studiot

This thread is not about reality. Reality must include all manner of things which are neither facts, nor truths, such as ignorances, mistakes, lies, deceptions, disguises, plays and many more. Facts can indeed change. Data books such as Kay and Laby, Lange, CRC handbook, Merck, International Critical Tables etc are vast collections of interconnected facts. Occasionally small changes are made to one of these facts and the effect ripples through the whole data set.

What about facts we know to exist, but don't know what they are ? What is the date of the death of Charles Brewster Ross? It must be a fact but no one has any means to determine what that date is.

Marx had a point, some workers lived in appalling conditions in Britain. But that does not invalidate my point which was not to tar everyone with the same brush. I doubt for instance, that all the slaves in America lived in greater luxury than the best conditions in Britain. We are not all murderers, just because there are some murderers amongst us. It is of interest that the British were not only the inventors of capitalism but the most ruthless proponents of it But on the other hand they were also the leaders and example setters in abolishing slavery and giving workers better conditions.

My example of the arch bridge would be an example of static emergence. A possible example of dynamic emergence might be the maths schoolmaster's favourite surprise. "The contact point with the ground in a rolling wheel is not moving since it has a forward velocity as part of the system exactly equal and opposite to its backward velocity by virtue of its rotation." My trying to be too brief again. I meant that I was applying tried and tested classifications static and dynamic to emergence, not that such application is well trodden. Complex systems, such as those of exchemist, would be of the dynamic type. In a way the emergent property is a result of dynamic equilibrium of constant change.

I don’t agree with this. For example, one wouldn’t expect to see emergence in a simple harmonic oscillator; but if you had eg a very large ensemble of double pendulums all somehow influencing one another, it might be a different story. I think the complexity of the systems plays a role, and perhaps also the types of dynamics within it (linear? Non-linear? Chaotic?). Of course these terms need to be made precise. My apologies, I didn't make it properly clear, that this was a quote from a brand new book "Physics Fixes Everything" I do not support this view, but I thought it should be included as the trend seemed to be moving this way. In fact classifying notions into weak and strong versions also seems to be gaining popularity, another trend I do not support. If I were to classify emergence I would tend towards static emergence v dynamic emergence, a well trodden classification. To my mind emergence is something that occurs reliably and repeatedly in a system only in certain specialised circumstances as opposed to the many other circumstances that can and do pertain for that system.

Well I can't agree with that trite statement about winners and loosers. Whilst exploitation can be the case, for example the British East India Company, from Robert Owen to the great Quaker foundations (Cadburys, Clarks, etc) capitalism worked very well for all.

Well, three different posts with three different views of 'emergent'. Exactly as @MigL predicts. I think the reversibility issue is a very big deal indeed, since if the paper Markus referred to is correct that gravity is emergent, and if you can reverse the its emergence you could reverse or negate gravity. I note no one has addressed the proposals put forward in the passage I quoted. My understanding of emergence is somewhere between exchemist's aggregate description and that of StringJunky. I agree the emergent phenomenon is sometimes surprising but I don't agree that it is never calculable or predictable. I have to confess my answer to the question, at least at the moment is sometimes reversible. Perhaps some examples (all welcome here) might help clarify matters. 1) If a bake a sponge cake is the result of the baking unpredictable ? It is irreversible. Is is emergent ? 2) If I take a pile of bricks or blocks and arrange them in a certain way a structure emerges which has the additional property of spanning gaps and supporting loads moving across that gap. That is how arch bridges are built. This property only becomes extant when the last block is placed. If I place the blocks in any other configuration the property does not emerge. However it is reversible. I could dismantle the arrangement and even re erect it somewhere else, as many times as I wish. And so long as I kept to the correct configuration the spanning and load bearing property would reemerge each time. So is emergence a one time, one shot phenomenon ? Or must it repeat every time the correct configuration occurs ? Many thanks for the thoughts and replies so far.

Emergence is a popular hot topic word these days, and has been offered by @Markus Hanke in another thread in relation to gravity. So the question arises "Can the Genie be put back in the bottle ?" Or is emergence reversible or irreversible or even irrelevant as one Physicist has written a book he believes to show ? Note this choice is non binary and cannot be addressed by classical logic alone. My list of choices is always irreversible / sometimes irreversible / never irreversible but I will add irrelevant out of deference. Obviously your answer has implications for gravity and many other phenomena.

. It's so much more interesting to trade experiences than insults. Thank you. +1

But not all of them refuse. A couple of years ago we were asked where there was a good place to set up camp by a lone elderly guy on a bicycle. In the end we gave him a bed for the night and it turned out that he was excellent company during the evening. Over dinner, he turned out to be a professor of geology at the University of Otago who was doing the grand tour. One night in the West Country and then on to the East coast where he was heading for Norway in a couple of days.

I have absolutely no idea what you mean by this. The same words as what ? Really ? Didn't you also say ? You are the one who has misread posts by others (who I note have all taken you to task) . You completely misread my post, which was an answer to a specific and very sensitive post from Markus Hanke. It had nothing to do with dogs or whistling and provided no cause to demand 'reference' in such a peremptory manner. Yes I am aware of some rough sleepers who refuse conventional accommodation (We support a local charity called Open Door which provides this). Please note the emboldened word 'some'. In my original post I used italics, apparently that was not good enough. The actual comment was supplementary to that of Markus, who did not mention the few who refuse, as is the right in English Law.

Thank you for expressing my doubts so clearly +1

The you clearly did not read what I said correctly.

BBC NewsSecrets of birdsongs' 'spectacular diversity' revealedA scientific study has revealed the acoustic secret that connects all birdsong - and it is surprisingly simple

Agreed. And yours is a good answer +1. I would just like to add that some rough sleepers in the UK choose to avoid accommodation available to them.

Indeed yes, and these should be fully explored. But we are not there yet.

A world of caution about politics , journalism and statistics. In the UK, reporting 'Energy' statistics or making policy decisions about them is a variable beast. For some years 'Energy' usage has been measured here by gas consumption, sometime domestic only, sometimes commercial, sometimes both. Both fuel oils and electricity consumption were ignored. Policy rebates such as the winter fuel payment were based on gas consumption statistics. The recent announcement of our wonderful (!*! ?) new prime minister that he was cutting energy bills by removing some tax on 'Energy', refers to electricity bills only. So which 'Energy Requirement' is the OP referring to ?

There, and here is me thinking that D'Alembert's Paradox is just an artifact of oversimplification, that actually yields acceptable results in certain (quite many) cases. But I hope you will agree with me that there is no such thing as an actual point load - it is an idealisation. Yet we apply vector mechanics to them all the time.

I hoped I had provided enough information to explain what I meant about the effect of the impact. If you want more detail please say and I will be happy to oblige. As regards vulcanism, this was nothing new at that time. The Deccan traps eruptions started before Chicxulub and lasted three quarters of a million years, whilst the impact lasted a few hours. Yes I think the Deccan was the second largest known system of volcanic eruptions, the largest being the Siberian traps nearly 200 million years earlier, which last a couple of million years. But also I expect you are aware that human seismology detects activity, on the other side of the world, even from human sized explosions. https://www.science.org/doi/10.1126/science.aau2422

Yes I'm inclined to support this view. Something that is pretty important to Science in general is the way we knowingly use false models, because they give the right answer. Examples would be Maxwell's mesh currents, Imaginary forces, simplified equations and so on. Is D'Alembert's Paradox a truth a fact or an artifact ?

You don't need to be an expert to understand that the impact wasn't powerful enough have a very big effect on the larger body of the Earth (as a body) , although the effect on life more generally was obviously immense. The evidence for this is that the Earth was not shifted appreciably from its orbit, its spin was almost unaffected, it did not flip or shift spin axis appreciably. It should also be noted that, although by far the largest factor in the extinction, there was also an accumulation over time of other important factors, unrelated to the impact.

I have too much respect for you to want to sound pernickety. What I am doing is sounding a note of caution about oversimplification and the theoretical physicist's habit (pun intended) of packing too much into too few terms, leading to the danger of circular arguments. For instance the term 'states' by itself is not as detailed and precise as the original thermodynamic definition of 'state'. For QM only energy is considered, but then you need a definition of energy, invoking the danger of circular arguments. Considering Relativity v Navier Stokes. By not including compressibility and viscosity variables you will arrive at the conclusion that there is zero force on a circular object in a flow. Physicists would love to drop the Lambda term in the GR packed equation, for the sake of 'elegance', which is a similar mistake (in my opinion). [math]{G_{\mu \nu }} + \Lambda {g_{\mu \nu }} = \frac{{8\pi G}}{{{c^4}}}{T_{\mu \nu }}[/math]

I do think the underlined is an unfortunate example since the word bachelor has (had) several meaning; the original one having nothing to do with marital status. Your point about certainty is on better mathematical ground as one of the meanings of a probability of 1.

One mathematical comment here. Just because two different physical systems obey the same mathematical equation(s) or structure over some or all part of their range does not mean they are the same. Mathematical analogues are very useful and it is remarkable how few equations we make do with. How many different physical systems obey Laplace' equation for instance ? We are in danger of falsely conflating such systems in the case of entropy, just because we can identify similar structures incompletely different physical systems. Other aspects of each such system may not be so similar.

You guys might like to explore this website, which is also the website associated with the book I reviewed in the lounge. Emergence is a particular topic The Material World - Physics Fixes All the FactsComplex systems seem to magically emerge from the interactions of their parts. A whirlpool emerges from water molecules. A living cell from organic molecules. You emerge from the cells of your body Markus mentions Navier Stokes. A word of caution here. In the 19th cent Messers Navier and Stokes constructed their equation to include all known contributory variables, which is why it is so difficult to solve. In the 20th cent Messers Black and Scholes thought they would do the same with economic systems. Unfortunately they did not do such a thorough job, which is why computer implementations of their equation caused the instability and stock market crash of 2008. We should beware of what we wish for when declaring emergence, we might well find something quite different from what we expect.