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IOW, if you slice up a cube, 1 Mpc on a side, into 1000 smaller cubes, what is the variation in the content of each cube? Repeat, with a cube 10 Mpc on a side. Repeat, with a cube 100 Mpc on a side. ... You can think of 'content of each cube' as 'how many galaxies are in this cube?' (The P(k) in the Tegmark webpage has a precise, quantitative definition of these ideas; the data are from SDSS). If the universe gets smoother, as you go up in scale, then the variation in content, among the 1000 cubes, gets smaller (as the cube from which they were made gets bigger). Quote:
The observations are that, no matter what waveband you observe in (other than those in which the CMB is detectable), the more carefully you observe, the less 'diffuse background radiation' you see ('the night sky is dark'). This is (or was) a paradox - if the universe is static, infinite, and homogeneous (on scales above~100 Mpc, say), then it should shine as brightly as the surface of the Sun. So, to what extent can DEILE match the observations that the night sky is dark (that there is, apparently, no diffuse background radiation, other than the CMB)? |
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Let's make sure we have a common basis for discussion, shall we? The "Hubble constant", H0 is simply the slope of the line in the Hubble diagram - a plot of redshift against distance - at the present time (that's the subscript 0). From a observational point of view, we can ask "to what extent do the data, when plotted in a Hubble diagram, fall on a straight line?" (within the limits of the errors, of course) If the data do so fall, then the Hubble constant is constant. And one interpretation of such a straight line is that there has been no change in the rate of expansion of the universe, as far back/away as the furthest data points on the diagram. If, on the other hand, the data show a clear ("above the noise") trend away from a straight line, then the Hubble constant is not constant. A simple approach is then to see, in such a case, if the data fall on a line that can be described, so the residuals are "just noise", in terms of two parameters, H0 (the Hubble constant 'now') and a deceleration parameter, q0. My question to you can now be rephrased as "Can you provide observational data showing that the deceleration parameter, in the Hubble diagram, is zero (within the limits of the noise in the data)?" My assertion, way back in this thread, is that there are now hundreds (thousands?) of good, independent data to show that the deceleration parameter is not zero (here is a popular page showing this; here is a somewhat dated backgrounder; and here is the wiki page on the Hubble constant). Quote:
(I will address the first [snipped] part of your post later) |
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Assuming the “standard” interpretation of red shift, the observation to-be-explained is the Hubble relation: dr/dt = H*r > 0 (r > 5 Mpc) [1] Initially, a hypothesis was put forward, that there was a big explosion in the past. But that didn’t work, due to the horizon and flatness problems. So a 2nd hypothesis, Inflation, was added to the 1st. But then, along came acceleration problem. So a 3rd hypothesis, Dark Energy, was added to the first two! And you can clearly see that the DEILE hypothesis does not jibe with these other 3 hypotheses, so you are assuming something must be wrong with it. But the DEILE hypothesis is a different hypothesis. It must be judged on its own merits, not on its compatibility with the preexisting, convoluted conjectures it is intended to supplant! Consider just the Hubble relation [1], and compare it to an observation made long before Hubble’s: dr/dt < 0 (on average, r < 5 Mpc) [2] The DEILE hypothesis it that [2] explains [1]. [2] is associated with the release of energy, which we see as radiation. [1] is associated with a gain in energy, per the law of gravity. The energy released by [2] explains the energy required by [1]. It doesn’t work in a Newtonian universe with one fixed, absolute frame-of-reference, but in the everything-is-relative real universe, local contraction occurring simultaneously with non-local expansion is not a problem. Or is it? You are continuing to ignore this assertion, that the universe is fundamentally bipolar or dualistic. Remember, the idea that light had to be either a particle or a wave was a stumbling block to progress for a long time. You cannot understand light until you accept that it is doing two things at once: waving and "particlizing." And you cannot understand the cosmos until you accept it is both expanding and contracting. Your statement, “The expansion of the universe is automatic…well, contraction is also a solution…” reflects an either-or prejudice. If you do not see that the universe is contracting [2] even as it is expanding [1], then you are not seeing the forest for the trees. You could be literally missing half the picture, and my words befuddle you, because they describe the part you are not seeing. But so far, you have not weighed-in decisively on either side of this key observation. |
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![]() The important point is that DEILE is a theory of evolution. It aims to explain the instantaneous rate of change, the present 73 ppt/yr expansion for r > 5 Mpc, not the structure. Nonetheless, the DEILE belief that “H is constant until proven otherwise,” as we saw above in the math-section, translates to a much longer history. So there has been much more than 14 byr for the observed structure to form. At the same time, central to the DEILE hypothesis is the assumption that the universe is “flat,” or uniform, from “large” scales off to infinity. The graphs seem to show that variation approaches zero at large scales. Is that a correct interpretation? If so, the DEILE hypothesis rests on this observed large-scale uniformity, on the one hand, while providing plenty of time for small-scale structures to form, on the other. Quote:
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Keep in mind, this is to a first approximation. When I say “constant-H,” I really mean “changes very slowly.” In the DEILE hypothesis, the expansion rate is related to the contraction rate, that is (approximately) the star formation rate. The star formation rate is known to be slowing down, so H should be slowly decreasing. But let us be clear on what the real bone of contention is here. The basic observation is: remote objects are (apparently) receding, and the remoter the object, the faster is the apparent recession. The question is this: Was that recession velocity attained all-at-once, or was it attained gradually over billions of years? In the BBT picture, the recession velocity is assumed to have been attained essentially all-at-once, during the Inflation era. In the DEILE picture, recession velocity is attained at an infinitesimal rate over cosmic time-scales. The difference between these two ideas is the difference between Creationism and Evolution. In the Genesis story, life is created all-at-once. In one divinely inspired moment, God creates all the plants and animals (and disease-causing microbes…what was He thinking!?!). In the evolution story, these things take “billions and billions” of years. Now, there is nothing to say God could not have done it all-at-once, a la Genesis. But evolution is a much more natural explanation. Likewise, there is nothing to say that Inflation could not have accelerated an entire galaxy to half the speed of light in a trillionth of femtosecond, a la the BBT. But the DEILE hypothesis, that it took “billions and billions” of years to reach such velocity, is a much more natural explanation. So the DEILE hypothesis explains one observation (on-going expansion) based on another observation (on-going contraction). It is simple and natural, and makes no ad-hoc conjectures. The BBT, on the other hand, attempts to explain the same observation by invoking 3 completely unnatural ad-hoc conjectures, while simultaneously completely ignoring the on-going contraction. |
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But whether it is dark or light, something is supplying energy to remote objects, so the distance between remote objects is increasing, i.e. space is expanding. The EMS is also the starting point of the observation that all gravitational systems are in flux. The moon is spiraling out; Phoebos and Charon are spiraling in. No gravitational system will hold perfectly still. Every system, when you examine it at the level of parts-per-trillion per year, is changing, plus or minus. So we should expect that the universe at-large is like every sub-system of which it is comprised: changing! Quote:
Second, I would say, isn’t it obvious something is wrong with the BB model? The math is only as good as the model it is based on, after all. Part of the “wrongness” with the model, however, is the part you keep ignoring, so I can see how it would not be obvious to you. And that part is the duality; the (net) contraction occurring at distances < 5 Mpc even as the (net) expansion is occurring at distance > 5 Mpc. It’s just completely absent from the models. It’s not to be found anywhere in the equations, which express but one distance scale, r. But there are two distance scales in the universe: r < 5 Mpc and r > 5 Mpc. In the former realm, dr/dt (net) is a negative number; in the latter, dr/dt = H*r, a positive number. If your model does not include these two different distance scales, it does not reflect reality. The math may be bullet-proof, but if the model does not take into account these two realms, it’s just a paper tiger. The DEILE takes duality to heart. In fact, duality is the heart of the DEILE. The universe is doing both. The one (local contraction) explains the other (non-local expansion). |
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If you are "asserting [...] the expansion is accelerating at a rate equal to H*v", then we need to look at a different diagram, one plotting acceleration against speed. Can you provide a link to such a diagram? Alternatively, can you confirm that you have, yourself, found the (acceleration, speed) data, plotted it, and could (in principle) share it with us? |
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Or maybe not: "So there has been much more than 14 byr for the observed structure to form" How much longer? Why haven't we found galaxies or quasars (or GRBs) with redshifts of 10, 30, 100, ... 1 million? Quote:
Specifically, there's nothing which tells me what the diffuse, background electromagnetic radiation should be, in the DEILE universe. How bright would it be? How would that background brightness vary, across the various EM wavebands? |
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But the disconnect has a lot to do with interpretation. Technically, all we have are some spectrums of remote-looking points of light. So the question is, what are we looking at? What the observers do is characterize the spectrum in a certain, and say, “This looks like a type 1a SN, a standard-candle of known peak absolute magnitude X.” And they plot the observed magnitude against the observed red-shift on a graph. If the expansion is unchanging, and all the assumptions about the points-of-light are correct, you get a straight line, magnitude-vs-redshift. If the expansion is slowing down, however, as predicted by the BBT prior to 1998, the line will curve down at large redshift. If the expansion is accelerating, as “postdicted” by the DEILE, the line will curve up. So how do we determine if the line is straight, curved up or curved down? This is very difficult, and was not done definitively until 1998. But why was this observation so hard to make? First, as a point I have made repeatedly, the expansion does not really stand out from local variant motion until about 5 Mpc, so there is no “line” at all on the LHS of the graph, its just data points all over the place. Then when you get out past 5 Mpc, everything is pretty faint, and there are few good distance indicators, so it is very difficult to get rid of the noise, and make the data settle down into something clearly “trending up” or “trending down,” i.e. accelerating or decelerating. Here’s the kicker: if you follow my math in post 91, you will recognize that I am arguing that the expansion is exponential: r(t) = r(0)*e^(H*t) {r being distance; t being time} This means that velocity-vs-time is an exponential curve (things go faster and faster). But when the value of the exponent is such a small number (0.0000000073/yr), it looks very much like a straight line, until you get to immense distances! And since the data points are all over the map, about all we can see is that the line curves up, and we can argue ‘til the cows come home whether it is an upward-curving exponential curve, as per the simple DEILE thesis, or some other kind of up-ward trending curve, per the fancy-dancy mainstream BB-plus-Inflation-plus-DE FRW universe with GR and tensor-matrix algebra. In the limited range where the data are clear, the simple DEILE model and the convoluted BBT are indistinguishable. This is why I keep saying there are two ways to interpret the data. But precisely because there is not clear-cut observational distinction between the models, we must return to the more fundamental concept: duality. At distance scales of less than 5 Mpc, the average distance between things is decreasing; at distance scales greater than 5 Mpc, the average distance between things is increasing. Mathematically: dr(ave.)/dt < 0 for r > 5 Mpc dr(ave.)/dt = H*r > 0 for r < 5 Mpc In other words, there are two fundamental realms to consider: the near and the far. In the near, there is a net falling-in. Only when you go to immense distance is there a net falling away. Now consider this observation in the context of Einstein’s famous conclusion that GR showed the universe must “expand or contract.” Quote:
This duality is so fundamental to the DEILE picture, yet so “looked past” (i.e. ignored) by the BBT that we must come to an understanding on this. Is the universe doing one-or-the-other, or is it doing both? Are you in agreement with the Ground Observation of the DEILE thesis, that the universe is in fact doing both? If not, what are you picturing? If we are not in agreement on this most essential issue, I have no idea what “world view” you are subscribing to. Last edited by Peter Wilson : 17-June-2006 at 08:28 PM. |
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I can make neither head nor tail of what "H" is supposed to be, in your idea, Peter Wilson - the (local?) constant of proportionality between speed and distance? between the (local?) acceleration and speed? something to do with "expansion"*??
So, what "r > 5 Mpc" observational data leads (or could lead, if one were to do the number crunching) to a determination of the (local) value of H, in the DEILE idea? *"r(t) = r(0)e^(H*t)", whatever "r" and "t" may be. |
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Unfortunately, I misplaced the graphs (did the exercise in 2003), and my graphic skills are wanting anyway (for those who haven’t noticed that my Figures 1 & 2 are no longer viewable on MySpace…phooey on them!), so I’m having difficulty sharing the graph showing that a(dv/dt) = H*v is a good fit with the observations, thus H-is-constant is a good starting assumption. Nonetheless, with a little imagination you can see that this is so. Picture an exponential curve. Now look at the Hubble Diagram. You can see that there is a range over which the exponential curve fits the data points. Quote:
As I’ve tried to make clear above, the H-is-constant assumption fits the observations out to the point where GR significantly changes the picture, and I cannot say if it does or does not fit the observations beyond that point. So I can say something like, “The observations are consistent with a model in which H has been more-or-less constant for the last 5 byr,” but I can make no such statement going back 98 byr! And again, because in the DEILE hypothesis the expansion rate, H, is proportional to the contraction rate (basically the rate of star formation and galaxy growth), it should decrease with time as star formation and galaxy merging slows down. So the only definitive answer to your question I can give at this point is: Since the time of photonic decoupling (the formation of the CMB), structure in the universe has had much more than 14 byr to form, but probably substantially less than 98 byr. This inability to give an exact reckoning of the time available for structure formation is not a deficiency in the theory, however. The DEILE is about the present, not the past. All statements about the past are ancillary to the hypothesis, that the present rate of local contraction (r < 5 Mpc) supplies more than enough energy to drive the observed rate (0.00000000073/yr) of non-local (r > 5 Mpc) expansion. |
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