sethoflagos

Recent discussions in the thread https://www.scienceforums.net/topic/128407-the-nature-of-time/ have got me scratching my head again over the relationship between past-present-future in both the quantum and classical realms. My starting point is case 1 of Bohm's variant of the Einstein-Podolsky-Rosen paradox in which Charlie at point C will operate a gadget to launch an entangled spin singlet along the x axis: an electron leftward towards Alice at point A and a positron towards Bob at point B. At some point Charlie will simultaneously release the pair and broadcast a light speed timing signal to alert Alice and Bob of when they should measure the z-spin of their respective particles. As the tests are made Alice and Bob similarly broadcast the results of their measurements. For simplicity's sake Alice, Bob and Charlie are all stationary within their common inertial reference frame, but sufficiently distant for the two measurements to be non-local. Consider what is recorded by independent observers in arbitrary inertial reference frames. Am I correct in thinking that: a) all observers will agree that Charlie's timing signal occurred before either of Alice and Bob's measurement signals. b) irrespective of the actual distance between point A and point B, some will observe Alice make the first measurement, some Bob. c) some few observers may observe simultaneous measurement signals from Alice and Bob and have no problem interpreting this as instantaneous collapse of the wave function at point of measurement. d) other observers may deduce that wave function collapse must have occurred before Alice's measurement; others that it occurred before Bob's. e) there are apparently different 'histories' being observed by different observers suggesting that there are different timelines of the wave function in play. And now we get into the speculative rabbit hole. f) if there are different histories being observed does this not imply that different observers are seeing different stages in a dynamic editing process of the wave function - ie that history is undergoing a transformation from a superposition of possible futures to a classically deterministic past for example. g) the paradoxes chiefly arise from seeing entanglement as some sort of physical link stretching across space, rather than connections within the complex vector space in which the wave function is set. h) for 'reasons' linkages within this complex vector space between 'gadget' at t=0 (specifically!) and electron-positron pair at t>0 are not unreasonable in themselves, and being unobservable, cannot pass real information to the past, and therefore do not conflict with causality. i) therefore an interpretation of the commencement of Alice's measurement process of a z+ electron inducing an overwrite of its wavefunction back to the gadget, and forwards again as an unambiguous z- positron for Bob would seem to resolve the paradox. j) simultaneous measurements by Alice and Bob imply the need for some sort of handshaking back and forth until the wave function resolves to a consistent solution. I stress that these are just general impressions of subjects that I find challenging, that have sunk in over the years and must surely break down at some point in the reasoning. But I'd be most grateful to find out where they do actually begin to collapse.

Lucky you!

What @Bufofrog says is true. And yet condensing steam can readily provide the highest heat transfer coefficients commonly found in industrial processes, often up to 15,000 Wm-2K-1. This is typically 5 times higher than for liquid heat transfer media. Another factor to consider is that the strong thermal convection above your cooking pot draws a lot of air into the steam rising from it that both cools it and provides a partially insulating 'mitten'. Immersing your hand in a stream of pure dry saturated steam would be an altogether different experience. Not to be tried at home or anywhere else for that matter.

Just sneaked a look at your profile to find out where you're based and it doesn't say. Lagos is similarly placed in that 'dusk' is very short as the sun drops vertically.

And what you see depends quite sensitively on that island lying between you and the sun's disc, hence much of the year someone else gets to see it.

If this is occurring just after sunset, could it not be a shadow cast by that island from below your horizon. This should cut out the red end of the spectrum leaving just a blue backfill from Rayleigh scattering.

If the analogy holds into the 2nd Law I get the result: (a/aref)^[3(k-1)] >= Tref/T where k is the isentropic constant, T is the bulk temperature of the universe and the ref subscript indicates values at some arbitrary reference time. This is the sort of thing I was thinking about as the 2nd Law setting constraints on the rate of expansion. I've uploaded my working as an attachment if anyone's interested. Univ. Expansion.docx

IFF omega = 1 exactly. Not sure if this will display correctly, but did we lose a minus sign somewhere? If so it, appears that any divergence from 1 would increase with time making it a metastable solution at best. This was how I saw the problem presented somewhere, but it's now clear from your explanation that one can view it from the other direction - zero curvature on the largest scales imposes omega =1. It still looks as if something is being driven towards an asymptote. Your post is going to take me a while to absorb. You've mentioned this analogy between FLRW and gas expansion before. Many thanks for taking the time to present it so clearly.

I think what started me thinking along these lines is the density parameter of the universe being so very close to 1. Not only is it a curious value for a random number, but I see no clear reason why omega shouldn't vary with time. Unless of course the balance of its various components is being continuously and dynamically adjusted in order to drive it toward unity. I've not a clue regarding a possible mechanism, but it just has a sort of 2nd Law feel to it.

It's a very old metaphor for a quick, natural exit.

Are you talking about disease of the young or the old? There's a difference. During my lifetime there have been significant global reductions in mortality of the young and one would hope that this positive trend will continue. However, as one who has seen most of his former friends and work colleagues pass on, I would suggest that there are positives in not exiting this world to a fanfare of dementia and double incontinence. We are mortal and sooner or later something will get us. There are a whole raft of fatal conditions that evolution has not eradicated because there is no advantage to the survival of our genes in doing so. This is part of the human condition whether we choose to accept it or not. There does come a time when the survival of our offspring is best served by the removal of our burden on them. It would seem selfish not to accept this. Better to make peace with oneself, and when the time comes, accept pneumonia as the old person's friend. There are many much worse ways to go.

How many of these statements can be paraphrased as: 'Significant variation in property X would reduce the ability of the universe to meet the spatial volume and particle diversity requirements of the 2nd Law of Thermodynamics.' All of them I think. I have a nagging suspicion that the cart may be being put before the horse. Perhaps the universe simply does what it is obliged to do to meet the 2nd Law. The settings of the various coupling constants etc then become less of a 'lucky lottery ticket' and more of a forced asymptotic approach to optimum values.

With the possible exception of whatever beast lies lurking in the heart of a black hole, there is no such property as 'incompressible'. The term simply betrays a lack of ambition in mustering the scale of forces necessary to facilitate the compression. Neutron stars would make pretty effective car presses. Even for Saabs and Volvos.

How does the OP manage to cope with that most unsafe of environments, real life with its utterly unbearable lack of any retrospective editing facility?

I think I owe @Ken Fabianand @exchemistan apology here. I took a closer look at the overall changes in gravitational potential energy due to isothermal nett downward diffusion of CO2 in the atmospheric column and obtained a result I didn't expect. For sure, descent of CO2, and the corresponding ascent of an equimolar flow of the lighter gases does result in a small local reduction in GPE, However, It also results in a small local reduction in pressure due to the reduced mass of the air above, and this results in expansion. The figure is tiny, but it is not local - it raises the entire air column above it with a corresponding increase in GPE. As far as I can tell, the two effects cancel out exactly at least when subject to a uniform gravitational field. So wiith zero contribution from GPE and enthalpy, the only drivers for Total Free Energy are the entropy terms which favour a constant mole ratio. I'm sure variation of gravity with height must have some small second order effect. Because centrifuges again, where such gradients are many orders of magnitude greater.

A while ago I highlighted this paper https://www.liebertpub.com/doi/10.1089/ast.2022.0027 ... which - well just glance through it at least. It describes a catalytic conveyor belt for churning out a steady stream of modestly sized RNA sequences. Which when coupled with a mechanism to produce its raw material input nucleoside phosphate monomers (see https://www.cambridge.org/core/journals/quarterly-reviews-of-biophysics/article/nucleic-acids-function-and-potential-for-abiogenesis/842529B9BDAD6E86F7919827725C1931) ... appears to have the potential to fast-track evolution of the apparently highly improbable by a factor of many orders of magnitude. Obviously, there is still a long way to go with this, but the bottom line is that we know with certainty that the first stirrings of life were present on earth very early in its history. And recent progress as described above are a credible basis for suspecting that the mechanisms may have been non-magickal.

Fleetwood Mac's Rumours album. Not really my kind of music, but they were a part of my 'growing up' and the passing of Christine Perfect/McVie has knocked me a bit off kilter. A tear in the eye when I listen to 'Songbird'.

I presume the near simultaneous disappearance of 2 reputation points from my posts on this topic, and your reappearance on this site are not unconnected events. Just to be clear. None of negative reps you received for the quoted post came from me. They are the result of how others perceived your behaviour.

Everything we have ever observed regarding the 2nd Law of Thermodynamics flatly refutes the idea of reincarnation as a global destiny. It is entirely the wrong picture to have in your head as to the nature of entropy. Our destiny is to boldly go where no one has been before. The future cannot ever revisit the past. Having said that, of the many 'pop science' definitions of entropy that have been kicking around for the last century and a half, I've found the greatest assistance from picturing an increasing entropy as a measure of increasing global diversity. It has at least the virtue of a more positive vibe than 'chaos'. Or 'gunk'.

When you refer to 'an old keurig machine' are we talking about a coffee machine? In which case it will probably be the air purge pump. Google tells me that these typically have a maximum rated air output pressure of 350 mmHg.

An interesting point that got me puzzling over the differences in Stokes drag between the macroscopic and molecular. We know from school chemistry that one mole of say, hydrogen at stp can occupy a sphere of radius 0.175 metres and present a surface area of 0.096 m2. Not much to resist the quarter of a Newton or so of buoyancy forces propelling it upwards. But what happens when the hydrogen is diluted? It's still the same 2 grammes of hydrogen experiencing the same 0.26 N force, but now each molecule is an isolated 'sphere' of radius 4.46 nm in an ocean of heavier particles. And the total area presented for drag to act upon is a little over 150 km2. I'm sure I've probably taken a few liberties in extrapolating viscous behaviour below the sub-micron scale. However, nine orders of magnitude is a pretty comfortable safety margin to conclude that buoyancy probably has considerably less impact at the molecular level than our everyday macroscopic experience might lead us to expect.

Rather than extract heat from the engine block, you could in principle raise superheated steam from the far greater heat output in the exhaust. This is the principle employed in Combined Cycle Gas Turbine (CCGT) power stations where each gas turbine exhausts into a Heat Recovery Steam Generator (HRSG) for driving a supplementary steam turbine. This increases station electrical output by about 50% for a given fuel consumption. Not a very practical proposition for a car though.

Now you've sparked my interest! The Reynolds and Chilton-Colburn analogies describe strong correlations between the flows of heat, mass and momentum which apply irrespective of whether the transport mechanism is via molecular diffusion or eddy diffusion. Essentially, the direction of transport of each is so as to flatten the gradient driving it. For instance, one thing I am well aware of is that the further your hydrogen plume moves away from the source, the more dilute the hydrogen becomes due to convective admixture of air, and correspondingly, the higher the concentration of hydrogen in the surrounding atmosphere. The trend is uniformly toward equalisation of concentration. The gradient tends toward zero. I don't see the thermodynamic exception you're referring to, and am curious since it suggests a significant and unappreciated asymmetry in what I understood to be a very consistent picture.

@Ken Fabian seems to be effectively stating that the maximum random-direction particle velocity due to thermal agitation exceeds the local bulk velocity of the ascending/expanding plume. Therefore at any point in the plume, some of the hydrogen content must be travelling downwards. Is there a flaw in this logic? It does appear consistent with the Briggs equations and Gaussian dispersion equation used in dispersion studies of flue and flare stacks that I've had some (albeit limited) exposure to.

'Weather' tends to keep the troposphere very well mixed as you suggest. Ozone is a rather strange fish on several counts. The long and short of it is that it has a short half life at normal sea level temperatures so it's natural distribution is generally limited to the frigid upper atmosphere where it's created.