Physicists have shown that alternative theories that propose a smooth start to the universe cannot work. An international team of researchers from the Max Planck Institute for Gravitational Physics in Potsdam and the Perimeter Institute in Canada has finally been able to show that the “smooth beginning” cannot create a universe like ours.
The Big Bang is a pretty solid theory when it comes to explaining the universe, but all our physics breaks down when we try to understand the first instant of the universe. Daring new theories and several new approaches have used well-established physics to try to explain what’s so far inexplicable.
Two famous hypotheses were proposed in the 1980s to solve the Big Bang. Cosmologists James Hartle and Stephen Hawking suggested the “no-boundary proposal”, which supposes based on quantum mechanical analysis that the universe had no beginning.
Another proposed idea tried to solve the infinite matter density issue. The universe started with a finite amount of matter in a singularity, a single point with zero volume according to relativity, and that’s one of the things that breaks the theory. To solve that, Alexander Vilenkin put forward a “tunneling proposal”, where he employed the principle of quantum tunneling to explain how a finite matter density can create our universe.
These two ideas require the universe to be smooth. There’s no dramatic jump into existence. No ta-dah! Physics, as we know it, was at work before and after what we call the Big Bang. But while they explain the beginning, they fall apart in the long run.
As reported in Physical Review D and currently online at arXiv, when the two scenarios are extrapolated, they produce huge quantum fluctuations that stop the growth of the universe in its tracks.
“Hence the 'no-boundary proposal' does not imply a large universe like the one we live in, but rather tiny curved universes that would collapse immediately,” co-author Jean-Luc Lehners, from Max Planck Institute for Gravitational Physics, said in a statement.
Working this out required sophisticated mathematical analysis, so it’s not a surprise that only now physicists have been able to work out the consequences of these 35-year-old theories. The team is now looking at possible ways to save the smooth universe proposals if other factors are at play.
The Big Bang, with its mysteries and impossibilities, lives to fight another day, but the time will come when somebody somewhere has the right idea to finally explain how everything we see came to be.