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![]() One thing keeping it afloat, however, is that there is no mainstream answer to the problem. DEILE model could be wrong, but until something better one comes along… Adding to the difficulty in sinking DEILE model is that it is an extension, not a guess. That is, most other proposals to explain luminosity-redshift curve (i.e. “acceleration”) make a guess that “something” is not as it appears. Perhaps c is not constant…maybe G changes with time. They show that such a hypothesis produces a “pretty good fit.” Then Sylas carves up the results. But DEILE is not a guess at what could be, it is an extension of what is. The effect of sunlight in the solar system—relative to its absence—is to cause the average distance between objects to increase…dust the most. DEILE merely extends this observation to infinity…and it is hard to prove a negative. It is hard to prove that what we see happening in solar system has nothing to do with what we see happening at infinity ![]() DEILE also is an extension of the duality. All finite gravitational systems have dualistic tendency: the central, dense region grows denser; the spacious, outer part(s) grow more spacious. Again, it is difficult to prove the contrary that the duality does not end on expansion at infinity. The above questions/objections revolve around the extent of the extension: Sure, radiation can push dust around; but galaxies? The skepticism may be well founded. Frame-dragging is a good analogy of what I mean by that. I could argue that frame-dragging (from GR) is causing the moon’s orbit to expand. I would be “correct” in the sense that frame-dragging is real, and in the earth-moon system it causes moon’s orbit to expand. But I would be incorrect in stating that frame-dragging explains the observed 10E-10/yr expansion, because—as I recall—frame-dragging has an effect more than 1000 times smaller than Newtonian tidal effects. So frame-dragging is real, and it would have a small net-expansive effect in earth-moon system, but it does not explain the all of it…not even 1/10th of 1 % of it. In like manner, the effect of radiation I am describing should produce a small, non-zero net expansion. It may not explain all of observed expansion; it may not even explain 1/10th of 1 % of it. But radiation has some small, expansive effect. This effect—whatever its magnitude—must be taken into account before we turn to other explanations. As to how dust pushes back, as Nereid would suggest, we invoke laws of physics on an as-needed basis : conservation of linear momentum. When a photon gets absorbed by dust particle, a certain quantity of linear momentum, hv/c, or something like that, is imparted to dust particle. We can, in principle, trace the origin of this back to some other quantum system in the sun that emitted photon. It recoils; it loses the linear momentum the dust gains. The force of radiation pressure on dust is therefore equal and opposite to force exerted on sun. The sun’s radiation pushes outward with 70 trillion pounds of force, and the universe pushes back equally ![]() Granted, 70 trillion pounds of force is “almost nothing” in the grand scheme of things. But every star in universe is doing likewise. So to model universe, you have to model infinite centers-of-gravity all “pulling” against each other gravitationally, and all are “pushing” against each other radiantly (because centers-of-gravity tend to get hot and radiate like hell). So what happens in the sea of infinite time and space, with an infinite number of centers-of-gravity all pulling and all pushing? The long-term result of this tug-of-war between push and pull is not immediately obvious, but with a little reflection, we should not be surprised at what we see: dense regions growing denser and spacious regions growing spaciouser. And Yes, Nereid, dust is transparent to gamma and radio waves. Every substance has its “absorption spectrum.” Dust just happens to be particularly absorbent near the peak emission range of most stars, and hydrogen particularly transparent. But all-and-everything makes some contribution, at some wavelength, at some distance. It is said that it would take 10 light-years of lead to stop neutrinos. Well, between here and infinity lies 10 lys of lead. The neutrinos the sun spews forth make an impact…though it be far, far away. Space is nearly transparent to many types of radiation, but it is not perfectly so to any. Every part of the 70 trillion pounds of force the sun puts out makes an impact somewhere, sometime. For DEILE model, the effect of this outward-directed radiation pressure is crucial. Here is an instance where DEILE model apparently flatly contradicts known laws of physics: Typical Mainstream Description: "The star was found to have a ring of dusty debris in 1983 along with some other young stars (Jean Cote, 1987). Then, in 1991 astronomers learned that this debris ring was unusually warm and close to its parent star, unlike other disks that are farther out and so colder (Aumann and Probst, 1991, pp. 266 and 269). This dust, given its known properties, should spiral into a star within 20,000 years, according to current theories of physics and star formation. "[emphasis added] source I do not know what exactly they took into consideration in their “current theories,” but there are at least 3 factors at work: 1. Orbital velocity of dust 2. Size of dust 3. Radial velocity of radiation field Number 3 is typically left out in explanations of the effect, e.g. wikipedia. When #3 is taken into consideration, conclusion is that only dust very near the star will spiral in. In the case of our sun, this condition is met only well inside Mercury’s orbit. This subtlety—that real radiation sources rotate, and therefore, their radiation fields, too—completely changes the picture. I do not know the particulars of Zeta Leporis, the star in question in the above quote, but in general, the region close to a star where orbital velocity exceeds relative velocity of the radiation field is small and finite, whereas the region where orbital velocity is less than the velocity of the radiation field is large and infinite. Ergo, in general, of the two forces at work—outward-directed radiation pressure and inward-acting Poynting-Robertson drag—radiation pressure is going to win more often than not. Ergo, the general tendency of radiation is to push bodies away from the radiation source, as comet tails demonstrate, not towards it, as above sources suggest. Finally, as to how it can move galaxies: I’ve already described how dust—being pushed away from any bright source—tends to gather between stars where radiation is equal in all directions. Following this logic, dust should get expelled from the galaxy…except gravitational tug of gas in the disc hauls it back in. Thus radiation field between galaxies couples to dust within them, which is gravitationally coupled to gas, which is coupled to the stars. Ergo dust acts as a buffer, coupling reaction-force to galaxy as a whole. So all the galaxies in universe are not only pulling on each other gravitationally, they are all pushing against each other, radiantly. In GR, radiant energy is an attractive force, like matter. As with dust, which “in theory” should spiral into the sun but is observed to spiral away, I believe there is something being overlooked. I am not sure what it is, but my understanding is that GR is a “general” theory and does not take into account specifics of electromagnetic and other types of radiation. Cosmologists keep looking for an “anti-gravity” force. Well, virtually every visible object in the universe is a source of anti-gravity force—the sun’s contribution being about 70 trillion pounds. When the anti-gravity effect of starlight is shown to be not enough to explain observed expansion, then we look for “exotic” energy sources. Then someone can give DEILE hypothesis the coupe de grace. But as it stands—to my understanding—radiation in GR produces an attractive force, not an expansive one, hence there must be “something else” (i.e. DE) producing the expansive force. As with the pre-1998 “slowing” of expansion, the mainstream does not even have the “direction” of radiation pressure right. I just don’t see how the effect of radiation—which under local conditions has an irrefutable expansive effect—can have the opposite effect under GR. It just does not add up.
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PW -- Plant Whisperer |
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First, H is most certainly NOT transparent, blue-ward of the Lyman limit. Second, 'most stars' is irrelevant (or, if you prefer, marginally relevant); what counts is the integrated SED of a galaxy ... to which 'most stars' contribute little (they're too dim), and where they do contribute (in the infrared), 'most dust' is transparent. Third, at least in rich clusters, stars (and dust, and all the mass in galaxies) is pretty much irrelevant ... the known mass of inter-galactic gas (actually plasma) far exceeds that of the mass in galaxies. Fourth, in terms of numbers of photons, the CMB outnumbers all the emissions from all the stars, dust, galaxies, hot plasma, cold gas, ... combined (and dust is essentially transparent to the CMB .... except, of course, that it radiates in this waveband!) Fifth, outside of spiral and (some) irregular galaxies, there is (essentially) no dust. (and so on). So if dust is so important, then why doesn't DEILE work ONLY on spiral (and some irregular) galaxies? And why isn't hydrogen gas far more important in star-burst galaxies (where the SED is dominated by UV, from the massive stars in the star-bursts)? Quote:
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Do you mean that you have it in terms of energy density?
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One of the variables, however, is star-formation rate, which is observed to be falling. As I understand Sylas' analysis, for exponential model to match data, H cannot be “constant,” but must fall by 6% (or something) per billion years, which is in the same neighborhood as drop-off in star-formation rate. It is this prediction of DEILE that is within 1 OOM of observations, but more to my relief, at least in the right direction! As for how all the other factors enter into calculation of H: that is what I am uncertain of to many OOMs. The influence of one variable—star formation rate—is in right direction and to within 1 OOM, but I have no idea if the sum-total influence of the many variables is correct within any number of OOMs.
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What I mean is, when I do the energy estimate, there is enough energy to drive expansion; when I do the force estimate, however--as most people would guess--radiation pressure is not up to the task.
I suppose most people would conclude, "End of subject," and move on. As indicated above, I am almost ready to myself However, small voice keeps saying, "Don't give up," and the topic remains intriguing because there is no accepted answer to the mystery. In the popular reckoning, main difference between Newton's gravity and GR is tossing out absolute notions of space and time: both can bend and stretch, boggling the mind. But as for the problem of expansion of space, the problem with Newton's gravity is that it does not deal with infinity: Newton simply lacked the mathematical tools necessary to take on infinity. These tools (tensor-matrix algebra and the like) are over-my-head, so I am stuck trying to solve infinity problem with finite math...and results are unconvincing, to say the least. Calculating the gravitational energy of a two-body system is trivial. I assume everyone understands that calculating the energy of an infinite-body system is much more difficult. The only way I can wrap my mind around the infinity problem, is on a per-kilogram basis. The energy-output side of the equation—on a per-kilogram basis—is intuitively obvious: we can see so-much energy being radiated by visible matter, and Newton’s laws tell us there is so-much mass out there, so you simply divide energy output by mass. But how much energy is involved in the expansion? It is equally obvious this is much more difficult. Equations of GR give you an answer, but are not expressed in per-kg basis, however, so I do not know what they are saying in the paradigm I understand. And GR—to my understanding—does not include duality, nor reaction-force described above, so I am mistrustful of its results…besides the equations being in a different paradigm. But back to mechanism problem: if radiation pressure is enough to move dust, but not galaxies, how can it be causing expansion of space? I have to admit, I am almost out of rope here…but the usual caveats apply: infinity can be very counter-intuitive. I have done the estimate another way, and while I will not claim to have done it “right” this time, the answer I get I find very intriguing. If I can manage to explain why I find it so intriguing, perhaps those who—like me, are a little intimidated with tensor matrix algebra—will find it interesting also. Briefly, my estimate goes like this: radiation pressure is not enough to move galaxies at observed rate. However, when doing the energy estimate in Newtonian terms, a paradox arises. And the only way out of the paradox—that I can see—is to have space expand, per GR. So I am left with a mystery: force estimate says radiation no-can-do expansion; energy paradox of radiation, however, says space must expand. So I can get no further than my “grain of truth” position outlined a few posts back, that radiation has to have some expansive effect, but it may not be enough to explain the observed expansion rate.
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PW -- Plant Whisperer |
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When an elevator goes down, it loses potential energy, and when a star shines, it loses potential energy. Likewise, when an elevator goes up, it gains energy, and as the universe expands, it is in effect "going up," i.e. gaining energy. What I am arguing is that energy being gained by universe as it expands comes from the energy being lost by the stars as they form and shine.
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I don't remember - does ~5 Mpc come from some derivation (within DEILE)? Or is it simply what we observe (and so is yet another thing which DEILE needs to show is consistent)? |
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Light energy is radiant energy put out by stars, and is what we see when we look up at the stars at night.
Dark Energy (DE) is a term, in equations of General Relativity, required to reconcile theory with observed accelerating expansion.
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Sure, if the density of the earth-moon system were 26 OOMs less and expanding at same rate, the energy required would be about 26 OOMs less. But on a per-kilogram basis, it is about the same Take-II on energy estimate: As a refresher, the infinity Ground Assumption: If we can see a great distance and it looks essential uniform all the way, we assume beyond horizon is more of the same. If things are different beyond the 14 bly horizon, we can never know what the answer is, so it is only sensible basis for calculation. From the assumption, it follows that if we can correctly calculate what happens in one region, then same should happen everywhere, and we have the answer for the whole of it. To make the estimate tractable, we’ll make the usual simplifying assumptions…as far as they take us. As usual, refer to Figure 1; in particular the bottom cube (print it if you have not done so already ). The clump in the middle represents our local group of galaxies at present time in on-going freefall. NOVA, by the way, had a great animation of galaxy aggregation on the other night. At any rate, the congregation of galaxies is radiating away energy at rate estimated in Post 31 of 2E-8 j/s/kg (E= exponent of 10). The dimension of cube is 5 Mpc, the distance at which Hubble expansion overtakes local motion. Density of matter is cosmic value, 3E-27 kg/m^3.1st, convert distance to SI: 5 Mpc*3.3E6 ly/Mpc*5.9E12 miles/ly*1600 m/mile = 1.6E23 meters. The amount of matter in cube is: (1.6E23 m)^3*3E-27 kg/m^3 = 1.1E43 kg. Using mass of sun=2E30 kg, mass per cube is 5.5 trillion suns. Most is dark, however, so only 550 billion solar masses of radiant matter. In Oct. Sky&Tel article about upcoming collision between Milky Way and Andromeda, mass of the two-galaxy system is given as 3 trillion suns. So “at this time,” most of matter in our particular cube is contained in just two behemoths. Per the radiant power estimate, output of galaxy cluster is: 1.1E43 kg*2E-8 j/kg-s = 2.3E35 watts Using sun power output of 4E26 watts, this is 600 million sun-equivalent stars. Same article puts number of stars in Milky Way and Andromeda together at 700 billion stars. Most stars are much dimmer than Sol, which is why my estimated number of “standard-suns” is much lower than mainstream estimate of number of stars in the system. Estimate is on conservative side. In Newtonian approximation, we cannot ask: how much energy does it take to increase the size of every cube? This is not allowed. Nonetheless, it is easy to imagine a Newtonian 1st approximation. We can, in principle, calculate the power needed to expand any finite number of bodies in Euclidean space, and look for a convergence. I.e, calculate how much power is required to expand 2-body system at Hubble rate; then we can calculate power required to expand a 3-body system; a 4-body system; etc. Keep adding bodies in stable orbit around common center, and power-per-body required to expand system into pre-existing space should converge. We then guess that this is the energy required to expand a system with an infinite number of bodies ![]() At any rate, we’ll use the 2-body estimate as starting point. We will guess that the convergence value for infinity is the value of 2-body system multiplied by some geometry factor, say (4/3)Pi^3. So we consider a 2-body system consisting of just our local cluster of galaxies and the cube-next-door. We simplify calculation by assuming all the mass of the 2 clusters is concentrated in 2 point-masses in mutual orbit. Distance between them is the dimension of the cube, 5 Mpc or 1.6E23 m. Force between clumps, using F=G*m1*m2/r^2= 6.7E-11 N-m^2/kg^2*(1.1E43 kg)^2/(1.6E23 m)^2= 3.5E29 N Power is force times velocity (velocity of expansion), and expansion velocity is Hr: P = 3.5E29 N*5 Mpc*72,000 m/s/Mpc = 1.3E35 watts On per-kg basis: 1.3E35 watts/2.2E43 kg = 6E-9 j/kg-s In other words, using simplest approximation we can imagine—a finite-mass Newtonian universe consisting of only 2 “particles” (galaxy clusters) in mutual orbit—the energy required to expand such a system at Hubble rate, 1.3E35 watts, is the same as estimated radiant output of all that mass, 2.3E35 watts. In spherical-cow approximation, it looks like a closed system: gravitational energy is being gained at same rate radiant energy is being lost! Coincidence?
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PW -- Plant Whisperer |
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Or is ~5 Mpc what DEILE uses because it "is distance at which relative motion of galaxies within a cluster--up to 300 km/s--is overtaken by Hubble expansion" (i.e. an 'external' parameter plugged into DEILE to make it 'work')? |
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The 5 Mpc number--like 2E-8 j/s/kg estimated radiant power output--is an observable quantity.
In no way, shape or form were either of these numbers picked "to make DEILE work." Both of these number are my "best guess," because mainstream does not use these parameters, so I had to estimate them myself. I welcome refinements to these numbers by anyone.
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PW -- Plant Whisperer |
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The precise manner in which GR handles infinity and actual radiant power output (as opposed to my estimates) may change picture slightly, but central assertion stands: radiant power output of visible matter cannot be ignored.
The skepticism at this point revolves around mechanism: Yes, gravitational and radiant energy are the same in your rough-cut estimate, but this is could be coincidence. The universe is filling up with radiant energy. Ever more is being added; so what? In your 2-body Newtonian approximation of infinity(?), the gravitational force between two galaxy clusters to be overcome is 3.5E29 N. How does this 3.5E29 N compare to the radiation pressure generated by the two clusters, bearing in mind that both are mostly transparent in most wavelengths, so that the coupling of this force—whatever its magnitude—is expected to be very small, as you have argued? As indicated in earlier post and intuition would suggest, force calculation comes up short. There are 6E8 sun-equivalent stars in each cluster in above estimate, each one putting out 7E13 lb-f radiation pressure. I forget exact conversion factor between lb-f and N, but it is less than 1 OOM, and you can double the number by including pressure from both clusters, yet it is still only 10^23 N, at least 6 OOMs short. But wait… First of all, in mainstream DE model, same difficulty arises. Suppose, for sake of example, decay of dark matter turns out to be source of dark energy Same problem exists. We imagine the mysterious source of DE has been identified: it’s dark matter decaying into neutralinomos, or some such. How does this work? Existence of neutralinomos was undetectable in earthly laboratories until recently, when the new mega-giga-terra eV collider came on-line at CERN in Switzerland, and predicted quark-neutralinomo interaction was definitively detected. Neutralinomo interaction with ordinary matter is extremely feeble, which is why we missed them for so long. So how do these barely-interacting particles push galaxies apart? You’ve identified the source of the energy. Great. How does it work?For the moment, DEILE will ignore mechanism problem that plagues all DE models. Recall, infinity is a house of mirrors, as any one who has pondered Olbers’ paradox can attest. Newtonian gravitational energy requirement to expand 2-body system of real-world proportions, at observed Hubble rate, is approximately the same as radiant energy output of said 2-body system. This is telling us something. The only way I can think about infinity problem is in per-kilogram terms. I have shown what numbers result from that way of looking at problem. The equations of GR, however, are not expressed in per-kg basis; I have no idea what they would say if they were. It’s tricky, because in GR, “mass” is not strictly conserved, but rather mass/energy is. Throw a kilogram of matter into a black hole. It gets so hot and radiates away so much energy on the way down, the BH gains only 0.9 kg of mass, the other 0.1 kg being dispersed to cosmos at large in form of heat and light. Nonetheless, apparent equality still holds. Each cube is converting mass to radiant energy at rate of 1E35 watts, which by E=mc^2 is 1E18 kg/s. But while our galaxy cluster/cube is turning mass-into-radiation at rate of 1E18 kg/s, it is simultaneously gaining gravitational energy wrt everything beyond 5 Mpc at same rate, 1E18 kg/s ![]() In Euclidean space, an infinite universe suffers from Olbers’ paradox or a heat-death, depending on how you look at it. Non-conservation of space per GR solves this problem by allowing more space as-needed. Only mystery is, where is energy coming from to expand it? I’ve shown the observed 10^(-8) j/s/kg radiant energy output is significant. If equations of GR correctly represent reality, then somewhere in equations is a place for this 1E-8 j/s/kg energy-term. Only place I see in equations for it is DE. QED: Dark energy is light energy. Don’t ask me how it works. I’m just saying, it adds up ![]()
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PW -- Plant Whisperer |
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Only light is the energy in theuniverse.
F = G ( Ma + i Ea / c2 ) ( Mb + i Eb / c2 ) / r2 F = G Ma Mb / r2 − (G / c4) Ea Eb / r2 + i ( G Ea Mb / ( r2 c2 ) + G Ma Eb / ( r2 c2 )) The real part is Re( F ) = Fg+s, but I don't know how to deal with the imaginary part ; Im( F ) = G Ea Mb / ( r2 c2 ) + G Ma Eb / ( r2 c2 ). So an existing substance is to be described as S = M + i E / c2 . In a certain independent area, if M + E / c2 = constant ( in other words when M desceases by ΔM, E will increases by ΔE = ΔM c2 ), then abs( S ) = will be minimum when M = E / c2, because abs( S ) = root( M2 + E2 / c4 ). |
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IIRC, you have no mechanism ... no way to convert an observed space-density of photons (or integrated photon energies) into an expansion (or contraction) rate, other than for the universe as a whole, right? (I could easily have missed something important here!) What I am leading up to is: with the space density of photons varying so greatly, from near an O or B supergiant (say), or the accretion disk of a quasar, to the outskirts of a loose group of galaxies, why don't we see comparably huge variations in the expansion (or contraction) rate of the corresponding (relatively small) pieces of space? |
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We can wait until Peter Wilson replies, of course, but I think you'll find that DEILE and inflation (and whatever else that S&T article covers) are unrelated - DEILE is about the Hubble expansion, and H0 = ~70 km/s/Mpc.
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Regarding bright O & B super-giants and the more exotic: as I recall, radiation pressure from these bright sources blasts out huge bubbles around them. Local expansion rate in such systems may be high, but as we’ve seen, it depends on size/absorption characteristics of material, while on cosmic scale, everything is expanding together, or “co-moving,” as is said. Also recall that around a single radiant source, while expansion velocity for a particular body depends on its mass and cross-section, it does not depend on distance. Throw all these considerations into the soup-pot of infinity, and stir Like some voters in recent election, I’ve had to “change-sides” on CP estimate, now that slip of 26 decimal places in energy estimate has been corrected, according to latest study Anyway, current argument is that Coupling Parameter, CP, should equal exactly 1. Think radioactivity. If I have a finite lump of radioactive material, and it decays at finite rate, no matter how much I begin with, or how slow the rate, after a finite amount of time, every quantum within that lump will decay.You can make same argument about finite number of photons that leave the sun. All radiation has a non-zero extinction rate in universe, so all wavelengths decay exponentially—if slowly—with distance. Every quantum of radiation emitted by sun eventually interacts with another quantum somewhere, sometime. So integrated over all time-and-space, CP=1. As for how…one mystery at a time, please. The question was, or is, What is dark energy? Not, How does it work? Red-shifted photons lose electromagnetic energy from point of view of both sender and receiver, but sender and receiver are both gaining gravitational energy with respect to each other. Looking at the numbers, it appears as if energy in one form is transmogrifying into another. Don’t ask me how. Summarizing again: Observed density of universe: 3E-27 kg/m^3 Observed expansion rate: 2E-18 /s Estimated power required to expand (Newtonian) universe at observed rate: 1E-8 j/s/kg Estimated radiant power output of visible universe: 2E-8 j/kg/s At this point, I’d say we need mainstream value of radiant power output, not PW estimate. Nereid, you seem concerned about value of inflection distance, so we should get mainstream number for that, too. And while we’re at it, perhaps we can get someone who can navigate GR to tell us how much DE in mainstream GR model is required to produce observed expansion…in layman’s terms (!!!), i.e. SI units, or j/kg/s. Then we can compare the two numbers. If there’s a shortfall…then there’s a shortfall. But until then…there’s your answer ![]()
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PW -- Plant Whisperer |
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PW -- Plant Whisperer |
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