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Please uncle Google, can I have a holiday to Saturn?

My wife's car tries to read speed limit signs,

Dad's car does that.

and it works great about 90% of the time,

And that.

but it has really unfortunate failure modes, like reading a 35 mph limit as 85 mph.

It may do that, but since it's Dad (or me) driving not the car this has no consequence other than an irritated beeping from the console.

Is yours hooked up to some sort of cruise control, or something? The only time I've seen that (in a rental), I R'd-TFM and set the maximum cruise-control speed to 28mph - the default built-up area speed. Your software may vary. (I don't think we came within 100 miles of a road with a 70mph speed limit in that car. All the roads imposed other limits, regardless of signage.)

All of those are problems, and harder to detect compared to speeding. But the uniform opinion of crash investigators is that speed is a major worsening factor in almost all incidents.

If you're driving distracted - or drunk - at 20mph (32 km/h), and you hit a pedestrian, the odds are good that the pedestrian will survive. The same incident at 30 mph (50km/h) is more likely than not to have you in court for dearth by dangerous driving, if not manslaughter.

The UK used to have 20mph limits

The UK outside Wales etc etc. A couple of years ago, Wales changed the default speed limit in built-up areas (so, if there are street lights, unless you can see signage to the contrary) to 20 mph (32 km/h, IIRC) and the Scottish government are considering following suit. (20 mph zones are already common here ; this would just change the default.)

Doesn't upset me.

I wonder what the government of Ulster are doing? Probably fighting over who killed King Billy, or whatever their obsession is.

Additionally there is absolutely NO passing on the right.

That's an explicit German driving rule is it? It's considered dangerously bad behaviour on UK roads and it'll probably have the driving test examiner heading home for an early bath, pink slip dispensed to you. But it's not explicitly banned.

I'd noticed that the Autobahn attitude to "lane discipline" was stricter than in the UK (or, for that matter, the Netherlands, Spain, France, the UAE, Tanzania, Benin and the USA - the other countries I've driven in) but I didn't know it was an explicit rule.

Which is, of course, why if you move within Europe to another country, you have a year to convert your home-country driving licence into a $new_country$ national license, including passing the standard test in $new_country$.

What was her name ... Anne Sacoulas? The US CIA operative who fled a death-by-dangerous-driving prosecution because she forgot which side of the road she should have been on. That, or she was drunk (which is the general opinion in Britain). Whatever - the problem wasn't the offence, it was the cover up. So un-topical.

Have you driven on the Autobahn? It's designed for speed in places

It's also bloody scary.

You're pootling along at 150 (km/h, whatever that is in US furlongs per Canadian syrup-pour), doing your regular check on the rear mirror every 5 seconds and suddenly there's a Porsche up your arse with headlights on full.

Drivers also have more training than we get here.

Lane discipline (using the correct lane for the operation you're doing this second, not where you'll be turning in 3 hours) seemed stricter, compared to the bylanes and backroads of Bavaria.

I was glad to get to the airport (which I was in good time for).

Too bad scientists can't create a cure for ignorant morons

We leave that to the military-industrial complex.

Unfortunately for you it doesn't change the fact that the USA colossally shat the bed and left a brown stain all the way to the bathroom when it came to COVID19.

It was as good as that?

Don't worry - when the next major epidemic comes along, you'll have a chance of doing worse. All these cases of bird flu are increasing the count if viruses, and so the probability of a cross-over and natural gain of function. Because that's what microbes do.

if you have a valid US medical license, you can obtain a provincial one within a few weeks.

There will be quacks.

Do you mean that you can get a provisional provincial licence quickly, and a national license after appropriate probationary period(s). (Regulations will be different ; formularies include different compounds at different dosages or combinations.)

IIUC, your argument is assuming the same ribosome mechanism.

Since it is the ribosome which does the binding onto (and so, to some degree, selection of) the base-pair triple, before offering up an amino acid monomer to the growing protein chain, that effectively means that for each triple of base pairs (codons) you need a different ribozyme and a different base-pair sequence. So that would be between 23 and 40-several different ribozymes structures and sequences. Some of the ribozymes could be insensitive to the third base pair in a codon. For example, the codons for glycine, the simplest amino acid, follow this pattern - GGN [Guanine, Guanine, aNything] gives glycine in the output molecule. But whether or not the same base sequence and ribozyme molecule are used to produce those interactions, I don't know. There's no reason to expect it to be so (multiple base pair sequences can produce comparable enzyme activity - which is what ribozymes are).

Theoretically, if there were common structures involved in attaching a new amino acid to a growing protein, then they could use a conserved RNA sequence. But the section that "recognises" the codon are in general different, the section that holds the unattached amino acid residue is of necessity different, the section that forms the enzymatically active pocket (where the attachment condensation reaction takes place is of necessity different ... and that doesn't leave a lot else where there can be much commonality. There might be structural elements that hold the other components in set mutual configurations, but that's equally not a sensitive part of the structure.

But the ribosome, itself, is part of the evolved machinery.

Errr, yes. for 23~40-several ribozymes.

I don't think we have a good idea of just how it evolved.

I think everyone would agree with you there. The evidence has been eaten. Repeatedly. The hints of an earlier 2-base pair coding are suggestive, but by no means everyone accepts that interpretation.

And some experiments have shown that the selection of amino acids used can be altered

Absolutely. The basic structure of these experiments is "select one of the three STOP codons available"; engineer a new ribozyme that attaches to that and adds a "not natural" amino acid into it's place (IIRC, selenium-containing amino acids are popular - they behave similarly to sulphur-containing amino-acids, cross-link protein chains into nets in "interesting" ways, and commit the GMO to living out of the chemistry lab, there being no natural sources of that amino acid) ; insert the biochemical support mechanisms for handling that amino acid in the cell ; and then build some special protein that contains the new amino acid, which would act as a "flag" that your GMO is working as intended. It has been done several times, using different amino acids. You might get your PhD for doing it again, but that would be a journeyman demonstration of competence, not a sign of remarkable brilliance.

So ISTM that live that evovolved independently might will use a different selection of amino acids, and different coding systems.

I think everyone involved with the subject would agree with you on that. The "substitute a 24th amino acid experiments" just described show that is so.

(Nobody seems to be suggesting alternative nucleotides, though.)

Absolutely people have proposed that, and AIUI shown that these can work . It's not just minor substitutions on a purine core (adenine and guanine, and artificial variants) or a pyrimidine core (cytosine, uracil, and thymine) ; other similarly complementary molecule pairs have been designed and tested in the lab and should work. One of the stimuli for such work has been the logical flow "this molecule has been found in space" ; "it has a planar form with reactive bits at the edge" ; "this is similar to DNA/ RNA ; can it work like that?" then showing to some degree of detail that yes, you can build life-like systems using these different molecules.

Life on Earth is composed of a number of polymeric molecules - molecules composed of chains of small, simple molecules. The nucleic acids are one such group of molecules, composed of five distinct "nucleobases" (A, G, C, T, and U ; potentially hundreds of others that aren't used in nature). Proteins are another such group of molecules, made of natural and artificial amino acids (23 natural, potentially thousands of others not found in living systems). Carbohydrates (sugars, more complex carbohydrates, up to cellulose and lignin ; sometimes intimately cross-linked with proteins) are a third group of "biopolymers" with around a dozen basic units frequently used in nature and hundreds (thousands, even ; carbs can get really complex ; they're fully worse than clay minerals - and I say that as a mineralogist ! ) of possible non-natural (or rarely-used-in-nature) alternative monomers. About the only major group of "life molecules" that isn't a polymer of simpler monomer units are the "fatty acids", which lots of organisms use as "energy bank" compounds.

The monomers used by terrestrial life tend to include the simpler ends of the potential ranges of these molecule families (glycine is the simplest amino acid ; glucose is the simplest sugar), but of necessity they extend out into the more complex variants on the particular molecule class, where the number of possible molecules explodes, while the number of molecules actually used remains in the few-dozen range.

Even restricting oneself to a biochemistry broadly similar to ours (nucleic acids for genetics ; proteins for enzymes ; carbohydrates and proteins for structure ; fatty acids for energy storage) there are million, possibly billions of potential biochemistries similar to ours, with very similar overall energy requirements. There doesn't seem to be any particular reason why "our" selection is special.

Then we get onto the complex bit : the structure of the molecules. If you look back on the history of wrong ideas that Crick and Watson (and others) had about the structure of DNA (and RNA, but they didn't really concern themselves with that), you'll see that even within nucleic acids you can potentially have a variety of different structures which could be more stable under different conditions. You evidently know about DNA and RNA. There is also "PNA" (with a protein "chain" instead of a sugar-phosphate "chain") as a possible alternative. Other proposed structures included 4-strand chains (with either doubly-bonding nucleobases, or alternating singly-bonded ones), chains with the nucleobases on the outside of the chain ...

We know well what system is used on Earth. We have no strong reason to believe that that is the only possible system. Even the division of biochemical purposes above (genetic ; enzymatic ; structural ; energy storage) is a distillation of terrestrial biochemistry. But it doesn't really mean that a different way of doing things is impossible - just that we haven't looked elsewhere for an alternative.

If I had my 'druthers (EN_US : "I'd rather that ..." becomes "I'd ruther ..." then " 'druthers" ; same root as "ruthless" and "to rue"), when some spacecraft takes a good sniff of Europa's geyser debris they'll find fragments of a PNA using different nucleobases, and the protein chain made with some amino acids outside the normal terrestrial gamut. Then we'd have good grounds for thinking that life could be "everywhere". (Everywhere with a solvent phase.)

Yeah, that was an interesting paper. Convenient timing that it appeared out of my bit bucket at almost the same time as this thread's subject.

I remember one of the author's names - Kroupa. Can't remeber where from though.

Précising it :

A model for forming the SMBH : build a very large ("hypermassive" - uggh! ; save your superlatives for when you need them!) star cluster of "quasar luminosity" ; the big stars die, forming lots (~10^5) of stellar mass black holes ; merge those rapidly (thanks to drag from the cluster's uncondensed gas, large stars emissions, etc) to form a SMBH in order-of(100 million years) ; there are lots of black holes in the near-centre parts of the galaxy waiting to be mopped up.

Alternatively, the environs of the galactic core (lots of gas, complex and varying gravitation fields) are good for forming large stars, some of which will evolve into BHs.

The authors prefer this option and go on to model the expected number of BHs in the galactic nuclear cluster (that term, not identical to either SGR-A*, or Sagittarius-A, needs to come into the regular lexicon). "[T]he corresponding black hole number density is roughly 2 * 10^8 per cubic parsec" - which should be compared to our local density of around 1 star (any size) per cubic parsec. That's going to scatter light from any source appreciably!

A lot of stars in the nuclear cluster are going to hit a BH before they run out of fuel and do their own internal boom. That'll be fun to watch. From a distance. If he weren't already dead, Asimov would be moving Trantor to somewhere less ... entertaining.

The effect of all those BHs in the nuclear cluster constitute a "star grinder" that smashes up a lot of stars that find themselves in the galactic core. That grinding will also produce a lot of random(-ish) gas cloud debris which will impose a viscous drag on anything passing through. (As I remember from @PlutoKiller's course on the "small bodies" of the Solar system.

There's a provocative suggestion that hypervelocity stars seen in the galactic halo could come from disrupted pairs, with the other half of the pair being stuck in the "star grinder" near SGR-A*.

Again, that'll be fun to observe.

From a safe distance.

Oh, about here looks good.

With only successful 19 submissions accepted in your time on here, it looks as if you don't have anything better to do.

Complained recently about the poor quality of articles on Slashdot?

Well you know what to do about it. More often.

Did you read the sentence in summary where I typed "(The authors also anticipate the "what about these big black holes spiralling together?" question : quote "and the amplitude of gravitational waves generated by the binary black holes is negligible".)"?

I wrote those words (explaining the paper's wording) because I thought that users might think of precisely this question.

Sigh - not even reading the fucking summary.

On Earth, most igneous silica-rich rocks are formed by the re-melting of a previous generation of igneous rock which itself has typically been formed by settling-out of a "cumulate" fraction of iron-magnesium-rich (and relatively silica-poor) minerals from a "primordial" magma ocean phase. That remelting is a common event in a scenario of plate tectonics, with a relatively high proportion of volatiles (principally water) in the melt. In the much drier chemistry of the Moon, that's rarer. The Moon's structure froze before there was time for that second generation of melting.

Such a second phase of melting would have helped to concentrate "incompatible" elements into this sort of magma. That it is very rare on the Moon suggests how few high-grade ore deposits there are likely to be on the Moon. In recent buzz words - there are lots of rare earth elements up there, but you'll have to process millions of tonnes of low-grade ore to get them.

The low density of the rocks in this structure is supported by gravity data from the GRAIL (Gravity Recovery and Interior Laboratory) mission of the early 2010s. That mission's whole-Moon survey is how we know there isn't a lot of this material up there.

I suspect the choice of base-pair to amino acid correspondence is arbitrary.

Very likely it's not arbitrary. The assignment of codon triples to types of amino acid (more or less hydrophobic; compactness or length of side chain) is thought unlikely to be "arbitrary" but has considerable resilience to substitutions. Flip one codon and you might get a different amino acid, but it's likely to have a similar hydrophobicity, or a similar side-chain length. For some of the commonest amino acids, flip that third base in a codon and you get the same amino acid. The occurrence of events like that in the universal (well, almost universal) encoding has the appearence of a selected encoding system, not an arbitrary or random one.

One thing that has come out repeatedly in such analyses of the coding system is that it was probably originally based on 2-base codons, not 3-base codons, originally encoding just 15 amino acids (plus a STOP codon). Whether that pre-dates or post-dates the (proposed ; not certain, but popular) "RNA-world" stage is an open argument. (As is "RNA-world" itself.)

What information there is in the coding system is debated. That there is information in there is less argued. You'll have to look long and hard to find someone who actually believes the code is "random" - though it is be a common hypothesis to evaluate as a null when looking for the significance of characteristics of the coding system.