A new theory in cosmology may hold the key to its origin. Aly Aziz discusses further.
The Big Bang Theory. Yes, it is the catchy title for a television show on RTÉ, but for cosmologists, it is also the grand theory that explains the origin of all that is observable in our universe, from our neighboring planets to galaxies billions of light years away.
What is the Big Bang theory? In 1929, Edwin Hubble (not only a distinguished astronomer, but a semi-pro boxer) made the critical observation that galaxies were moving away from one another in all directions. Much like marked dots on a balloon would move away from one another when it is inflated.
What made his discovery ground breaking was his observation that the further the distance a galaxy was to an observer, the faster it was moving away. Now imagine going back in time billions of years. One could hypothesize that all of the material in the universe had not yet expanded as much, and would therefore be much closer together.
If you were to look even further back in time, all matter would be concentrated to a single finite point. That is essentially how the Big Bang 17theory came to fruition.
To put it simply, the theory states that the universe began when all matter and energy, concentrated to a single point, exploded and expanded. This gave rise to the stars and galaxies we see today. In fact, we are still witnessing that state of cosmic expansion.
Logically, one would ask: what happened before the Big Bang? That is akin to asking: What is north of the North Pole? In other words, no one knows, because the laws of physics break down at such high-nay infinite-values. But recently, an exciting new theory may hold a clue to that question.
To explain what happened at that critical point, theorists are now transcending how they visualise space. Albert Einstein’s groundbreaking equations of relativity allowed physicists to view space as a homogenous fabric, like a sheet of silk.
However a new theory called ‘loop gravity’ has emerged. It allows the model of space to be divided into small pieces instead, analogous to cells making up a honeycomb. These pieces of space are on the order of 10-35 metres in size.
To understand how small that is, imagine cutting a strand of hair down the middle, then taking one half and cutting that one down the middle. Now repeat that process 106 times. The final thickness of that strand is how thick a piece of space would be.
When using this new model, the laws of physics do not break down at the Big Bang. In fact, a very peculiar entity emerges; gravity works in reverse. In our everyday world, gravity is an attractive process. But in the model incorporating ‘loop gravity,’ when all matter in our universe is jammed into a single piece of space, gravity reverses. It becomes a repulsive force, causing space to expand. We are still witnessing that expansion.
So, what happened at the Big Bang? One possible scenario is that the initial state, or the single point of matter, arose when a pre-existing universe like ours collapsed. Due to the attractive force of gravity from matter inside of it, at some point the universe stopped expanding. It then started condensing instead.
This led to the formation of the ‘initial state’. Eventually with space becoming so packed and the density growing unimaginably high, gravity switched from being attractive to being repulsive. Then the universe started expanding again.
This process is what cosmologists refer to as a ‘bounce’. Every time the universe expands, it hits a certain point… and then starts collapsing, only to create a new universe.
But how many of such bounces have there been? What happened before the first bounce? As with the Big Bang, and so many aspects of cosmology and physics, the more we seem to learn, the more questions we have.
Research continues in this field, but it will be some time before we can definitively answer the question of where our universe began. In fact, we may never know.