When cosmologists trace the history of the universe back to the first few nanoseconds, they encounter a metaphysical barrier that no current mathematical bridge can suffice. This is because physicists have yet been able to devise a theory of quantum gravity. Nevertheless, there are various cosmological scenarios about what may have triggered the big bang. Although these scenarios are nothing more than mathematical speculations, the following list contains hypotheses that might hint at the correct answer.
Chaotic Inflation: Physicists believe that prior to the initial big bang, the universe underwent a state of rapid, cosmic expansion. What actually caused this rapid, cosmic expansion is unknown. One scenario developed by the physicist Andrei Linde is known as chaotic inflation. This hypothesis involves scalar fields, which are mathematical constructs used to account for the accelerated expansion of the universe.
Prior to the initial big bang, Linde speculates a scalar field was rapidly fluctuating. Every once in a while, a patch of this scalar field happened to become smooth. According to reasonable, dynamical assumptions, that smooth patch then “blew up”, became smooth, and turned into the inflationary period that scientists think preceding the big bang. Essentially, chaotic inflation posits an eternal universe on par with the steady state model of the cosmos.
Quantum Tunneling: Quantum tunneling is a phenomena that occurs regularly on quantum scales. For example, a person is incapable of passing through a wall because the potential energy stored in the wall is greater than the kinetic energy stored in the person. In quantum theory, however, particles are capable of tunneling through barriers. The odds of this occurring at macro scales is improbable but statistically possible.
In wave mechanics, the possible states that a particle can occupy are smeared throughout a mathematical construct known as the wave-function. The wave-function consists of real and imaginary numbers. Since the universe is a quantum mechanical system, the wave-function of particles can be applied to the universe as a whole. In theory, it is possible that a prior universe to our own contracted to a point, quantum tunneled through a barrier and created a new universe on the other side. When the wave-function of the universe is quantum tunneling, it begins to oscillated, which creates the inflationary period that preceded our big bang. Within this barrier, the wave-function consists of imaginary momentum and time, which are interpreted as “chaos” or “nothing.”
God: Postulating God as the explanation of the universe is more philosophical, though no less speculative, than the scientific hypotheses previously highlighted. In particular, if every event in the universe is preceded by a cause, then it follows that the universe itself must have a cause. Given that the big bang brought space and time into existence, the cause of the universe would have to transcend space and time. The only objects believed to be able to occupy a domain where space and time are absence are minds and abstract objects. Since abstract objects do not cause events, it follows the cause of the universe must be a mind. Of course, one can pick holes in this argument. Nevertheless, is postulating an intelligent cause behind the universe any less plausible than postulating an ensemble of infinite universes?
Whether it be chaotic inflation, quantum tunneling or a metaphysical intelligence, what actually brought the universe into existence is a question that remains shrouded in mystery. Yet science is a method based upon falsification. Rather paradoxically, the same methods that claim we may know everything also cast doubt that we can know anything for certain. This being the case, what triggered the big bang may be a question forever outside scientific limits.
By Nathan Cranford