“The foolish reject what they see and not what they think; the wise reject what they think and not what they see.”
Huang Po (d. 850 C.E.)
The Big Bang Theory isn't what it used to be. New discoveries have led to modifications that are so significant that most people have no idea what scientists are thinking. In fact, the theory has changed so drastically that there isn't even a bang involved. There is no limit to the volume of the universe, and even the word universe has been replaced with "observable universe", except that in common speech, "universe" is the word that scientists frequently use instead of "observable universe." That is, the two terms, quite different in meaning, are being used interchangeably.
In order to understand what happened to the theory, it is necessary not to conflate concepts that have developed at different times. Scientists don't talk much about the changes in the theory so as not to confuse the listener, or possibly to avoid appearing wrong. At my age, however, I have a unique perspective. I can remember the universe when it was a very small place. That, in itself, is something many people forget, and many scientists would like to forget.
The central elements of the story are well known. Hubble (and others) noted that the distant galaxies were red shifted proportional to their distance and suggested the galaxies were receding from us faster as their distance was greater. Lamaitre imagined reversing the expansion and figured that, all other things being equal, all of the mass in the universe must have been in the same place at the same time. The devil is in the details.
As I said, the universe was a much smaller place when I was young. The most distant galaxies known were only about 6 billion light-years from Earth. It was reasonable to think that there was an explosion that hurled matter away from a single collection of matter, and that the distant galaxies had much more momentum than those closer to us. From the perspective of any point in the universe, all other galaxies would appear to be receding, but given a finite amount of matter, there would be a limit to the universe beyond which there would be no more galaxies. A spherical universe was suggested, and graphics that purport to show the structure of the universe all show this assumption. Two principles were discovered that belied this comfortable picture of the universe.
The two principles are the Cosmological Principle and the Copernican Principle. More about these later and what they seem to imply.
In the meantime, discoveries have shown the universe to be extremely large - much larger than earlier observations had indicated. In 1975, for example, a galaxy was discovered that was 8 billion light-years away. It became increasingly apparent that matter could not have traveled to the radius of the "observable universe" without exceeding the speed of light. The first major change was to postulate a "plasma" that had no mass but expanded due to explosive power, followed almost immediately by the concept of "inflation" when an explosion of plasma alone was noted to be an inadequate explanation for the distribution of matter.
Then, supposedly, the inflation stopped after the plasma cooled, and matter appeared everywhere.
And then it started up again, or slowed down (take your pick).
And now, it seems to be accelerating.
The fact is that, if you examine the universe and how it behaves, there is no connection to the original inflation, hypothetical plasma, or cooling. It simply expands and appears to be accelerating. Lamaitre’s observation that the galaxies are separating only begins after the appearance of matter. All of the galaxies were therefore never in the same place (as matter) at the same time.
The diameter of the "observable universe", after extrapolating the expansion to the present time, is about 94 billion light-years. Do not imagine that what we can see and extrapolate is all there is, although there are some that would imply that. This brings us back to the two principles mentioned above.
The cosmological principle says that the universe, the whole universe, is "isotropic and homogeneous" on the large scale. That means that it is uniform throughout - not just as far as can be seen, but for the extent of the universe - which seems to be infinite. There seems to be some confusion on the part of astrophysicists when they say, "The universe has no center, and it has no edge." Some are talking only about "space" and others mean that the universe is, in some multidimensional sense, “spherical”, however the cosmological principle says that if there is space, it is filled with the same density of mass - everywhere.
On the other hand, the implications of an unbounded edgeless universe have not totally escaped some cosmologists:
Stephen Hawking“The quantum theory of gravity has opened up a new possibility, in which there would be no boundary to space-time …. The universe would be completely self-contained and not affected by anything outside itself. It would neither be created nor destroyed. It would just be…. [If] the universe is really completely self contained, having no boundary or edge, it would have neither beginning nor end: it would simply be.”
The Copernican Principle says that there is no perspective that is more correct than any other perspective (similar to relativity). One could be on a distant galaxy and the universe would look the same in terms of the isotropy and homogeneity of the universe. There is no "last galaxy" beyond which there are no galaxies - the universe is not an island in the middle of emptiness.
But, and this is a big but, the Big Bang theory has two implicit assumptions: The mass in the universe is finite (and could therefore have been in one place) and the mass in the universe is fixed (from the First Law of Thermodynamics which also assumes that the universe is a closed system).
We'll leave the "apparent contradiction" of an infinite universe that follows the Cosmological and Copernican principles for now and move to another issue: Density of matter.
Ignoring for the moment the Plasma inflation, cooling and supposed precipitation of mass that later formed galaxies, Lemaitre and others have said that, if galaxies are receding from us, and have been for the entire history of the (observable) universe (since the appearance of matter), then at one time the galaxies were closer together than they are now. Given that the distant galaxies emitted light in the past, we are effectively looking back in time as we look outwards into the universe from Earth. If the universe is truly about 13.72 billion years old (the whole universe), we can now trace the entire history of the universe in the small sample we can see. We are effectively examining fossils of the universe.
So galaxies were supposedly closer together 4 billion years ago than today, and even closer together 8 billion years ago. But our observations show that the density of mass is constant throughout the history of the universe. On a large scale, the distribution of galaxies is "uniform" (although there is lumpiness to the observable universe due to the gravitational interactions of the mass, the lumpiness has no difference past to present).
How can one reconcile the Cosmological Principle and the Copernican Principle with the Big Bang theory? How can you reconcile the observed uniform distribution of galaxies with the expanding universe? How can you reconcile the speed limit of light with an extent of the universe which appears to be infinite? How can the matter in the whole universe be both infinite and finite? Why is Earth at the center of the universe (excuse me, "observable universe"), and what does that suggest about the dimensions of the universe? Six impossible things to consider before breakfast.
I am not the first to notice these "apparent" discrepancies in how the universe is supposed to be and how it is. This is where the explanations begin to sound like rationalizations.
Here is one astronomer's explanation for a layman regarding the density of galaxies:
“If we define the ‘density of galaxies’ as the number of galaxies per unit volume, then the density does in fact decrease as time goes on (it was greater in the past than it is now). But the question specifically related to what we observe in galaxy catalogs. Can you tell that the density of the universe was greater in the past than it is now by looking at the distribution of objects on the sky? No. Why not?
Imagine that you're looking at a very distant galaxy in one part of the sky, and then compare it to another very distant galaxy in another part of the sky. The angular separation of those two galaxies can be very large. So you could say that it ‘looks’ like they're billions of light-years apart. But yet in the very distant past, when the universe was much much smaller than it is now, they were physically very close together. So you can't really measure the density of the universe at that early time by counting up galaxies and dividing by the volume they appear to occupy just as you would in a universe that wasn't expanding. The expansion of the universe means that objects that were very close together at the time they emitted the light that we're now seeing are spread out over the sky in a way that wouldn't happen in a universe that wasn't expanding.”
To be clearer, the astronomer is referring to the FLRW metric which relies on "comoving points." That is the official explanation for why the density of galaxies varies from what is observed. It is a complicated mathematical maneuver that relies on a coordinate grid that changes as the universe expands.
Realistically, however, what is being implied is that you can't trust your eyes or the instruments that amplify our vision. In the sense that the galaxies are not currently where they appear to be, this is true simply because light takes time to travel. What is being suggested, however, is that the light from the distant galaxies curved as the universe expanded. While we know that light can curve around a body that has gravity, curving light from the expansion of space is speculative at best.
A coordinate graph that curves space according to theory means that the theory must first be correct, but what if space is not curved? What if the light that left the galaxies traveled in a straight line? Then the angular separation is an accurate reflection of the way that part of space was at the time the light left those galaxies. The FLRW metric is an attempt to force fit observed reality into theory.
Consider the following hypothetical example: Take a galaxy 13 billion light-years away and a group of galaxies at 10 billion light-years away that is between the galaxy at 13 billion light-years and Earth. Now take another galaxy at 13 billion light-years away on the same diameter through Earth but 180 degrees opposite (diametrically opposed) and another group of galaxies at 10 billion light-years from Earth between the more distant galaxy and Earth. We can tell that the 13 billion year old galaxies are on the other side of the groups of galaxies because the light will travel through the groups of galaxies and undergo gravitational lensing. Diagrammatically, it would appear something like this:
A1…B1……….Earth………B2…A2
According to the theory that the more distant galaxies are closer together than the ones that are closer to Earth, A1 is closer to A2 than B1 is to B2. That the light is traveling straight (except as modified by gravity) is unequivocal, and the conclusion is absurd. Preposterous. It would be like saying that Russian nesting dolls (babushka dolls) fit into one another such that the largest doll fits into the next smallest, until they all fit into the very smallest.
The final nail in the coffin of the FLRW metric as an explanation for the density of galaxies in the past is the galaxies themselves. The FLRW metric suggests that we are seeing space curved so that the distance between galaxies is magnified, which is supposed to explain why the density appears to be the same as today (nearby galaxies). For this to be true, it would have to be true not only of galactic separation, but also the galaxies themselves. Inspection of the galaxies, however, shows that they are the correct dimensions for that distance. That is, the galaxies are not magnified. Their apparent size is not affected by distance except as we should expect by their distance alone. Their spectra and luminosities confirm that the galaxies have not been magnified or distorted in any way. Galactic size relative to galactic separation proves that what we see is what was actually there (in the past).
A video that uses the CBR and WMAP to show that the geometry of the universe is flat can be found here.
A video that uses the CBR and WMAP to show that the geometry of the universe is flat can be found here.
Astronomers are no longer trying to incorporate new data into a coherent paradigm. They are looking for ways to make data go away or conform, especially if the data is discrepant to the theory. Some dwarf galaxies have been estimated to be 15 billion years old, but that just won't do! Some new galaxies have formed within 1-2 billion light-years of the Earth, but this won't do! Some older galaxies have been found in the periphery of the observable universe, but this won't do!
It is a happy coincidence for modern cosmologists that the resolution of the Hubble Telescope is about 14 billion light-years. "Fuzzy glow-worms" are visible at distances greater than 13 billion light-years from Earth, and some astronomers are content to say that no further formed galaxies will be found beyond that (i.e. before that). The furthest galaxy has been dated, based on red shift, to have formed within about 300 million years of the Big Bang. Curiously, the diagrams that show star formation, before galaxy formation, suggest (still) that stars began to form about 400 million years after the Big Bang. Hawking's book, A Brief History of Time, suggests that "protogalaxies" were forming at 1 billion years after the Big Bang.
Clearly, the time scale for development that was postulated before the new discoveries was incorrect. That, in and of itself, does not invalidate the theory. One might be forgiven for wondering what it would take to falsify the Big Bang Theory. J. S. Haldane famously quipped that a rabbit in the Precambrian would falsify the theory of evolution. Although that is so unlikely as to be (probably) impossible, it at least provides a benchmark for what it would take to falsify evolutionary theory. I think that the equivalent datum that would falsify the Big Bang Theory would be a mature spiral galaxy at redshift z>10 (in other words, further away than 13.2 billion light-years). The most distant galaxy observed is a tiny smudge at redshift z=10 seen with the Hubble Ultra Deep Field. It is currently the only candidate for a galaxy that far away (and that long ago). Remember that in 1975, the most distant object detected was a redshift of z=1 (about 8 billion light-years from Earth).
Realistically, it would take much more than a single galaxy. It would take a lot of these kinds of galaxies such that the distribution and maturity is the same at that redshift as it is in the rest of the "observable universe." There is a telescope that is set to be launched in 2014 said to be capable of good resolution at z=10 (and perhaps beyond - for some distance/redshift).
But who am I kidding? The theory would simply change. Ages of galaxies would be recalibrated. An explanation related to curved light would be used to explain that the "light travel time" to the distant galaxies made them appear further away than they actually are. The "new" furthest galaxy would become the "last galaxy" candidate, and the theory would become more complicated. Think not? This is already happening in some circles. I think they are trying to make a silk purse out of a sow’s ear.
What if there were a simple theory that involved expansion of space, fit all of the observed data, and was consistent with the Cosmological and Copernican Principles - and even explained them? What if this theory also explained the anomalies that plague modern cosmology? What if this theory predicted the uniformity of galaxies throughout distance and time - the mature spiral galaxies at z>10 (that have yet to be observed)?
Such a theory would make the stars accessible and understandable to everyone. Just as Copernicus eliminated the need for Ptolemy's epicycles to explain the path of the planets, such a theory would eliminate the need for the FLRW metric to explain the difference between the observed density of matter and the predicted density of matter. Laws of physics would still hold, and the finite would not be infinite nor the infinite finite. Many of the features of the universe described as "anomalies" would be understood.
There might be some unfortunate consequences. Mathematicians would see their imaginary castles in the sky dissolve in heaps of imaginary numbers. Books entitled "Big Bang Theory" would be quaint reminders of an error of deduction similar to Omphalos by Grosse.
There could also be wonderful consequences! Phenomena that were thought to be lost in a quantum soup will be amenable to at least the potential for investigation. The very nature of "space" will need to be reconsidered. It will elevate the discussion from the strictly theoretical to the physically verifiable similar to the discussions regarding a divine act of creation versus evolution. We have the fossils, and we only need to distinguish them from the rocks to appreciate a true history of the universe.
Joseph Ernst
