Ken Fabian

What obvious engineering solution? How is lack of permission the principle impediment?

All the documentation and eyewitness "testimony", from watching the launch to the many amateur radio enthusiasts who - by aiming their receivers at the moon - listened in isn't enough? It didn't make it to the moon but I recall a demo from before the mission of a flag "waver" that was developed to give the flag movement; a bent wire in a sleeve within the top of the flag that turned by a small motor. But I think the actual movement of the actual flag was attributed to static electricity.

In a sense, yes; not pre-existing planetary bodies but ones that coalesced in the early formation of the solar system and underwent differentiation from their own gravity and subsequently got broken up by later collisions. Metallic cores that formed when these proto-planets were hot and molten are where the nickel-iron we find now came from. Surely that was Nickel-Iron, but it has been common to refer to metal meteorites as "Iron". So far as I know meteorite metal is always Ni-Fe and the only pure iron found in meteorites are small crystals and tiny nodules within a nickel-iron matrix (and not independent of it). I have previously done some searches to learn whether pure iron or other relatively pure metals (like nuggets and seams of precious metals) are going to be found in asteroids myself - pure iron being more widely useful than alloys with nickel, although the nickel content is a lot more valuable in metal price terms, probably exceeding any precious metal value. I could not find any references to any metallic meteorite sample that was not nickel-iron, with other metals (eg cobalt, Platinum Group Metals) well mixed (in solution) within them. It appears to be a case of processes that mix them occurring but with an ongoing absence of conceivable processes that can separate them again. (I asked this at https://space.stackexchange.com/questions/27329/can-we-expect-to-find-pure-iron-or-only-nickel-iron-alloys-in-asteroids - and someone answered with a claim to have found a very high, near pure iron content meteorite but he couldn't find any experts who agreed that it was a meteorite and not something with human/terrestrial origins.)

@Markus Hanke Thanks for the reply. I have to admit my level of ignorance has not decreased by much; I will defer to people who know more than me and take it as given that the mass within black holes affecting space-time outside it with gravity isn't a contradiction.

Another question out of ignorance - How does a black hole's gravity influence matter around it if it's mass cannot have a causal effect? Is gravity's effect not causal?

I'd be pleased to be wrong but don't really expect any such loopholes; ignorance allows room for speculation... and makes it more likely I am wrong. A singularity, where the laws of physics break down but that doesn't mean anything could happen; maybe the very opposite - is there anything more inert than what is in a black hole?

Whatever happens on the other side of the event horizon of a black hole there is still mass and gravity interacting with spacetime and matter in the present. I am no physicist but it does seem that out of the things we cannot yet explain within a unified theory of everything gravity is up near or at the top. I would like to think that leaves room for some of those "magic" possibilities - FTL, reactionless drives, anti-gravity - but I remain very doubtful that will be the case.

@mistermack I am still inclined towards boreholes into bedrock as the most widely available inter-seasonal thermal storage for heating buildings. High temperature storage can do other things but probably can't do building heating as cost effectively. It looks even better when large scale, ie district heating rather than one building at a time From what I could find out about the Drake Landing example - and in keeping with my prior understanding - such heat masses need to be "primed" before the heat losses to surrounding rock slow sufficiently to give effective insulation; the first few years a lot more heat went in than came out but once the ground mass had gained enough heat the net flow out got a lot closer to the flow in. They claim Coefficient of Performance of 30 after the system was fully operational, ie 30x more heat than (non-solar) energy requirements, with more recent addition of solar PV to run the electricals. No heat pumps in that example so the storage mass must be hot enough to deliver water at temperatures high enough. Bigger storage mass and lower temperatures would use heat pumps.

There are examples of district heating using seasonal thermal storage using aquifers, tanks and the ground itself, eg like Drake Landing Solar Community in Alberta Canada that has 144 boreholes 34 metres into rock used as a heat store, replenished seasonally by solar collectors on the garages of participating homes during Summer. Not quite all their heating but always over 90%. Not sure what it would take for them to get to 100%. I do think there is a lot of potential for ground source heat pumps for colder climates. Interesting that large buildings with borehole or thermal wall geothermal heating and cooling often have to have a cooling bypass to shed heat rather than pump it all into the thermal mass, because overall they are a heat source; the seasonal differences between taking heat out (Winter) and adding heat in (Summer) being out of balance can make the ground mass too hot (losing system efficiency?) over a few years. Clearly we can use deep ground as inter-seasonal thermal storage and the rate of heat conduction is low enough that the surrounding rock is effectively it's insulation when the scale is large enough. So far as I can tell the up front capital costs are the barrier - despite often being cost effective over the longer term.

I am not sure that pumped hydro could be viable at such small scales, with such small differences in elevation. (I did attempt working out how much energy stored in 1 metric ton of water at 10m elevation and 100% efficiency but got caught by the conversion from joules to kWh (divide by 3.6 x 106 ?) and got about 10 Watt hours but I have serious doubts I did the calculation correctly. Anyone know?). A few thousand tons of water would need stronger construction than the usual rooftop. Wouldn't heated water in an insulated tank do energy storage better on mass required basis? I think pumped hydro will only be viable at large scales where natural geography favours it. Much simpler and cheaper at household level to add batteries. Ours work very reliably. Not sufficient for full heating (in a poorly insulated home in a mild climate) but significantly supplementing wood fired heating; we'd need about 3X current battery to ditch the wood but not much more solar. With respect to our costs it is more expensive than not having grid connected solar and batteries, but not a lot more (with value of blackout backup difficult to assess but a bonus). With power prices surging higher that may even have shifted to less expensive.

Apparently Berlin has one of the biggest district heating systems in the world already in place - a couple of thousand km of pipework, with 3/4 of Berlin homes heated that way. A lot of it is waste heat from other energy use (co-generation) rather than made for the purpose. I suspect the "13 hours" refers to what will be available with expected use, not the time it can hold heat if none of it were being used. Whether heat pumps running from electricity would do it better or not making use of that infrastructure gives a big starting advantage to this kind of thermal storage over building pumped hydro and heating individual homes by other means. It may take an energy crisis or two and time to get significantly more pumped hydro, with reluctance to make those kinds of investments until it is clear it is essential, ie catching up or just in time rather than surging ahead of near future needs.

So many issues, fun in a thought experiment kind of way but for actually moving big blocks of stone... no. If I am getting this right there is a trench that is mercury tight that can be opened up ahead and filled in behind and sealed to be fully mercury tight at every stage, with that excavation/reconstruction being done whilst full (or else mercury ladled out each time - no suction can lift mercury higher than about 760mm). Enough mercury to float the block forward a small way (that still leaves room for the excavation/reconstruction ahead and behind), ladle out the mercury, fill in behind, open up in front, refill, repeat. Wider trench and more mercury for any bends. Fully recover the mercury for re-use without losing significant amounts ... This is supposed to be an easier way to move big blocks of stone?

This would be my preferred method for moving the regular building stones, a method for which there is some archaeological evidence (and some accompanying disagreement). https://www.ling.upenn.edu/~jason2/papers/pyramid.htm These kinds of objects (of unknown purpose) have been found. I'd try wrapping leather straps around to hold it all together - This style was "invented" as a possible solution and tried successfully - but there is no indication of Egyptians having used this type -

Seems like part B of the question is about responsibility for emissions for suppliers of fossil fuels, which arguably includes legal ramifications. Emissions accounting is, quite reasonably (and for practicality) done on a nation by nation basis. Emissions responsibility or culpability isn't so easily compartmentalised geographically except in the sense that climate policy in practice leaves any considerations of culpability to individual nations, which could, if they choose, apply to exports of fossil fuels as well as to the embodied emissions in the goods and commodities traded. Mostly these are being addressed (or proposed to be) via those border adjustment mechanisms, which in practice are about compensating for different climate policies and carbon pricing. As a short term market response, yes. But all else does not remain the same; the longer term response can be increased investment in alternatives, which will also enjoy a relative price advantage. A "never again" response by nations and governments that take the climate issue seriously is likely to push harder for those alternatives irrespective of any immediate crisis management, with rising costs of existing fossil fuel dependence a strong incentive even apart from climate and emissions considerations.

It appears to be a well established legal principle that suppliers of products that cause harm are liable for those harms, irrespective of the benefits of those products - even though courts appear reluctant to rule that way with respect to fossil fuel suppliers and emissions. More usually courts rule on something done at small scales where direct culpability can be assigned - the actions of these people/companies caused these specific harms, without multigenerational, multinational and economy damaging complications - which rulings discourage those same activities by others at much larger scales, before they get too big. Some "duty of care" arguments have succeeded, but courts around the world appear reluctant to grasp this nettle firmly. The arguments that the end user alone bears culpability are widely referred to as "the drug dealers' defense" (along with "but they'll only buy their heroin... coal and oil and gas from someone else"). I think there is culpability at all levels but institutional large scale culpability should trump that of individuals. I suspect that politically it has been advantageous to the opponents of strong action to turn the Environmentalist calls for individual responsibility as the principle response back against their objectives; the general reluctance to adopt personal frugality and belief it makes little difference is used to encourage community reluctance to make demands of institutions.

I note that Australia's government(s) have preferred to view emissions as a fossil fuel consumer responsibility and not a supplier responsibility. Making it an end user responsibility makes Australia's contribution 1.3% whereas if viewed as a supplier responsibility Australia would be 6-8% of global emissions. I don't expect that to change with the new Australian government although they do appear to take the whole issue more seriously than the previous "conservative" government.

There are getting to be less and less unknown unknowns; there was a lot of room for Lord Kelvin to get that wrong but a lot less room now given the progress in science up until now. Knowing more can open up more real opportunities for technology but will also close imaginary ones off.

One data point, yes. But it is 100% of all known data points. That sounds like a very good starting point. I think we (interested scientists) can generate a lot of ideas about what chemical processes can lead to life and will get better at modeling what is possible as well as what is likely.

Some thought has been put into what signatures we might look for - from one side of that question there are efforts like Sara Seager et al to build a comprehensive list of possible volatile compounds. The presence of chemicals that are not in thermodynamic equilibrium - some active process needed to sustain them - seems to be a major criteria, but a lot of chemicals made by life on Earth are unlikely to occur without life. Determining what can or is likely to occur without life is another aspect. What astronomy requires to detect them and how far out is another question. Planets crossing their parent stars visible from Earth and near space will only be a small fraction. https://www.saraseager.com/wp-content/uploads/2020/07/Seager2016.pdf

How much interstellar exploration can a few grams do? What instruments can each carry? How about interstellar data transmissions? Even lots of them strung out as relays - receivers and transmitters and power source along the way needed in that case - I think not. Von Neumann machines look more likely to be successions of complexes of mining, refining, manufacturing machines than machines that can eat asteroid dirt and excrete copies of themselves - I think not. But tech that is thousands and millions of years ahead of us can overcome the obstacles suggests Time somehow erodes the laws of physics to allow magical technologies; we are closing in on a complete theory of everything and it doesn't look like it will support faster than light or time suspension or other magical shortcuts. I see science and tech development as S-curve not exponential or open ended. To the Question - echoing some other comments, vast distances and the limits the laws of physics impose - the difficulties in detection or travel across them - stand out as the most obvious and likely reasons we haven't found any aliens and why aliens have not found us. Any suggestion that we are being deliberately left alone requires evidence they are within range but are avoiding us - we don't have any. I think there is nothing but baseless conjecture to think that; I think not.

This isn't going to work, sorry. If something is turning CO2 into pure carbon, where is the oxygen going? What is powering the process? You can't make carbon from CO2 without using as much energy as carbon burning to make CO2 produces. Hydrocarbon combustion includes hydrogen becoming H2O but most of the energy is from carbon becoming CO2; any reverse process will use at least as much energy as burning the fuel produces with none left over for driving the car. Any collection of CO2 itself - leaving out any making it solid or conversion to "carbon flakes" - would accumulate around 3 times the weight of fuel burned, without considering the weight of the liquid metal and hardware required and the extra fuel consumption running it plus running a car that is much heavier. Battery electric cars powered by low/zero emissions energy are now a proven, viable low/zero emissions option. Major vehicle manufacturers are already committing to it.

I suspect modern physics is circling in on a complete understanding of the underlying physical nature of our universe - and I don't expect it to include opportunities for these kinds of technologies. Of course I would be pleased to be wrong. I see science and technological development following S-curve type progressions and think appearances of being exponential and open ended are illusory. I think that still leaves it open for a lot more technological progress, but probably not the giant leaps in spacecraft propulsion required to open up the possibility of interstellar travel.

I thought Einstein sought empirical evidence that his theory was correct; if it were true the bending of light by gravity would be demonstrated. If it were not correct that would be demonstrated too, but I don't think it was proposed as an attempt to disprove. Other people probably did see it like that. It works as Falsifiable in Popper's terms but not by any intent to conform to Popper's terms; Popper's ideas didn't get published until a couple of decades after the observations that showed Einstein was correct.

Assuming "ice age" refers to glacial maximum within this current ice age - Earth currently being in a glacial minimum within an ice age... No-one knows but climate history and understanding of climate change suggest thousands to tens of thousands of years and with it possibly delayed or even prevented by long term persistence of raised CO2. Not within the lifetimes of any person now living, unless some extreme and enduring rise in volcanic activity occurs first, that is sufficient to induce and sustain large scale expansion of global snow cover. That kind of volcanic activity would be a very strong hint.

I think the dispute becomes about creation versus abiogenesis, rather than versus evolution.