Age of the Universe is Meaningless!!! (Reference frame questions)

No. In fact, the approximate magnitude for temperature of the CMBR was predicted well in advance of its discovery, as early as 1948. Early estimates were in the right ball park given the accuracy of the data they were using. They tended to be a bit high in part because they underestimated the age of the universe. The subsequently observed temperature is a very close fit to what we expect from the current estimates of age (13.7 billion, to within a percent or two).An important prediction made in 1949 was "on the order of 5K", appearing in Remarks on the Evolution of the Expanding Universe by Alpher and Herman in Phys. Rev. 75, pp 1089—1095 (1949). That paper also gave a second prediction of about 1K for a different set of assumptions. The most recent measurements give 2.725K. What makes this powerful support for the Big Bang is not the precise temperature, but the Planck (blackbody) spectrum of the radiation, predicted in 1934 and confirmed in 1992. (Readable refs: Ned Wright's CMB page; and a good discussion by JPL astronomer Tim Thompson at the BadAstronomy forum.) Excellent question; you have put your finger on a major unsolved problem in modern cosmology. We don't know how large scale structure arises. But stay tuned; this is an active research area. Expect new insights when dark matter is figured out better.Back when the currently visible portion of the universe was compressed to within a region of about the size of an egg, it was probably during the inflationary epoch. The universe might not have been particularly homogenous prior to inflation; but inflation is something that made it homogenous. Details are a bit peripheral to our main discussion. The point is that once inflation was finished, the universe was extremely homogenous, but not quite perfectly so. There are tiny "ripples" which are interpreted as effects of vastly expanded quantum fluctuations. These ripples were detected by the WMAP spacecraft. Here is an image showing the resolution of the CMBR sky map from WMAP data; revealing differences of a few millionths of a degree, corresponding to tiny variations in homogeneity.
The problem is that the ripples don't appear quite big enough to account for large scale structure that has subsequently developed in the universe. On the other hand, we can't pick out dark matter in the CMB maps. I have no easy answers to this one. But for further reading, try these:

• Key theory of galaxy formation no longer conflicts with observations — a June 2004 press release from Uni of Chicago. This reports work by Andrey Kravtsov, with new simulations that explain the observed frequency of dwarf galaxies, which is less than had previously been expected. A major basis of the solution was simply more detailed and fine grained computer simulation of existing models.
• Astronomers see era of rapid galaxy formation; an interesting NSF press release setting out some of the puzzles.
• Giant Galaxy String Defies Models of How Universe Evolved, by Australian astronomer Paul Francis. This concerns large scale structure inferred in the early universe. His FAQ is particularly good.

600 km/s is fairly insignificant by comparison with cosmological red shift. It corresponds to a z factor of about 0.002; but most cosmological red shifts are much bigger than this.Note that my previous post indicated a velocity of 600 km/sec with respect to the CMBR. Actually, this is the inferred velocity of the local group of galaxies; the actual velocity of the Sun with respect to CMB is 369 km/s. Details in The CMB Dipole: The Most Recent Measurement And Some History (1996) by Charles H. Lineweaver (astro-ph/9609034).Since the Hubble constant is 71 km/sec/MPc, a 600 km/sec separation speed corresponds to about 8.5 MPc, or 27 million light years. Our "local group" of galaxies are all gravitationally bound together, and the group has a diameter of about 2 MPc. Cosmological red shift only becomes significant well beyond the local group.To put this in perspective, have a look at this Atlas of the Universe. Within 100 million light years there are about 2500 large galaxies, and 25000 dwarf galaxies. This corresponds to the "Virgo SuperCluster". However, there are hundreds of billions of large galaxies in the visible universe.It is not really possible to be in regions of space where the CMBR is "hotter" or "cooler", because this radiation comes from every direction, and has been travelling for 13.4 billion years. It is indeed a verified fact, in so far as science deals in facts, that all points in the visible universe have an equivalent claim to being central. A better way of putting it is that the expansion of space does not have a center. All of visible space is expanding. This question mixes up acceleration or deceleration of space with motions of matter in space. They are different things. Our velocity, in the sense of the local velocity in space of the material from which we are made, is something that changes over time under the influence of gravitational forces in a way that is hard to extrapolate. The rates of expansion can be extrapolated back quite effectively up to a point; but inflation puts some big question marks on extrapolations into the very early universe. An important recent discovery in cosmology is that the rate of expansion of space appears to be accelerating; but this has nothing to do with local motions in space. No, I don't think you can say that. Space and time are tied together, but to get to the details of how they are tied together would require us to get into the rather hairy maths of general relativity. The informal qualitative descriptions are basically attempts to explain the solutions of these equations to folks like you and I who don't think easily in terms of tensors. You can't really think up credible new informal descriptions without having a solid grasp of the maths which they attempt to explain.I've skipped a few questions here about time "changing". I can't see anything useful there; I think you are rambling. There is no point trying to come up with analogies unless you really have a solid grasp of the phenomena you are trying to explain. It is quite possible to define co-ordinate systems in which time "changes"; but that is just a way of assigning numbers to points in space time. However you assign the numbers, it must still represent the basic phenomenon that as time passes in the universe, available space expands. It is a real measurable phenomenon, with definite observable consequences.The most useful time and distance co-ordinates are linked to something concrete. For example, a year is the time it takes for Earth to orbit the Sun; a second is the time it takes to get 9,192,631,770 cycles of characteristic radiation from a ceasium-133 atom. If you just make time speed up or slow down by inventing a new arbitrary co-ordinate system, you find that everything speeds up, which is pretty meaningless. I don't see the connection between your questions and the text of mine you have quoted. Sure, various properties of matter change with time. Do you mean something special by "property of its existence"? The question about "perhaps H-bar got short enough for matter to condense" is, no offence intended, gibberish. In so far as one can give an answer to such a question, the answer is NO; it is not saying the same thing.When you let a gas expand, it will cool. That is basic physics. The expansion of space itself is a bit difference to expansion of a gas within space; but it still has a cooling effect. Expansion of space will even cool photons, effectively by stretching the wavelength; but I can't think of a simple analogue for such cooling in Newtonian physics.There are many timelines available on-line to list the various events considered to have occurred as the universe expanded and cooled. Here are two good timelines, from the Cambridge Cosmology Group; and Ned Wright's Brief History of the Universe. They both help indicate what is speculative and what is more reliably known. We do know what the expansion of space means. The physics for expanding space is almost a century old, and it is very well understood indeed. We don't know all the details of how rapidly or what drives it and so on; but the notion of what expansion means is very well understood indeed.The analogies of balloons, and explosions, and rising dough, and many others, are all attempts to help explain physics to non-experts. That's all. In actual scientific work, explosions are certainly not used as an approximation. The explosion is one of the worst analogies of all. No. Galactic red shifts point to expansion of space, not to motion through space. The tiny shifts due to motion through space are only useful for a few nearby galaxies. They are swamped by cosmological redshift for all the rest, and this is due to expansion of space.The CMBR is radiation that used to be very hot indeed, but is redshifted by an enormous factor to be very cold. This is redshift is due to expansion of space as well. Expansion of space does not produce movement of matter through space. It does have various effects, like cooling and redshifts.By periodicity of redshift I presume you mean quantization of redshift. This is now pretty solidly disproven by the very detailed surveys now available of vastly more of the universe.Hope all that helps; you've covered a lot of ground!Cheers -- Sylas

Thanks a lot for your reply and information. Okay, here is an example of what I meant by saying one thing and thinking another. I realize it is very hard to approximate our understanding with everyday language, but this makes absolutely no sense to me. Maybe what you are saying is that all the matter and energy of the visible universe was simply hotter? How can we say that the universe has width? Every point in the universe is the center and you cannot get outside of the universe with a measuring stick to see that, well yes, it is about the width of an egg. Okay, let me ask this, how FAR did the CMBR travel to reach us? I assume you'll say: 13.4 billion light years. As we keep going back in time, the apparent 'distance' it traveled would be less and less until at the BB it would have to travel almost no distance at all to reach the center wherever you are. I assume this is how we get the idea of 'size' when referring to the size of the egg moments after the BB. But as I've said above, it seems meaningless to refer to the 'size' of the universe since the universe IS size so to speak. I mean you can't say that the dimension of length is such and such units long.So instead of extrapolating back spacially, why not extrapolate back in time? Why not define the progress of the universe by how 'fast' time flows instead of how short or long a distance energy must travel to get to the center? Both are equally paradoxical, but both say the same thing. Now time flows slow enough that light takes 13.4 billion years to reach us, but close to the big bang time flowed fast enough that energy could roam to the center much 'quicker'. Perhaps all the math has been worked out with the first idea in mind since we naturally think of time as a fixed dimension. But you are right... I'm not willing to get into all the hairy mathematical proofs and find out. This is true... I have grasped the idea in my mind, but trying to explain it is another story... much less trying to prove it mathematically. You're right, everything speeds up. Okay, take your ceasium clock back 4 billion years. It will still tick away at 9,192,631,770 Hz, but you will find that the CMBR has been traveling only 9.4 billion light years to reach you. So do you conclude that the 'size' of the universe shrank or that the time flow of the universe increased? It seems to me that both conclusions are one in the same, its only harder to imagine a change in time flow rather than a change in the size of the universe even though both analogies are paradoxical. Well, its getting late and this is slightly off subject so I'll refrain from trying to explain myself better.Thanks again; you've been very helpful. I won't be around to reply again for another week.

Difficult, isn't it?The problem is simply that our everyday intuitions don't work. I am saying what I mean in the above extract, and it is a consequence of expansion of space. I'm not saying it was simply hotter; I really am saying that there is a notion of width, and expansion, and curvature, all applied to empty space.As indicated previously, ultimately this is described mathematically. But tensor maths and Riemannian geometry and general relativity are a bit advanced for an introduction, so we use some analogies.You can speak sensibly of the size of the Earth without getting outside the Earth. There is a finite amount of available space on the Earth, and you can measure how much there is without needing to get out into space. And if somehow the radius of the Earth was increasing, then the amount of space would get larger (like a balloon). We do something like this for the universe; but in three dimensions rather than in two dimensions like the surface of the Earth.You don't need to get outside the universe to recognize and measure its expansion; and indeed the expansion of space means that all of the space that is now visible used to be contained within a much smaller region. This is not just dispersal of objects by moving them through space, it really is expansion of space itself. Measuring distance is not quite that simple when you are working in an expanding space; but yes, a reasonable way to think of it is to consider that the CMBR has travelled 13.4 billion light years. Actually, I made an error in my last post. The universe is 13.7 billion years old, and the CMBR started when then universe was 379,000 years old, which is a tiny tiny fraction of a billion. (I mixed up billions and millions) So the CMBR is 13.7 billion years old, and has travelled 13.7 billion light years.However, the size and expansion of the universe is not as you have described it above. To get a handle on how weird this is, consider two photons of CMBR coming to us from opposite directions. They were emitted from two atoms, which are at present a long long way apart (about 42 billion light years). But when those two atoms emitted the photons we now see, they were quite close together, because since then the space between them has expanded.What you really need is a simple introduction; but the question is — what level? My favourite reference is Ned Wright’s Cosmology Tutorial, and FAQ but it is undergraduate college level. NASA has some good stuff at Origin and Destiny of the Universe as part of their Imagine the Universe series, and Cosmology 101 at the WMAP pages. Bear in mind that all tutorials are using analogies and approximations, and thus can say things that might sound superficially inconsistent with each other. This is often just a case of explaining the same fundamentals in different ways. I personally think Ned Wright’s material is the best I’ve seen on-line.[skip a few points]You aren’t getting this. The expansion of the universe has nothing whatsoever to do with the CMBR being at a lesser age 4 billion years ago. It really is expansion of space itself. It is not the same as altering time flow. You can’t get the same thing by altering time flows.Consider this. Imagine you live on a planet, and except that the planet is increasing in size. You try to explain this to someone, but they keep insisting that perhaps it just means clocks ran at a different speed in the past. That person does not yet understand about expansion. It IS NOT the same as changes in time flow. It REALLY IS expansion of space. It’s hard to understand, but not impossible. It is only impossible if you insist on trying to work from your own intuitions rather than making the hard effort of learning what it really involves. You won’t be able to learn about it overnight. You’ll need to do a fair bit of reading. There are good books available as well.Best of luck with it all. I’m happy to keep answering questions; but that can only take you so far. Ultimately it will need a lot of study of your own.Cheers -- Sylas

Sylas It is even more difficult since the colloquial use of terms is not the same as the science use of those terms.Einstein started his arguement for special relativity on the difficulty present in the term space.The scenario he set up started with 2 people,one on board a train moving at constant velocity the other on the ground outside this train.Here is the thought experiment.Imagine the man aboard the train goes to a window and drops a ball from there to the ground.Now,neglecting air resistance to simplify things,the man on the train will witness the ball to descend straight down to the earth since from his perspective he and the train can be considered to be motionless while everything moves pastthe train towards the rear.The person on the ground in the meantime witnesses the ball to descend in a parabola curve in the direction of motion before impacting earth. This leads one to ask which is the proper geometry to account for two different paths? This in turn leads to other consequences concerning the other things we measure.This is how relativity in the special case plays out. Matter at the beginning{10*-43 sec and on}is not the same as matter we know of today.Energy is not ,as many textbooks state,the capacity to do work.From this website http://home.pacifier.com/~ppenn/whatis2.html Energy equals mass times the constant of velocity of light squared.These two are equivalent and are the point of conservation laws.When energy is added to the state of matter in a given scenario we detect an increase in mass as a consequence. When we release enrgy into the manefestation of forces{strong weak electromagnetic gravity} we find the books balanced by a decrease in mass.We unforunately use terms such as chemical energy potential energy etc. even though they are the results of the four forces I might be wrong on this but i belive the CMBR permeates all space. Indeed if you place your television on a channel that produces "snow" about 1/3 to 1/2 of that snow is a result of the background radiation.Just my two cents worth.

You are quite correct: the CMBR permeates all of space. It was on this forum that I first learned about the impact of CMBR on a TV. I think you've overstated the proportion a bit -- as did I when I first described it. Most sources seem indicate the snow is about 1 to 10% due to CMBR. This page describes how to get as high a proportion of CMBR as you can.Cheers -- Sylas

Thanks for your reply. You're right, I probably have no real grounds for debate until I've understood the mathematical proofs rather than the analogies created from them.But while we're at it, I'll just give it one more try. From a mathematical perspective, we can view the position of a particle as
X(t)=t^2
This means the particle is accelerating in the positive x-direction. But we can just as easily say t(x)=SQRT(x). I don't see any logical or mathematical reason why time must always be the independent variable and space the dependent variable. The only reason I see is a practical one. We experience time as a sort of a constant flow and therefore we don't have words or frame of reference to describe a change in time flow. But we can mathematically go from dx/dt to dt/dx by taking 1 over both sides of the equation and it is still an equality. Anyway, if this is still gibberish, you need not reply to this argument. I assume there is a mathematical equation that this is analogous to, but in plain english it is gibberish. For something to 'expand' by definition it must take up more space. If space is expanding, of what does it take up more? For something to have 'size' it has to have locality and boundaries. If every point in space is the center, it can have no edges to measure between. Perhaps scientists should coin a new word for this behavior of space, but it certainly shouldn't be called 'expansion'. It is a fundamental change in the nature of the universe describable not by words, but only by formulas (which can all have their time derivatives inverted).Thanks for your links and answering many of my questions. I haven't really done a lot of reading about this since I read The Elegant Universe several years ago, and I've forgotten a lot since then. I do need to do more reading before I can seriously debate this topic, but it's fun to think about.

You're doing fine, Hangdawg13. It is confusing, and I've been trying these last few days to get to grips with some of the maths myself, and having trouble with it. I think we can still get a long way without the maths, however. The universe does take up more space. Space itself takes up more space.The easiest visualization is for a "closed" universe. A closed universe has a finite number of galaxies, but no edge. That may sound impossible gibberish; but it isn't. It is a plain accurate description. Put yourself in the position of someone who has only ever heard of a flat Earth; and has no concept of the sphere. Tell them that if you start walking in any direction, then eventually you get back to you starting point. Gibberish? No; an accurate description of one consequence of the Earth being a "closed" two dimensional surface. If everyone on Earth has a square kilometer of there own, there is only room for about 500 million. If you've only ever thought of a flat earth, that sounds like gibberish. Why can't the people who are furthest away go a bit further and map out more area? Because the Earth is a closed curved surface, with a finite area. Of if you measure out a very large circle on the Earth, the circumference of the circle turns out to be less than 2*pi*r! Think about it...The same thing can happen in a three dimensional space. If you head out in a particular direction (at many times faster than light, so that you can get around before the universe expands too much to prevent you finishing the journey), you will eventually come back around to where you started. If the universe is "closed", then it has a finite volume, even though there is no boundary or edge. So there is only space for a finite number of galaxies.Since the universe has a volume, it can expand; and that is exactly what it is doing. Over time, there is more space available. The distance "around" the universe, being the longest "straight" line before it comes back to the starting point, is getting longer.We can extend this to a "flat" or "open" universe as well. In these cases, the simplest models are for infinite amounts of space; but we can still speak sensibly of expansion. A very large sphere in an "open" universe might have a surface area greater than 4*pi*r². One quality of expansion is that if you take objects sufficiently far apart, the distance between them is increasing, even if those objects are moving towards each other as fast as they can (speed of light).You could have the same thing if you were living on an expanding planet. Even if you walk towards some destination, the distance remaining can actually increase, if you are sufficiently far around the planet for the expansion to overwhelm your walking speed. Nope. It really is expansion. The words fits perfectly. It is the right word. These things can be described by words. I'm not suggesting you can't understand without the maths; but cautioning that the simpler unmathematical descriptions, though accurate as far as they go, still tend to be less complete. In the same way, we can explain an orbit intuitively, but when you can deal with it mathematically you get a deeper appreciation. So don't be put off; the maths is not essential.But expansion is definitely the right word for what the universe is doing.Cheers -- Sylas