To start with this article the question is, what if time had no beginning? To get into context a bit we must go back in time and space to the era of the Big Bang, where we ran into a singularity. So far, the Theory of General Relativity has provided us with the best understanding of the universe, tracing its evolution back to the singularity. To go further, and to know what was before the singularity, if there was a “before”, physicists turn to quantum gravity.
Did time ever begin? It’s hard to decide which answer is more disturbing, in the beginning there might have been a beginning, or maybe there was no beginning. Our Universe may have always existed, and a new theory of quantum gravity reveals how it might work.
The team used a new theory of quantum gravity, called causal set theory. According to this theory, space and time break up into discrete chunks of space-time. At a certain level, there is a fundamental unit of space-time. Using this causal ensemble approach to explore the beginning of the Universe, scientists discovered that the Universe may not have had a beginning, that it has always existed in the infinite past and only recently evolved into what we call the Big Bang.
Both quantum physics and general relativity have turned out to be extraordinarily effective theories in dismantling the mysteries of the Universe. However, quantum gravity remains elusive and is perhaps the most frustrating problem facing modern physics. General relativity, on the other hand, is the most powerful and comprehensive description of gravity ever devised. But unfortunately it has its limitations, in certain specific places like black holes and the beginning of the Universe, the math of general relativity just breaks down.
Stephen Hawking was the one who managed to show that General Relativity (GR) breaks down at the Big Bang singularity, but he left open the possibility that the Big Bang is not the beginning of time, but was preceded by an era of quantum gravity. that cannot be captured by the RG. Therefore, the question of the beginning of time must be addressed within a theory of quantum gravity, the authors explain.
Causal set theory reinvents spacetime as a series of discrete chunks, or “atoms,” of spacetime. This theory would put strict limits on the proximity of events in space and time, since they cannot be closer than the size of the ‘atom’. For example, if you are looking at your screen reading this, everything seems smooth and continuous. But if you were to look at the same screen through a magnifying glass, you would be able to see the pixels that divide the space, and you would realize that it is impossible to bring two images on your screen closer than a single pixel, explains Live Science.
The causal set approach clearly eliminates the Big Bang singularity problem because, in theory, singularities cannot possibly exist. That is, it would be impossible for matter to be compressed into infinitely tiny points; they cannot be smaller than the size of a space-time atom. This is where we return to the initial question, without a Big Bang singularity, what would the beginning of our Universe look like?
There’s still a lot of work around here, but physicists say that what we perceive as the Big Bang may have been just a particular moment in the evolution of this ever-existing causal set, not a true beginning.
The article is published in the arXiv database.
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