Cosmologists have defined three different classifications of stars based on their elemental makeup. Population I or those that contain relatively large concentrations of the heavy metals, Population II or those that have much less and Population III which are composed entirely hydrogen, helium and very small amounts of lithium and beryllium no heavy metals. Although Population III, stars have not yet been observationally confirmed their existence is predicted in the Big Bang model.
According to that theory, the early universe consisted of hydrogen and helium, with trace amounts of lithium and beryllium, but no heavier elements. Through the process of stellar evolution, the first stars synthesized the metals from hydrogen and helium by nuclear reactions in their cores, which were then dispersed when they exploded. Therefore, it is assumed the first stars to evolve would have lower metal content that those that came later.
However, as was mentioned earlier the fact that no Pop III stars have been observed despite the intense efforts by the cosmological community and the fact that the technology is advance enough to do so contradicts that assumption.
Even so many cosmologists still feel the big bang it is a valid model for describing evolution of our universe by suggesting that there are several reasons why they have not yet been observed.
The first is as the oldest population of stars, the majority of Pop III stars would have exhausted their fuel supplies long ago and would now be observed as remnants (white dwarfs, neutron stars or black holes), the original composition of which is nearly impossible to determine. However, this alone cannot explain the absence of Pop III stars, as those with the lowest masses should still be present (albeit difficult to observe due to their extremely low luminosities) in the Galaxy population today.
Another explanation is that stars sweep up gas from the interstellar medium as they move through it, and this may contaminate the outer layers of Pop III stars. This would give Pop III stars the appearance of metal-poor Pop II stars.
A more plausible explanation is that the metals produced in the cores of the Pop III stars have been dredged up to the surface by convection. Such â€˜self-contaminatedâ€™ Pop III stars would also most likely be misclassified as metal-poor Pop II stars.
The currently favored explanation for the lack of observed Pop III stars is that the Pop III generation of stars were all high mass stars, with masses ranging from 60 to 300 times that of the Sun. In other words, no low mass Pop III stars were ever formed. This is supported by recent theoretical models, which show that primordial stars possessed much higher masses than the stars we see in the Universe today. If this bias in the mass distribution of primordial stars were the case, then all Pop III stars would have exhausted their fuel supplies long ago and would now be present only as remnants.
However, there are several other problems with the big bang model, which are not so easy to explain away.
For example the Big Bang theory postulates the universe emerged from what is called a singularity where the laws of physics breakdown and is expanding from the tremendously hot dense environment associated with it. Additionally it assumes the momentum generated by the heat of that environment is sustaining the expansion.
However, it has difficulty explaining where the energy originated to cause its expansion.
The reason this presents a problem is because the law of conservation of energy/mass says that in a closed system it cannot be created or destroyed.
However, proponents of the big bang model assume, as was just mentioned the energy powering the universe’s expansion came from a tremendously hot dense environment yet it cannot explain where the energy found in that environment came from. In other words they would like us to believe that it was created out of nothing, which would be a violation of the law of conservation of energy/mass.
Additionally because it also assumes that it emerged from a singularity were the laws of physics do not apply they are unable to define the initial condition required to predict how that evolution began. In other words the entire mathematical structure of the big bang model is based on an unknowable quantity which can be chosen to make it fit many different universes, including the one we occupy.
Yet there is another explanation for origin of our expanding universe that does not violate any of the accepted physical laws and makes a great deal more sense than assuming its expansive energy originated out of nothing.
We know from observations the equation E=mc^2 defines the equivalence between mass and energy in an environment and since mass is associated with the attractive properties of gravity it also tells us because of this equivalence the momentum associated with the universe’s expansion also posse those attractive properties. However, the law of conservation of energy/mass tells us that in a closed system the creation of it cannot exceed the gravitational energy associated with the total energy/mass in the universe.
However, not all of the energy of associated with the universeâ€™s expansion is directed towards it because of the random motion of its components. For example, observations indicate that some stars and galaxies are moving towards not away us. Therefore, not all of the energy present at the time of its origin is directed towards its expansion.
Additionally we know from observation that the universe is nearly flat with respect to its mass and energy. Many physics assume this means that it will continue expand forever, but it is always slowing down, reaching a dead stop in an infinite amount of time.
However, because some of the momentum of its components is not directed towards its expansion the total gravitational contractive properties of will eventually exceed that of its expansive components. Therefore, at some point in time its gravitation contractive potential must exceed the kinetic energy of its expansion because as just mentioned not all of its kinetic energy is directed towards its expansion. Therefore, at that point, in time the universe will have to enter a contractive phase.
(Many physicists would disagree because recent observations suggest that a force called Dark energy is causing the expansion of the universe accelerate. Therefore, they believe that its expansion will continue forever. However, as was shown in the article “Dark Energy and the evolution of the universe” if one assumes the law of conservation of mass/energy is valid, as we have done here than the gravitational contractive properties of its mass equivalent will eventually have to exceed its expansive energy. Therefore, the universe must at some time in the future enter a contractive phase.)
We know from observations that heat is generated when we compress a gas and that this heat creates pressure that opposes further contractions.
Similarly, the contraction of the universe will create heat, which will oppose its further contractions.
The velocity of contraction will increase until the momentum of the galaxies, planets, components of the universe equals the radiation pressure generated by the heat of its contraction.
At this point in time, the total kinetic energy of the collapsing universe would be equal and oppositely directed with respect to the radiation pressure associated with the heat of its collapse. From this point on the velocity of the contraction will slow due to the radiation pressure and be maintained by the momentum associated with the remaining mass component of the universe.
However, after a certain point in time the heat and radiation pressure generated by its contraction will become great enough to ionize the remaining mass and cause it to reexpand because the expansive forces associated with the radiation pressure caused by its collapse will exceed the contractive forces associated with its mass.
This will result in the universe entering an expansive phase and going through another age of recombination when the comic background radiation was emitted. The reason it will experience an age of recombination as it passes through each cycle is because the heat of its collapse would be great enough to completely ionize all forms of matter.
However, at some point in time the contraction phase will begin again because as mentioned earlier its kinetic energy cannot exceed the gravitational energy associated with the total mass/energy in the universe.
Since the universe is a closed system, the amplitude of the expansions and contractions will remain constant because the law of conservation of mass/energy dictates the total mass and energy in a closed system remains constant.
This results in the universe experiencing in a never-ending cycle of expansions and contractions of equal magnitudes.
If this theoretical model is valid the heat generated by the collapse of the universe must raise the temperature to a point where most of the atomic nuclei become dissociated into their component parts and electrons would be strip off making the universe opaque to radiation. It would remain that way until it entered the expansion phase and cooled enough to allow matter to recapture and hold on to them.
However, this model does not assume the universe had its beginning in a supper hot singularly as the big bang model suggest but in a slightly cooler environment were some nuclei that were created during the previous expansion and contraction phase would remain intact.
In other words, the reason why we have been unable to observe any Population III which are composed entirely hydrogen, helium and very small amounts of lithium and beryllium no heavy metals is because those heavy metals were already in the mix when they were formed.
One could quantify this scenario by calculating the temperature and pressure which would result the ratio the heavy metals to the lighter elements to be equal to what it is in the earliest stars that are observable. Then starting from that point in time, using those as the initial parameters and the current laws of physics determine if the universe would have evolved to what is it today. If so, it would have a tendency to be more creditable than the current Big Bang model because its beginning has a foundation in the laws of physics and not in a singularity as that model does.
Additionally it is true using the currently accepted laws of physics and the concept of a singularly as its starting point one can with considerable accuracy predict how our universe evolved. However, those predictions are based on the initial conditions found in a singular and since as was just mention those laws cannot be applied to it they can never be fully validated.
However, the above theoretical model can make just as accurate perditions which can be fully validated or falsified because there is no place in the universes evolution where the laws of physics cannot be applied.
Copyright 2016 Jeffrey O’Callaghan