Ken Fabian

The Genesis Project sounds like hubris to me. And there are some big assumptions about our ability to tell from afar if the planet is sterile or if there is any native life present or, I suppose, life seeded by other Panspermists. Probes that must be pared down to barest functional minimum to support the mission objective of seeding planets don't sound like they will be capable of the comprehensive planetary survey required to determine if life is present.

I don't think we will have failed as a species if Earth life fails to spread beyond Earth or outlive it. Billions of years seems like an extremely generous allotment.

I think the question probably belongs in Psychology or perhaps Religion - Panspermia as a matter of naturalistic rather than strictly religious belief in human destiny to spread themselves and terrestrial life into space or something. Why we might support it is only tangentially about expanding knowledge. I don't think entertaining such ideas is really about doing science.

On 1/23/2022 at 8:04 AM, Genady said:

This question appeared in another thread, but it was OT there, so I post it anew.

When we find a promising but sterile world, shouldn't we throw some archaea there with a purpose to spread life? After all, if / when we all go extinct here on Earth, then 4 billion years of evolution will go down the drain. This way we would be instrumental in saving the life. Nobody on Earth but us is capable of doing so.

Were this readily achievable, perhaps it would be something to consider in detail. As long as it isn't, I would say no. I wouldn't say yes even as a hypothetical because, hypothetically, there would be a lot of considerations, including that it closes off opportunities for life apart from Terrestrial. That might even include closing it off to other Panspermist inclined species or upsetting species that might object to Panspermia. I don't see it as anything like sailing ship era practices of leaving animals like goats in anticipation of later visits - it won't be about humans and preparing worlds for future visits or colonisation; it offers nothing that tangibly benefits those doing it.

If it primarily about introducing extremophile micro-organisms it won't save the great diversity of Earth life from extinction - and if people cared enough about that we'd be doing a lot more to preserve and protect them a lot nearer to home.

For all that it would seem to be noble and uplifting in ways people would support I suspect most people most of the time won't really care that much and I'm not sure those commenting here are going to be representative of attitudes at large. A sustained effort to convince people that it is worthwhile might be needed - and more likely aimed at evoking crude emotional responses (like with promoting colonisation of Mars) rather than based in deep reasoning.

I do wonder if there are likely to even be worlds capable of sustaining life that fail to develop it (as a possibly inevitable consequence of being capable of it plus billions of years of opportunities). Capable of sustaining life but not having any could be exceptional - but we don't know.

It would be a difficult process to determine if a world capable of supporting life is in fact lifeless - check every undersea vent and artesian resevoir? Sending automated probe/seeders with limited capabilities to assess - working on too simplistic assessment criteria, eg gross atmospheric indicators - seems unwise.

I suppose nations or coalitions might consider such things if they become capable of it and it is popular and widely supported. It isn't something normally within the duties of care or scope of governments as we have them.

19 hours ago, Evomumbojumbo said:

When I read these posts regarding mutations I find it hard to believe that anyone thinks that mutations are the mechanism by which DNA coding for new anatomical structures is created. 
it goes against all coding principles, garbage in, garbage out.
 

What are "coding principles"? Why are they relevant to biological evolution?

Most mutations will be either irrelevant or "garbage" but those that are deleterious get taken out by natural selection. Development of new anatomical structures is rare and  much less likely after they have already evolved and successful organisms that reproduce in vast numbers already have them. Most of the significant and complex anatomical structures go back a long way; the advantage of crude sight when everyone else is blind is much greater than when everyone else has eyesight with hundreds of millions of years of evolution behind them.

Hard to believe is not a science based conclusion. It isn't even scientific skepticism; true skepticism includes a commitment to learn rather than simply argue the negative.

13 hours ago, Genady said:

This movement of the ground rotates vehicle's wheels. The rotating wheels rotate the propeller. Propeller pushes the air backward and the vehicle forward. This accelerates the vehicle and it starts moving relative to air.

Um, if the ground rotates the wheels using vehicle momentum to turn the propeller it will slow the yacht/vehicle down in direct proportion to the (ideal) thrust. To me that doesn't appear to explain it.

The bike vid example you provided did a better job, showing that there is still wind interaction with the moving vane as it passes through still air, and in the correct direction. I think it got me thinking in the right direction but it hasn't got me to the finish line. Unless that IS the finish line?

The notion that those vanes are acting much like a keel/centreboard keeps coming to mind - like the way the wheels prevent a sideways motion so a tangential force only produces motion along a predetermined line rather than principally a means of providing power; not sure that is helpful or not. It is fundamental to conventional sailing of course but in this case the vane's motion is connected to the ground, not the yacht... and I may be just circling back on myself...

12 hours ago, mistermack said:

I'll have another go. 

And that didn't really help either - which could be more about my comprehension than the quality of explanation.

I may yet encounter an explanation that better suits my comprehension and I expect I'll keep coming back to this until I have understood it..

14 hours ago, Arthur Smith said:

The important point to be aware of is Blackbird in its downwind mode is using a propellor, not a turbine. The propellor is being powered by a chain driven from the wheels, it is not driving the wheels. Until the vehicle nears windspeed it is not contributing to the vehicle's motion. The propellor pitch is variable. Imagine pitch set to zero thrust (blades at right angles to wind direction). The vehicle approaches wind speed more quickly, then stabilized at just under windspeed (due to rolling resistance). Then pitch is set to achieve maximum thrust. The question is can that thrust exceed the wheel drag and that larger force cause the vehicle to accelerate beyond windspeed. The pro-argument is that gearing allows a smaller force times larger distance to produce a larger force times smaller distance.

Like the other explanations, that didn't help.

What will probably be missed by those outside Australia (and by many within) was the Australian conservative government trying from day one to implicate a popular progressive State government, that they take a poke at at every possible opportunity. And there may have been questionable decisions at the State bureaucrat level but the deflections to Victoria's goverment looked politically gratuitous to me.

The issuing of visas is an Australian government responsibility. Even basic questions like "did you fill out the application yourself" (normally an absolute requirement) seemed to come back with the kinds of answers that lead to rejecting a visa. If you aren't a sports star. Along with the obvious "have you had the required vaccinations". State bureaucrats signed off on the medical exemption (questionable but on the basis of some immunity from having had covid) and the visa rules allowed that possibility but probably shouldn't where no attempts to get vaccinated have been or will be made.

This did mess with my head - mostly I kept getting to what I named the "wind barrier" - the point at which the speed of the yacht equals speed of the wind - and thinking it can't be right; how can it accelerate through the wind lull? The explanations i read tended to leave me more bewildered, not less. Even now I'm not sure I really understand, although Genady's bike video example helped - with me mentally converting the rising "deflector" into a rotating vane; at "wind barrier" speed it still interacts with the (moving) vane - okay - but in my own head I'm not quite there. In a more vague, intellectual sense I see that there can be different ways to tap the energy from two bodies with momentum moving past each other,

On 1/14/2022 at 10:38 PM, Arthur Smith said:

The various demos convince me.

As for "seeing is believing" - up to a point, sure, but I note that that is what illusionists rely upon to have people believe what isn't true, or else we'd all be pulling coins out of our kid's ears for them to spend instead of our wallets. Many a scam has worked because appearances can be deceptive, like the chess playing "Mechanical Turk" as an historical example.

I note there were demos of this long before Blackbird - but I'm surprised I wasn't aware of it.

I think we may yet see practical applications - some boats are using these kinds of rotors, more experimental and novelty so far but decarbonising shipping is a real issue. There are the vertical turbine types but... how about Flettner Rotors?

DWFTTW messes with my head but so do Flettner Rotors; how does spinning a tube make it move sideways in the wind?

3 hours ago, swansont said:

Why would storage space be limitless on a space station? 

Perhaps that would be limitless storage space near a space station? Still could be a LOT of room towards the core if the principle living and working spaces are near the circumference for pseudo-gravity.

I don't know how heavy the construction can get with materials like nickel-iron and hold together when spun up but it seems clear that to dodge the cosmic rays/solar wind it needs to be a lot thicker walled than we usually think of for space construction.

I'd go for an asteroid/space station combination or perhaps spinning habitats within asteroids - constructed using refined iron and steels (byproduct of refining Nickel and mixed Platinum Group Metals for export) as well as unrefined nickel-iron that is available in extraordinary abundance.

I'm not sure the Moon or Mars will have anything that a well chosen asteroid or perhaps a Mars moon wouldn't. Earth however, will be the source of much that is essential.

Mostly citizen science is about collecting data (or specimens) rather than doing anything with that data - sometimes tedious and uninspiring work, sometimes not going to happen at all unless volunteers do it. What is made of that data is what is going to take the scientific expertise.

6 hours ago, Genady said:

What problem?

Regulars will know I remain unconvinced of pretty much everything about Mars colonies, from the economics to the fundamental reasons for doing it. I'm sure low gravity would present problems - not all would be deal breaking scale problems except if viability of a colony is already doubtful (which I do;) you don't want any unresolved issues like that.

Problems from low gravity? Some kinds of physical labour will be more difficult; we rely a lot on friction from being held down by gravity to get traction and leverage when we engage in physical activities. But some kinds will be easier - if you have a good grip on something (and traction) it will be lighter to lift. But outdoors you'll be wearing a spacesuit - more weight, so better traction but more dead weight... err, dead mass (momentum/inertia) to carry, plus the restrictive movement and thick gloves, so dexterity will be difficult. Indoors - very high or padded ceilings?

I recall seeing estimates of "ordinary" manual tasks taking about 3x longer in a spacesuit, I suppose in zero-gee - I'm not sure if that included getting in and out of them and time spent on suit maintenance. Maybe the suits can have power assist - but cost more, weigh more, have more things to maintain and to wear out and replace and fail. But if they need to become, in effect, robots with people in them to work efficiently, it may be better to leave out the people.

We don't know how Mars gravity might affect long term health, or how gestation and childhood growth and development might be affected. Like some other commenters I think it will be better to figure that out before committing to any colonisation attempts.

If it comes down to it some kind of centrifuge habitat arrangement might be needed to enable colonisation, which would make habitat construction under exceptionally difficult conditions a lot more difficult.

I think there is a LOT of basic preliminary work that hasn't been done but needs to be to even know enough to judge if colonisation of Mars can be viable. I haven't even seen so much as a comprehensive list of the essential minerals a colony would require, let alone any decent mineral surveys mapping their locations, the extent of reserves in them or what will be required to exploit them. The "bootstraps" approach - just go there and then figure things out as you go - isn't really an option; it seems like the worst possible kind of planning and management for safety and success in such extreme circumstances.

On the other hand (and more recently) NASA also says, contradicting https://www.nasa.gov/feature/goddard/nasa-study-mass-gains-of-antarctic-ice-sheet-greater-than-losses  - from Grace Satellite gravimetric data -

Quote

- between 2002 and 2020, Antarctica shed approximately 150 gigatons of ice per year, causing global sea level to rise by 0.4 millimeters per year.

And -

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Areas in East Antarctica experienced modest amounts of mass gain due to increased snow accumulation. However, this gain is more than offset by significant ice mass loss on the West Antarctic Ice Sheet (dark red) over the 19-year period.

I am not sure how the different data is reconciled. I would note that data based on ice and snow surface elevations have innate potential to be misleading about mass changes - I'm inclined to think the gravimetric data has less room to mislead.

5 hours ago, mistermack said:

That sounds like a heck of a lot. Were they talking about a shield that could completely block out the Sun? To "correct" the climate, it would surely be only necessary to block a small proportion of the total sunlight. At a guess, less than one percent. 

My source - Sanchez and McInnes - were looking at blocking the amount estimated to be needed - about 1.7% of sunlight.

Quote

The scale of the geoengineering scheme studied here is clearly vast, and requires a leap of the imagination over current space engineering endeavours. It has been argued nevertheless that the cost of such an endeavour will still be comparable to other terrestrial geoengineering proposals [2]. In terms of human engineering projects, the mass and scale of the sunshades will also be similar to current terrestrial civil engineering projects such as the Chinese Three Gorges Dam [20], and require a mass production of coated thin material equivalent to the current world decadal production of aluminium foil.

As much mass as Three Gorges Dam, but in space. I suppose the grand space dreamers will suggest we "just" mine the moon or asteroids.

I didn't see any estimates of how long the hardware would last or how much ongoing maintenance; given how speculative it is that might look like a minor detail. I think that without extraordinary advances in space capabilities (and even then) this isn't a climate solution we can use.

On 1/7/2022 at 6:58 AM, Ken Fabian said:

No unpowered objects will stay where they are put; the light pressure and solar wind will blow the foil away.

For L1 positioning most of the light pressure may be compensated for by placement closer to the Sun - ie Sunward of L1. I hadn't considered that. I don't think that will work for anything in low orbit - and it would still not be stable near L1, ie still requires the means to align and move, but with less fuel.

On 1/7/2022 at 6:58 AM, Ken Fabian said:

My understanding is these approaches also are likely to result in regional climate changes above and beyond simply being overall cooler.

Doing a bit of reading reveals that it is hypothetically possible to have some active control over the relative dimming regionally as well as tropics vs poles - via paired occulting discs (iiuc) and that ability to move and align. I wasn't aware of that.

These issues are a long way from solved and it still leaves us with ocean pH change - maybe more so if space shades are used as the excuse to allow ongoing and unconstrained emissions.

Those aside we are still talking about (according to that source) about 10⁷ - 10⁸  metric tons for the array itself. The array will not be the entirety of what needs to be launched. So far there has been around 20,000 metric tons total launched into space - with much of that to low orbits and expected to return to Earth as orbits degrade. At US$1m per ton to launch 10's and 100's of millions of tons gets extremely expensive - and still extremely expensive even if we see costs reduced by another order of magnitude, ie US$1,000,000,000,000 - $10,000,000,000,000 .

I don't think it is possible to grow space launch capabilities that much or in time for it to be much help on our climate problem, especially for a major project that doesn't generate any income directly.

Aside from the technical matters... who pays for it?

2 hours ago, Kevin_Hall said:

we put a bunch of Al foil 10 microns thick and reflect the solar flux over the daytime part of the planet.

No unpowered objects will stay where they are put; the light pressure and solar wind will blow the foil away. Any mirrors/shades in space need to be able to do station keeping - ie move about with drives to keep them in place and aligned. There will be more mass than just foil.

My understanding is these approaches also are likely to result in regional climate changes above and beyond simply being overall cooler.

If emissions continue the ocean pH impacts will not be resolved.

I don't think there are any "just do x" solutions that are better or cheaper or quicker or easier or more compelling than a primary solution of "just build an an abundance of clean energy". I suppose it has value to explore the feasibility of all options but not at the expense of the options we already have or are close to viability.

My impression is that the space based ones are championed principally by the grand space dreamers for whom greatly expanding space capabilities and getting lots of humans into space - often with the express intention of being able to leave Earth and it's problems behind - are their priority. It won't go well to abuse and misuse the legitimate concerns about climate change to advance quite different goals and ambitions.

5 hours ago, exchemist said:

For rocket fuel I can't see this has much advantage over simply producing hydrogen, which is a well established rocket fuel already.

I think Hydrogen's greatest downside is it is difficult to store. That includes being bulky compared to other kinds of rocket fuel. It is challenging to use when all the infrastructure is on Earth and most of it gets used within minutes of launch; producing Hydrogen on Mars and using it for launching return journeys for example would be a lot more difficult. As would any long range missions, where the storage duration becomes an issue.

I don't know if carbonaceous asteroid material could be used to produce hydrocarbon liquid fuels - it seems likely it could.

I like the idea of an intelligent, tool using octopoidal form, which would, of course, have to differ in many ways to octopuses as we know them. Evolve from an octopus or evolve differently, from a common cephalapod ancestor? Convergent evolution in the ocean of a distant exoplanet, that bear resemblance in form to octopuses? They wouldn't be octopuses.
 

Quote

 

Hunting packs roaming the ocean floor, holding stiff spines with stone points bound to them, that extended their reach, that gave them food sources their tool-less kin couldn't access.

Skinspeaking silently as they hunted in the bright daytime waters, click chattering carelessly on their leisurely return, arguing about the crazy plan to make a tidal fish trap close to their communal home nest, that meant working in air.

Only to get trapped in turn by a human colonist, who thought the specimen was delicious when quick-boiled with a squeeze of lemon. And those little spear-like things and the bits of braided cords, they were totally natural and nothing to indicate anything but if the Department of Interstellar Colonisation found out colonists could have their rights revoked. What spear thingies?

 

On 1/2/2022 at 12:32 PM, mistermack said:

I think it's an incredibly stupid step to take.

I don't think we can assume that if German Greens had just supported nuclear then EnergieWende and emissions reductions would be more successful and more advanced. We can decry the historic and ideological baggage that makes most Environmentalist orgs anti-nuclear and free market capitalists anti-climate action; both left nuclear hanging in the breeze just when the winds of change blew through. But I believe it was the latter that was pivotal; it wouldn't have been up to Greens except mainstream politics handed the issue, the podium, the microphone to them. I am cynical enough to think wind and solar got mainstream support over nuclear because they were expected to make no difference.

In an alt-history timeline Greens divided on nuclear may well have led to overall weaker action on climate and clean energy; certainly the German coal and gas interests would have taken advantage of internal disagreement, without supporting nuclear. Reduced early support for wind and solar - EnergieWende being a driving force for making them globally mainstream - could easily have been a consequence, leaving us all further behind at this point.

Greens expect longer term RE growth to displace the gas as well as the nuclear; I am not prepared to declare they were or are wrong to make RE their focus and distrust nuclear and the "just use nuclear" arguments. Germany is a major industrial nation and despite the economic alarmist fear of being economically ruined by RE, it has grown whilst significantly reducing both emissions intensity and total emissions. Even after nuclear closures (past the short term reverberations) Germany's economy has grown and emissions have gone down. The leadership has changed so we will need to see how they proceed.

To establish itself as a primary clean energy option nuclear now it needs those low cost, fast to build, ultra safe modular nuclear power plants - but they are decades overdue and look unlikely to ever be low cost - perhaps they are not so simple and easy and reliable and safe as the optimistic advocates like to make out.

I suggest that whilst support from "green" advocacy might help nuclear it isn't essential;  the essential support base nuclear absolutely has to have is still supporting fossil fuels and opposing the shift to clean energy. In any encounter with a nuclear supporter I put the odds above even that they will dispute the validity of climate science; with friends like that... Above even for the commenters at sites like atomicinsights.com - I suspect that thread of climate science denial running through nuclear advocacy is there in Germany too, despite appearances that climate science denial is not widespread there.

2 hours ago, Kevin_Hall said:

Is it actually possible to reduce plastic waste into rocket fuel?

Given plastic waste can be turned into liquid hydrocarbons and those can be used as rocket fuel - yes. It doesn't look like an efficient means of either reducing plastic pollution or producing rocket fuel.

Ultimately we need to shift to recyclable/decomposable plastics and make rocket fuels using low emissions methods.

In the sense that extremists imposing their will on everyone else - veganism would be a hindrance. But I think true of pretty much every kind of extreme ideology that is uncompromising.

The best outcomes look to be in the compromises - the reduced meat eating for health, supply chains that are more environmentally sustainable, minimising animal suffering . I haven't been impressed enough to want to learn more - I rarely eat meat because I don't like it much and I don't like cruel animal husbandry but I eat eggs and milk products regularly. I don't think food proscriptions work - and I am personally familiar with a common human failing; knowing better but doing it anyway.

8 hours ago, studiot said:

That actually was a reference to a TV programme I saw about industrialised methods of growing tomatoes (and other veg), where they actually wish to exclude all creatures, other than human.

So it was a reference to a Vegan world without any other creatures whatsoever.

I don't know much about the practicalities of proposed Vegan food production and have tended to be tolerant of Vegan activism that exposes cruel farming practices and promotes eating plant based diets, without any in-depth understanding of their deeper beliefs and aims. Studiot makes a good point that it isn't possible to grow food naturally and exclude animal life.

I am more familiar with Permaculture ideas, that use animals and incorporates them systematically. I once heard a then unknown Bill Mollison speak about incorporating chickens into gardening systems around the time the first Permaculture books were published; the final tally of potential useful functions was impressive, as were the practical means of designing gardens, pens and runs to support those uses. It all seemed very practical - a synthesis of existing ideas being the principle "out of the box" idea. He didn't strike me as unthinking and uncompromising (although there are now Permaculture extremists too) and use of the products of science and industry were not rejected - their use was minimised but not excluded.

I agree with Peterkin that Vegans are not a major influence; even the promoting of plant based foods doesn't depend on them.

6 hours ago, mistermack said:

Just by the way, does anybody else think that there is a link between the Germans closing their nuclear power plants, and the spiralling price of gas in Europe? Surely no coincidence. And a signpost to future trends in energy prices. 

You sure you want to derail the thread with a German nuclear vs renewables sidetrack?

In answer to the question, no, I think that is oversimplistic - it may play some part in short term demand driven volatility but there is too much else going on, including Russia playing games with supply availability.

How much German supply comes via long term contracts at fixed prices and how much is vulnerable to short term variability? How well did they anticipate Covid would impact economic activity - declines and rebounds - as well as anticipate how nuclear closures would affect demand? How well does Germany manage gas reserves?

Gas prices have been and are very volatile all around the world quite independently of German policy to phase out of nuclear - which is a tiny portion of global demand.

My hope is they will double down on renewables as a response to price volatility and gas market games as well as continue to push ahead with a transition away from fossil fuels, but I don't know how post-Merkel Germany will manage Energiewende into the longer term.

On the face of it, I would have favored keeping the nuclear plants for their working life, for the low emissions, but my understanding of the in's and out's of German energy and climate politics is limited. But I do think failure of large parts of German politics to fight for nuclear is down to the same kinds of apathy and hostility to strong climate policies we see everywhere - handing the issue to others in "you care so much, you fix it" style, whilst supporting coal and gas. "Not like that" isn't alternative policy.

So far the alarmist economic doomist fears of renewable energy have failed to eventuate although short term volatility still gets treated like evidence of fundamental failure. Germany is still the biggest and most successful industrial nation of Europe.

I still think overcoming vulnerabilities and limitations is what intelligence does best - I think the intelligence and problem solving capability matters much more than any baseline of physical abilities, although without some ability to hold and manipulate things tools would be more difficult. But I hesitate to say impossible. Co-opting other creatures? We make structures like hedges out of living things, we use other animals to utilize resources we can't use directly and make them into usable things.

I don't see the short life span of octopi - or their marine nature - as nearly as much of an impediment as being mostly solitary and lacking language is.

With language the lessons learned by an individual can be passed on to others - to youngsters of the next generation. No individual human can hold all knowledge - and our own example shows it is not necessary.  Individual intelligences that are not social? Even that seems possible to me - but may require the long lifespan and mutability/adaptability of form might help.

Octopi probably wouldn't find land as intimidating as some other marine creatures - some do go from rock pool to rock pool across dry land when seeking food.

A species that cannot hold a spear or throw anything may still be able to make traps. I suspect I would be in serious trouble if I had to hunt live prey by throwing things at them but I think I would be capable of making traps.

We are not adapted to live in space - yet we go there. We use fire - and are not adapted to handle it or survive it.

We only have one example of intelligence capable of the kinds of technology we have - we don't know enough to even suggest a tech using intelligence having that form is more or less capable or likely. Or appreciate the kinds of technologies we don't have and may not recognise.

We do have examples of other physical forms finding, making and using tools as well as cooperating on tasks individuals are incapable of. Even, I suggest, examples of animals that engage in reasoning and problem solving. I suspect strong human prejudices on what form intelligent aliens might take - and perhaps an unhealthy measure of self deception about our innate superiority.

I see no basis to conclude that plants are unlikely evolve intelligence or evolve movement - there are venus fly traps and other exceptions and just using time lapse gives a whole different perspective on plants and movement.

Going by the human example I see no basis to conclude that, having crossed interstellar space, aliens are unlikely to be hostile. We can't even be assured that if humans achieved such a feat, that we would not covet the target world and it's resource or that humans would never do xenocide.

I think if we are honest we will concede that humans are quite capable of such things - and of finding justifications before, during and after. Or, where justifications seem inadequate - scapegoats. We may even be predisposed to doing such things.

I am not sure we would recognise some kinds of intelligent aliens and I think we would be capable of wiping them out just by mistake by simply failing to recognise them as intelligent.

And should any intelligent aliens take violent exception to human presence in their territory - on the basis that doing so is justified as self defense. If a child is caught and killed by an intelligent carnivorous plant on it's own world would humans refrain from retribution? We ARE the consummate nest raiders but we won't tolerate anything that raids our nests; any onworld human presence that has committed itself to survival by colonisation will be capable of wiping out alien species to assure that survival.

15 hours ago, beecee said:

Perhaps the "human resemblance" evolutionary process, is simply the most favoured to reach advanced intelligence and associated abilities. What I mean is that while an Octupus is obviously "intelligent" it is still confined somewhat by its evolutionary path.

I don't think there is a "human resemblance evolutionary process" and there are no known advanced intelligent aliens that have that form. It seems like rank anthropomorphising to presume it is superior or even necessary - if that is what that prejudice is.

Whilst hands with opposable thumbs at the ends of upper arms of visually capable bipeds appear a very good way to make and use tools (to humans) I don't see it is a requirement; birds build complex nests with beaks and even manipulate tools and Octopuses ('pi?) can do it with suction cup fitted tentacles.

But I suspect that physical capabilities are amongst the least essential - mental and communicative abilities can work around a lot of physical limitations, including by making teamwork possible. One beak to hold the work piece, another to steady the anvil and two more to work the hammer? Isn't much of human success a result of tools and techniques that work around the physical limitations of individuals?

Might that ability to work around physical limitations be a crucial marker of an "intelligent" tool using species? Where is the lower threshold for physical abilities? When starting off a lower base the achievements look greater, not less.