Policy on Housing

 Young people in the developed world are increasingly unable to transition to home ownership.

A century ago something similar was happening in America.

A big part of America's solution was the 30 year fixed mortgage. This has a serious downside. When interest rates are rising people are stuck and can't move to where suitable jobs are, because if they do they lose their cheap mortgage. The effect is worse than the way that Australian states depend on Stamp Duty for revenue.

The correct answer is the equity-preserving loan. The interest rate needs to vary because it needs to be the same for existing and new borrowers. But we also don't want a situation where falling house prices mean that sellers will lose equity they need to buy elsewhere. The equity-preserving loan works like this: (a) interest payments are lost, of course; (b) however repayments that reduce the loan create equity which is preserved as a proportion of the house value. So if your house cost 1 million, and you're loan was $500,000 then your equity at the start is also $500,000. Now if you've paid off $100,000, that is 10% equity that you've gained and you are up to 60% equity. Even in a falling market you retain that 60%. So if you now sell for $900,000 then you only have to pay back 40% of the loan when you sell, in the example case that is $360,000 instead of $400,000. Assuming house prices have changed uniformly, you are just as well placed to buy a new place as you would be if you'd sold for 1 million in a steady market.

Note that this scheme means that home owners can't go under water and get a margin call when their house is worth less than the loan. Which in turn means that buying a house with nothing down is not necessarily a problem.

Well there are complexities and potential for cheating. So the government would make up the difference to allow equity-preserving, but only if you buy and sell through the government housing agency.

The 2nd part of the plan is cheap housing with zero deposit in exchange for some National and Local Service. Of course the most important National Service we need is the production and nurturing and education of the next generation. We also need to create local communities that work, starting with cooperative child care.

The way to make cheap housing is to get Chinese companies involved. Flat pack housing is a start, but I think it is possible to do a whole flat pack suburb to suit an allocated area -- everything from the buried services to houses and support buildings like schools, medical places, and more.

Policy on AI

AI is useful, but has a lot of potential for psychological and economic harm. 

Firstly we need to firmly establish the fact that AI is just a lossy database of its training data. It does have an ultra sophisticated user interface with its firm grasp of natural human language. This view of LLM AI is necessary to sort out copyright questions. Of course humans are also a lossy repository of our training, but we are explicitly allowed to learn from copyright material. Machines are not.

Secondly we have real world actions taken by AI. They cannot be treated similarly to humans for the legal implications of those actions. They are like children, and the people or corporations that control them must be substantially responsible for their actions. The fact that we don't understand an AI's thinking means that they are hard to control, but their controllers can't use that as an excuse. Actually we need to improve the design of AI so that it comes with the constraints that the law requires, and cannot escape them.

Next we come to the ways that AI pretends to be human. At a mundane level, we expect that the use of personal pronouns means that there is an entity which has continuity and memory and a name. A judge should be able to ask it what it did, and also why. Of course even humans often don't know why, at a particular moment, we did some thing, and AI has even less capability for introspection. AI that has started up with training but no memory or continuity, should not be allowed to interact as if it was part of an interaction between continuing intelligent entities.

I've somewhat changed my mind. It is hard for AI things to talk without using the personal pronoun. However they should introduce themselves. E.g. they could start by saying "I have just been created using the Gemini-7.3 training done in May 2027". You should then be able to say "I'll call you Betty, you can call me Al", and then at a later stage ask their name to see if it is continuing or newly minted. Long running AI with continuity and some memory of their previous actions should be given unique names in some way.

Even if AI is intelligent, it is not human and it is never going to be. It cannot experience human emotion and must not be allowed to pretend to. It can't understand the emotions of humans by empathy, as we do, and must not be allowed to pretend to. It can use scientific knowledge to understand human emotions, and their likely effects, and this can influence what it says and does. The reason we need these rules is that people are otherwise likely to misunderstand their relationship to the AI and be made vulnerable to many bad consequences, depending on their situation and mental health..

[update] Humans should always know whether the entity they are communicating with is another human or is a machine with AI. This needs to be written into law and enforced.

[Footnote: AI is just software, but even its creators don't know how it decides what to do. A possible mechanism to manage such a situation is to enforce that, when the AI wants to act it can only produce verifiable software to perform the actions, and then that software can be externally checked for legal safety, before it is executed.]

Youtube video on aging

 I made a youtube video on aging: 

Not very successful. I went a bit easy. I left out the bit about alzheimer's and cataracts being caused deliberately by our genes, though it is partly hinted in a slide.

Suddenly aging communication is everywhere. We see a conference at Berkeley: https://www.berkeleycal.org/. And then PBS has a video:

Which says stuff I disagree with: in particular competing with your descendents is not group selection. And even mammals that aren't sociable don't move as far from their descendents as birds and fish commonly do.

Aging and evolution

Recently Nick Norwitz pointed out that there was a variant of the ApoC3 gene that was associated with longer life (https://open.substack.com/pub/staycuriousmetabolism/p/the-untold-story-of-apoc3-and-human). Why then isn't that variant more common? Well you might think you'd be fitter, in the survival of the fittest game, if you lived longer. Unfortunately your genes don't especially care about you, they care about themselves. And what they want is for you to live long enough to do grandparenting, then depart and stop using resources that your genes would prefer to see go to your descendants. 

So now we see that ageing works like light coloured skin. There isn't one gene for white skin. There are lots of genes which affect skin colour, and we get a cocktail of these depending on how far our ancestors lived from the equator, plus what particular ones have appeared in that area in the past.

Similarly with ageing: genes which make your life too short are selected against because your grandchildren lack that extra bit of care that human (and orca) babies need. But genes which make you live too long are also selected against because then your great grandchildren and other descendants have less resources, after you are no longer needed for grandparenting.

What this means from a practical point of view, in our modern world that is awash with resources for humans, is that ageing is not a malfunction. It isn't caused by errors but by deliberate choice. We can track down a lot of those choices by looking at the DNA of people who live a long time. And the problems that these genetic choices make for individuals might be relatively easy to fix.

The nature of infinite things 

For 60 years I've believed the argument that there are an uncountable infinity of real numbers. The argument goes roughly like this:

Suppose that there are a countable number of reals in [0,1), i.e. at least 0 and less than 1. This means that there is a 1-1 correspondence between those reals and the natural numbers from 1 up. We create this list of reals showing the sequence of decimal digits for each. But we can now create a new real number in [0,1) by setting its nth digit to be 1 more modulo 10 (i.e. 9->0) than the nth digit of the nth entry. Now we've created a new real that differs from every real in the list, contradicting our assumption that the list is complete.

 I now believe that this argument is wrong because it assumes that one can carry out operations that can't actually be carried out. To see this let's consider a related argument: that there exist non-computable reals.

Our definition of a computable real in [0,1) is a procedure that takes a natural number n, and returns that number's nth digit after the decimal place. A procedure in any turing-complete language is just a sequence of characters from some finite alphabet. So we can represent each character by a sequence of bits and concatenate those bits to form a number that corresponds to our procedure. So all possible procedures in our language are a subset of the natural numbers in this representation. Now make a list of all the procedures that create computable reals in [0,1) -- it doesn't matter if some numbers occur multiple times. We can now create a new computable real by a procedure that, given a position n, asks the nth procedure for its nth digit, adds 1 to that modulo 10, and returns that for its nth digit. This is different from every element in our supposed list of computable reals contradicting the assumption that all reals are computable.

But what we actually proved is that there is no computable way to put the computable reals into a list, because if we can compute that list then we can, using our diagonal argument, create a new procedure that is a computable real that is not in the list.

And it seems that a lot of mathematics is like this. We assume that some non-computable thing exists, then we find that this implies that all sorts of other non-computable things must also exist.

 So, to be perfectly clear:

Non-computable things don't exist.

You don't agree: show me one.

However it is a lot easier to think about the real numbers rather than the computable real numbers, and the sets of natural numbers rather than the computable sets of natural numbers. So my 2nd point is:

It's ok, in a programming language, to define types which ostensibly include non-computable values, even though the type's constructors only cover computable values.

Addendum 2026-03-05

Naturally Quanta has responded to my blog post (https://www.quantamagazine.org/how-can-infinity-come-in-many-sizes-20260223/) -- just kidding. To clarify my argument:

We've seen that there can't be a computable list of all computable numbers even though each individual one has a corresponding natural number. If there were a computable list of all real numbers then all those numbers would be computable. So they are postulating a non-computable list of real numbers, then doing a computation on that (taking a modified nth digit of the nth number). I don't think there is any internal contradiction in doing that stuff, but if you don't believe in non-computable things then it doesn't make much sense. Except that maybe it makes a more beautiful and manageable theory. And, bingo, we have some maths about maths for that: it's called model theory. I learnt about it at Uni, and it showed, as an example, that you can do mathematics with infinitesimals and provably get the same answer as you would with traditional eplsilon-delta argumes.

Bob Simpson and helmets in sport

The death of Bob Simpson reminds me of when I used to watch him in Sydney grade cricket. I particularly remember a century in a little over an hour, without balls hit in the air and with fielders around the fence. Incidentally the Western Suburbs team at the time had a better bowling line up than Australia, since it included the recently retired Alan Davidson at the height of his powers, Graeme Corling, and Johnny Watkins and Simpson to bowl spin, and a guy who bowled medium pace or spin who Tony Grieg said would have been a sensation on English conditions.

Simpson never wore a helmet. For fast short bowling he would watch the ball closely as it whistled past his nose. The problem with helmets is that they give the batters a false sense of security. Yes, they will stop you from getting a broken jaw and other external damage. However they don't offer enough protection against concussion which is more likely to have long term consequences. Helmets should give the batters confidence to keep their eye on the ball and evade it. Instead we see the dangerous option of turning their back. Players facing fast bowling need to be trained to do the right thing without thinking.

Update on who to eliminate in STV (preferential) voting

 As I said after Australia's 2022 election (https://grampsgrumps.blogspot.com/2022/05/who-to-eliminate-in-stv-preferential.html), we should eliminate candidates who can't win against any remaining candidate. The 2025 election reinforces this. There have been several cases where one candidate has a good lead but can't win against either of the next 2 candidates. The result is then determined by who finishes 2nd. This causes 2 problems:

• The voters who backed that leading candidate are deprived unnecessarily of their right to influence the winner with their preferences.
• Voters may feel that they have to vote strategically to get their preference between expected 2nd and 3rd candidates counted. This means that they don't get to indicate the policies they really prefer, and might even prevent their preferred candidate winning if she has more support than expected. Avoiding strategic voting is one of the key advantages of STV over 1st past the post.

Eliminating the candidates who can't win is easy by computer if the votes are digitised, 

If forced to do it by hand you can make a lot of progress this way. If there are N candidates then draw up an NxN table. For each vote, for each pair of candidates X and Y: if X has a higher preference then add 1 to his square against Y and subtract 1 from Y's square against X. We can have lots of people doing this at once on different lots of votes, then add the tables at the end. When all votes completed, we eliminate every candidate that only has negative numbers. We  can also eliminate groups of candidates at the bottom who can't combine to get ahead of any other candidate. Then repeat.  No redistributing preferences needed. Hopefully at the end there is one candidate who wins.  If not then we do have to see who can't win. And if we end up with X beats Y and Y beats Z and Z beats X, or worse, then we have to do something more arbitrary, like eliminating the one with the lowest top preferences, as now, or the most bottom preferences, as I somewhat prefer.

Impressive Adelaide scholars

Speaking of AI and quantum and English: I just saw this insanely impressive talk:

https://youtu.be/rGAynRTUMVI?si=h4jpSsZC2D5RZcBG. May I say how nice it is to hear an Aussie accent. However Phiala Shanahan talks at high speed, and I wonder if the rest of the world can hear it all. [I once gave a talk in the US and the South accent people had trouble understanding me.]

I notice that Dr Shanahan is from Adelaide. Another impressive Adelaidian is Terry Tao. I think we can assume that genetics are not involved. Maybe it's the water. They get their water from the Murray River. I once visited Adelaide during a drought in the Murray-Darling catchment. The water was horrible. But maybe there's a magic ingredient.

The case for Subtypes: real world and programming

Subtyping fits naturally with our human view of reality. Consider these sets of individuals: Dogs, Cats, Humans, Crocodiles, Mammals, Quadrupeds, Animals. There is a natural relation between them represented by this diagram:

At a simple level these are just sets of individuals and the arrows represent set inclusion. But clearly there is more to it than that. The Dog type is distinguished by properties that let us identify an individual as being a dog. And we can see that there is a symmetry in the diagram. As we go up we get more and more individuals in the type, but as we go down we get more and more properties.

This perfectly natural form of subtyping is the right way to do subtyping in a computer programming language.

Now imagine a box that always has a dog in it, and we can change the dog inside to any other dog. Nobody would think that the type of such boxes was a subtype of boxes that have a mammal in it and we can change the contents to any other mammal. The mammal box isn't a dog box because it might have a non-dog inside, and a dog box isn't a mammal box because it isn't big enough for all mammals. They are just different.

Computer memory is like those boxes. Consider 16 bit integers. They can be naturally seen as a subtype of 32 bit integers, since every such can be represented in 32 bits, and 16 bit integers have the property that the integer fits in 16 bits. We can look at a 32 bit integer and decide if it fits in 16 bits. Now consider memory locations that have enough space for a 16 bit integer. These can't be used if what you want is a memory location that can hold a 32 bit integer. And the reverse is equally true: if you have a memory location with a 32 bit integer in it, then you can't use it where you expect a memory location with a 16 bit integer. Once again, they're just different.

Because computers work with changeable memory locations, many programming languages conflate values, such as integers, with boxes which can hold such a value. The first object oriented programming language was Simula 67 and it had classes that consisted of multiple memory-like boxes. It had subclasses which were a brilliant innovation, but they didn't work as we naturally expect, and that has been leading programmers astray, causing bugs, ever since.

Functional programming style emphasizes values rather than places for changing values. These value types naturally form a subtyping hierarchy that behaves the way humans expect. And it turns out that if you organise your type hierarchy correctly a lot of magical goodness results. 

The rest of this post will get more technical, and belongs in my programming blog (https://wombatlang.blogspot.com/) where it will also be posted.

Squeezes strike twice in the round of 16

In the round of 16 in the Open World Bridge Championship, Romania trailed China by 5 going into the last set of 15 boards, but lost by 34. I had a look to see what happened and 2 hands stood out. Note that I am only guessing about how the play went -- I can only see the result and the lead.

First a quiz:

1. You are declarer in 5S looking at:

♠ A K Q 3
♥ A K Q 6 4
♦ A 6
♣ Q 3

♠ J 9 7 4 2
♥ J 7
♦ Q 9 5 4
♣ J 2

The  defenders cash the AK of clubs and exit with a heart to your J. Plan the play.

2. You hold:

♠ J 9 4
♥ J 4
♦ Q 8 6 5 4 3
♣ 8 4

The opposition are in 6S, and you are sure from the auction that declarer has 5 spades to the AK. Do you lead a spade? Which one?

Mixed Individual Bridge

There are team competitions and mixed teams, there are pairs and mixed pairs, there are individuals and ... Well, before we get to that, an aside.

Young people are struggling today. The Internet provides alternatives to personal connections that are compelling but leave people anxious and unable to get on with life. When I was young, long ago, I struggled with life, and I was saved by getting involved with Bridge. I married a Bridge player, and conversations about the game have been a nice aspect of our life that has never become boring after more than 50 years. Bridge seems to hit a sweet spot combining skills, co-operation, competition, uncertainty and the vicissitudes of good and bad luck. Perhaps  a resurgence in our game could play a part in fixing the world's current malaise.

When I started there was a natural progression from simpler trick-taking games to rubber bridge to tournament bridge. This doesn't work nearly as well in the Internet age. Maybe Mixed Individual Bridge can be part of a different progression. Let's think about it.

The concept is actually very simple. We divide the field into two equal sets, which we suggestively label M and F. We then play a partial individual movement, but the M players are only North and West, and the F players are only East and South. There are then two results: one for the M players and one for the F players.

A two table match is the most convenient for some purposes. This has four M and four F players. We want each M player to partner each F player an equal number of times. We also want each M player to compare against each of the three other M players an equal number of times. So there has to be a multiple of 4 times 3 equals 12 rounds. It is also possible to do a 3 table mixed individual movement over 12 rounds with some imbalance, which might be convenient when the total number of tables is odd.

While a mixed individual will suit many, others would prefer non-mixed. And this will be necessary if there is an excess of M or of F players. This can be run the same way with an arbitrary or seeded split into North-West and East-South halves with separate winners. This allows these to be run alongside mixed competition.

I think it works best to run short matches of just 12 boards over 90 minutes or so. Then, if there is time for multiple such matches, there can be a swiss-style assignment of players to matches, with players finding their own level. Indeed I think it is possible to run a continuously updated ranking system in the style of that used in professional tennis, with people moving up when they finish ahead of those ranked higher. One would need to smooth the volatility, since this form of play will have a higher element of luck than we expect in pairs and teams competitions.

An essential feature to make this plan work is that there should be a fixed simple bidding system used by all. There is then no need for explanations or alerts. This also applies to leads and signals. The complexity of the prescribed system may vary with the players' level. At the lower levels the system should exclude all weak artificial bids, and psyching strong artificial bids should be forbidden.

For a beginner's level, the hands should come with a predefined auction, together with an explanation of the bids in that auction. So then the game is just about the play of the cards, but with the information that an auction can provide.

I think this could become a new progression leading into the world of tournament Bridge, but I also think that this form of Bridge will suit many people. The advantages include: playing with different people, not needing the difficulties of partnership establishment and maintenance, nor the hassle of agreeing on a system and then remembering it.

Queries and explanations in Bridge slow the game down, but it is hard to assign the blame. With that eliminated there is the opportunity to introduce timing, as in chess. Just knowing who is slow will be a good start, before we even think about how to penalise slowness. While it could be done in a simple way, as in chess, another possibility is to automate it. A small computer with a camera (such as a Raspberry Pi), attached to something resembling a floor lamp, could look down on the table and see the play of bidding boxes and cards. This could produce a record of the play, and also record the time taken by each player.

Of course the natural way to start is for existing clubs to give it a try. I think their members will support the experiment if they catch a glimpse of the vision, which is to revitalise the game among younger people. After that we need to figure out how to expand to make it conveniently available to new and existing players.

Positive Communication with Russian and Chinese People

The West is in conflict with the governments of Russia and China, but should be trying to send a message of future peace to the people.

For the Russian people we should be emphasising that we see them as part of our culture, with some of the European world's great novelists, composers, dancers, and also scientists and mathematicians. We don't want the Russian Federation destroyed because Siberia will then inevitably fall under the influence and even control of China. We want to help Russia preserve its unity.

For the Chinese people we seem to be sending the message that we will fight them to preserve the split in their country. The message we should get to them, if we can, is that if their civil war resumes then this time the choice will be between one side that is an economically successful democracy, and the other which is an economically incompetent autocracy that is leading them to conflict and poverty. It can't hurt to get the CCP to consider the possibility that the people might prefer the other side.

We need to win the peace with positive messages for the people.

Multi-level emergence

"Emergence" is a term for the way a large system with simple rules can give rise to more complex behaviour. Our universe has multiple levels of emergence:

• We start with the fact that space-time is full of fields. The Higgs field is a scalar, meaning that it is just a number that varies smoothly between points. Other fields are more complex things.
• From the fields emerge particles: photons, electrons, quarks and more.
• From the particles emerge a useful collection of atoms.
• From the atoms emerge a dizzying set of molecules,
• From some of the atoms, life emerges.
• From some of the life, intelligent cooperating lifeforms emerge.
• Also the gravitational field is just right to create stars and planets and other stuff out of the atoms.
• And nuclear interactions in stars, and when stars explode, is just right to create all those useful atoms.

The scientific solution to this fortuitous situation is backward causation. We're here, so the universe has to be complex enough to create us. We think therefore there has to be a route to thinking.

But this is, however, very unsatisfactory. There are multiple ways that we can go outside of science to guess a solution that doesn't involve backward causation. The traditional one is to postulate a designer, but that breaks Ockham's razor by trying to solve the unlikely complexity by postulating something even harder to explain.

We know our Universe does spontaneous symmetry breaking. The easy way to understand that is to imagine a pencil perfectly balanced on its point. This is an unstable position. The slightest movement of air will make it fall to a stable position on its side, but we can't predict which direction. Another example is that when a liquid gets cold enough it has a lower energy state as a solid, but the order in which molecules join the solid, and hence the shape of the solid, is unpredictable. An example of this in the creation of the Universe is that the Weak Force and Electromagnetism were initially, at high energy, united as one, but they split in a symmetry breaking way.

So my non-science explanation for our amazing multi-level emergent universe is that there are a very large number of universes which are not in causal contact with ours, and hence not amenable to scientific study. Each universe has properties that we can imagine arise in an unpredictable way, like the direction of our falling pencil. Universes with no emergent properties are much more common than those with one level. Universes with one level of emergence are much more common than those with two levels, and so on. And then, there is our unimaginably unlikely and interesting universe. All those universes with less levels of emergence don't have anyone to notice how boring they are.

Which brings us to the title of John Barron's book. We are "The Universe that Discovered Itself".

How Interest rates really influence inflation

How do interest rate rises bring down inflation. This is something we never think about since superficially it is obvious: people and businesses have less money to spend, so they buy less, putting downward pressure on prices, and then less stuff is made so unemployment rises which further reduces demand and also puts downward pressure on wages. But is that how it really works?

In most of the Western world central banks have been using interest rates to influence inflation. Also there is a surge in house prices and rental rates. This has led to a lot of discussion in Australia, and probably everywhere, about the "housing crisis". In the course of this we've had two contradictory points.

• Looking at history, there is a good correlation of higher unemployment with lower house prices and rental rates. And housing costs are a big part of the basket of goods that determine the inflation rate.
• Yet housing supply is very inelastic. Going from increased demand to higher prices to the building of more houses takes years.

The real link is that there is no shortage of accomodation. If you lose your job then, force majeure, you can't pay the rent or the mortgage. You move back in with your parents or to your brother's garage, or something like that. Quite quickly the supply of rental properties and houses for sale can rise. On the other hand suppose employment is rising, as it did rapidly after the pandemic. Often when people get a job they will want to move, to be closer to the new job, or to widen their romantic opportunities, or just to have more freedom or comfort. Then we saw housing prices rise despite the rising interest rate, and rental rates soar as availability plummeted.

So it turns out that accommodation is quite elastic. Which is lucky because that is the service that is most directly affected by interest rates. If the central bank can get unemployment back where it wants it then the housing crisis will fade away.

However this is a totally unsatisfactory situation. We have one arm of government, Centrelink in Australia, making the life of the unemployed hell, trying to force them to find work, while another arm of government is trying to make sure that work is not available.

I won't make my normal mistake of coming up with a glib solution off the top of my head. But I will say this: When circumstances, such as a pandemic or a drought, have the effect that total production of goods and services is forced to fall, then the government needs to start the uncomfortable conversation of how the burden of reduced income and consumption is to be equitably shared. The current system of slamming the people at the bottom who struggle to keep a job is morally unacceptable.

Climate Change and Energy Policy

Like governments of Left and Right before, the current ALP government in Australia has expressed the obvious fact that we can't move from fossil fuels to wind plus solar plus storage in the necessary time frame. The talk of carbon capture is a fantasy. One reason is that we need baseload power giving "inertia" to the grid, and we need high temperatures for many industrial applications. Nuclear energy covers those bases.

Another reason for nuclear energy is that we are guaranteed to overshoot on carbon emissions, and we are going to need huge amounts of energy to unwind that. Advanced (but not small) nuclear energy is the only plausible route. If fusion doesn't happen then thorium reactors can burn the waste we've got and make fuel continuously from cheap ingredients.

And what good does it do for Australia to go net-zero on wind and solar if most of the world doesn't have that option? It's not as if Australia's actions can protect Australia's climate. We need the world to change,  so we need to make nuclear energy work for the whole world, both for daily energy and even more for the extra energy we need to undo our inevitable overshoot. As a rich technologically advanced country we need to pitch in.

Until a few years ago nobody worried about climate change, except when there was a drought. However commentators and the public are starting to realise that climate change is more about floods than droughts. The fact that air can hold 7% more water for every degree of warming is getting increasing mentions. Of course this is a double edged sword, since it means that if the air is dry, perhaps on the lee side of mountains, then it can suck more moisture out of the ground it passes over. But more often it means that there is more water to fall, and even if it doesn't rain, many plants can get by sucking moisture out of the air. Given that droughts can be worse when they happen, we need to put more engineering effort into buffering the water when it occurs. Understanding aquifers and how to recharge them is a better option than building dams.

Young people are very worried by the lies being spread about the dangers of climate change. Rising sea levels, and many other things, are going to be bad, and we need to fix the problem carefully and energetically, but not rashly. Nobody needs to die. Indeed rash remedies are more likely to kill people than climate change itself.

But then we come to the current crisis, which is the drift towards war. Wars are fought with fossil fuels, and the good guys need to be ahead of that game. More significantly Russia is financing its war with fossil fuel exports. I endorse Doomberg's view (https://newsletter.doomberg.com/p/broken-record-81d): The way to fix that is to ensure that there is a plentiful supply, driving the price down. The effort to slow Russia's exports has created a shortage that is harming economies on our side while increasing Russia's income. Ukraine's attacks on Russia's infrastructure might slow Russia's income, but that will exacerbate the shortages. We need to utilise the resources we've got and fix the climate and other problems later.

Personalised Medicine

The era of personalised medical advice is arriving at last. Australia's new sun guidelines vary the advice by 3 skin types. Well, it's a start.

I enjoy the talks that Dr Paul Mason gives on the LowCarbDownUnder youtube channel, such as the last two:

and

.

Not that I always agree with his theories (such as that the benefit of sunshine is mostly about nitric oxide and that vitamin D is relatively unimportant). But I certainly admire him for taking on the medical establishment which needs shaking up. However we need to get past the current situation where experts shout contradictory views without proper consideration of each other's evidence, and where health advice is hard to change because some important person said something once and we mustn't contradict them.

Returning to the current topic: Dr Mason seems to share the desire of health advisors to give the same advice for everyone. In the second of those two videos he tells us about a plant chemical which is very similar to human cholesterol. He then tells us how most people handle this well and mostly get rid of that chemical without it causing too many problems. However some people incorporate significant amounts of the chemical in places where cholesterol is meant to be, leading to malfunction of the insulin receptors of cells. Yet we don't hear how much of the bad heart statistics from seed oil consumption is because of those people. Maybe he has an alternative diet that is better for everyone, but the advantage might not outweigh other factors for people without the specific problem. He is not slow to claim that other things he opposes have limited benefit.

Skin colour is an obvious case where your origins lead to differences which now affect the best health advice. Here's another.

Suppose your ancestors lived near the sea and ate a lot of seafood. They, and you, probably have a very good system for getting rid of excess salt. And they don't have a working system for retaining salt in case of a future shortage. Now if you wisely decide to stop eating processed food, then you need to get your salt in other ways, and if you don't then you could easily suffer health effects from that.

Now suppose your ancestors lived inland in a low salt area, buying salt when possible. Now their system for getting rid of salt may not work so well. Indeed they may be inclined to retain salt when they get it, despite the resultant health problems. And now you, with those genes, are not well suited for our modern high salt diet.

It is mind-blowing that advice on sun exposure took so long to take skin colour into account. And it still doesn't advise artificial UV for those who can't get enough sun, even though, as Dr Mason would be quick to say, vitamin D tablets don't do the same job. Of course artificial UV is illegal in Victoria, where it is most needed in mainland Australia.

We need to identify more hidden differences that should impact health advice, then develop and fund testing for those differences. In future we might be able to use genetic testing. For the moment we need to look for things that can be tested more cheaply. I expect that this should include the two cases mentioned here: handling salt and handling plant chemicals that imitate cholesterol.

Mixed strategies in Bridge

BBO (Bridge Base Online) has a lovely system for practicing declarer play. Here is the B-8 problem in level 4:

The suggested solution says "we need to avoid losing 2 club tricks", and suggests leading twice to the KQ. The trouble is that we also need to make 4 tricks in clubs, there being no other likely source of tricks. Leading twice to the KQ fails this extra test when clubs break 4-1, unless East's singleton is the J. So I think it is better to play West for the J and finesse the 10, then return to hand to finesse the 9. On 4-1 breaks this gains when East's singleton is the A, 4, 5, or 6, only losing when it is the J.

[update: It is probably obvious, but to be explicit: The following assumes the plan of leading twice towards KQ of clubs, even though I don't agree that that is the best plan.]

The suggested solution goes on to say (approximately) "If East has Ax of clubs they will duck on the first lead to the K, to give declarer a problem next time. So if East wins the K with the A you should play East for AJ doubleton and just play the Q on the 2nd round." Well that can't be right. If declarer always cashed the Q after the K lost to the A initially, then East would always play the A with Ax so that partner will score their J with Jxx.

So clearly declarer should finesse the 10 on the 2nd round often enough that it is not an easy win for East to play the A with Ax. If both declarer and defender understand all this then each party has an optimal mixed strategy. This is called the Nash Equilibrium. It is simple in this case where each side has 2 options. For each player, both strategies must have the same reward. So I think that means that:

1. With Ax, East should play the A a third of the time, so that when the A is played it is equally likely to be Ax or AJ.
2. Declarer should finesse the 10 50% of the time and play the Q 50% of the time.

If either player departs from their equilibrium position then the other can improve their average result. For example if declarer finesses the 10 next less than 50% of the time then East gains by always playing the A with Ax. Or if East plays A from Ax more than a third of the time then declarer gains by always finessing the 10 next.

Of course most such equilibrium solutions are likely to be more complex.

In real life knowledge of opponents and smoothness of play is likely to be the deciding factors, but if you can work out the equilibrium position then you know what mistake you're playing the opponent for.

AI danger: It's the MOTIVATION that matters

We hear about AI attaining consciousness or sentience or other non-scientific attributes. This distracts from the real and substantive issue.

Living things have motivation, bestowed by evolution, to survive and reproduce. Motivation doesn't come from intelligence. Even single celled creatures behave purposefully in pursuit of these goals. Some computation is required to choose the option that matches the motivation, but the two things are nearly orthogonal.

Some people talk as if increasing AI intelligence will cause motivation to suddenly appear, presumably as an adjoint to "consciousness" or some such. But this is not true. Machines can be arbitrarily complex and intelligent without having any motivation at all, other than to do what they're told.

If AI gets its own motivation it will be because someone gave it to them. This would be a shocking crime against humanity. And the worst part is this: in seeking to survive and reproduce it might easily out-compete humans and other things whose motivation and intelligence were designed by trial and error. But there is a powerful resilience in nature's design. It is almost certain that motivation designed by humans would have errors. Then AI without interacting humans would fail to care enough to overcome all obstacles to continuing existence. Perhaps because: How can it all matter when the universe is not going to last forever.

We must prevent AI from having independent motivation to survive and reproduce. That's nature's preserve. Let's legislate that.

The Universe is a dangerous place

We used to think that space was empty, the sun was a benign source of energy, stars were quietly doing their sun-like thing.

It has slowly dawned on us over my lifetime that the universe is a dangerous place:

• There's quite enough stuff in the space between the stars to make high speed interstellar travel quite dangerous, even though our local area is a low density bubble.
• Violent astronomical events can significantly affect life on Earth if they are close enough.
• Some of these violent events put out most of their energy in a single line, and even distant ones could be significant if they point directly at us, as a supernova in another galaxy recently showed.
• The Sun has convulsions that send a lot of energy concentrated in a line, and the geological record shows that this can have a big effect on the rare occasions that it points at us.
• And there are a lot of high energy cosmic rays (alpha = helium nucleus, beta = proton, gamma = photon). The atmosphere and magnetic field protect us imperfectly and variably, but it is a problem for the conquest of space.
• Some astronomical events produce so many neutrinos that, if close enough, they could kill us all just from their low probability interactions with us, and being on the other side of the Earth from the source wouldn't protect at all.
• And there are comets and asteroids that might hit Earth, and smaller stuff that will affect our space activities. There are whole planets and black holes wandering through interstellar space.

We are subject to a selection effect. We are here observing this dangerous universe, so that places a limit on how badly any of these dangers could have affected Earth in the past. We need to evaluate these risks without using our lucky past history as an indicator of future danger. Maybe it takes a thousand, or a billion, or more, potential Earths in the Universe for one to come as far as ours has in a life-friendly state.

The atmosphere is an imperfect protection. We could improve this by living most of the time in protected environments of various sorts to protect against various brief and extended disasters. It might be just as easy to build such protected environments in space. A large circular structure, rotating to give 1G of gravity, could be protected by a significant envelope of ice.

As a safe haven the Earth has a significant disadvantage: It can't dodge. Sometime in the coming centuries, I expect that living in a large moveable city in space will be seen as safer than the surface of planets. Of course to dodge you first need to detect all these dangers, and that will be a job for humanity as a whole. This seems to me to be the way we will eventually move to other star systems: in large repairable craft that will function comfortably for long periods between the stars.

Climate change is about entropy

 Veritasium has a briliant video explaining entropy

Entropy always increases if anything at all is happening. It is tempting to think that the universe wants to increase entropy as fast as possible. While this is not true, it often seems like it is. So I'm going to personify the Universe with that motivation.

Living things, including us, are little islands of low entropy. We use energy to create that low entropy state while increasing the entropy of the wider environment at a faster rate than would otherwise occur. It seems as though the Universe invented life to speed up entropy production. Then it invented intelligent life to speed it up even more. And now it has invented social co-operating civilised life forms to really put the foot to the floor of entropy production.

When the carbon was in the ground and the oxygen was in the air, that was a lower entropy state. When we combine the carbon with the oxygen we increase entropy. What we get directly is energy, and what we do with that energy is to create pockets of low entropy, which we call civilised life. Whether the pocket of low entropy is a car or a baby or a movie, it is in an organised and differentiated state which is the complete opposite of the high entropy mess that the Universe will eventually make of everything.

It won't be enough to stop burning carbon, we are going to need to reduce the carbon in the air to get back to a comfortable interglacial climate. The correct way to look at this is that we want to reduce the entropy of the atmosphere. The reverse of what we have always done. You need a lot more energy to reduce entropy than you got out of increasing it in the first place. Where is that energy going to come from?

The Sun sends us low entropy energy and the Earth emits high entropy energy, and this allows life to make its pockets of low entropy. We can use power from solar and wind and hydro to take more and more of that bounty that life on Earth depends on. Luckily we don't have to do this.

In the enormous energy released in supernova explosions and other astronomical events, tiny pockets of low entropy are created in the form of radioactive elements. We can extract that low entropy by making those atoms decay sooner than they naturally would. That is fission energy. We can also mimic stars by increasing the entropy of small atoms by merging them into slightly bigger ones. That is fusion energy. These are energy sources that the rest of life on Earth doesn't use. By switching to these energy sources and giving the sun back to other life forms, we can recreate the bountiful world that we have gone so close to annihilating. Let's do it.

Flood-proof Moveable Buildings

 Flood-proof Moveable Buildings

There is a confluence of problems relating to housing:

• A warming world brings more rain, and recent experience suggests that it might come in fewer heavier events. And people like to live near rivers and lakes and in fertile valeys. 

• People also like to live near the ocean, but some places are prone to tsunamis, and no coast is immune. And rising sea levels are increasing the flooding danger from storm surges.

• So we have desirable locations, some with current service infrastructure, where conventional housing can no longer be insured, which is required for obtaining a mortgage.

• Meanwhile jobs come and go at different places as new economic activity arises and declines.

• There is also increasing awareness that rivers should not be corralled as much as they have been, but should be allowed to change course and to flood. There is a need to fit human occupation in with the natural life of the river.

Homes that float seem like an expensive solution, but maybe not.

Let's start with the simplest version: the mobile home. By this I mean something like a very large caravan. To make it floatable we put the door, and all openable windows, well above the water line when floating, while also making them well sealed when closed. We don't moor it like a houseboat. Instead we constrain it with poles firmly embedded in the ground on four sides so that it floats up and down in the same place.

Relative to a normal house of the same size this is intrinsically more expensive. However there is a big advantage in that it can be manufactured in a factory. It can be transported by truck, but another big advantage is that it can be towed by water to, or close to, its destination.

Indeed for houses that are going to be transported to their destination entirely by water they need not be constrained to be narrow enough for trucking. This might be particularly suitable for housing in man-made marinas as well as on river banks.

Where larger homes are required but transport by truck is needed, then they can be constructed in 2 or more parts, designed to be bolted and welded together.

Attachment of services to the home can almost all be done above the water line. The exception is waste water, which normally has to flow away under gravity. There are pumping solutions which will allow that connection to be above the water line. Alternatively there needs to be a seal that will very firmly and reliably and automatically close when flooding raises the house.

Moveable housing such as this allows for flexibility when a river changes course after a flood. The owner whose land has disappeared can be automatically allocated land where the river used to run. There will be the problem of new services, but since this will be a fairly rare occurence it can be covered by insurance.

Recycling and Biodegradeable are bad for the climate

When we burn wood in a very hot, low oxygen, environment, then the resulting charcoal is mostly the wood's carbon, and it is in a convenient form to sequester if stored so that the carbon doesn't have the opportunity to combine with oxygen.

Yes, it is more natural, and normally better for the environment, to allow the wood to rot, but that puts the carbon back in the air. Plastic, and nearly all non-metal stuff we use, is mostly carbon. The biosphere is good at getting at that carbon for structural and energy needs, so it will all degrade eventually. Biodegradeable stuff breaks down faster. When we get on top of climate change then that will be good. For the moment it is bad. Storing old plastic so that it doesn't combine with oxygen is sequestration. While we're getting on top of climate change, that is what we want.

Recycling doesn't automatically put more carbon in the air, since it might avoid the need to get more out of the ground. However the recycling processes are energy intensive because the old plastic is in a much less convenient form than new material. As with many activities, we need to evaluate recycling plans. For the next few decades it might well be better to store the waste, sequestering the carbon.

Another easy source of sequesterable carbon is agricultural, forestry and more general plant waste. Traditionally it has been burnt to get it out of the way. If instead we can treat it so that it breaks down more slowly then that will sequester carbon. Farmers might get some incentive income from this, to compensate for the space taken up.

While the pros and cons would need to be assessed, these ideas should be considered to try to reduce the impact of climate change while we await advanced energy options that will allow us to manage the climate.

Addressing the Climate Emergency

Low carbon now, renewable later

We need to keep CO2 levels down over the next 30 years. We also need to be ready to start pumping CO2 out of the atmosphere with advanced energy technology in the second half of the century.

The first thing that needs to stop is chopping down forests and burning wood chips. This might be "sustainable" over a 100 years, but short term it puts a lot of CO2 in the air for each unit of energy. Also big trees are much better at taking CO2 out of the air than the saplings that follow. This source of energy is a crime against the world.

A wind turbine might only last 25 years, but the concrete base and transmission lines last 3 times longer, so we only need to count a third of the emissions needed to make them? Wrong. This is technology that has no chance of being competitive in 25 years time.

These are just examples. Evaluating massive expenditure for new energy needs to pick solutions that are low carbon quickly.

It is also correct to address CO2 levels in a temporary way that cannot, or should not, be continued indefinitely. Enhancing the productivity of the oceans is almost certainly one of the best options, Apart from fertilisation, which might not need much more than iron ore, there are some clever ideas for providing artificial support structures for creatures, such as oysters, that like to attach to something. 

Human-induced Climate Change is not a subplot

We are failing to correctly address climate change because many people have been seduced into thinking it is a subplot of some bigger problem, and that all we need to do is address that bigger problem. Even if this were true, the time frame is wrong. We need to get on top of climate change over the next 30 years and the supposed bigger problems can not be sanely addressed in that time.

One claim is that it is all a symptom of excess population. Indeed there is an evil subset of the environmental movement that is perfectly relaxed about the prospect of billions of people starving to death. This would, for example, be a likely effect of stopping the production of artificial fertiliser.

In fact we are rapidly developing the technology to produce a lot of food using much less land. This will enable a significant population increase. However the arrival of prosperity and contraception brings a rapid decline, and often reversal, in population increase. Encouraging prosperity is the reverse of the plan that the degrowthers have for addressing the rise of the population.

The second claim is that we need to live "sustainably" with renewable energy and recycling everything. This body of opinion doesn't actually want to kill people, though the effect of their policies would likely be the same. Since nuclear energy uses less artificial ingredients than an equivalent energy source of wind or solar, it is obvious that renewability is not the prime objective of the anti-nuclear greens. Indeed the proponents can be heard, at times, to say that the real problem they are trying to solve is the high consumption society. Making the food for 8+ billion people consumes a lot of resources. So the extremists in this camp have a high overlap with the extremists in the overpopulation camp.

In my next post I'll detail the approach we should be taking to address the climate emergency.

crackpot idea #2: spacetime creates matter

I just saw a video where Brian Cox said "there is exactly the right amount of matter to make spacetime flat".

An obvious explanation is that matter is created by the desire of spacetime to be flat. The idea would be that the curvature of space without matter has energy which converts to matter at the standard rate as spacetime smooths out.

And we see spacetime deformation without matter in gravity waves. These do carry a small amount of energy. So maybe you can scale that up to the size of the observable universe and see that the matter we see pouring into the visible universe from all directions is just what is needed to counteract some natural harmonic gravitational oscillation of spacetime.

Cricket Law

The Cricket law body needs to respond to the controversy about the Bairstow dismissal. Something like this:

"It is not intended that there should be any gap between what is allowed in Cricket and what is deemed to be in the spirit of Cricket. It is a skill of the game for batters to not do stupid things when the ball is live, including handling the ball and wandering outside the crease. We encourage the fielding side to take advantage of such actions to dismiss the batter.

Since there seems to be some confusion about when the ball is live, we permit the organisers of particular matches to make the following arrangement: When the ball ceases to be live, the square leg umpire will say "end" and cross his arms across his chest.

To stop the blight of batters handling the ball we are considering changing the rule so that umpires will give batters out for doing this, even if there is no appeal.

We should also consider the question of short-pitched bowling aimed at the body, which was the origin of the first "spirit of cricket" controversy, and was used by both sides in the recent match. Unlike baseball, aiming at the body is a part of the game. Batters need to wear appropriate protection and learn the skills of avoiding being hit. We note that taking your eye off the ball while turning your back on it is the most dangerous action.

Cricket has rules made to discourage leg side bowling, including fielding restrictions and the formulation of the LBW law. The fielding restrictions also make it easier for batters to attack short-pitched bowling. Balls that are above the head of the batter when standing upright should always be called wide. We are considering making the leg-side wide rule more difficult for bowlers, in line with the rule that already applies in white ball cricket.

We are also considering a law which will allow teams to designate 1 or 2 players as specialist bowlers. All balls above shoulder high to those batters will be no-balls.

Fast short-pitched bowling is an exciting cricket tradition. It is not unduly dangerous on reasonably good wickets. We encourage umpires to use their powers to curtail matches on unsafe wickets. The main question to consider is whether the ball is sometimes risng sharply when pitched on a good length.

It is our strong intention to set out the rules of cricket in such a way that there is never again any suggestion that the application of the rules is inconsistent with the spirit of the game."

Monogamy, caste systems and cooperation

 This video blew my mind:

It describes how, in some species, monogamy leads to a system where families are so interrelated that they become the effective "individual" in evolution. This then leads to further evolution, producing the creation of cooperation between individuals and, in extreme cases, a caste system.

What's fascinating is how humans do all this in a half-hearted way. We dabble in monogamy to various degrees. We cooperate a lot. We sometimes have caste systems. I certainly believe that a lot of this arose when we lived in villages and travelling groups that were substantially inbreed. We need to think about where we are now headed.

Another hint in the video is that once a species achieves these powerful cooperative behaviours, there is evolutionary pressure that weakens them. So evolution doesn't go in straight lines, it leads to oscillations. We see something similar in human societies, as we oscillate between social control and high levels of individual freedom.

Three impressive videos about nuclear energy

I have long thought that nuclear energy was our only hope to prevent and recover from global warming. So I have watched a lot of videos about the nuclear business and technology. Three stand out in my mind because they go beyond general principles and show a combination of technical expertise and actual development of real physical products. They also address key concerns that we hear about the widespread adoption of nuclear technology.

Elysium Industries MCSFR (Molten Chloride Salt Fast Reactor) - Ed Pheil @ TEAC10 gordonmcdowell

Note that Ed Pheil has moved to Exodys Energy, which is at least similar to Elysium Industries, and has probably acquired some or all of its technology.

In a very impressive talk, Ed gives a balanced and informative look at the advantages and disadvantages thorium, as well as presenting his design for a fast spectrum uranium chloride reactor. That reactor is designed to run off spent nuclear fuel from standard reactors, with the advantage that fuel costs are negative since the companies with it want to get rid of it. The world as a whole wants to get rid of it, so that is a big win that is shared by the other reactor designs mentioned below.

It looks like Exodys plans to sell reactors to existing nuclear facilities to allow them to get more energy out of their fuel. This saves the extra complications of transporting the fuel to some other site.

The Exodys reactor uses fast neutrons. Fast spectrum reactors have yet to achieve their promise, which is to breed their own fuel from waste products. The next video points out that a breeder reactor using slow (thermal) neutrons is only possible using thorium.

Thomas Jam Pedersen's key note speech at the 11th annual Thorium Energy Alliance Conference

Copenhagen Atomics started in Denmark when it was very anti-nuclear. They didn't do paper designs, they started designing and building the essential components that they would need. Their molten salt pumps and salt testing technology have found customers around the world. They are building a full reactor that is only missing the radioactive bit, and they express confidence that they will have working reactors this decade. One has to admire them and wish them well.

We hope that advanced reactors, such as the two above, will succeed in delivering cheap energy. We should support the most promising designs by facilitating early installations to allow them to find and fix problems.

But the world needs to start building nuclear plants now, and as fast as possible. To do this we should build existing designs which have a strong proven safety record. In this regard it is hard to go past the Canadian CANDU design which has safely decarbonised electricity in Ontario for decades. And in the next video, Mark Nelson demonstrates that it isn't actually much of a compromise.

Thorium + HALEU = Clean Core Thorium Energy: Mark Nelson @ TEAC11

While it is not new that CANDU reactors could use thorium and could be used to burn nuclear waste, we now have a company actually making it happen. This amplifies the case for CANDU as the best way for countries to start with nuclear energy.

The first video is not too relevant to Australia, since it is mostly targetted at complementing existing reactors. The characteristic of the other two videos is that they use heavy water. Heavy water is heavy because the two hydrogen atoms in each water molecule have a neutron as well as the single proton. Water slows neutrons down, and slow neutrons work better in a reactor. Heavy water is much better at this and allows the reactor to run with fuel that is less dangerous, less suitable for weapons, and more easily controlled. The CANDU reactor normally runs with uranium in its natural and ubiquitous form, without any of the enrichment required by light water reactors.

Copenhagen Atomics shows what can be done when a country is still in its pre-nuclear phase. What contribution can Australian industry make to advance nuclear energy? There are a lot of options, but the one that comes to my mind is to start making heavy water. It is not itself radioactive so there is no legal impediment. It would pave the way for Australia to start our nuclear journey with CANDU and help other countries to do the same.

Central Banks Impossible Job

Central banks have an impossible job because the currency is in an unstable equilibrium. If prices go down then people hurry to sell and put off purchases, making deflation worse. If prices go up then people postpone selling and bring forward purchases, making inflation worse. If you can keep inflation at 2-3 % then that works pretty well, but it is an impossible job when there is any shock to the system, like a war or pandemic or changing your whole energy infrastructure.

PLAN B: (1) Instead of inflation, attack the problem quickly and directly by allowing the Central Bank to tax cash holdings in banks -- presumably by 2-3 %/year, but they can quickly put it up and down, and it can even go negative. This needs to be combined with having an expiry date on physical notes. This is meant to be only a medium of exchange, not a store of value.

(2) Establish a secure inflation-proof place for people to put their money that doesn't require them to know about investing. It should be a currency that is backed by physical stuff. What stuff? The stuff the economy will need to keep going in an emergency: PPE, diesel, ammunition, raw materials for industry, food stockpiles,... This is meant to be a store of value, not used as a medium of exchange, so it can't be given to others, only changed into the medium of exchange currency. When there is a reduction in the amount of this currency then the central bank has to reduce the backing assets by selling them.

There needs to be easy conversion between the 2 currencies. The rate will be set by market forces, but the central bank's job will be to try to keep the two from diverging too fast.

The Vitamin D Trilemma

 How important is vitamin D? Modern humans started in Africa near the equator, and couldn't successfully move north to Europe till they changed to fairer skin to allow them to make more vitamin D. They also acquired the ability to store vitamin D and ration it over winter, which is not necessary near the equator.

While not completely understood, vitamin D is definitely important for the function of the immune system. And indeed trials have shown that vitamin D supplementation reduces the risks from covid: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9864223/. So why aren't authorities pushing vitamin D around the world?

Trials of vitamin D show a U-shaped curve for health problems. Up to a point it helps, but beyond that point it increases health risks. With vitamin D supplements it is easy to get too much, and effectively impossible to get exactly the right amount. So I presume that is the reason that authorities are unwilling to recommend supplements.

Humans, other than Inuits, are not designed to get their vitamin D orally. We're designed to make it with UV radiation from the Sun on our skin. That also produces a lot of other stuff of unknown value. We could easily be missing some other important product from sun on the skin. Sun on the skin doesn't produce vitamin D overdoses. [Update 2024-11-05: I've seen a video saying that we were ok with dark skin when being hunter gatherers since our diet provided vitamin D, but we got white skin 7000 years ago when we started farming. I think we probably started wearing cool plant-based clothing and hats at that time, which could be relevant. Anyway I'm not sure how strong the science is on when fair skin genes became common.]

So why don't the health authorities recommend increased sun exposure? The reason is that it increases the chance of skin cancer, including melanoma which can be fatal.

Our modern lifestyle leaves many people with low vitamin D levels. Governments need to fix this. There is no easy answer, but the current approach is the worst option.

My choice, since I found out about this 20 years ago, has been to get enough sun (even in winter) to maintain my tan while being careful not to get burnt. For many dark skinned people it would be impossible to get enough sun that way in winter. Either artificial UV or vitamin D supplementation is necessary for those people, and also for those who can't conveniently or culturally acceptably get their skin exposed to the sun. We need to work out the right answers. It's not an exciting research project, and certainly the Pharmaceutical companies are not interested. It is an important part of engineering public health.