studiot

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.

Have you seen the comments on this in my previous post? I said there would be more Look at these notes about equilibrium, and perhaps Wikipedia. The idea is that a system is in stable equilibrium if following a small displacement or disturbance it returns to the original state. Unstable equilibrium it moves (rapidly) to another state Metastable equilibrium if it may do either. My example is a marble in a bowl (stable) a marble on a bowl (unstable) a marble on a ledge (metastable) The importance of this is that it provides a restorative mechanism for the process of disturbance without feedback. More of this later.

Please check your definitions. There are umpteen explanations and diagrams on the net. Yes that is correct Yes that is correct The water, and other geological cycles, are still processes. Note that most chemical reactions are actually multistep and the kinetics can be very complicated. I prefer to use the word stage rather than step because step I can then Identify a stage with a formal state and a step which is part of the way and may be near instantaneous. I will address other points more fully later

The climate in any given place depends firstly upon where that place is on Earth. So land today above the 70th parallel (Greenland, Antartica etc) experiences an arctic climate. But location is not the only factor. The 30th parallel runs through the Missippi Delta, Florida and the Yangtse. It also runs through the Himalaya and the Sierra Madre which experience quite a different climate. These differences are basically due to the elevation of the two mountainous area compared to the at or near sea level locations. Over time, both location and elevation are brought about by plate tectonic activity. My apologies for the poor spelling in my previous post. Other factor include the proximity of water bodies and the wind system. Again we find that the Monsoon is caused by the presence of the Himalaya, ( Waters of the World by Sarah Dry) which in turn is caused by tectonic activity. There are also other lesser factors such shielding and orbital factors which determine the climate at a given location, but it is tectonics that place the land there (or not). I don't think there is one single citation that contains all the explanationsyou have to draw from a variety of sources. The BBC documentary series I referred to in (I think) my 3rd post also discusses some of this.

How much calcium carbone would be decomposed on present day Venus, given the following information Venus surface temp about 450oC Surface pressure 95 bars On Earth at 1 bar calcium starts to decompose at about 650oC Try again. Firstly I said that over time the Earth has been in several different (persistent) states. Life in those early states could not exist today and life today could not exist in those early states. I think you will find that Gaia assumed that the current state has always existed, which is definitely not true. I think it is wise to be careful with terminology here. Weather (and thereofore weathering) is driven by insolation reaching the surface. Climate is largely controlled by plate techtonics. For example the precambrian 'snowball earth' occurred because plate tectonics at that time clustered pretty well all the land at a pole in one giant supercontinent. At the time of formation of most of England, tectonics dictated that the piece of crust that would eventually become England, lay in tropical latitudes experiencing a tropical climate under a shallow sea. Today of course, we enjoy the 'cool temperate climate' , at temperate latitudes halfway to the other pole. Exchemist quoted the carbon cycle for discussion and I think this is very good idea. One point about the carbon cycle is that the process is well, cyclic. Cyclic processes have neither input not output and feedback is therefore inapplicable. Exchemist further makes the point that the carbon cycle consists of several stages or sub processes which have the capacity to accumulate or disperse carbon so a complete passage round the cycle is a very complicated affair which takes a long time and can be subject to further external influences.

Gaia is a very seductive notion that offers great comfort. Unfortunately it does not accord with our observations and experience. Since it is nevertheless a great subject for discussion I am going right back to the beginning and giving @Agent Smith +1 for introducing it. I can't tell if he is still follwing this but I seem to remember from a couple of years ago that his main interest is biology ( there was an interesting foray into mathematics) and main language French. Most of the discussion to date has centered on processes. Yet Gaia is about a state. So it is important to distinguish between states and processes. States may be instantaneous, transient or persistent (steady state). They are described by the 'values' of a number of variables called state variables. Processes evaluate these state variables and come in many varieties. These values may be quantitative or qualitative. Some processes have an input and a definite output or result. Feedback is such a process. But there is a larger category which is 'self reinforcing' or 'regenerative' or 'auto-correcting' or 'auto-regulating'. Chemical buffers, for instance, have no input or output. There are also categories best associated with the equilibrium concepts of stable, unstable and metastable. These do not have an input or output and best represent the Gaia hypothesis. Gaia suggests that there is an ideal state for the Earth. In fact I have already observed that there have been several stable states in the past, persistent over timescales orders of magnitude greater than our current arcadian, benevolent Gaia. There are many interesting points for expanded discussion here, if anybody is interested.

All +1

Oh mon Dieu La plus ca change la plus c'est la meme chose.

Please do not do this. I first thought you simply quoted me and had not responded. Replies should not be place within the quote you are responding to. What do you mean flip it horizontally and why would you do it ? pH is the dependent variable and volume of added acid is the independent one Do you know the difference ? You cannot specify the pH - that is the whole point of a buffer. And yes it is a form of self regulation. But you can specify how much acid is added.

Are you trying to transfer logic or power with these pulses ? And are you working against a fluid at 5000 psi? Perhaps you could flesh out the detail a bit more ? Also perhaps a diaphragm might have better sealing, response/recovery time than a piston. 2 inch displacement at 5000 psi, on a repetitive basis, is quite a tall order.

First a warning Be careful about the use of the terms open and closed systems. An open system can exchange energy, matter, momentum and charge with its surroundings. A closed system can exchange energy and momentum but not matter or charge with its surroundings. An isolated system cannot exchange either energy, matter, momentum, or charge with its surroundings. Some use closed when they really mean isolated, but I think you mean closed. However, as joigus +1 has pointed out, it is not that simple. The Sun generates particles of high energy and momentum. They do not constitute a great influx of mass but most are charged and if these were to 'land' on Earth our environment would be very different. Luckily for us Earth has an unusually strong magnetic field, as planets go, which deflects most of these and interactions only take place in the far upper atmousphere. Further in the past larger masses with enormous momentum have arrived. An example would be the asteroid that killed the dinosaurs. You should also realise that Earth's atmousphere was very different in the more distant past. In fact it has undergone at least two major changes of composition, firstly after hundred of millions of years of near continual rain on the original rocks created the conditions for life and then even more dramatic changes by life itself from an anoxic state to an oxygen rich state. The technical term for the stabilisation we current enjoy, but climate change is degrading, is buffering. In particular the carbonate and bicarbonate buffers in the oceans. Note here that fresh water (lakes and rivers) have no such buffer. Here is a schematic of this effect.

If you can get to BBC iplayer there is a most revealing set of four programmes, released in 2023 containing the most up to date picture of the story of the Earth and life on it. In particular the billions of years that passed whilst the atmousphere was too hazy for the correct wavelengths for photosynthesis to get through so the only life was not plant or animal. Also the peculiar sequence of events that occurred for the steps from a barren planet to the present very fragile balance and just how fragile that balance is. I thoroughly recommend watching these. https://www.bbc.co.uk/iplayer/episodes/p0fpwhhm/earth

Incidentally, Wikipedia on Gaia is a little short of a complete history. Like many ideas, Gaia was floating around many centres of learning. Lovelock just formalised it, but the idea was incorporated for instance into Conan Doyle's fictional character Professor Challenger.

Not exactly, no. The second reaction does not produce sunlight. Again not exactly, no. In fact the degradation to a lower form of energy supports normal thermodynamic theory as well as evolution and other types of change.

@rufus mosley Your original post was rather too widely set, as can be seen from the range and breadth of the replies. I note you haven't replied to any of them, although you have been back since you first posted. If you are still interested in the subject (and it is an interesting one) please tighten up on the seeting in which we are supposed to discuss this.

Would not a negative logic OR gate not achieve your objective with both inputs set to false ?

Take a look a a bar of plumbers bar solder. It is easily strong enough to write with. Don't forget theat the Romans invented lead plumbing. Here is some current data, I don't have information on the roman mix, but the modern bar is only 60 - 70 % lead. https://soldersandfluxes.co.uk/product/grade-d-1-2-kg-bar-pack-of-1/ I think lead marking has more permanancy than charcoal, but as previously noted both have been used. The original question asked about pencils. The significant innovation with the pencil is the casing holding the marking material.