What does it mean for space-time itself to expand? Expand into what? What caused the big bang? What caused inflation? If time itself began with the big bang then how could the big bang “start” before time existed? How can we have cause and effect without time?
The big bang theory of the universe has much in common with the Universe of Aristotle and Ptolemy of the solar system.
Aristotle and Ptolemy held that the sun and all of the planets orbited the earth. We can see exactly the same distance, and by extension time, in all directions. The microwave background glow is nearly uniform in all directions. Again we find ourselves at the center of the universe.
They relied upon epicycles, circular orbits within circular orbits, to explain the motions of the Sun and planets around the earth. Modern cosmology requires a cosmically constant, dark matter, dark energy, inflation, and expansion. No combination of cosmological constant value, age of the universe, and matter within the universe, dark matter and dark energy included, can simultaneously be self-consistent and consistent with the observed universe.
The net effect of a positive cosmological constant is to create a negative gravitational force that drives the expansion of the universe. As the universe expands, matter and energy are spread out over more physical space and thus their gravitational attraction is diminished.
The work done by the vacuum during expansion provides exactly the amount of energy to fill the new volume to the same density, therefore the cosmological constant remains constant and by extension the repulsive gravitational force driving expansion remains constant while gravitational attraction diminishes as matter and energy become less dense.
This conflicts with another ad-hoc requirement of the big bang theory, inflation, a period of rapid expansion. If the cosmological constant remains truly constant and thus it’s gravitational repulsive force remains constant, then what we should observe is a logarithmic increase in the expansion rate from the point of the big bang forward which is inconsistent with inflation.
Decades ago I read a book by Eric Learner entitled, “The Big Bang Never Happened”. The central thesis of the book is that the universe is a “steady-state” universe that has always and will always exist. While there were some errors of logic, the view presented of a possible steady state universe is interesting if incomplete.
An element of his theory was that electromagnetic forces play a far greater role in the evolution of the universe than do gravitational forces. This mechanism allowed for example the transfer of angular momentum from young rapidly rotating stars to a forming planetary system.
Eric postulates some mechanism gradually reduces a photons energy over distance other than Doppler shift caused by the motion of expansion. This is referred to as the “tired light” theory. Quantized red shift red shift and descrepencies between the red shifts in cores of spiral galaxies and their spiral arms supports this notion. And yes I do realize you get Doppler broadening because of the rotation of the galaxies.
When I saw the first Hubble deep field images, the galaxies I saw were markedly different than modern galaxies, oddly shaped, irregular, and clumpy. For a long time that shifted my perspective away from a steady state universe. If not a big bang, there appeared at least to be a universe that had undergone substantial evolution over time.
But then I saw images of nearby galaxies in ultraviolet light. Low and behold, they were oddly shaped, irregular, and clumpy. In fact they looked amazingly like the galaxies in the deep field hubble images. And then it occurred to me the deep field images taken in visible light were actually seeing extreme UV from the distant galaxies red shifted into the visible spectrum. The reason these galaxies appeared oddly shaped, irregular, and clumpy is because looking in the visible spectrum here, we are only seeing the regions of active star formation with young very hot stars which have substantial spectral output in the extreme UV range. The major portions of those galaxies were invisible to us looking at them in the visible spectrum.
When the first deep field images came back from the Spitzer, looking at the far infrared light, light that originated as visible light when it left those distant galaxies, what I saw were large spiral galaxies and other familiar forms. The universe then looked very much as it does today.
Carbon monoxide has been detected in the spectrum of the oldest quasar examined. Big bang theorists suggest that this is because the first generation of stars were very massive and short lived and rapidly converted hydrogen to heavy elements, exploded into super novas and distributed these elements throughout the early universe. But an alternate explanation is that the metalicy of the universe has been maintained roughly constant through some unknown mechanism over the eons.
Distant Quasars Probe End of Cosmic Dark Ages by Lori Stiles is an interesting article dealing width distant quasers.
|“But we see a lot of other elements around those early quasars,” Fan said. “We see evidence of carbon, nitrogen, iron and other elements, and itâ€™s not clear how these elements got there. There is as much iron, proportionate to the population of those early systems, as there is in mature galaxies nearby.”
The tiny red dot in the center of this image is the most distant quasar ever discovered. The object is roughly 13 billion light years away. UA astronomer Xiaohui Fan led the Sloan Ditigal Sky Survey that discovered this and other ancient quasars.(Photo: Sloan Digital Sky Survey)
This doesn’t seem to argue for a big bang followed by a universe in which hydrogen is converted to heavy elements in stars. It would seem that there is some mechanism maintaining some sort of equilibrium, removing heavy elements and providing fresh hydrogen over the possibly unbounded life of the universe. If that is the case it also favors the idea that what we see when we look out 13.6 billion light years is a horizon of sorts. The universe might be infinite, or merely more enourmous than we presently appreciate.