2024-11-07

Just for a change, some EarthArχiv as a change from Astronomy.

Still working the backlog, but it looks as if I've got to cut my own HTML to manage Blogger's stylistic incompetence.


Eclogites

Eclogites and basement terrane tectonics in the northern arm of the Grenville orogen, NW Scotland

Many years ago, I went walking in the highlands, all over. One place I circled around - literally - was the eclogite field on Beinn Sgritheall to the south of Glenelg, on the coast opposite Barrisdale in Knoydart. Wonderful area. And I've always been interested in eclogites, granulites, and ultra-deep metamorphics. Comes of getting started on the Lewisian foreland, I suppose.

(Oh, you've got to love the OS speelung-chokers. I'm sure they have a good reason for having "Barisdale" farm overlooking "Barrisdale Bay". Hang on! Sandaig - the place "Ring of Bright Water" was set - is in the paper's field area too. And I now have a GPX first-draft of a route for getting to the localities, "Eclogites-v1.gpx" ; that'll need some more work.)

Anyway, I spotted this article going by on EarthArxiv (which I don't pay enough attention to, I know). Even if it doesn't contain much in the way of field guides to this eclogite field, it still interests me. I'm sadly out of practice at this stuff - too long looking at (per Mike Lappin) "crustal ephemera which haven't been down to 100km for 100 Myr, and are clearly nowhere near equilibrium, so can be safely ignored. Otherwise known as the oil industry.

So, what is going on here? They seem to have evidence (structural, geochemical) that these eclogites were obducted onto the Lewisian (Laurentian, even) foreland in the Grenvillian orogeny, about 1200 Myr ago - before the Caledonian orogeny that formed most of Scotland ; before the preceding deposition of the Moinian and Torridonian (very approximate correlates) and their orogeny under the Caledonian ; back into the late assembly of the Laurentian foreland itself, these eclogites were obducted onto the foreland as an ophiolite.

Ah, approaching Real Geology : Pressure-temperature estimations obtained from various lithologies, including the eclogites, indicate peak metamorphic conditions of c. 20 kbar and 730-750°C, consistent with burial to depths of c. 70 km.. but do they give locations? "The eclogites are typically composed of garnet + omphacite + rutile + quartz (Sanders, 1989)" sounds like some fun rocks for the collection. "Omphacite grains occur with symplectites of diopside and plagioclase and are replaced around their rims by hornblende. Rutile has been replaced round the rims by ilmenite" sounds like some good hand-specimen textures are possible.

Oh goody - most of their locations are coastal. That turns an area search into a linear search. Where's my maps - sheet 32 or 33, IIRC.

Geological map of the Glenelg peninsula as far E as Ratagain, showing sampling locations for the eclogites.

I'd better go pack the tent!

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Thorne-Żytkow Objects

https://arxiv.org/pdf/2410.02896

T-Ż objects are (arguably) theoretical objects where a compact body - a white dwarf or a black hole - becomes entrained in an otherwise normal star, with lots of interesting consequences for both the behaviour of the object and it's evolution. The really interesting thing is, such a peculiar internal state may not be that obvious from the outside.

I wrote a post about these a while ago (2023-05), when some authors discussed whether or not the Sun could actually be hosting such a stellar viper in it's thermonuclear bosom. Their conclusions were that it would be hard to tell, even if the Sun had acquired it's internal parasite early in it's evolution. The energy produced by the accretion of matter onto an asteroid-mass primordial BH would to large degree replace the energy yield from thermonuclear fusion.

Obviously, other people find these objects interesting, in a train-wreck sort of way. This paper is an early version of a chapter on the bodies for an astrophysics textbook/ review forthcoming from Elsevier.

Sections cover :

  1. Formation,
  2. Internal Structure and Evolution,
  3. and their final fates,

Bearing in mind that none of these bodies have been observed (though proposals have been made - and disputed), the constraints of reality upon theory are relatively slight. More ink will be spilt!

Formation

Thorne and Żytkow originally considered the collapse of a large star's core without the normal disruption of it's envelope in nova/ supernova. However doing this without getting a large amount of "thermonuclear ash" ("metals" to an astrophysicist - any nuclei heavier than helium) on the surface of the resulting body seems challenging. And we have a wealth of spectroscopic data from many such events which do reveal various (super-)nova remnants - but no Thorne-Żytkow Objects.

Thorne and Żytkow also considered merger scenarios where a closely orbiting pair of stars, the heavier of which (most-rapidly evolving) becomes a neutron star (or black hole), and which could then inspiral into it's companion (with various requirements for ejecting material from the pair to conserve energy and angular momentum. That's a complex process, inherently variable ; hard to predict. Examples have been proposed. And disputed.

Direct collision is thought (by some) to be the most plausible formation path, particularly in the dense cores of globular clusters or molecular clouds (which the most massive stars don't have time to migrate away from before evolving into compact-body-hood. Again, the details can be complex - closing energy and angular momentum have to be accounted for.

Internal Structure and Evolution,

The main model is that the compact body has a zone near it's surface where the infall energy of the rest of the system releases large amounts of energy, producing a zone where outwards radiation is dominant, and supports the rest of the star's mass against inflow (exactly as Eddington discussed in the 1920s for formation of regular stars, leading to ideas of the Eddington limit. Beyond this "radiative zone" the star is convective as for normal stars. Potentially, with black-hole cored Thorne and Żytkow objects, the accretionary radiative zone can be surrounded by a conventional nuclear-fusing core, then it's radiative-limited zone, then the convective zone. Distinguishing these from conventional giant to super-giant stars could be very "challenging". If, however, this core material gets mixed into the upper parts of the star, that potentially is observable.

Understanding the nuclear reactions in such systems remains both controversial and challenging. Signals from both stable and unstable nuclear species have been considered.

Understanding the evolution of the objects is obviously complex. Some solutions suggest a Thorne-Żytkow object might have a shorter lifetime than the same mass regular star ; some calculations suggest the Thorne- Żytkow object could have a longer lifetime than the regular star.

And their final fates,

Like many large stars, there are multiple routes to mass loss for Thorne- Żytkow object through their evolution. The envelope mass might decrease enough that the accretionary structures can radiate through to the surface, which would rapidly radiate down to being a regular (-ish) neutron star. Or the NS could collapse to a black hole, triggering an (abnormal, ?) supernova. Many of the models produce periods of pulsation in the Thorne- Żytkow object (another potential observable?).

Fun objects, Thorne- Żytkow objects. The universe should contain such strange objects. Whether it does or not remains to be seen.

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A veritable slew of book chapters in preprint.

Wolf-Rayet stars

W-R stars are getting a deal of attention with the focus on recurrent novae and (potential) supernovæ. That's not particularly because being a WR star is associated with the SN process(-es), but because they're by definition evolved massive stars with a strong stellar wind, which means they've already run a lot of their short life. On the other hand, a powerful WR stage can lead to so much mass loss (into a large planetary nebula) that the star falls out of the window in which a SN can occur. The high mass (Mini >e; ~20 M (before late-stage mass loss) and high luminosity makes for very short lifetimes (for a 20 M star, 3.7~5.5 million years ; for a 40 M star, 2.6 to less than 1.0 million years), which in turn means the stars die (as planetary nebulae, or supernovae) still in their natal molecular clouds. Often they are part of the dismantling process of the collapsing of the cloud. But why am I trying to summarise a review paper?
The death of WR stars - there is some evidence of SN being sourced from WR stars, but other arguments that they are too compact to form SN and instead collapse directly. This latter scenario is argued for from the geometry of SNR-BH couples such as Cygnus X-1.

Small Bodies in the Distant Solar System

No, I'm not going to get into the "Is Pluto () a planet?" question. If I'd had my 'druthers, I'd have gone for an intrinsic property of planets vs dwarf planets vs other "small bodies", probably based on the "potato radius", self-rounding or something geological. but I can live with the IAU's extrinsic orbit-clearing definition. Hal Levison's "hand-waving" argument about formation mechanisms holds water too. Argument, as far as I'm concerned, over. Yes, I grew up with 9 planets in my Solar system too. I also watched the discovery of Charon, the increasing puzzlement over Pluto's minuscule size, the initial mapping by mutual occultations, and the discovery of the outer Solar System (3rd or 4th most massive element, to date, is Pluto ♇ ) ; maybe the geometrically largest. Science is a process of improving approximations to the truth, and if the solar system has a 9th planet, we've not seen it yet. That said, @PlutoKiller@Twitter.com (the social media handle of the discoverer of Eris, the most massive (known ; to-date) outer Solar system body) has been quiet lately - maybe he's found something?
Rant over. Debate not engaged with.

This is a proto-chapter for another Elsevier book. Probably not the same astrophysics book as the previous entry, but there's no law against them having multiple in production at one time.

This "key point" is one of the less "stamp collecting" parts of the field : "The sizes and shapes of Kuiper Belt objects tell us about the details of planet formation, while Kuiper Belt orbital distribution puts constraints exactly how and when the giant planets migrated."

That there are now over 3000 known TNOs brings statistics to the subject of the outer Solar system, in the same way that the Kuiper telescope brought statistics to the subject of planetary systems in general. The classical a [semi-major axis ; orbital energy] vs. eccentricity (e) plot, reveals the sculpting of the Kuiper belt by interaction with Neptune (incidentally, clarifying why Neptune is a planet and Pluto isn't), while the a vs. inclination (i) plot shows that something has been sculpting the Kuiper Belt (Outer Solar system) by dragging everything through the nit-comb of small-number-integer resonances with Neptune.

Detecting, recognising, and calculating the orbits of TNOs is a noisy, bias-prone topic. What the biases are (per instrument/ methodology), how severe they are, and how to de-bias observations towards estimating the underlying population parameters, are important topics. Once orbits have been calculated, they can be classified. But classifications can change over time, as interactions with Neptune (and to a lesser degree, Uranus, Jupiter, Saturn, potentially Planet9 [Brown, Batygin 2016] ...) lead to the orbit evolving over periods of more than a few million years ; few thousand orbits. Classification is a moving goal in many cases, and needs to be tested in all cases. Not all trans-Neptunian Objects are Kuiper Belt Objects ; there are various other classes, some of which enter the inner Solar system (e.g. Centaurs).

The composition of TNOs/ KBOs are generally only available by spectroscopy (if you can get the time on a light-bucket) or colour in different filters (if you can't get the light-bucket time). This gives a hint of evolution, from the polymerisation of surface organic matter to dark-red "tholin" mixtures. The properties of TNOs eventually tend towards those of the dust of the outer Solar system, which can be compared to the dust- and debris- disks surrounding other stars. A 2024 result from the dust-detector on the New Horizons spacecraft [Doner et al (2024), Feb.] suggests that there is more dust than models of the 2010s would suggest, pointing to the Kuiper Belt being more populous and extending further from the Sun than thought in the 2010s.

Atmospheres of Solar System Moons and Pluto

Review article on ... well, as the title says. Io excepted, these are N2 - CH4 dominated atmospheres, with the outer bodies (Pluto, Triton) developing seasonal methane frosts. Io is different - it's atmosphere is dominated by SO2 with minor SO, but these components can freeze out rapidly when Io goes into eclipse behind Jupiter. Complicated systems, worth review.

Detection prospects for the GW background of Galactic (sub)solar mass primordial black holes

The prospect of (sub)solar mass primordial black holes comes up on an almost monthly basis when people are discussing the problem of Dark Matter. Last year someone, for reasons not at all clear, speculated that the putative "Planet9" [of Brown & Batygin, 2016, as modified] might be such a "primordial" black hole. It's a pretty dead idea - if they were present in significant amounts (mass-wise), then we'd have seen them in gravitational lensing experiments (observation projects) like MACHO and OGLE. They're not(MACHO, <25% of necessary dark mass) there. To mis-quote Feynmann, a beautiful hypothesis slain by an ugly fact.

Anyway, this paper suggests that moderste mass, sub-stellar black holes (so, presumably "primordial"), particulalrly those in highly eccentric orbits, might be marginally detectable by the in-work LISA mission, and more detectable by planned missions such as DECIGO.

Back to top. And that, I think is enough for this one. Plough through more backlog now.

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2024-10-25

Site re-layout ; continuing with the backlog.

Continuing to fight through the backlog

For reasons not entirely obvious, my blog "title" and description had started to overlay the top of the actual content. Not sure when that started, but I've got rid of it now. Too many options there, and it's less than clear what means what. [This seems to apply across multiple "themes" ; has blogger applied some "downdate" and broken existing things?] Nope, it's still doing it. Now the title is nailed to the window, and the posts, sidebars, etc scroll over its top.Ah - maybe if I move the "title" and "description" into the "NavBar"? Nope, that didn't work. You can't move those bits out of their containers. Switching to a "classic" theme has solved the overscrolling error. The sidebars overprint the main body, so can I fix that? OK, so now, because blogger want to put bullshit thingsd on their menu, I havev to learn even more HTML to get away from their shit. Slow. Hand. Clap. Blogger. Sod this, that's enough for today.

And that's enough for this post.


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2024-10-24

Backlog after the Mars paper.

More backlog.

Still catching up with the backlog. for a change, I'm looking at my most-recent listing.


And that's another couple of days worth skim-read.

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2024-10-21

Tri-axial Mars - the Mars Kim Stanley Robinson forgot

A synchronous moon as a possible cause of Mars’ initial triaxiality

https://arxiv.org/pdf/2408.14725

This came out of the backlog. Some editing from that.

28 August 2024 - A synchronous moon as a possible cause of Mars’ initial triaxiality

Oh, that's interesting. Mars presents a lot of questions because it is the closest Earth-a-like we can study in any detail.

On the other hand, many people forget how different Mars is to Earth (@twitter.com@elonmusk - are you listening? Of course not - you talk, not listen.) Yes (FTFA), "It turns out that a moon of less than a third of the lunar mass was capable of producing a sufficient initial triaxiality." may be true, but it glosses over that Mars is now (and probably always was) one tenth of Earth's mass. Is that comparison with the Moon in absolute mass, or relative mass? In either case it is ridiculously larger than Phobos or Deimos, or their combination.

Where did this Moon go? And why?

I saw an interesting SETI "lunchtime lecture" on the Martian "hemispheric dichotomy" (N. Polar Basin vs Southern Highlands) a number of years ago. Accepting the "giant impact" hypothesis for that structure (itself a natural expectation of "hierarchical growth" [should that be "oligarchic growth"? From Wiki, The next stage is called oligarchic accretion. It is characterized by the dominance of several hundred of the largest bodies - oligarchs - which continue to slowly accrete planetesimals. No body other than the oligarchs can grow. ] - little things accrete to make bigger things - models of planetary growth), then the possibility that after the last "giant impact" the body is significantly non-spherical becomes ... well, plausible, but not guaranteed. Late-stage impacts are going to deliver a lot of energy so that the planet is effectively a droplet of a low-viscosity fluid. And you've got to have a large enough body ("Moon-size", or larger ; the Moon is about 1.25% of the mass of the Earth), close enough to affect the shape of the (slowly) cooling mass.

Time to RTFP!

"Motivation :" Mars’ triaxiality makes itself most evident through the equatorial ellipticity produced by the Tharsis Rise and by a less prominent elevation located almost diametrically opposite to Tharsis and constituted by Syrtis Major Planum and an adjacent part of Terra Sabaea Yeah, well we all know Tharsis - volcanoes, possibly still recently active. Maybe a mark of "single plate tectonics and where the heat gets out. Tharsis, volcanic peaks excluded, is about 7km above the mean elevation of the planet (or is it to a reference elevation, not a "mean" - a bit of Martian cartography I'll have to check up on) while the elevation he gives for Terra Sabaea is only 2.1~2.3 km. The author then goes on to consider the ellipticity of Mars without the Tharsis contribution (which the mappers, Zuber and Smith (1997), had also considered). Even [without Tharsis] Mars retained much of its triaxiality. - Which I'll take as read. They then propose the initiation of a "seed" triaxial component from their putative moon, later amplified by tectonic processes dumping heat and magma onto the Tharsis high point. Unfortunately, this gets rather iffy already. Mars is reported to undergo a lot more "polar wander" than Earth (justifying the horrible SF consequences of losing the Moon, and all sorts of other doom) and that the current near-polar position of the North Polar Basin and the (sub-equatorial) Tharsis bulge are near-coincidence. I don't think you can have both at the same time. I agree with this next quote - but am not blind to the problems of moons turning up then going away : The seed asymmetry of the equator was considerable if the synchronous moon existed already at the magma-ocean epoch, and was weaker if the moon showed up at the solidification stage.

Whence had it come, whither gone?

The author's title, not mine. But yes, it's a big question.

Had the impact happened during the magma-ocean stage, it would hardly have influenced the subsequent development of Mars’ global structure.

I couldn't put it more succinctly myself. See my above "droplet of a low-viscosity fluid" comment.

On the other hand, had it [a large impact] happened during the formation of crust, it may have, speculatively, left some signature - whence the question arises whether that impact could be the one responsible for the north-south hemispherical dichotomy, a theme beyond the scope of our study.

I don't think the author has seen Marinova's SETI lecture on her work, or the associated papers. Her modelling of a Polar-basin forming impact has the redistribution of 10~20 km thickness of crustal thickness from the (putative) impact site to the rest (other 2/3) of Mars' surface - which would literally outweigh this proposed minor lunar re-shaping. There's the non-trivial point too that the crust and upper mantle would have isostatically adjusted towards following the (gravitational) spheroid or (rotational ellipsoid. Rocks are not solid, even on a cold, dead planet like Mars - they creep under forces.

He doesn't really address the "whence" question - he lists some features of protoplanetary discs, and says they might be factors, while ignoring the blunt fact that most people in the field accept the really large satellites in the Solar system (Luna, Charon) are the products of "giant impacts", and this "Nerio" (some Roman mythological associate of Mars/ Ares) would fall into that category too.

What does he say about "whither"? Well, he blames it on the LHB (Late Heavy Bombardment), with a proviso that it would have to have been early in the LHB, so that later LHB impacts would overprint the expected equator-biased impacts from bits of the moon falling to Mars.

Colour me unconvinced on that front. It's plausible, but far from convincing. The whole "LHB" concept is itself rather dependent on a relatively small number of radiometric dates from a relatively small area of the Moon, all rather close to the Imbrium Basin. There are geological challenges from terrestrial observations too. It's an idea seriously needing better support (e.g. from sample-return missions from the Lunar far-side).

The remaining 27 pages of the paper are mathematical arguments which are over my head. The author obviously thinks they show that his sequence of events is mathematically plausible, and I'm willing to accept that (besides, it's plain from the reference list, that this is his field, and he's worked with many others in this area, and presummably they accept this work when they reviewed the paper. "plausible" ≠ "true".

My summary : plausible, but I don't think it's likely. Worth a read ; not worth studying the maths (which I assume is correct).


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2024-10-13 More backlog, up to tri-axial Mars)

Between one thing and another (which includes my laptop deciding to power-down half-way through an OS upgrade), a week of inactivity. Fortunately, nowt published, so let's see what is in the pile.


2024-10-12

Have to get back into the habit

/styles

Bloody hell, pushing 3 months since I touched this. Got to get back into this. 6 weeks visiting Dad didn't help, but I've got to get back into the habit.

So, what other things are in today's (well, yesterday's) list from Arχiv ?

And that's enough for this effort.


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2024-10-09

My Favourite Caving

My Favorite Caving

When I were nobbut a spotty young shit-bagger, we had a sudden rush of cavings when CBU. Shakers completely blinded, OBM gushing over the top of the shakers, sand-trap level sensors plummeting - which is why I hauled myself down to the shaker house to see what was going on. The poor shaker hand (Zander, it was ; not long after he was made up to derrickman) was standing on the shakers, desperately shovelling to try to un-blind the shakers, and looking anguishedly at the squwak box to call the driller. So, I phoned upstairs (Terry French on the brake) told Frenchy what was going on, he cut the pumps back and we got things under control.

While we were getting the hole clean, this little beauty came up.

"Block 22" is a licensing district of the North Sea, a little east of the infamous Forties field. I didn't know the stratigraphy of the North Sea very well then, but I'm pretty confident in my assignment of it to the Miocene ; I might even go as far as the "Lark Formation", but I wouldn't go to the gallows over that. It's a thick mudrock series above the productive Forties and Andrew sandstones (new name : Mey Sandstone ; it's not worth trying to keep up with the ever-changing nomenclature).

30cm end-to-end is pretty unhealthily respectable for a caving. This was not a healthy borehole, but we did manage to get the casing down, IIRC. Bit of a struggle, but we did it.

It's not particularly obvious from the pictures, but the caving is strongly curved, concave towards the camera. When measured, the inner diameter was pretty close to 17.5 inches. I didn't realise this at the time, but that was a good sign - which I'll discuss later when we look at the other side. For now, note the sub-parallel sub-horizontal scratches at various places, including just above-right of the printed label. I interpret these as being scratches made by the bit (or possibly some of the downhole tools, but I think we were on a fairly simple BHA because we were on an appraisal well - more or less vertical.

Let's flip it over.

[Hmmm, definite depth-of-field effect there. The "feathered" convex-to-camera surface is in focus in the middle of the field, but towards the edge of the caving it's out of focus.]

From the geometry of the cutting, this was a surface within the rock, which failed because of stresses within the rock which weren't counterbalanced by the drilling mud. That (and 8 other functions) is what mud is for. (The formal title of my job then was "mud logger", not shit-bagger.)

On this surface there is a faint "feather" structure with a central spine running circumfrentially to the wellbore and many plumes splaying out to either side. This is the mark of the propagation of the initial fracture when the rock failed. What triggered the failure isn't clear - maybe a large microfossil, or an existing fracture or vein.

This next picture zooms in on the "feather structure". It's worth putting this into your mental collection of "search images". You see this structure in your cuttings dish (or in more obvious cavings) and you know you've got a pore pressure problem, regardless of what pore pressure modellers, mud men, Uncle Tom Cobbley or even the company man says. They can ignore the problem, or rub woad into their communal belly button and pray for it to go away. But you, youngling-geologist, have to report it.

Zooming in further, I wonder what dragged across the caving to cause this tool mark. I was pretty careful handling it - "Pretty! Precioussss!" - keeping it in a paper bag to slow it's drying, avoiding point sources of heat, carefully wrapped in my kit bag to go home. I don't know if this happened coming up the hole, or on surface.

The Company Man got a batter cutting - nearly 50% of the wellbore circumference. But he kept it on the shelf above the radiator in his office and it crumbled to dust the day before my crew change. He tried bribery and corruption to get mine. Once. " Precioussss!" Didn't work. Again, I did tell him "don't dry it too aggressively". Not responsible for advice not taken.

cm and mm scale ; the other side of this scale has American bananas. I've had to do too many conversions for people who can't handle a different unit system to what they grew up with.

This last picture is taken with "oblique illumination" to show the "feather structure" better. It has around a half-mm relief from the general surface.

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Filed under geoPr0n, which is a very specific type of Pr0n.

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2024-07-23

2024-07-23 World's Tiniest Violin .com, .org, .net, ... none squatted ?


To my (mild) astonishment, nobody has snagged, used, or even cyber-squatted "World's Tiniest Violin" in any of it's obvious permutations worldstiniestviolin.org, worldstiniestviolin.com, worldstiniestviolin.net, worlds-tiniest-violin.org (etc). worldstiniestviolin.mil or .gov would be entertaining, if rather ... revalatory.

I should do something about that.


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2024-07-23 Slashdot Submission : Cocaine with sharks on it's Lasers. Or something like that.

An article submitted to Slashdot. It should have the elements necessary to make the cut, but you never know. Also, 27 other people may have submitted it.


The BBC are reporting sharks have tested positive for cocaine. A bakers dozen of sharpnose sharks which were captured off the coast near Rio de Janeiro were tested for the drug in liver and muscle tissue samples and returned positive results at concentrations as much as 100 times higher than previously reported for other aquatic creatures.

The research was published in Science of the Total Environment. The little-known "sharpnose" sharks were examined because they spend their entire lives in coastal waters, and so are likely more exposed to drugs from human activities than the more cinematic species starring in "Cocaine Shark" or "Cocaine Sharks", two recent productions on the subject featuring hammerheads and tiger sharks (the "trash cans of the sea").

The likeliest source is effluent from drug processing labs inland, though the snorting population of Rio may have pissed their contribution in to the sewers too. (Which begs the question - does nobody make cocaine-reclaiming filters for users - or enterprising apartment block concierges? Yet?)

Whether cocaine is changing the behaviour of the sharks is not known. Perhaps it would affect their aim with their head-mount lasers, bringing their conquest of the land with it's tasty, tasty humans closer. Hollywood, hopefully, has (tyop!) the answers.


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2024-06-26

2024-05-21 A little archaeological rant. ; Youtube comment formatting.

First find versus first occurence..

I was watching some thing on YouTube, about the "mysterious" "perforated batons" found across Eurasia for 50,000-odd years. Conventional theory has that they're tools for making some sort of rope - maybe plant-stem cordage, rather than sinew ... maybe also good for preparing sinew. No huge mystery there. But why are most 1- or 2 hole, but a few 3- or even 4-hole batons? Clearly not totally solved, but the "rope preparation/ handling tool" is pretty strong.

But I came up with this little rant, which is more generally applicable, and I think it's worth keeping a copy of. (YT comments use the USENET convention of *bold*, [hyphen]strikethrough[hyphen] or _italic_ AFAIK. I really ought to check up on their formatting rules.)

@YouTubeCommentator5527 "As it turns out they were invented 72.000 - 60.000 years ago"

They were invented before 72-60 kyr BP ; the oldest successfully dated finds are dated to 72-60 kyr BP.

In general, finding a technological artefact means you've found a widespread, popular, well-developed technology. The first several thousand years of a Palaeolithic "Leonardo of Ug", slaving away trying to get his "throw sticks at mammoth, but harder" device to work properly probably resulted in 1 small pile of broken prototypes outside a single ivory tower [mammoth ivory? it was used as a boulding material] at "Ug". But 10 years after he got it working, every single "Ug[X], of Ug" would have had one. A year later, their neighbours the Uggs of Ugli wanted ones, with "go-faster" stripes. Then Marketing came up with a "better" name (an atlatl - really?) ... and soon everyone on the continent had one. Including the inevitable ones that get lost.

The odds of finding those prototypes are far worse than finding the effective, widespread production model. Where is Benz's first "automobile"? One copy, in one single museum. Where are the Model-T Fords? In every second ditch, and abandoned barn ; broken by the side of innumerable roads. Everywhere.

I like that rant. I'm going to save it for re-use! Polish it a bit. If he weren't ded, yet, I'd apologise to Pterry for mis-(?)appropriating Leonardo of Quirm's Palaeolithic ancestor for a starring rôle.

From the same video, but quoting someone un-named : "the easiest way to be wrong about our ancestors is to underestimate them." Very true. Grahaam Hancock and the "Ancient Aliens" people don't dare think that, becaasue it would harm their sales.


YouTube Comment Formatting markup

Inevitably, there's a video. 25MB to download (plus adverts if you don't block them) to express what takes less than a line of text (all above - there is no more). Sheesh. It's also one of those incredibly annoying American drawls where you need to connect your phone to the defibrilator to get wake-up calls for a new byte of information. That is modern communications?

OK, I needed to edit that for clarity. The USENET encoding was of the form :

[tag] [no whitespace] emphasised text [no whitespace] [tag]

… and that seems to be what YT expects too. Reasonable enough - no need for wheel re-invention here. Somebody will probably try redesigning it to use picking from several thousand near-identical emojis, becauuse that is somehow "easier" than using a keyboard. [Shrug]

Now I need to focus on that Venus article.
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