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By homogeneous on the largest scale I am referring to billion-light-year scales. And, most importantly, I'm referring to the observation that there isn't a single direction in space or in time of a more compact universe as would be expected if we lived in an expanding universe. The issues of structure of the near and far universe are far from being definitively resolved at this time. Major new finding have been occurring just this past couple decades. For example, a whole class of galaxies called Low Surface Brightness Galaxies have been discovered. They may number as many as the bright ones. Needless to say, these will be difficult if not impossible to observe at cosmologically great distances.
As the illustration I've included on this page demonstrates our universe is very clumpy. According to the Big Bang model, a model which is "way over its sell by date," as a recent email correspondent wrote, in the Big Bang beginning the outpourings of matter and energy were extremely smooth. The cosmic background radiation that is smooth to better than one part in a hundred thousand is claimed to be the relic of the Big Bang fireball. How the universe got to be so clumpy when it supposedly started out so smooth is one of the major problems for the model. Eric Lerner, (author of The Big Bang Never Happened: A Startling Refutation of the Dominate Theory of the Origin of the Universe [1991]) informs us of the dilemma that the Big Bangers face:
TOO BIG FOR THE BIG BANGThe supercluster complexes directly contradict the homogeneity assumed by the Big Bang. This homogeneity has always been a problem, since it's clear that the universe is so clumpy: how did it get that way if it started out so smooth? The general answer has been that there were very tiny clumps in the early universe; through gravitational attraction these clumps gradually grew bigger and bigger, forming stars, galaxies, and clusters. Of course, the bigger the clump, the longer the time to form.
For stars, a few million years is enough, for galaxies one or two billion years are needed. Clusters take even longer. By the time superclusters were discovered, there was an obvious difficulty, and in the eighties cosmologists were hard at work trying to overcome them. Tully’s objects made the situation impossible—they were just too big to have formed in the twenty billion years since the Big Bang.
It’s not hard to see why. By observing the redshifts of galaxies, astronomers can see not only how far away they are, but roughly how fast they move relative to one another—their true speed, ignoring the Hubble velocities that increase with distance. Remember, redshifts indicate how fast an object is moving away from us. Redshifts increase with distance, but also with an object’s own speed, relative to the objects around it. It’s possible to sort these two velocities out, using other distance measurements, such as the one Tully and Fischer devised. It turns out that galaxies almost never move much faster than a thousand kilometers per second, about one-three-hundredth as fast as the speed of light.
Thus, in the (at most) twenty billion years since the Big Bang, a galaxy, or the matter that would make up a galaxy, could have moved only about sixty-five million light-years. But if you start out with matter spread smoothly through space, and if you can move it only sixty-five million light-years, you just can’t build up objects as vast and dense as Tully’s complexes. For these objects to form, matter must have moved at least 270 million light-years. This would have taken around eighty billion years at one thousand kilometers per second, four times longer than the time allowed by the Big Bang theorists.
The situation is really worse than this, because the matter would first have to accelerate to this speed. Even before this, a seed mass big enough to attract matter over such distances would have to form. So an age of one hundred billion years for such complexes is conservative. Simply put, if Tully’s objects exist, the universe cannot have begun twenty billion years ago.
The initial reaction of most cosmologists to Tully’s observations was to reject them altogether. “I think Tully is just connecting the dots in claiming to see these clusters of clusters,” Marc Davis, a Berkeley cosmologist, commented dismissively. But that position has become increasingly untenable. During 1987 Tully carefully analyzed his data, proving that it is extremely unlikely that the clustering could have come about as a chance arrangement of random scattered clusters, or as a result of flaws in his calculations.
In 1990 the existence of these huge objects was confirmed by several teams of astronomers. The most dramatic work was that of Margaret J. Geller and John P. Huchra of the Harvard-Smithsonian Center for Astrophysics, who are mapping all galaxies within about six hundred million light-years of earth. In November of 1989 they announced their latest results, revealing what they called the “Great Wall,” a huge sheet of galaxies stretching in every direction off the region mapped (Fig. 1.5). The sheet, more than two hundred million light-years across and seven hundred million light-years long, but only about twenty million light-years thick, coincides exactly with the supercluster complex mapped by Tully. The difference is that the new results involve over five thousand individual galaxies, and thus are almost impossible to question as statistical flukes.
Still larger structures were uncovered by an international team of American, British, and Hungarian observers, including David Koo of Lick Observatory and T. J. Broadhurst of the University of Durham, in England. The team looked very deeply into space in two opposing directions, scanning only narrow “wells” in space. To their surprise they found galaxies clustered in thin bands, evenly spaced some six hundred million light-years apart like the rungs of a titanic ladder. The entire pattern stretched across a quarter of a diameter of the observable universe, a distance of over seven billion light-years. The galaxies seemed to be moving very slowly relative to one another—no more than five hundred kilometers per second. At that speed, the gigantic void-and-shell pattern appears to have taken at least 150 billion years to form—seven or eight times the number of years since the Big Bang allegedly took place.
Notes:R. Brent Tully and J. Richard Fisher are the authors of the Nearby Galaxies Atlas (Cambridge University Press, 1987). At Brent Tully's web page one can find a really neat download of a journey through our supercluster complex. It's a large file, good enough for 28 seconds of a television science show. Download it during non peak periods if you use a regular modem. Once you have saved it to a file in your computer it will quickly play everytime.
