Supercomputers may unlock the universe’s greatest mystery about what happened before the Big Bang

A groundbreaking study published in Living Reviews in Relativity proposes a novel computational method to investigate one of the universe's greatest mysteries: what preceded the Big Bang, thereby challenging long-standing assumptions in cosmology.

The research, led by cosmologist Eugene Lim of King's College London, along with astrophysicists Katy Clough of Queen Mary University of London and Josu Aurrekoetxea of Oxford University, introduces the application of numerical relativity to cosmological questions.

This approach utilizes advanced computer simulations to solve Einstein's equations of general relativity under extreme conditions, where traditional analytical methods fail.

Challenging traditional assumptions

Einstein's general relativity has been instrumental in understanding cosmic phenomena. However, when tracing the universe back to its earliest moments, the equations often lead to singularities, points of infinite density and temperature, where the laws of physics cease to function predictably.

To navigate these complexities, cosmologists typically assume the universe is homogeneous and isotropic, meaning it appears the same in every direction. While this assumption simplifies calculations, it may not accurately reflect the universe's state during the Big Bang. Lim likens this approach to searching for a lost object only where light is available, neglecting the vast, unlit areas where the object might actually be.

Numerical relativity

Numerical relativity emerged in the 1960s and 1970s to model complex scenarios like black hole collisions, which cannot be solved analytically. The method gained prominence in 2005 when it successfully simulated gravitational waves from merging black holes, a milestone that earned the LIGO collaboration the Nobel Prize in Physics in 2017.

Building on this success, Lim and his colleagues propose extending numerical relativity to cosmology, allowing for the exploration of scenarios with varying initial conditions, such as those predicted by string theory.

Exploring cosmic inflation

One of the central puzzles in cosmology is cosmic inflation, the rapid expansion of the universe in its earliest moments. While inflation explains the large-scale uniformity of the universe, the mechanisms behind this sudden growth remain unclear.

Traditional models assume a homogeneous and isotropic universe, but numerical relativity can accommodate more complex initial states, providing a platform to test various inflationary models and their underlying theories.

The study also delves into speculative but intriguing concepts such as the multiverse and cyclic universes. Numerical relativity could simulate potential collisions between our universe and others, offering insights into the multiverse hypothesis.

Additionally, it may shed light on the possibility of a cyclic universe, one that undergoes repeated cycles of expansion and contraction, known as "bounces," by modeling scenarios where strong gravitational effects challenge the assumptions of homogeneity and isotropy.

The integration of numerical relativity into cosmological research represents a significant advancement in the field.

Lim and his team aim to bridge the gap between cosmology and numerical relativity, encouraging collaboration between researchers to tackle some of the most profound questions in science.