sethoflagos

Engineers and chemists generally have opposing views on whether thermodynamic work performed BY a system ON its surroundings is a positive or negative quantity. Engineers tend to the historic thermodynamics tradition of treating it as positive. Quoting from https://en.wikipedia.org/wiki/Work_(thermodynamics) It's a persistent source of confusion. Negative signs often appear and disappear in these calculations as the various equations are modified to fit a preferred convention.

I lost my harp in Sam Frank's disco

Of course, though $755.00 is a lot of coins, and it is a highly instructive question for a reason I didn't anticipate (or at least bother to check in advance). It turns out that I'd wrongly assumed that the standard coin masses have no large common denominator whereas your reference indicates that five dimes and two quarters actually have indentical mass and value. This guarantees that if there is one solution, there are many: just substitute five dimes for two quarters as many times as you like. Let us start by guessing there are no quarters. So nickels and dimes sum to $755.00 and 25.242 kg. Two variables; two equations which simply solve to 2,100 nickels: 6,500 dimes. Yay!! Integers!! So we have a solution!! Do the same for one quarter and we get 2,100 nickels again but a non-integer number of dimes (6,497.5) so we can reject this one. But for two quarters we get another solution 2,100 nickels: 6,495 dimes - ie we've taken the first solution and exchanged 5 dimes for 2 quarters. And so on... So we can do no better than state that the box contains $105 worth of nickels and $650 dollars of mixed dimes and quarters... ... because: Will you please elaborate? The above example illustrates this very well. If instead of 5.67g we set the mass of the quarter to 5.669g, we retain the previous solution of 2,100:6,500:0 however, the slight deviation from a large common denominator introduces increasingly large deviations from integer values which invalidates all other potential candidates. This is easily demonstrated with a simple Excel spreadsheet (I've omitted lines 16 - 3,200 for sanity's sake) Your methodology requires significant common denominantors in alloy composition figures to keep the number of permutations of composition down to a manageable finite number (to facilitate a brute force computational sieve), but component densities should ideally be irrational numbers (which in actuality we'd expect them to be) to prevent the existence of multiple integer solutions. For purposes of my argument, any equal incremental step process is essentially based on stepping through integers. I'd often wondered in the past why banks etc. went to the trouble of counting coins individually rather than just weighing them in batches and exploiting the limited possible combinations to compute the value. Now I've a clearer picture. Thank you for that.

On the contrary, your point is abundantly clear. But I think that bird has flown a while back. The mystery is not in the mineralogy, it's in the mathematical method. Please refrain from tabling dead cats. The topic is metallurgy. What we have here is effectively a closed box containing material of a precise given weight and monetary value. Given no further information I have no idea what the contents are. However, if I'm told the contents consist solely of nickles, quarters and dimes, I think I might be able to work it out. Restricting a search solely to integer roots of equations provides a massive simplification.

Still to this day a Tolkien fan. Similarly, I can find the rather odd physics of the Minecraft universe fully engaging. It can be every bit as satisfying to design and build automated processes in that reality as in this one. Absolutely! And now that the kids are all grown up, why restrict oneself to a single path anyway?

It can be IFF: - You know all the components beforehand - The components have significantly different elemental densities - Elemental densities have no significantly large common denominator - The alloying process does not induce a volume change - Compositions are precise integer percentages by mass (or moles, volume etc) - Alloy lattice is flawless - Density measurements are accurate to ~ 4 significant figures +

If integer values are used for component mass percentages in calculating this 'Archimedean' density function, then performing a brute force scan of the inverse function for integer solutions can recover those input integer values.

Different vein. Science may help provide some understanding of what paths are at least feasible, whether meaningful or absurd. Religion may be one such path. But one of restricted choice largely of someone else's choosing. Utterly absurd in my view but others may differ. Personality, I'm not averse to a little absurdity now and then. But preferably absurdities of my own choosing.

+1 The referenced discussion document makes no allowance that I can find for alloy density being a function of a lattice structure specific to that alloy. Rather, as you seem to suspect, alloy densities are simply assumed to be mass weighted averages of elemental densities. As far as I can tell, such a weighted average is calculated from an alloy composition constructed from integer component percentages, and of the infinite potential compositions that match that density, the composition that most closely yields integer percentage values is picked as the 'Most Probable Composition'. It's a few years since I studied statistical analysis techniques and I think I must have missed the lecture on the Hogwarts Sorting Hat. Best guess:- deadcatting.

Because almost all of the assumptions are only approximations of real world gas behaviour under similar atmospheric conditions to those we are all routinely familiar with at earth's surface. For simple, non-critical cases these approximations are often close enough for the differences to be unimportant. However, for more complicated, more critical situations, it is necessary to replace the less valid assumptions with empirically grounded correlations specific to the use-case. And to do this you need a thorough working understanding of what those assumptions are in the first place. O, yes and in passing - if you don't have that thorough working understanding, you don't even get to judge what counts as simple and non-critical.

Does that effect actually prevent one from choosing to reduce sugar consumption? Does adverising actually prevent one from choosing to reduce sugar consumption? If your answer to either of these questions is something other than 'no' then I refer you to Bob Newhart: Maybe I'm missing your point. But for now I'll stick with the word 'choice'.

Sounds rather like a plea of 'not guilty' on grounds of diminished responsibility. Good luck in court with that argument. State of mind is rarely uninvolved in any significant choice we make.

You might like to have a look at "The emergence of a collective sensory response threshold in ant colonies" Gal & Kronauer, PNAS, 2022

@Munim : Why is the best agreed estimation of the dawn of the universe unsuitable as a t=0 from which all other times can be measured? For a closed system, a pure crystalline solid of any arbitrary size has only one permutation at absolute zero (ground state) and an entropy of zero. It is not totally inconceivable that the initial entropy of the universe was zero. @Munim : Entropy increases with the logarithm of system volume so how can an ever-expanding universe reach equilibrium? @Munim : Thermodynamic equilibrium does not preclude, for example, isentropic events... @Munim : ... but it may preclude life as we know it, Jim! So time may continue with no one left to experience it.

You might be interested in a further related article in Nature: 'Multistage lithospheric drips control active basin formation within an uplifting orogenic plateau'. PDF here. This analysis differs from the OP article in that the upper mantle delamination seems to be driven purely by isostatic imbalance and does not require a subduction induced Raleigh-Taylor current to shear it free. Again, it focuses on relatively modern fold zones, but is potentially more general in its global applicability. For a mental picture, Anton Petrov has put together quite a good Youtube video overview of it at:

In this thread, as almost universally elsewhere, the word 'chaos' is being misused. As a scientific concept it is a blundering shorthand for 'deterministic chaos' or a bounded degree of uncertainty in the evolution of certain systems. It does not imply 'utterly random' as in common usage and theological context. Monkeys evolve directly into slightly different forms of monkey: not guppies or petunias. It's a red-flag word for me, so wherever the likes of Dim exploit the ambiguity of 'chaos' for their own nefarious ends, I automatically substitute 'diversity'. It usually helps lift the fog.

No-one? How about Tectonic Explorer? I can make no qualified judgment of its correspondence to reality, but it is fun to play with. Your notion that earth's continental crust was formed on the dark side of a tidally-locked planet that was subsequently spun up by 'space-whips' is not supported by the geological record. Counter evidence just on geological grounds include ancient deltaic tidal rhythmite deposits etc

Isn't this a fair approximation of a low density ideal gas? They do at low enough temperatures. TdS = d (CvT) is a tough ODE to solve as you approach absolute zero if Cv doesn't disappear in tandem. I'd still expect them to act in accordance with Newton's 1st Law. In essence, that's all I'm trying to reconcile.

This seems to suggest that maybe admittance of a particle in a 'forbidden' quantum state into an already occupied space is impossible as it would require a superluminal value of momentum to achieve the necessary energy density? This picture at least has the virtues of a) the energy of repulsion is derived from the particle's own KE and b) the force carrier for momentum transfer can be whatever is appropriate for that class of particle eg. virtual photons for electrons etc. I'm pretty comfortable with the old derivation of degeneracy pressure in the classic Fermi paper attached where eqns. 7, 8, 9 pretty well form my understanding of ideal gas heat capacity and entropy at low temperatures. As far as my old day job necessitated anyway. Clearly there's a bridge somewhere that I need to find... I'm in no position to question this. But it seems to be an observation rather than an explanation. Fermi Quantisation of MIG.pdf

Then which of the remaining fundamental forces manifest as degeneracy pressure, and what, if any, is the force carrying particle? Sorry, I did try to export this quote into a new topic, but I couldn't find the right button.

Because evolution tends to respond to increasing environmental diversity by increasing biological diversity which, in turn, increases environmental diversity. A fundamentally unstable and unpredictable system.

Thank you, yes. That's the distinction I was attempting to refer to.

Is it truly a failure of logic? Bad arguments based on false premises can still be logically flawless. We get a bit challenged in our definitions when assuming all arguments are presented in good faith. Sometimes they are not. The problems can lie in ethos or pathos rather than logos.

Do you really think that biology teachers are beating the jesuits at their own game?

Perhaps more particularly, and for a variety of reasons, many are drawn to explore the boundaries of accepted practice of the previous generation. All parents must I think see this in the behaviour of their children. It's how they learn. And it is fundamentally unstable. Another of nature's little jokes at our conceits.