Ken Fabian

May have been more like a crayon stick in workshops and construction sites than used for writing on parchment or in wax or on papyrus. Thick enough to not bend. Being soft would make it easy to hammer a new point if necessary. If I were using them I'd want a wrap between fingers and lead but they may not have been aware of lead poisoning. Could have though; getting fingers gone shiny metallic from handling it would be obvious and I believe stone floors were polished with blocks of lead so successions of slaves doing it getting similar debilitation could have been noticed, so... use only cheap slaves? I suppose there could have been a lively interest in poisons as well as cures in some quarters.

In cold weather it will be more a case of cold air going in and colder air going out at the air source side of the system - the air doesn't have to be warm or hot in human terms - with the difference in heat content between cold and colder air delivered (in water heaters) to the water in the tank. If you install one inside in a heated space your HPHW will warm water quicker by parasitising the warmth in the air and cooling it, ie you will lose out on the space heating side. Better to put them outside or only in ventilated, unheated inside spaces. With systems suited to those temperatures. We have one (outside) and it does work very well for (is built for) Australian conditions - we rarely get below zero temperatures where we live and it only gets that cold overnight and early morning with daytime temperatures higher. We set ours to run on a timer from about mid-morning to mid-afternoon to take advantage of solar pv on our roof as well as warmer air temperatures; it is a rare day where that draws any power from the solar batteries and rarer still that we draw power from the grid because the batteries as well as PV are too low. Small household using a smaller unit that draws about 500W for 2-3 hrs a day in warm seasons and 4-5 hours in winter. But I'm not entirely convinced it will be better value for money compared to having enough more PV on the roof and running a regular resistance heater - the HPHW is a lot more expensive to buy and a lot depends on how long it lasts. (Still cheaper than "passive" solar hot water systems, the sort it replaced though). New solar installs tend to be signficantly larger than our older system - at less cost - and the panels can be expected to last beyond 30 years, where the HPHW probably do well to last more than 10 years. Upgrading the PV isn't as simple as adding more panels; wiring and inverter upgrades would be involved. Externet, I seem to recall a thread from you about use of stored hot water to supplement home heating (?) . Probably not what you had in mind - this is more about combining hot water and house heating using heat pump hot water that makes significantly higher temperatures and time shifting the heating load within each 24 hr period to take best advantage of when electricity prices are lowest. Also can do summer cooling. Taking advantage of heat pumps being more efficient during daytime is one of the parameters the system works with. I came across it here https://www.volts.wtf/p/heat-pumps-with-thermal-batteries (an interview - a bit of reading to get to the grit) The company's site - https://www.harvest-thermal.com/product#tank This isn't for off-grid although elements of it probably could be. For interseasonal heat storage it seems to me that borehole type ground source heat pumps offer the best option, but need costs to come down, especially the drilling costs.

I'm not impressed by the equivalency arguments. I think it is a false equivalence between things that cause human suffering for which no or only deeply inadequate solutions exist and with fusion to do what a range of technologies already do successfully, just to do it better, maybe, in a future far beyond the time frames we have for doing low emissions energy better. Medical science is not concentrated into a few programs and a few approaches; the advances come from wide ranging research, from fundamental science outwards, lots of which does get abandoned for not panning out within a timeframe and budget.

Technological progress has not been greatly diminished - or diminished at all - by the US not extending the Apollo space program.

Believing all will be lost if fusion programs get defunded sounds like spirited defense of the sunk cost fallacy. More than 70 years so far and still not even close. If any program were closing in on a working reactor then yes, breaking it up will put the overall goal behind, but that is not the case. And I do think fusion can be revisited, that other high energy particle physics and other research programs are closely enough related that developments can be, will be, relevant to prospects of future fusion. A decade retooling for a renewed program based on actual prospects of success - which may very well require a markedly different approach, which might be held back by reluctance to let go of what isn't working - isn't that unreasonable. And I suspect ever more such R&D will be virtual, computer modeled and AI assisted.

Yet the majority of new electricity generation being added globally is now RE by a very large margin. If you want the impression nothing much has changed look to existing generation stocks - and dismiss 29% as a small amount. But for projecting forward look at the relative rates of growth. It isn't primarily driven by climate concerns, though those are there, so much as driven by demand for electricity generation at least cost - a profound underlying change, a tipping point crossed where nothing is the same after. Not that long since almost no-one would've believed that was possible - with a lot of people who still don't, let alone get a sense of the significance of that. EU is above 40% RE electricity (44% last year). Here in Australia, around 35% - where almost nothing apart from RE is being added. And adding more has never been cheaper. Global solar cell production looks set to reach 1TW a year within the next two years - at 20% capacity factor (GWh terms) that much solar is like adding 200 1GW nuclear stations a year. And now there are growing fears Chinese makers are tooling up to flood the world with cheap EV's as well as cheap solar panels.

More than 70 years so far without success and still no emerging pathway to anything expected to work - a very different case to chasing better light bulbs from a starting point of light bulbs that already work but don't last long and trying various alternative materials. Without taxpayer funding. I think if it is so extremely difficult to do at all that doesn't auger well for doing it reliably at low cost; even if it can be made to work it may not be commercially viable. I don't agree that fusion research should be abandoned but I can understand how people could hold the view that it should and I admit to some ambivalence, given the high costs and ongoing lack of success. I wouldn't count as indicative of a general lack of support for science and R&D to suggest it may be better to divert that funding and support to improving fission is a reasonable position to take - modular reactors (a technology that has been demonstrated to work) that can take advantage of economies of scale through mass manufacture are decades overdue. Other high energy research would continue to have direct and indirect relevance - and deliver spin offs. And where those developments really can be turned to making fusion work it can be revisited with improved knowledge.

Until the clean energy problem is solved by other means? Well yes, looks like we have no choice but do that anyway because fusion still doesn't work, so absolutely we should not stint on other clean energy related research even, arguably, at the expense of fusion programs. But I think that in the bigger scheme of things what we spend on it, including energy consumed by it isn't that big. Still I sort of agree that it shouldn't be sacrosanct, when by most standards it is gets very well funded despite still no reasonable expectation of working reactors any time soon. Anything else but the fusion dream and we'd have dumped the whole thing as a failure long ago. Interesting use of the word "wait". I think we will be doing clean energy successfully before we get working fusion - more confident of the former than latter. (still short of high confidence though but not for technology limitations) We can never know for sure that it won't work - so can argue funding should never cease, ever. But falling for the sunk cost fallacy is expensive. There are spin offs from major R&D like that of course, but other kinds of R&D get them too and the funding pie is finite; it is reasonable to ask where we draw the line. It is even reasonable to put the case that fusion still has no reasonable pathway to deliver abundant low cost energy and that funding fusion gets on that basis should be diverted to more achievable objectives. But as I said earlier I think we can afford a serious fusion development program or two as well as fund other areas of research; spending more elsewhere rather than cutting fusion research back.

I haven't looked deeply into this but first impressions... too small sample sizes for one. Mostly I suspect there was a shift upward in population where agriculture and civilisation had taken hold raising the proportion of total human population with lower brain size (as response and possibly adaptation to changed diet and even out of some pre-existing regional genetic variations) whilst everywhere else brains remained much the same as before. Any suggestion the whole human population changed like that, simultaneously around 3,000 years ago lacks a global cause - which would not result in the same genetic outcomes; all turning out the same isn't how evolution works without selection or gene flow. Gene flow within that time to present - Middle East to Europe and Asia, Europe to Americas, Oceania - ought to be largely traceable through DNA, but I don't know that anyone has done those studies.

There are Lithium batteries all through our home now - phones, shavers, remote speakers, torches (lanterns), leaf blowers, push mower, ride-on mower, brushcutter, drills, grinders... oh, and solar batteries that are much more than all those added together, and I'm sure I've missed a few.* Not an EV yet but only until costs come down and/or the used EV market grows. Some are Lithium Iron Phosphate (solar batteries, ride-on mower) that don't catch fire - although every electrical appliance can potentially catch fire from electrical faults, which can go on to start battery fires. Seems to me keeping the quality high - having safety standards - is more important than any "free" market access to cheap low quality batteries and chargers. Or to EV's with batteries and chargers that don't meet minimum standards. Those standards are likely to keep getting reviewed and updated in light of real world incidents as well as testing regimes, as they should. Fears that China will flood the world with cheap EV's (can't make this stuff up) are seeing efforts to save ICE manufacturers (who got what they wanted and in Aesop's race style have rested on their ICE achievements) with big tariffs and import bans. But any imports into markets like US, Europe or here in Australia DO have to meet stringent safety standards - and Chinese manufacturers appear as capable as anyone else of meeting and beating them. *(Add on edit - missed the laptop I've been typing on; talk about missing what is right in front of me. 2 in use plus another older one, rarely used)

Not sure myself whether I was completely serious either. A question of to what extent people want to change themselves versus want others to change and treat them differently. Social anxieties have limited my potential but I still count myself fortunate and have led a good life; I can see how improving my social skills could have benefited me but better social skills of everyone else - a community wide improvement with others doing the work - is quite appealing. Easier.

Might. Don't know how effective with "incel" syndrome sufferers. Having such courses for everyone who needs them, not just afford them (and want them) could be a stretch.

There are no school courses in social skills - nor much we would count as remedial ones (counseling, cognitive behavior therapy?) - but a lot of people could benefit from them. Assuming such skills can be understood, taught and learned.

An unanswerable question. It seems unlikely. Even very unlikely. Apart from beavers and humans not sure any make dams, so an uncommon behavior. Some will dig for water and leave holes that fill with water. Was that intentional? Elephants seem like ones that could have the intelligence for that to be intentional behavior. But how would we ever know, even with existing animals that we can observe? "Dinosaurs" of today do make nests and sometimes use tools (with small, different brains) - how much better or worse than their ancestors we don't know. That some animals can ape behaviors they observe has been observed but unless they get benefits from it those behaviors aren't going to persist. As an aside, there are benefits in seasonally dry environments to slowing water flows; there are advocates of doing that, including by pushing logs into watercourses. It will retain water holes longer but also slows the loss of underground water in adjoining soils, which gives more plant growth and food. Behaviors that lead to more food can develop even without conscious awareness of it.

Smaller ones dispersed late but most of the rubble still hitting should reduce damage. Larger ones, no, with significant consequences just from atmospheric heating from a large enough debris cloud, without big surface impacts. Doing it far enough out that dispersal means few or preferably none of significance hitting Earth (including atmosphere) would be the intention. But this has already been discussed. I think we are just repeating what has already been said - disagreeing without resolution - so unless something new comes up I'll withdraw from the discussion. Been interesting, got me reading things I hadn't come across before, not a waste of time. Thanks all.

I think humans evolved without clear biological triggers and rutting times for mating, with a strong anytime sex drive that isn't precisely aimed in their place. Sexual attraction can get linked to a wide variety of potential turn-on's as sexuality develops. Humans can get aroused by a variety of triggers, all the way to nothing more than imagination. Seems to be a lot of bisexuality and a lot of people who preference their own sex are still capable of hetero sex and lots do have children. And want to have children. And appear happy to have children, male or female. Survival for humans is all about survival of the group and sexual competition gone to extremes, especially amongst males who can get their way by force and can claim many mates can be very damaging to the group; a strong sex drive when not everyone gets a mate can lead to benefits to the group from those who miss out having access to other kinds of sex, ie less fights. For females missing out too, because they are one out of several and denied outside opportunities by possessive males, as well as males missing out by polygamy. Members of the group don't have to be parents to be engaged in activities that help the group's survival and feed and protect the group's children.

Just my understanding that evolution of a gravity bound cloud of material should settle into a ring (or possibly more than one) that can coalesce over longer time into a second object or more than one. I think much will depend on how much total rotational momentum of the "system" created and I don't know what the time scales would be to become a ring... centuries, millennia, more? I would expect that close proximity detonations would explosively vaporize surface material and the shock wave of that will travel through the object. I'm still inclined to consider penetrating munitions, even as a preparatory first strike ahead of a second dispersing nuclear blast; if there is one area of engineering that we don't stint on, that we are very good, at it is weaponry. A real asteroid threat would be worth more than one device.

@zapatos If detonations can't give loose rubble enough impetus to escape it's own gravity that would be a mission gone wrong. Avoiding missions going wrong would be important. I'm thinking of what happens with inadequate dispersal, with rocks moving about within a weak gravity well - I would expect any bits coming back in towards the centre of gravity will bounce off each other, not coalesce, some gaining enough momentum to escape in the process, some losing it and orbiting closer. I expect it would take a long time to settle and I think any persistent configuration is more likely to end up as 2 or more smaller rubble piles orbiting each other, possibly after a long time as a larger one with a ring before that. Significant solid portions within what we think (wrongly) is loose rubble might be very problematic. Detonations intended to disperse will be external, on one side, with shock waves within the asteroid as well as rocks outgassing and a range of directions for pieces dispersed, with variable speeds. That would not be like an inadequate detonation placed at the core where the material goes out and a most comes back the same direction. Which I think would make a cloud of loose material that, again, would "coalesce" as a ring with enough time. Yes, sorry, I missed a few posts along the way and was thinking of asteroids from further out. The asteroids that orbit near, inside and just outside Earth's orbit do present challenges for detection but I wouldn't think those are insurmountable. The challenges for any deflection might turn out to be less for such asteroids as long as we have the early detection due to lower delta-v requirements to reach them. Detection will need to move beyond Earth based observatories to get as complete a database as possible - and improving detection is surely the immediate priority.

Seems to me that would give us more time, not less. And I expect it has happened - and equally likely to reach us that way as inbound. Large objects should be identifiable from any direction and well before any passage around the sun - and identifying and tracking should be (and is) the space agency priority. And (not sure) but may be potential for gravity sling and more effective deflection with less energy can be done when it is closest to the sun? The Nuclear Devices for Planetary Defense link does suggest potential for explosive dispersal and also that a late response might have little choice but to rely on that. I can't see that as likely; the gravity of such objects - even the large ones - is small. Even if it doesn't disperse most of the debris that isn't dispersed will end up orbiting, not coalescing.

Not missed out but it doesn't stand out as an option except in the sense that at small scale it would be the easiest to attempt using existing technologies. According the the Nuclear Devices for Planetary Defense link (included in the quote I used - KI being Kinetic Impactor) - 605 metric tons is a LOT of mass to launch, far beyond existing capabilities. And (if I understand it) high speed impacts shed a lot of energy as heat and explosively, not all will be delivered as changed momentum in line with the direction of the impact. Not necessarily a problem and possibly advantage if sideways deflection does it better. I still look at meteorite defense as a longer term challenge; yes one could be identified tomorrow but the odds favor not. In terms of odds a too ambitious "being prepared" program could look like waste - Note that this looks at risks from objects within the solar system - there remains the possibility, if very low likelihood, of large objects from outside the observable solar system.

I'm with Airbrush on this and think nuclear devices delivered by variants of existing rockets would be the preferred means, probably the only one possible any time soon. Longer term - and I do think meteor defense is best viewed as long term - other options may become possible. Delivered and it is done versus delivered and just getting started. Much more deflection from less payload. Shorter mission times. Uses familiar technologies with lots of existing knowhow and capability. The links people have provided, including yours appear to support that although different asteroid examples and different units make direct comparisons a bit tricky - at least for me. https://arxiv.org/pdf/physics/0608157 with Apophis (320m diameter, 46 million metric tons) as example for a 1 ton gravity tractor - 3.7mm per sec per year (? Someone else should check units and arithmetic?) https://ntrs.nasa.gov/api/citations/20205008370/downloads/Nuclear_Devices_for_Planetary_Defense_ASCEND_2020_FINAL_2020-10-02.pdf with 560m diameter object and 550kg payload - 65 to 165mm per sec in a few seconds to minutes with a single 1 megaton nuclear device for a significantly larger object. Having the device stationary with respect to the asteroid seems to be preferred over one coming at it at high velocity but not sure how that would work directly along the trajectory.They look to smaller than 1 Mt explosions as preferred - several small ones better than one bigger one. Spinning object? Having a quick search for rotation rates - it sounds like a large rubble pile would max out at 1/4 rotation per hour, slow enough for a nuclear detonation to give directional push. Small ones would be suitable for dispersing blasts. Too close to Earth? The "nuclear devices" paper deems several months of warning as a short warning, late response scenario and doing the detonations more than a month out from expected impact is considered a rapid response. I can't see that as an EMP risk to Earth that far out. Anything as close as the moon will be days at most away - too late, kiss arses bye bye. Nukes not designed for use in space? I expect some probably are even if that isn't advertised; the potential for nuclear warfare to happen in space has been known a long time; it may be against arms agreements to put any into space but military planners always look beyond existing treaties if only on an Irish basis - to be sure, to be sure.

I can see why you might think that - a course that 'begins' where it crosses Earth's orbit ought to be an orbit that crosses that orbit again. But orbits aren't really that precisely repeating, with precession etc. Any deflection that reduces or increases it's velocity along its trajectory for example will result in orbits that probably won't ever come close again. This seems like an experiment that would be worthwhile running. I'd still look at penetrating munitions too, to see if we can blow material out directionally.

Well if you read on I did add 'maybe'. The first link I looked at was to estimates of what a 1 ton spacecraft could do, without including any estimates of how much fuel or reaction mass or the time and fuel to get it into place; I think those will be significant. A thruster on a broad pad would allow higher thrusts, to the limits of the asteroid's integrity and I suspect it doesn't matter which way the orbit gets altered, that if it is changed in almost any way (except maybe intentionally in particular directions) it won't be a future collision hazard, so thrusters could be placed at one of the poles to allow continuous push. But, again, I am doubtful rockets pushing it or pulling it would be a preferred approach and the time and rocketry constraints will favor other means. Maybe even a different approach, like an up-scaled version of this to toss rocks at faster than escape velocity, plus a robot to load them into it -

No it won't. Deflection at any point in it's orbit will make a new orbit and new trajectory and it will be less likely any Earth crossing orbit object will ever cross Earth's orbit again.

MigL (and not only MigL) makes a good point - the objects will be very different in composition as well as size and make very different challenges. Likewise for Earth orbit crossing asteroids with knowable orbits, (lots of lead time and potential to rendezvous on it's way outwards between perihelion before aphelion with much lower delta-v than the other way) and incoming comets or asteroids out of deep space that give much less warning. Different too between one expected to hit on it's inbound approach or hit outbound after perihelion and passage around the sun. Potential for solar electric propulsion. Rendezvous with an object from far out on the inward approach before Earth's orbit needs a lot more delta-v to match course further out in the solar system and solar electric propulsion would not help. If collision is predicted for after passing around the Sun then rendezvous between Earth and Sun and nudging it as it passes closest to the sun may give some potential gravity slingshot gain - if that is possible. But any approach that requires a rendezvous uses a lot of energy moving a spacecraft into matching trajectory, energy that could be delivered DART style more directly. Still not convinced much is gained by gravity tractors over direct thrust, with a broad pad, mat or mesh to spread the load. Maybe. But I am actually more doubtful that any kind of slow thrust will be preferred, however "mounted", as compared to other approaches. If it is not huge and is loose rubble (looser will tend to go with smaller) and there is enough time to use Gravity Tractors then I expect explosive scattering would still do the job quicker and more reliably. Nothing delivers more energy or makes more energetic explosions than thermonuclear detonations - and much more energy can be delivered that way for similar payloads. It isn't just the mass of propellant for GT snigging (Aust/NZ term for dragging logs by chain or cable) but the propellant to get there. DART style kinetic energy transfer seems to have a lot going for it. On a first consideration it seems like a kinetic impact would simply transfer momentum directly opposite to the impact but (if I understand it) a high speed impact sheds a lot of energy explosively and that is outward from the object's surface in meteorite style - so a tangential impact should blow material sideways to the direction of the impact and direction of the object. Whether the changes are better tangentially or by reducing (or speeding up) the object by a front-on or rear-on blast isn't clear to me; it could be effectively equivalent. Mention was made of penetrating munitions; loose rubble piles would be especially susceptible. Any kind of solid metallic ones, maybe not so successful. Sorry, this makes no sense. Likewise there are no straight trajectories - every time it will be a moving object aiming to meet a moving object where their gravity-curved trajectories cross.