The universe as we know it began 13.8 billion years ago from a singularity, which quickly expanded billions and billions of times. This is commonly known as the Big Bang theory, and although there’s an overwhelming amount of supporting evidence, it doesn’t answer all the questions about the beginning of the cosmos.
Since the theory is not perfect, over the years more complex ideas have been added to the original concept of the Big Bang in order to explain the apparent simplicity of the large-scale structure of the universe.
Recently, however, researchers Dr Steffen Gielen from Imperial College London and Dr Neil Turok from the Perimeter Institute for Theoretical Physics in Canada looked for a way to go back to a simpler system. One solution, they discovered, was to turn the Big Bang into a Big Bounce.
According to their research, published in Physical Review Letters, the laws of quantum mechanics prevent the formation of a singularity. This idea is known as conformal symmetry, and it is the same reason why electrons don’t just fall onto protons.
“Quantum mechanics saves us when things break down,” said Gielen in a statement. “It saves electrons from falling in and destroying atoms, so maybe it could also save the early universe from such violent beginnings and endings as the Big Bang and Big Crunch.”
The two main theories in physics are quantum mechanics and relativity, but when they are combined they don’t work well together. The scientists assume a purely quantum mechanics system with a universe dominated by radiation, very similar to the condition just after the Big Bang.
“The big surprise in our work is that we could describe the earliest moments of the hot Big Bang quantum mechanically, under very reasonable and minimal assumptions about the matter present in the universe,” said Dr Turok. “Under these assumptions, the Big Bang was a ‘bounce’, in which contraction reversed to expansion.”
The Big Bounce is actually forbidden in relativity, but it could be allowed in a more general "theory of everything," which can incorporate gravity and quantum mechanics.
“Our model’s ability to give a possible solution to the problem of the Big Bang opens the way to new explanations for the formation of the universe,” added Dr Gielen.
A good physical hypothesis doesn’t just explain what has been, it can also predict what is and what will be, so the researchers are investigating if their idea can account for the formation of galaxies and galaxy clusters.
They will also have to come up with a mechanism for the universe to actually start contracting. As far as we know from astrophysical observations, the universe will continue to expand forever.
