studiot

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.

I believe the Romans used a real lead stylus. What we know as the 'pencil' ie a soft marking core housed in a wooden casing was invented sometime in the 15th or 16th century. Sometime between the Romans, say AD 500 and AD 1500 graphite displaced lead but when is uncertain. https://kitkemp.com/a-short-sharp-history-of-the-pencil/ Charcoal sticks (without casing) have been used for marking for thousands of years.

I think you will find that copper - tin -antimony solder is mainly for the plumbing indistry since its three main properties are that it solders well to copper and brass but has relatively low electrical conductivity and is poison (lead) free). This mixture is usually sold without incorporated flux, unlike reels of electrical solder. Does your incorporate flux? https://www.amazon.co.uk/AIM-Solder-5167-Aquasol-B0B94M73NC/dp/B0B94M73NC https://www.copper.org/environment/water/e_p_lead.html https://www.waterregsuk.co.uk/downloads/public_area/guidance/publications/general/april_2021/9-04-02-soldersfluxes-v3-1web-_apr2021_.pdf

I note that you have been a member longer than I have and have contributed to several threads in your science area of Biology / Chemistry, and have good knowledge of the terminology in these areas. So let me start by pointing out that is not an equation. It is (an attempt at) a mathematical statement or expression. An equation is a statement or expression containing an equals sign. Not only does it fail to be an equation, it also fails to be a proper or valid expression since the connectives (add, multiply and divide) employed are all meant to form combinations of the objects referenced (200%, 4,3 and 2). The 200% object is of a different type from the other 3 and not conformable to combination with them. Sometimes objects of dissimilar types can be combined (as with complex numbers) but generally the rule is that dissimilar objects cannot be combined. As a biologist you will be familiar with the idea of 'counts'. I cannot tell without context whether the 4, 3 and 2 are simply numbers or actually counts.

Have you thought about symmetry ? If I take a hexagon and rotate it 60o about its centre, what change has occurred ?

So you are saying that this new calculation is simply an application of this? from this paper https://www.google.co.uk/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.rgnpublications.com/journals/index.php/jims/article/viewFile/252/229&ved=2ahUKEwjQ2fm934iHAxXgZEEAHdMYBrc4ChAWegQICBAB&usg=AOvVaw2wk5RR2G_aIiTmqkQoxzvZ In which case can we see the arithmetical / algebraic working (with proper definition of all parts) ?

Thank you John If the series sum is truly independent of lambda , I thought I put in a value and have a go at summing it. But I hit a stumbling block. What does the subscript (n-1) mean at the end ?

I really don't see the issue here. Many physical phenomena (perhaps most) have a spatial distribution so it is not suprising that something like scattering displays this characteristic, due to its statistical nature. And Pi is linked to spatial distributions both through the error function and the perfectly symmetrical ball in n dimensions. So any measurement of distribution will also include a measurement of Pi. But not this is only a measurement, not a mathematical derivation as in the Euler identity Since a perfectly spherically symmetrical distribution involves the volume, measuring the volume of an inflatable sphere is probably a much simpler way of achieving this end.

I'm glad to see you are taking a mathematical approach to this. One very important way we control waves is the ability to focus them. There is plenty of maths available covering this. This means that the spatial distribution of the wave is not the same in all directions. Another exploitable property of waves is resonance. Keep up the good work. +1

In Engineering we deal with real world objects called Bodies. Bodies can be affected by agents we call Forces according to specific rules. Individual forces cannot combine directly, but many forces can act on a single body - with the overall effect being a specific combination of the effect of each force acting individually. The same effect as all these combined forces can also be caused by a single suitably applied force called the resultant. Because both bodies and forces exist in the same geometrical universe or framework, there exists a correspondence between the geometry of the lengths and positions of the bodies and the geometry of the diagrams describing the forces. In fact one is a scale diagram of the other. For our present purposes forces acting on a by may be considered as a) Externally Imposed - These are called Loads b) Constraints on the Body by other bodies or forces - These are called Reactions c) Forces generated internally witin the body by the actions of (a) and (b) We will only need to examine (a) and (b). Rules for the actions of Forces on Bodies A force is a push or a pull All forces act only in straight lines, called their line of action. Forces cannot "turn corners" or "change direction" Interaction with a body may produce a new force in a different direction. Individual forces generally act on bodies at a single point called the point of application. A body for which the resultant of all acting forces is zero is said to be in equilibrium. A consequence of (5) is that a body with only a single non zero force acting on it cannot be in equilibrium. If a body is under the action of two forces it can only be in equilibrium if the two forces are acting along the same line. A body under the action of two or more (non zero) forces may always be brought into equilibrium by the application of an extra single force whcih is equal in magnitude but opposite in direction to the resultant of the original forces. This is callant the equilibrant. (This forms the force basis of the triangle of forces). The nature of the geometrical link between the configuration of the points of application and the directions and magnitudes of the applied forces enables a diagram called "The Polygon of Forces" to be either drawn or calculated. Scale drawing alone was once a popular method of obtainingt the Resultant/Equilibriant without calculation. The Triangle of Forces is simplest such polygon and uses three forces, two applied plus the resultant/equilibrant In the next post I will show how this is done using some simple example diagrams. I will also comment on where and why your information is correct or incorrect. I also think you are perhaps confusing the obtaining of a resultant by the triangle of forces with resolving a single force into components in specific directions, which the triangle can do for you because of the aforementioned geometric relationship. But this is a different calculation altogether.