studiot

The short answer is no, not on the evidence we have available to us. Do you have any evidence to support this ? Like for instance a comparison of the rocks on the existing Moon and those on Earth ? Or some other explanation of Rodinia and Pannotia ?

Well I'm sorry I bothered, I won't bother in future.

Lovely. +1 Meanwhile back to the 1960s, us thick and uncultered scientists had to do an auxiliary O level in History of Art, for the good of our souls. To my suprise I discovered the art teacher ran an after school project hand grinding and polishing lenses and mirrors for an astronomical telescope for the school. The project had being going for a couple of years by my time and was not expected to be finished before I left.

Yes it is disappointing that we have not yet even passed the first hurdle, that of sustained controlled fusion. Obviously this needs to be achieved before we can overcome the technological details of extracting worthwhile energies from the process. We don't yet know what sort of process we will have only that extraction stragegies will necessarily depend on the process. If the process simply produces heat, it seems most likely that there will be a steam turbine/generator at the end of the chain. But different avenues of possible processes have been explored since Zeta, the first attempt I was aware of. Knowledge of the then hardly understood processes of Magnetohydrodynamics and Plasma Physics has been greatly enhanced since that time, as have new magnetic methods using superconductors and other better magnetic materials and ignition methods using lasers. So the research and attempts have not been in vain. I still wonder if the final solution will not by direct generation by MHD methods. As to your point about pitching for funds and other backing, Sadly successive UK governments have been busy dismantling research establishments wholesale and even have a track record of cancelling projects that are working well. So many enterprises have to function in a stop-go, stop-go world, never finishing anything.

Claimed to be the hottest place on Earth https://www.bbc.co.uk/news/av/science-environment-59601560

My thoughts are that drawing on Navier Stokes as a comparison is not enough to posit dark energy or dark matter. N-S has the characteristic that, although difficult to insoluble, it arise purely from conventional dynamics. No additional Physics is necessary. Bringing the numbers game into consideration; The suggestion to messers Navier and Stokes that a large enough lump of metal could spontaneously explode would have been fanciful. But their work did predate knowledge of radioactivity. Later (and therefore additional Physics) can be used to predict the size of a lump of Uranium that will spontaneously explode as a fission bomb. The size is not of astronomical proportions. Astronomical sized bodies of lighter elements such as hydrogen, helium etc will spontaneously ignite in self sustaining fusion dynamics. I would suggest that both of these activities are emergent phenomena. So I suppose that N & S might have thought such phenomena emergent but with the addition of new Physics. Yes Physicists love to separate out or isolate effects. But can this always be achieved ? Consider adding 3 + 4 = 7 Yet if we add a vector of magnitude 3, separated out from a vector of magnitude 4 by orthogonality we get a vector of magnitude 5. Is this an 'emergent' pair ? More numbers The number of bricks to form my arch is irrelevant. The pieces may be much smaller than a brick - pebble sized - or much larger as large blocks of stone. Obviously many more small pieces will be needed to form the arch than from large pieces. It is even conceivable to form the arch of a single piece - you do not actually require two or more interacting pieces ! A small point about corbels. There is no emergent structural action in a corbel as there is in an an arch. Corbels and arches act in structurally different manners. Corbels work by supporting a bending moment in the bulk material , which has small but not zero tension stength The configuration is such as to allow the tension remain within these low limits. But in a true arch there is zero bending moment and zero tension. This really is an interesting thread, which is showing up some interesting answers.

How does any of this affect my technical comments ? Did the peer reviewers not ask what was being plotted on the axes ? The article I was presented with was almost certainly not peer reviewed. Perhaps the Nature article was, I don't know. Perhaps the Nature article told us what was being plotted on the graph axes. I lost the will to plough through paper, referring to paper, perhaps referring to........ Rayleigh introduced his waves in 1885, although these are not Rayleigh waves.

Well researched and reported. +1

Yes I understand that and I'm sure you understand that there is only one length, it is just that different observers will assess it differently. That is the point of my little story and the point swansont has been trying to drive home. I can't see how apparently accepting the OP false statement that there are two lengths as opposed to two assessments of one length helps.

Do you not think this statement gives the wrong impression ? Here is a story There is a long straight road through the middle of my village where the speed limit is the standard 30mph. However so many drivrs fail to observe the speed limit that the local neighbourhood watch has set up a speedwatch. They have two identical portable radar guns and their procedure is to calibrate or synchronise the guns by observing Jeff driving through the village, whilst standing together at the roadside. Having agreed that both guns give the same reading, Jim gets in the car with Jeff who follows behind a driver driving through the village. Jack stays by the roadside and reads the speed of the driver on his gun as a steady 40mph. In Jeff's car, Jim reads a different steady speed of 10mph on his gun. So does the errant driver have two speeds ?

OK so a single oscillator is not a wave and you cannot have a wave without a collection of oscillators. But does a collection of oscillators always make a wave or is there more to it ? So what is an 'event' and how are they distinguished ? And how does Smolin's definition conform or reduce to the standard definition of an event in spacetime ?

And ?

Thank you for the article. Sorry to pour a bit of cold water, but I have some doubts about the scientific veracity of both the article and its publication site. I am wary of a site that also offers articles like "Did Hubble discover God ? Einstein amazed" and "DNA code points to a creator" The article offers a description of wave motion that we teach as an introduction for 14 - 16 year olds at 'O' level. It has actually been known for a century and a half or more that there are more types of waves than transverse and longitudinal. Some (Rayleigh waves) are even named after the Physicist who studied them. This is not to say that the Hong Kong scientists have not discovered something interesting and perhaps new. But the article does not say what is vibrating in its diagrams. (Plots c and d) Pressure is not a vector. The demonstration device (in picture a) looks like some sort of focusing device. An array of sound sources. It is well known that the sound output is more and more narrowly focused the more speakers you put into a line array. This fact is used in stage speakers. Pictures d and e seem to me to show interference from multiple sound sources. However the group of pictures are entitled negative refract induced by the spin- orbital interaction in momentum space. The false colour appears to give intensity values, but intensity of what ? It does not say. So perhaps the scientists have engineered a clever way to manipulate sound.

Lovely pic +1 Perhaps you would like to consider and list the characteristics that make it emergent ?

Two things. You never told us what you are growing in this soil. Conventional gardening wisdom is that since to are relying on in place soil microbes to do anything to the dust, you will lower the nitrogen levels of the soil whilst they perform this task for you. In the long run it may improve the soil, but that will take more than a year and by then you will have more leaves.

confused or not listening ? I'm done with this thread.

You have asked this question in the relativity section, so you should expect answers pertinent to relativity. Objects in relativity theory do not travel two different paths at the same time. I was deliberately brief on quantum superposition as it has some quite different characteristics from classical superposition. I suggest you forget mixing the two. I have litrally dozens of textbooks describing superposition in electrical engineering, structural engineering, civil engineering, and several other disciplines. The technique goes back to the catapault where two pieces of elastic are used in superposition to fire a projectile.

Not if the blocvking object was big enough. There is a strong link between emergence, complexity and catastrophe theory. You should read up on Rene Thom https://mathshistory.st-andrews.ac.uk/TimesObituaries/Thom.html

That is why I said I don't know. We are in the best guess situation for life. And yours is as good as mine. Well I don't know of any charged particles that have no mass, so take your pick. A further thought about 3 particles and Markus Hanke's definition. An eclipse is a particular phenomenon concerning one particle blocking the light of the second from being received by the third. But this only occurs momentarily in a particular configuration. Can this be considered emergent ?

IMHO it has occupied far to large a % of the Physics curriculum for several decades now.

Neither of the particle pairs are entangled in my gravity or electrostatic examples. Ther is only one line between their centres and the relationship obeys the inverse square law along that. The PE is found by considering the work done in bringing one of the particles from infinity to its distance from the other one. "Can you say that?" Why not ? We don't know what sequence of events lead to life, but would life occur every time ? There have certainly been attempts to mix molecules thought to have mixed at random and they equally certainly haven't resulted in life.

Thank you for reading my long post. I tried to make it short but needed to get a lot in. Life - I don't know. Good question. One thing about life as an emergent phenomenon is that Physics expects reproducability. So every time you perform a particular procedure you get the same result. Is that an essential characteristic of emergence ? All my examples have this characteristic, but life doesn't. Not not less than 3, less than 2, ie a single component. Take electric charge or gravity. A single mass or a single charge has no potential energy. PE only arises (emerges) when you introduce a second mass or charge called a test mass or a test charge. But there is very little configuration you can do with only two participants.

Magic ? You 'started' this thead by introducing a difficult to define concept. Please don't introduce another one. I am glad to see folks working together in this knotty question here are some of my thoughts. Althought the thread is specifically aimed at Physics it is worth noting the meaning of emergence in other sciences and comparing. Also the age old technique of taking simple examples and seeing how they stack up against proposed definitions is valuable. So. 1) Emergence has long (centuries) been used to describe radical change or transformation in the biological sciences. For example the emergence of a butterfly from the pupa. Characteristics are that you cannot have a butterfly without a pupa, but once you have a butterfly you no longer have a pupa. The change is not reversible. You cannot resolve a butterfly into a pupa as you can with sinusoidal functions in my third example below. Note this example does not conform to Joigus' definition (which I like) so that definition is is not complete. OK back to applied maths (sorry physics) 2) 1+1 = 2, 3+5 = 8 in fact take any two or even lots of numbers and add themtogether and you will get another number. That is the result is contained within the set of all numbers. You do not move outside the set. But add all numbers in that set and you get infinity, which is not a number. So you have something that is not in the set ie outside the set. This example does conform to Joigus and the relationship is the additive property of individual numbers. 3) A more complicated example comes from the set of all continuous functions - commonly called C∞ - All sinusoids belong to this category. Like with the numbers above, adding any two or a large number get you another member of the set C∞. But adding an infinite number can get you you a function that is not continuous ie is discontinuous, notably a square wave. So once again takes you outside the set. Scary. 4) I potential energy an emergent phenomenon ? Particles, by themselves, do not possess PE. By configure two or a bunch of them and they suddenly possess PE by virtue of their configuration and their interaction relationship. The number of configured particles for this example of emergence does not have to be infinite. Indeed we can only determine what happens in some specific cases if they are infinite in number. 5) Take a pile of bricks. In most configurations the pile is unstable. But configure them into an arch and the configuration becomes very strong and stable. Again only finite number of participants is necessary. But in this case we also have extremal principles to apply.

Fair comment, people in different climates garden differently.

Have pity. A meteorologist is a guy who can look into a girl's eyes and tell whether.