studiot

Did you see the recent Countryfile program about the Chew Valley project ?

I agree that journalistic science can be quite misleading, especially when rushed to press. I really hope that a BBC Science Correspondent knows the difference between voltage and current, but I am not sure from this And this certainly says metals But I never thought about it till now, I just took it on trust. Nor had I heard of the nodule forming on a nucleation surface such as a shell fragment, but that makes sense.

Aren't nuclear subs prototypes for this ? They can stay submerged for long periods. You are also talking control theory here which has restricted definitions of balance, cyclic and feedback, as to for instance Gaia.

Contact potentials apply to all materials in any states, not just solid metals, though some contacts may be unobtainable. For instance Dowling showed the CP between liquid and solid bismuth in 1928. https://journals.aps.org/pr/abstract/10.1103/PhysRev.31.244 Seawater is a soup of ions and those nodules are a mix of many substances. Perhaps hydrogen is adsorbed on the nodule and released over a long time period. Whatever is going on is very complicated. As a student in the 1960s, I remember reading about those nodules in SCIAM. They were all set to mine them in those days, but it has never happened. But as far as I remember they were reported as metallic rather than oxides. One component was manganese.

Time to trot out the parable of the puddle ?

Isn't the contact potential the potential difference equal to the difference of the work functions ? So this should exist between any impurity and the base metal?

Thanks but that is not what I meant.

Does it have to be oxygen and hydrogen ? That is not the way ( biological) photosynthesis works.

If you weren't such a smart alec I would remark that Is exactly Higgs theory. But I doubt if you would know what I meant.

Why does the list sometimes report the members as 'last visited' and sometime 'online now ?' especially when the member looking the information is clearly online ?

Well the article does say that they have measured a (contact) voltage difference of the order of a Leclanche battery and there are plenty of possibilities for the impurities to be say 1.1 to 1.6 volts different in work function. If the main metal in the nodule is Iron then Calcium fits the bill. There is a convenient table on Wikipedia https://en.wikipedia.org/wiki/Work_function

https://www.bbc.co.uk/news/articles/c728ven2v9eo

That's where asking the internet comes in useful. Asking respectable sites like Wikipedia, Nasa and the friendly folks at ScienceForums. 1 I have told you several times that Gaia is an idea that works ie is self consistent. But it just does not happen to be in effect on Earth. 2 NASA's Daisyworld states explicitily that it only addresses one single factor Your idea of balance requires a multifactorial analysis. Gaia acknowledges this and offers a multifactorial balance. However I have also noted that has also been extended by mystical and (semi) religeous groups so if you are not going to use Lovelock's original you need to make that clear. Of further interest I pointed out that the original statement is basically a restatement of Lyell's Uniformitarianism. It is worth noting that, as with Gaia, the original "uniformity" (lyell never used the word uniformitarianism) has been hijacked by later workers for their own ends so I am posting the original 4 postulates. Gaia is a transcription of postulate 4 which I have starred. Note the first two postulates are the same as those used by physicists Newton and Einstein in their theories, that both space and time are homogeneous and istropic. I'm glad you pointed this out +1 I brings out what I have been trying to say that several terms used here are subject to contextual differences of definition. Balance, cycle, feedback being the most obvious. I've been watching your comments on feedback with increasing interest, and you raise important points a) because there is an awful lot of misunderstanding mixed in amongst the loose terminology, and b) because it gets really complicated really quickly. Loosely, feedback occurs whenever a process output is fed back into the input thereby modifying the subsequent output. However, there are some major provisos here, particularly with regard to causal links. 'Feedback' cannot as of current scientific concensus refer to the transfer of anything back to an earlier point in time. It therefore is not a transfer from an output back into the input that created that output. It is a transfer from an output phase into a subsequent input phase. Some examples may help explain: I'm glad you noticed this one. also +1 So what is the popular decision ? Should we include definitions in this thread or start a new one for that purpose ?

I have already complimented you on introducing DaisyWorld. But please realise its limitations. Yes Albedo is a very important factor, particularly as the ice sheets grow or recede. which might lead to an acceleration of change. But it is not the only factor and rarely the controlling factor. I found the video interesting, but NASA did not offer their mathematics. From their explanation I can deduce that they are using some kind of Volterra (predator-prey) equation, which is known to have chaotic features (sudden jumps and bifurcations in its solutions) in its phase space. It also depends upon where those ice sheets are (as well as their elevation) since the available insolation energy varies with position on the Earth. A further important effect is that of energy transport , which again is greatly affected by the disposition of the land masses. And the distribution of land masses is controlled by plate tectonics. So from the very earliest to the most recent times Very different regimes of atmouspheric pressure, temperature and composition have prevailed or persisted for long periods of time. During these periods quite different land and oceanic conditions pertained in respect of disposition of land and ice over the globe. Also quite different regimes of energy transport (ocean currents and atmouspheric winds) pertained. So it is not suprising that different forms of life appeared and disappeared over time. Two things follow from this. Our own particular set of circumstances which do indeed constitute a stable state and embody several mechanisms for resisting change (Gaia) have only persisted for a total of a few tens of millions of years so it cannot be said that The Gaia State is ideal, natural, normal for the Earth (or not) We can say that it is very convenient for our form of Life. Since the earliest forms of life did not use or generate oxygen through the chemistry Agent Smith has outlined and even those later ones that did we largely wiped out by the planetary environment 250 million years ago we cannot say that evolution had proceeded in a simple linear fashion to ourselves.

I see you studied English and Physics at school. Did you also study History? And in the over 40 years since 1981 what have been your sources for current affairs ? So let us start with a bit of History. Anything that can be made from oil can also be made from coal and used to be made during the first half of the 20th century. Known world reserves of coal 1.1 trillion tonnes (tonne = 1000 kilogrammes) coal contains perhaps 98% carbon. (google) Known world reserves of oil 1.2 trillion barrels (a barrel has a mass of 139 kg oil contains about 92% carbon) So in carbon terms coal outweighs oil by a factor of (1.1 x 1000 x 0.98) / (1.2 x 139 x 0.92) = 7 So are we really so short of resources ? During World War 2 Germany started with no sources of oil but plenty of coal, and was always squeezed thought the war and forced to manufacture synthetic fuel as a resul. During the aparteid embargos, South Africa was in the same position. Again during WW2 oil in Britain was rationed and some farmers garnered gas from chicken manure to powere their machinery. This tradition has continued into the second half of the 20th century and beyond. A modern improvement has been the rapid growth of the anaerobic biodigestor industry, which turns waste organic material into useful gas fuel and other products. Another modern innovation is the way advanced countries (also the greatest consumers) are recyclying ever increasing percentages of oil products, particularly plastics, or phasing them out in favour of renewable materials. Talking of plastics did you know that the first ever plastic is made from milk and still used in high quality glues and artists paints? In the lubricant world two major fronts of advancement have happened. Firstly the addition of inorganic substances to improve the lubricant performance. for example 'Moly' or Molybdenum Disulphide. Secondly the design of machinery has changed dramatically, being both much lighter and thefore imposing less bearing loads, and even going so far as needing no lubrication whatsoever, for example the change from magnetic platter hard drives to solid state. So perhaps you can see that Engineers and Scientists are not as green as they are cabbage looking, the real problem being the greed of those who control the resources and are looking for profit or power

I meant Which has a question mark at the end to indicate a question. If you are referring to the lattr part of my post, I was asking if the daisy model can cope with an event, cause by an external agent, similar to one which actually occurred on Earth and significantly change the course of both Earth's history and that of life on it. My ultimate point being that there were a somewhere between 5 and 10 events of this nature over the earth's geohistory.

More soberly they are apparantly one of the most dangerous animals in Africa, killing an average of 500 humans per year, as compared with a tally of 22 for lions.

Where did I say I disagreed with it ? It's a moot question "How does one disagree with a model ? It does what is does, no more no less" But if you wish me to question it, what does it say about the impact of an asteroid sufficient to wipe out 90% + of the existing life ? Your Harvard article refers to Daisy World as well.

Following the recent UK election

A report on research from the Royal Vetinary College posted in The Big Issue 15-21 july 2024, page 5

It has happened again, just as I clicked the submit button the typing vanished. At this point I was allegedly still logged in. A quick look round pages without leaving the thread, and then I found I was no longer logged in and invited to sign in. When I did I clicked on the reply to post again and all my typing was restored, including that which was typed in immediately before trying to submit, so there was no period of inactivity. Since this has happened before and if it genuinely can't be avoided then can someone at least add in a line of code to place a warning popup along the lines of "You are about to be logged off. Do you wish to continue ?"

The answers to these are already contained in my previous responses. Have you not read them, and taken them on board? I put a lot of work into them but you have only responded to a few of them. The Harvard article admits that what it means by the Gaia Hypothesis is rather different from the original, and only represents an observed stabilisation of the status quo of modern times. The modern times is crucial because there have been other stabilised environmental regimes on Earth, some lasting longer than ours and all very very different from ours. So much so that the original conditions that spawned life would be poisonous to us and equally our conditions would be poisonous to the original life on earth. A growth area in research in Applied Mathematics is the study of extremal points or maximal and minimal systems. Taking from this I am suggesting that our current modern Gaia is a local such phenomenon. Does this help ?

Interesting find. Thank you +1. Do you or does anyone else have comments on this pdf? I think it is easy to come away with the impression that Gaia is a done and dusted theory by reading it. No. In the light of StringJunky's Harvard article and your reply I think it wothwile agreeing on what we mean by 'feedback'. Yes my example is mechanical because mechanical examples can be much simpler. If you want chemical, Would you call auto-catalysis feedback ?

If you want to take this forward, I recommend you approach it from the point of view of the effective range of action of different forces. The force that holds the nucleus together, the force that holds the atom together and the force that holds the galaxies together operate of quite different distance scales and provide quantum fields at their respective ranges. The idea is not perfect but it provides a unifying overview.

Don't nap too long, your posts are normally pretty good and I for one would miss them. +1 for the comment though. Indeed so. Do you think quakes are indicative of stability or instability ? In fact their energy is a small portion of the energy that goes into mountain building and other tectonic processes. There is no feedback here. They are a classic demonstration of Monsiur thom's 'catastrophe theory'. https://en.wikipedia.org/wiki/Catastrophe_theory These are similar to the activation energy diagrams you refer to but they are not the same. The AE diagrams are plots or diagrams of energy. My sketches refer to a real world marble rolling about in a bowl, where it finds a stable position at the bottom and stays there. Jiggling the bowl to give a small displacement will temporarily move the marble some way up the side. But it will soon roll back. This provides a non feedback stabilising mechanism. The second picture shows the marble perched on top of the upturned bowl. The slightest vibration or puff of wind will set the marble rolling down the side and away. This is an unstable situation again with no feedback. Interesting thanks +1 It should be noted that the ideas of Gaia appeared when most earth scientists still clung to the Uniformitarianism of Hutton and Lyell. https://en.wikipedia.org/wiki/Uniformitarianism Today we know much better and I again recommend the Chris Packham videos which can also be obtained fromsellers for those who can't access the BBC iplayer. these can be obtained from many suppliers eg https://headrecords.co.uk/special-interest/earthchris-packham/p-bbcdvd4550 Yes yo uare quite right to ask for sources and the Packham DVD's, linked above contain all the references to your question, whchich is discussed in detail, as are many other questions like Where did the water come from ? What was the composition of the early atmousphere? Where did the oxygen come from ? How did life survive snowball earth ? What are the changes and implications for evolution that life has wrought? and many more.