out there ready to pounce on a claim after the husband's death?"

Bloodline fetichization. For its adherents, the fact that the kid you raised regards you as his father is much less important than the fact that his cells don't contain half your chromosomes.

Paul SB said...

And yet matrilineal descent is a tiny minority in state-level societies. You see it most commonly in tribe-level societies, primarily where fully-grown males tend to be gone for long periods of time, either on long-distance raiding expeditions or long-distance trading expeditions (caravan trade). Tibet is an interesting exception.

Jumper said...

Perhaps sterilizing the slaves was seen as merely a "good neighbor" policy much as we neuter our dogs not so much for our own benefit as for the benefit of the neighbors and the community in general.
I have no more to say. (I am so glad to change the subject... however this is good fuel for further thought on many topics, from structural feudalism to current thoughts on transgender issues.)

On pattern recognition, which likely many of us have seen recently:
In any case, the resemblance of excessive pattern recognition to blatant hallucination is also instructive, as hallucination is a classic symptom of insanity. It also happens to be an excellent theory of what is happening in the brain affected by hallucinogenic drugs.

Alex Tolley said...

hallucination is a classic symptom of insanity.

Let's clarify that. Believing your hallucinations are real is a sign of insanity.

I've had hallucinations when deprived of sleep. But I recognize them as unreal. However, suppose you were permanently kept sleep deprived, would those hallucinations start to seem real? We don't question the reality of our dreams when we are in them, so it doesn't seem impossible to believe hallucinations when you are ostensibly awake.

Jumper said...

Of course, I've had those too. I'd say someone who hallucinates all the time with no hallucinogenic drugs might have some medical problems.

Alex Tolley said...

I'd say someone who hallucinates all the time with no hallucinogenic drugs might have some medical problems.

Like people who claim to see and feel the invisible sky fairy's son? :)

David Brin said...

Alex & Jumper... that has been used as a device in countless sf'nals. In fact, I'm pretty sure I have.

Alex Tolley said...

Philae comet could be home to alien life, say top scientists.

Great headline, and very "Heart of the Comet". Unfortunately the scientists include Chandra Wickramasinghe who sees life as an explanation for phenomena everywhere he looks. Chances of this being true, close to zero IMO.

Alfred Differ said...

This isn't bogus pattern recognition. It's just hypothesis generation. It's what we scientists are supposed to do so our peers and students have something to shoot at with future experiments. For example, I think it is more likely there are long cycles regarding fluid flows within the Earth. I look at the pancake volcanoes on Venus and think it might be the place to learn about these long cycles because it doesn't have plates moving around destroying the evidence. How old is the oldest piece of oceanic crust at the bottom of the Pacific after all? We know hotspots matter, but do we really know the currents deep in the mantle and deeper still in the core?

The Three Body Problem is different again. That one is inherently unsolvable except in special cases. Knowing the rules of a physical model does not always lead to predictions that can be generated from pretty and ordered equations. Not all Diff Eq's have to have closed solutions. Sometimes you just have to do the integrations by brute force. So much numerical joy to be found proving yet again how silly it is to believe in a deterministic universe. 8)

A Jacksonian said...

The fun thing studying geology during the mid-'80s was that the field was still sorting itself after the work done on plate tectonics had established crustal plate movement. With the Alvarez's paper came a major challenge set to the field, as what they claimed could easily be demonstrated by just going to K-T boundary layers and taking a sample of that layer...or for some departments just pulling out their drill cores. If plate tectonics shifted our understanding of how planetary changes happened due to such movement, then the K-T theory expanded the reach of things that could change terrestrial environment into space.

What both plate tectonics and the K-T boundary theory did was also give a number of other items that could be checked to prove or disprove the theory. The only 'land bridge' that could be easily demonstrated were those due to simple shifts in water level due to glaciation, and that didn't explain the geographic distribution of species while tectonics did so. Likewise 3-axis shocked quartz and soot appearing with the boundary layer, and the hard cut-offs for survival mass, along with sole-survivor radiation of forams were outcomes that other theories did not have as features but an impact event did.

A theory must not only explain all of the past framework, and lay down a new one to supercede and also encapsulate the past known work, but must also generate up events or other phenomena which can be predicted and measured (like the bending of a light passing close to a star or frame dragging for Mercury's orbit for Einstein's work) that prior theories cannot predict as those are not things that they cover. Any hypothesis that can do all of that and then lay the groundwork for new work has a higher likelihood of having merit to it. If there is some astronomical object speeding along just slightly faster than our sun around the galaxy, then what else does it do? One would imagine that such a fingerprint of a thing like that would also disturb other parts of the observable galaxy in some way or be currently interacting with some other objects in a way not predicted by the current understanding of relative galactic motion.

One can have a right idea, like Weggener did for movement of continents, but be completely wrong on the mechanism, which was the case with him. The idea can be seen as having some relative merit, but by not being rigorous in mechanism it fell into disfavor. Identify the mechanism, link it to events and then give a novel proposal that can then be examined for other effects and you have something there that can suffer under scrutiny and examination. When the Alvarez's put out their concept of how the K-T extinction worked, they rang the dinnerbell and anyone able to simply disprove the hypothesis would have taken down one of the old guard of physics. He knew that science was a full contact sport, and his team played it that way. That was a good time to be learning geology.

David Brin said...

Chandra Wickramasinghe is a remnant colleague of Fred Hoyle who does solid science... but is also the focus figure of a borderline Cult of Panspermia that earns the epithet via havens of tendentious "science" such as the so-called Journal of Cosmology.

Having said that, let me add that I have no problem at all with positing the possibility that comets may have been the reactor vessels that cooked up the original primordial life-stuff. There was a period in the early solar system when decaying aluminum 26 from a recent supernova might have heated a trillion comets enough to give them liquid interiors protected by ice-cold shells. A hell of a bunch of test tubes. Indeed, might this account for the "sink-holes" that the Rosetta Probe seems to have found, at comet 67/P?

OTOH the dark, quasi-organic dust Philae and Rosetta see are far simpler to explain -- and WERE explained in my doctoral thesis -- as simply the same stuff as we already see in carbonaceous chondrites.

Alex Tolley said...

The talk that Richard Muller gave at SETI in 2009. You can see how he analyzed the data to get his 62my cycles and judge whether this is even correct. Without listening again, IIRC, his team needed to adjust the dating of some fossils to get the cycles, which were exposed with Fourier analysis and also wavelets.

What bothers me is that we know, or think we know, the events and possible causes of some of these extinction events, suggesting we don't need some distant phenomenon to explain it, although if the cycles are correct, the extinctions cannot be random as Raup has suggested in the past. Recent work has suggested that impacts can also cause massive volcanic activity, and with a possible identification of an impact site, might explain the onset of the Permian extinction.

Also recall that Muller also once supported the Nemesis hypothesis - a star bound to our solar system, and causing extinctions every 26my. Why the data could support a 26my and a 62my extinction cycle is rather strange, and suggests that this may be more in the eye of the beholder than real. In any case, Nemesis has been almost completely ruled out by the WISE mission.

This paper Nemesis is a Myth rules out cycles of period increases in impacts as a statistical artifact. This article in MIT Technology review conforms the 27my extinction cycle over 500my, but rules out the Nemesis explanation.

So where does that leave us? It seems that the older 26/27my extinction rate is apparently stronger than Muller's 62my cycle. If true, the lack of impact cycles suggests that the impact + vulcanism hypothesis is just coincidental. If the cause is something in the galaxy co-orbiting with the Sun, it must be very close to the galactic center. Perhaps it is a very intense beam of high energy electromagnetic radiation (UV/x-ray/gamma ray) that could penetrate the Earth's atmosphere.

David Brin said...

Alex, Rampino's new theory... that we pass through a dense plane of dark matter every 26 My or so, the pancake of the galactic plane, has a quirk. It suggests that BOTH comet falls and volcanic activity might be set off that way.

David Brin said...


Forrest Higgs said...

Glad to see that you've brought this one back up. I read the original articles about the periodicity of mass extinctions back in the 1980s. Most of the stuff I read then speculated on a brown dwarf or similar that was in a very long period orbit around our sun getting closer and disrupting the Oort Cloud which would dump stuff on us.

Nice to see you're thinking about this again, David.

Alex Tolley said...

Link to Muller talk at SETI: Discovery of Strong Cycles in Fossil Diversity. I'm afraid I was one of the questioners at the end (thank God I cannot be identified).

agimarc said...

Add the end of the Eocene as yet another minor extinction event some 34 MY ago. Global climate changed to colder and stayed that way ever since. Caldera outbreak going on in Colorado. Several large impacts - Chesapeake Bay and Popogai being the largest - clustered around that time.

If you want to have some real fun, start looking into the YD / Taurus Complex some 11k years ago. Cheers -

Doctor Mist said...

Agreed that chicken-littling over asteroids is more sensible than over The Beast. Even smarter, I submit, is to worry about Carrington events. We provably haven't had a civilization-destroying asteroid in at least thousands of years, but we had a Carrington event that would now lay us very low, only a few decades before it would have been relevant. Hardening our power grid wouldn't even be that expensive compared to asteroid survivability.

David Brin said...

DM we should have been spending on hardening EMP resistance for 50 years...

Don said...

Dark Matter and the Dinosaurs is about this same idea. I enjoyed it, I don't know if it stands to recent developments and discoveries or not. The author is a particle physicist, who not a crank, so it's not a waste of time.

In this brilliant exploration of our cosmic environment, the renowned particle physicist and New York Times bestselling author of Warped Passages and Knocking on Heaven’s Door uses her research into dark matter to illuminate the startling connections between the furthest reaches of space and life here on Earth.

siska said...
This comment has been removed by a blog administrator.
Rud Merriam said...

What about the 26 my cycle?

Assume a body orbiting closer to us. That requires less "power" to cause results on the Earth. The difference degree of catastrophe is possibly accounted for by alignment. When the Earth is above the galactic plane but the, uh hem, nemesis is below the impact is obviously less than when both are on the plane.

I'd suggest that the big failing is assuming there is only one nemesis. Nothing is unique in the galaxy so there should be many all having impacts at intermittent times.