Ken Fabian

I think the cases of very long hair are from people whose follicles don't go through the usual catagen (shedding) and telogen (resting) phases - they are stuck in the anagen phase (growth).

FlyerDave - I disagree. The (getting old) "solar and wind can't work at large scale" claims are collapsing in the face of real world evidence to the contrary. Not suited to everywhere of course but most of the world's population lives in places where it can. Most new electricity generation being deployed in the world is now solar and wind. Long running electricity generators are investing in them in preference to coal or gas or nuclear for sound economic reasons, and because they do work - and to some extent to avoid potential liability for emissions in the future. Including in France. They are not stand alone technologies - not sure any technologies are - and backup based on various kinds of storage as well as network interconnections and demand management will increasingly be a feature of grid networks that have growing amounts of them. Being based around energy storage, EV's can be a useful complementary technology that moderates demand variability within such a grid and better aligns it with variable energy availability. It is not uncommon for current EV owners to charge them using their own rooftop solar. Obviously this has limitations - yet I can foresee having an electricity supply contract that accommodates EV charging elsewhere within a nation's electricity grid, effectively allowing me to use my home PV contributions (with some surcharge) wherever I am. Car parking with EV charging I expect. It is likely to be a source of reserve storage for PV fitted homes - and vice versa. And home and EV storage may well be an emergency reserve for grid management to draw upon, under suitable contractual arrangements. What a climate responsible low to below zero emissions grid will look like is still uncertain but for a number of sound reasons wind and solar look likely to be prominent. Some nuclear is likely to be a feature but closer examination shows it is not the simple or effective or low cost emissions solution it is so often presumed to be.

Most current infrastructure will be replaced over that time as well as a lot more built - no matter which energy and emissions choices we make or fail to make. It is almost a given that whatever we do will be much more, at scales never seen before. Markets will reveal our limits as we approach them (even if foresight doesn't work) - if some important resources can't supply demand then the price goes up and other options will look better. Market forces (even without the conflicted politics) are against massive growth of nuclear - it is now cheaper to build solar and wind in most places; without clear overriding long range government policy plus lots of subsidy support it won't happen. The World Nuclear Association thinks we could reach 25% of global electricity with nuclear by 2050 - with strong US and other government backing for emissions reductions and strong carbon pricing to make it competitive with coal and gas; neither look likely and the same people who continue to claim we should build nuclear rather than Renewables tend to be the same ones who oppose strong climate policies like carbon pricing and policies that make fossil fuels less competitive. And even with strong government support, it is not the best and cheapest solution that advocates seem to believe. Wind and solar will reach that 25% target within the next decade, even with conflicted climate and energy politics. Electrification of transport - based around energy storage - complements intermittent and variable wind and solar supply, with charging cheapest when power is cheapest and an increasing ability to use smart management systems to take advantage of that.

I suppose some people think grapefruit are delicious but I am tempted to call you strange for that! Not that I eat lemons, except mixed with other things - perhaps mixed with other things I would like grapefruit too. Only needed perhaps twice a week, so effectiveness is not an issue. More surmising here, that enough bacteria are killed from the acidity to have a lasting affect. Jona173 - I suspect finding appropriate chemicals was more trial and error than any understanding of the chemistry and physiology of how antiperspirants work. I hadn't realised they cause sweat ducts to be physically blocked. I would have thought sweat would push past a gel blockage. Whether the sweating itself is impeded by the higher pressure or it is reabsorbed by the sweat duct is a question that comes to my mind next - and those would be different for eccrine sweat glands and apocrine. And I wonder whether that is a potential trigger for skin irritation.

The vinegar smell dissipates very quickly, but probably lemon juice would work as well. But why would anyone have grapefruit on hand?

I don't have any idea why they work - but after years of skin rashes in my armpits I switched to using a few drops of white vinegar instead of antiperspirants. Technically speaking it isn't one; it doesn't suppress perspiration, but does prevent unpleasant odors. I surmise that is by suppressing the bacteria responsible.

I don't think people frozen when they die will ever be revivable. Freezing healthy live people would seem to give more likelihood of success - the frogs that survive freezing were live and healthy, not dead when they got frozen. But I expect the process will kill anyone who tries it. Any volunteers? Until there are successful trials with mammals it is all speculation. I am not aware of any such successes. Science fiction themes using cryonics to make interstellar travel in a single lifetime possible are common enough - with healthy people. Not always freezing is used, sometimes induce torpor or hibernation - which seems to me (with zero real knowledge) more achievable.

That makes it sound simple. Cheap and easy, even. But I think the devil will be in the details and I think those details will remain prohibitive. Every piece of equipment, which has to perform under extreme conditions, has to be developed and built and tested and deployed, all at enormous cost. Robotics adds a level of complexity - developed entirely by Earth based industry with Earth based resources - and has a very long way to go to be really be considered a durable and reliable means to run remote mining and refining and launch vehicle refueling and refurbishing on the Moon. Surface collecting or other mining of what? I see no evidence there is going to be much in the way of concentrated ore bodies apart from meteorite fall sites and those will be nickel-iron rich but poor in almost everything else. And doing all this will make operating a tourist destination in space cheaper and easier? Which will somehow thrive and support more Moon mining because of Moon mining - and people will want to live there and somehow they will thrive? Sorry I just do not see how this would or even could work.

As I understand it the IR collected by the rectenna and converted to electricity would not be raising the temperature of the collector, and the re-radiated heat will be only from that portion that was not converted, plus diode or other heat loss - these are not converting 'heat' to energy but converting EMR. That should be independent of the temperature of the collector.

Whereas I don't see how we can develop space resources except as economically viable commodities for trade with Earth. I keep coming back to minimum pre-investment thresholds being very large for things like space mining - that starting small, such as is suggested by mining initially servicing in-space activities may not be feasible. And I also keep coming back to what are they doing in those space stations that makes enough income to support that mining as well as itself? Because it would be such a big project to establish mining, refining and space launch facilities on the Moon and it is way beyond economically viable to do so I think it will remain cheaper and easier to keep sending stuff up from Earth. Launch and other costs will remain a huge impediment - so I don't think these hypothetical space activities will lead to a thriving space 'economy'.

Perhaps 0ptical Rectennas (aka nantennas) could work as an alternative to air conditioning - in theory these should be able to convert IR to electricity and remove heat from the surrounds in the process. Like old style 'crystal' radios, they should convert EMR to electricity, independent of the temperatures of the radiant source and collector- the cooling would be from energy absorbed not becoming heat in the collector and not being re-radiated in turn. These currently don't work because diodes are not fast enough and are losing too much energy through heat loss - but that is not an intrinsic property of diodes and better ones remain a possibility . Of the many possible technologies we have not yet succeeded at, I rate Optical Rectennas as one with a lot of potential; they should be able to utilise bands like IR as well as visible light and be able to make use of ground heat that radiates up as well as atmospheric down radiation, ie will make power day and night. It may also have uses for energy recovery from low grade heat and make new kinds of thermal energy storage possible.

Not at all, however to kick off those grand space dreams I think it is essential. There is existing and then there is thriving; economic success is the very definition of a colony thriving. Especially as the costs to do anything in space are very high, the need is for extraordinary opportunities to generate sufficient income and I don't see them in any base on the Moon or Mars. I am not seeing them anywhere much beyond Earth orbit. I think raw nickel-iron is the best resource with economic potential space has. My 'vision' of a space mining industry would try for an absolute minimum processing (can space cold Ni-Fe be shattered to be more manageable? Cutting it into manageable portions could otherwise need a lot of energy and equipment). It would need to deliver very large quantities at very low prices to Earth markets, on the order of a thousand US$ per ton, delivered; if someone can find a low cost way to extract the precious metals out of it, so much the better, but wouldn't count on that as the way to make the venture work. I can see how that might use facilities and a workforce in Earth orbit. I remain doubtful the costs can be brought down that far, but my instinct is that, if raw Ni-Fe metal is abundant, it is the best existing opportunity. And instinct again says only big scale could work - and that requires a business plan that investors have a lot of confidence in; the economics have to stack up. If there is no space mining to service there may still be industrial processes - although they would have to be exceptionally high value, multi-millions per ton high. Drugs maybe? I'm not really seeing anything emerging from ISS work. I've heard of batches of below spec micro processors being sent up, heated in zero gee, to have defects clear up, but not using the ISS or manned rocket. Given the constant advances in manufacturing that could be a short-lived opportunity. Use of space resources is a threshold that could prove very hard to achieve; Beyond that I can see meteor defense becoming a serious long term space project, sustaining a continuing human presence in space.

In my view the renewed passion for going back to the moon is on shaky ground. My views on this are not secret - that I think there is no economic basis for such ventures and that without it it will struggle to be more than a feel good exercise in nationalist pride building through showcasing aerospace capabilities . It will be very, very difficult, dangerous, expensive and won't advance grand space dreams or advance humanity on Earth in any substantial way. If it does happen it will be reliant on continuing subsidised supply lines with transport costs that, even optimistically, be astronomical; it will still be multi-million US$ per ton to reach the Moon. The capital costs of a functional launch facility that can turn around, refuel and repair re-usable rockets is, well, astronomical. No mining will make sense except to reduce the huge costs for the most basic things like water and air - and if the most basic things are such a big deal the prospects of things growing from there are slim indeed.

Do you include the externalised costs - climate and health - as part of the cost calculation? I don't think any estimates of the costs for various energy sources will be valid if those externalities are excluded; if, as some efforts to quantify those costs show, the costs are likely to be quite high (above US$40 per metric ton of CO2 emitted) then there are sound economic reasons for turning to alternatives. Do we consider the opportunity cost as well? If productive agricultural land is diverted to biofuel production the production of other things gets curtailed. None of this looks simple to quantify or the results anything but estimates with wide error margins. If we choose to leave aside climate and respiratory health costs and look purely at the highly misleading immediate monetary values and act like those other costs don't exist, then it sounds like ethanol from corn is still a lot more expensive than fuel from crude oil. Sugarcane based ethanol costs look better but are still high. Yet the difference is not so great that a price hike for oil could not change the balance in favour of ethanol - Brazil produces ethanol for around 80c per US Gallon, which in many parts of the world (but not the US) would be considered cheap. If we choose to look at Energy Return on Energy Invested (EROI or EROEI) then oil looks like this (with rising costs as easy reserves get depleted and more difficult ones get exploited) - The losses are covered by using more crude oil and fuels made from it than hits the open market, times five - producing fossil fuels is a big source of global emissions. Add in climate change and we could choose to look at total energy, including the climate system's heat gain - in which case each MJ of energy from all sources (ultimately as waste heat) is eclipsed a hundredfold. If we faced an imminent ice age that might be useful heat - except the quantities of CO2 (arguably, it is more than any other substance we make) already exceed what would be needed to do that.

Doesn't gravity connect what is inside the event horizon with what is outside?

Maybe it's easier to comprehend rocket thrust as coming from pushing those gases away (like pushing against rocks as you throw them) rather than (incorrectly) the stream of gases pushing against something external (which is like the rocks hitting something after you throw them).

I'm inclined to let discussions play out so long as no-one is being rude or offensive. I found the topic already closed when I looked; very likely it would end up that way and no genuine breakthroughs would be revealed yet there is always opportunity to learn or teach. Or amuse. I would have asked if, having found a means to make low cost low emissions energy that could save the world from climate destabilisation, should an inventor withhold all knowledge of it? Saving the world isn't enough?

There have been efforts to quantify emissions from deforestation. I had a quick internet look and it doesn't appear to be simple - and some studies look purely at deforestation without consideration of reforestation and forest growth - or other GHG output like Methane - giving about 10% of global CO2 emissions between 2000-2005. Historical emissions will be more difficult to quantify. Not precise enough maybe, but deforestation has occurred in addition to great increase in fossil fuel burning; I don't see how, given the amount of fossil fuel burning, for which we do have good estimates, that deforestation would be the primary source of raised atmospheric CO2 in the present.

I think the sexual urge in humans is not precisely targeted - perhaps cannot be given that there is not a clear fertile oestrus period and a lot of sex is needed to result in reproductive success. There are a variety of potential triggers that have little or nothing to do with fertility - and yet it is a strong urge that can also be socially disruptive, especially for those who do not have socially sanctioned mates; outlets for that sex urge that do not provoke conflict include masturbation and homosexuality. I think homosexuality reduced sexual conflict and aided overall social bonding within groups of early humans. It seems clear that homosexual inclination or preference does not necessarily prevent hetero sex - lots of 'gay' people have and want to have children and can have hetero relationships to enable that - so only more extreme forms that prevent successful hetero sex would be unable to reproduce; less extreme forms do not get written out of the genome.

Environmental change can be good or bad depending on how much of a stake we have in stability and the absence of excessive or too rapid change. Australia's mountain pygmy possums are unlikely to survive global warming - were they equipped to think about it and tell us they would say that is an environmental change that is bad. Humans who accept that climate change is real and serious mostly appear to conclude it is bad for humanity and things we cherish, such as remnant natural ecosystems. We are still learning just how far reaching and persistent the consequences of micro-plastic waste are on marine life - and other environmental change is being found to have serious downsides. Take a very long view - and ignore the near term - and it becomes possible to conclude it is not bad. I would disagree.

Huh? What you mean is still not clear, but it sounds to me like you expect the occupants to experience less G-force than the overall acceleration of the spacecraft? If so, no - if you get acceleration, that makes (is?) the G-force - and the G-forces the ship and occupant experience will not be "equalled out" by putting the spacecraft in between two nuclear detonations. The idea of using nuclear pulse rockets has been around a long time but they will operate within the known laws of physics, which doesn't include a means to accelerate without the acceleration.

I don't understand what kind of beneficial "difference would equal out" effect you expect to occur. I don't seen how anything would be gained from detonating anything inside a spaceship. Designs exist for nuclear pulse rockets, such as "Orion" that detonate nuclear bombs behind a deflection plate with shock absorbers. Other kinds of nuclear pulse spacecraft have been proposed. Like above ground nuclear testing, proponents insist there is insufficient evidence that this could have harmful consequences in Earth's atmosphere. Not convinced this is a safe space technology, in or out of the atmosphere, but others may disagree.

Sounds like my mistake is thinking that the slice through a cone must be asymmetric top to bottom - that the part of the curve closest to the point of the cone would be different (tighter curve) than the part of the curve closest to the 'base' - and that it must be a different shape than what you get when you slice through a round cylinder. It seems counter-intuitive to me, that a slice through a cone makes the same shape as a slice through a cylinder. I had always thought an ellipse was like this - And if this is not the shape of a slice through a cone and is not an ellipse - what shape is it? (besides 'egg' shape)

No point trying showing me the equations - my algebra crashed and sank very early, on the rocks of factorisation. Is the shape made by an angled cross section of a round cylinder the same shape as the angled cross section of a cone? I have to say they look different to me - and my confusion about what is and what is not an ellipse is not being relieved so far.

My confusion is not diminishing. My command of correct terminology is poor, but yes, I do understand that there will be a range of angles within which a cross section through a cone that make a 'closed' shape called an ellipse - that at other angles it will make hyperbola and parabola, or at 90 degrees, a circle. (Although it makes my head hurt thinking about the precise angle, parallel to the side of the cone, where it stops being 'closed'.) 'Oval' can loosely describe a variety of shapes but I was thinking specifically of the closed curve you get with an angled cross section through a round cylinder - which I say is what the "sum of distances" definition of an ellipse describes - a curve that is symmetrical both ways. A cylinder may be seen as a special case of a cone - one with a 'point' of zero degrees - but a slice through a cone with other than zero degrees does not produce a curve that is symmetrical both ways. If you like, when I think of an ellipse I think of a shape where the semi-major axes are not equal - only the semi-minor axes are equal. I would call this eccentricity (like in an eccentric orbit) except the term looks already taken, for describing the difference between major axis and minor axis. I don't see how that shape can be made with the "sum of distances is constant" definition - seems like an additional parameter is required. What I think of as an ellipse resembles the cross section of an egg - but I would think an ellipse is it's very own, unique curve, not a combination of parabolic and transitionary curves; that will only be an approximation. Are you saying the conic section version of an 'ellipse' does not actually have a fatter 'bottom' than top? ('Top' being the part of the curve nearest the point of the cone) ie it will be mirrored top to bottom as well as left to right, and my belief that it resembles the egg cross section is just wrong?