New Approach To Einstein's Equations Might Tell Us What Happened Before The Big Bang

The evidence for the Big Bang is overwhelming, but we cannot describe what goes on in that event. We can’t accurately call it a moment; time as we know it did not exist. Our science stops making sense a fraction of a second after it happened. The equations simply do not work. But what if there was a way to push the equations not just to their limits, but beyond? This is what researchers are trying to do.

The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

A team at the Foundational Questions Institute is using complex computer simulations to solve Einstein’s equations numerically. This method is often used to solve equations and problems that have no generalized solution, such as the famous three-body problem. While relativity has exact solutions in a variety of environments and situations, it breaks down at the extreme. This is why it might be the crucial tool to push beyond the limits science is currently struggling with.

Numerical relativity was first developed in the 1960s and 70s to solve the question of how black holes merge, and in particular, the emission of gravitational waves. While relativity predicted the existence of gravitational waves, showing what form those waves will take cannot be done on paper and pen alone, no matter how well we know Einstein’s equations.

In a few weeks, it will be 10 years since the first detection of gravitational waves, showing that this approach to relativity can be successful at predicting relativity results when we cannot solve it exactly. So why not use this approach for other problems?

“I am most excited about using numerical relativity to explore how the Big Bang began, and how it can be used to solve some long-standing problems in string theories,” co-author Professor Eugene Lim, from King’s College London, told IFLScience.

The work, which is almost entirely done with funding from the UK Research Councils and Leverhulme Trust, is set to tackle the Big Bang and the period known as Cosmic Inflation, which took place for a fraction of a second after the beginning of the universe. The whole cosmos expanded at an incredible rate.

The existence of this inflationary period is necessary to explain how the universe is roughly the same everywhere we look. Without it, a lot of other things fall apart in our understanding of the universe. The problem is that we do not know what caused this inflation. That’s where numerical relativity comes into play.

“[B]ecause inflation itself is not a full theory, but a theory that must be derived from something more fundamental (in technical terms, we call inflation an "effective theory"),” Lim explained to IFLScience.

The approach has potential, and in the case of gravitational waves, it delivered. Numerical solutions of cosmic inflation might reveal conditions or requirements that could indicate fields, interactions, or properties that transcend the expected confines of our universe. Several theories, such as the cyclical universe (Big Bounce) and several multiverse hypotheses, go beyond both the space and time of our universe. If these hypotheses are correct, evidence might appear in these solutions.

That said, numerical relativity is not an easy task. We would have already done it otherwise. Still, computational breakthroughs allow for supercomputers to be up to the task, and the work to solve these problems is now going full steam ahead.

The study is published in the journal Living Reviews in Relativity.