an autodidact meets a dilettante…

‘Rise above yourself and grasp the world’ Archimedes – attribution

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water on Earth – no problemo

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water with bits of earth sticking out of it


So, as described in my last post, H2O in its various forms is plentiful in our solar system as well as beyond it. But, being more or less scientifically illiterate – despite decades of reading stuff on science – I can’t quite work out how liquid water is so abundant on the Earth’s surface. The story has long been told of water-iced asteroids in the time of the heavy bombardment being responsible, with the major proof being that these carbonaceous chondrite asteroids have, or had, the same signature of heavy (deuterium-rich) water as the water we find on Earth. While this seems a strong argument to me, how did the Earth manage to hold on to that water during those super-heated days? 

I’ve looked at this in a previous post, sort of, but I’m still not clear on the atmospheric conditions that brought about our soggy planet (much more soggy during the Mesozoic though). In any case, I’ve recently read that bonafide researchers on this topic have also been mystified about the sheer volume of water on Earth. 

Enter a new (to me) hypothesis, published in the Journal of Geophysical Research: Planets a little over a year ago. It argues – and other astrophysicists appear to be impressed by the reasoning and the detailed analysis in the paper – that the water came not only from asteroids but also from the solar nebula.

Solar nebula? Never heard of it, but apparently the concept has a long history. The so-called nebular hypothesis for the formation of our solar system was first proposed by Emanuel Swedenborg in the 1730s, and further elaborated by such luminaries as Immanuel Kant and Pierre-Simon Laplace later in the 18th century. Surprisingly for such an early contention, it has stood the test of time and survives today, though the details are still argued, and there are a few competing hypotheses. In any case, without going into too much detail, a nebula of dust and gas began to form around 4.6 billion years ago, and collapsed in on itself due to gravitational forces, spinning around a newly-formed sun. Out of this material, protoplanets gradually formed. 

Water in the Earth’s oceans has approximately the same D/H (deuterium to hydrogen) ratio as that of the above-mentioned asteroidal carbonaceous chondrites, so it has always seemed a safe bet that most if not all water came from those asteroids. Yet the sheer volume of water was still a problem. Jun Wu, the lead author of the recent paper, had this to say about the theoretical situation:

The solar nebula has been given the least attention among existing theories, although it was the predominant reservoir of hydrogen in our early solar system.

What has apparently added credence to the new hypothesis is that samples of hydrogen near the core of the Earth have significantly less deuterium and may fit better with the ratio of hydrogen in the solar nebula. Also the isotopic signatures of the noble gases helium and neon found in the Earth’s mantle fit the signatures of these gases from the time of the solar nebula. The explanation of how the lighter hydrogen found itself drawn to the Earth’s centre, in a process called isotropic fractionation, is provided in the paper, apparently. It’s a very interesting story, if true, and it may have implications for liquid water on habitable-zone exoplanets. That’s to say, there’s no reason for it not to be quite common. Here, to finish, are a couple of thought-provoking comments from members of the research team.

… there’s another way to think about sources of water in the solar system’s formative days. Because water is hydrogen plus oxygen, and oxygen is abundant, any source of hydrogen could have served as the origin of Earth’s water.

Our results suggest that forming water is likely inevitable on sufficiently large rocky planets in extrasolar systems.


How did Earth get its water?

Written by stewart henderson

December 27, 2019 at 6:32 pm

discussing mental health and illness

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Canto: I’ve been told I’m on the autism spectrum, by someone who’s not on it, presumably, but who’s also not an expert on such things, but I’m not sure who is.

Jacinta: Well of course we’re all on the autism spectrum, it depends on your location on it, I suppose, if you need to worry. ‘You’re sick’ is one of the oldest lines of abuse, but I’m reminded of a passage in The moral landscape, which I’m currently rereading. He describes a funny-but-not-so-funny piece of research by one D L Rosenhan:

… in which he and seven confederates had themselves committed to psychiatric hospitals in five different states in an effort to determine whether mental health professionals could detect the presence of the sane among the mentally ill. In order to get committed, each researcher complained of hearing a voice repeating the words ’empty’, ‘hollow and ‘thud’. Beyond that, each behaved perfectly normally. Upon winning admission to the psychiatric ward, the pseudo-patients stopped complaining of their symptoms and immediately sought to convince the doctors, nurses and staff that they felt fine and were fit to be released. This proved surprisingly difficult. While these genuinely sane patients wanted to leave the hospital, repeatedly declared that they experienced no symptoms, and became ‘paragons of cooperation’, their average length of hospitalisation was 19 days (ranging from 7 to 52 days), during which they were bombarded with an astounding range of powerful drugs (which they discreetly deposited in the toilet. None were pronounced healthy. Each was ultimately discharged with a diagnosis of schizophrenia ‘in remission’ (with the exception of one who received a diagnosis of bipolar disorder). Interestingly, while the doctors, nurses and staff were apparently blind to the presence of normal people on the ward, actual mental patients frequently remarked on the obvious sanity of the researchers, saying things like ‘You’re not crazy – you’re a journalist’.

S. Harris, The moral landscape, p142

Canto: Well, that’s a fascinating story, but let’s get skeptical. Has that study been replicated? We know how rarely that happens. And there are quite a few other questions worth asking. Wouldn’t most of the staff etc have been primed to assume these patients had a genuine mental illness? And surely only a small percentage would have had the authority to make a decision either way. Who exactly had them committed, what was the process, and what was the relationship between those doing the diagnosis and those engaging in treatment and daily care? Was there any fudging on the part of the pseudo-patients (who were apparently also the researchers) in order to prove their point (which presumably was that mental illness can be easily shammed)? And wouldn’t you expect other patients, many of whom wouldn’t believe in their own mental problems, to be supportive of the sanity of those around them?

Jacinta: Okay, those are some valid points, but are you prepared to accept that a lot of these mental conditions, such as bipolar disorder, borderline personality disorder (the name speaks volumes), attention deficit disorder, narcissistic whatever disorder and so on, are a little flakey around the edges?

Canto: Maybe, but with solid centres I’m sure. Depression is probably the most common of those mental conditions, and too much skepticism on that count could obviously lead to disaster. Take the case of South Korea, which has one of the highest suicide rates in the world. There appears to be a nationwide skepticism about mental health issues there, which clashes with high stress levels to create a crisis of care. Professional help is rarely sought and isn’t widely available. It raises the question of the value of skepticism in some areas.

Jacinta: I wonder if the rapid advances in neurophysiology can help us here. Mental health is all about the brain. In the above quote, the pseudo-patients were mostly diagnosed with schizophrenia. That’s surprising. In my naïveté I would’ve thought there was a neurological test for schizophrenia by now.

Canto: Well, the experiment described in The moral landscape dates from the early seventies, but currently there’s still no diagnostic test for schizophrenia based on the brain itself, it’s all about such symptoms as specific delusions and hallucinations, which could still be shammed I suppose, if anyone wanted to. But what about borderline personality disorder – I was told recently that it’s very real, in spite of the name.

Jacinta: Well, there appears to be a mystery about the causes, and a general confusion about the symptoms, which seem to be rather wide-ranging – though I suppose if a patient displays several of them you can safely conclude that she’s stark staring bonkers.

Canto: Yes that’s a thing about mental illness, quite seriously. You don’t need to be an expert to notice when people are behaving in a way that’s detrimental to themselves and others, especially if it’s a sharp deviation from previous behaviour. And if it’s a slow descent, as quite often depression can be, it’s harder to pick from that person’s standard lugubrious personality, so to speak. And in the end, maybe the labelling isn’t so important as the help and the treatment. But then, people love a label – they want to know precisely what’s wrong with them.

Jacinta: I suppose the difficulty with mental illness and labelling, as opposed to labelling other more ‘physical’ illnesses or injuries, is the near-ineffable complexity of the brain. For example, I notice that among the symptoms of borderline personality disorder are apparent behaviours that don’t really cohere in any way. This site places the symptom of uncertainty and indecisiveness along with extreme risk-taking and impulsiveness, and then there is fear of abandonment, and other odd behaviours which seem to head in different directions, seeming to have one thing alone in common – being extreme or abnormal.

Canto: Yes, again, behaviour that tends to harm the self or others.

Jacinta: At the moment, I think there are still too few connections between neurology and psychiatry and the treatment of mental illness, though it’s a matter of enormous complexity. I had thought, for example, that the role of the neurotransmitter dopamine was essential to our understanding of schizophrenia, but more recent research has found that the neurochemistry of the condition involves many other factors, including glutamate, GABA, acetylcholine and serotonin. There’s so much more work to be done. But we also need to be very aware of the social and cultural conditions that tip people over the edge into mental illness. Changes in the way our brain is functioning might be seen as proximal causes of an increase in depression and suicide, but it’s more likely that the ultimate causes have to do with the stresses that particular organisations, societies and cultures impose upon us.

Written by stewart henderson

June 30, 2019 at 12:45 pm