Blog

What if the Big Bang wasn’t truly the beginning?

A team of cosmologists is using the power of supercomputers to push past the limits of Einstein’s equations and explore mysteries once thought unsolvable. By applying numerical relativity—simulations that can model extreme conditions—they hope to uncover clues about what came before the Big Bang, whether the cosmos is part of a cycle of rebirths, or even if our universe once collided with another.

Simulating the Unsolvable: A New Path Before the Big Bang

It is often said that asking what came before the Big Bang is “unscientific” or even “meaningless.” Yet a recent paper published in Living Reviews in Relativity offers a different perspective. Written by FQxI cosmologist Eugene Lim (King’s College London, UK), astrophysicist Katy Clough (Queen Mary University of London, UK), and Josu Aurrekoetxea (Oxford University, UK), the study suggests that complex computer simulations could provide a way forward.

By using numerical methods to approximate Einstein’s equations of gravity under extreme conditions, the researchers argue that cosmologists may finally be able to investigate questions that have long seemed out of reach. These include what may have happened before the Big Bang, whether multiple universes exist, if our universe ever collided with another, or whether reality passes through repeated cycles of expansion and collapse.

Einstein’s equations of general relativity describe how gravity shapes the behavior of matter and energy in the universe. However, when traced back to the earliest moments of the cosmos, they break down. At that point, the equations predict a singularity, a state of infinite temperature and density where the known laws of physics no longer apply. In such conditions, cosmologists cannot rely on their usual assumptions to solve the equations. The same problem appears when trying to describe other extreme environments, such as the centers of black holes.

“You can search around the lamppost, but you can’t go far beyond the lamppost, where it’s dark–you just can’t solve those equations,” explains Lim. “Numerical relativity allows you to explore regions away from the lamppost.”

Beyond the Lamppost

Numerical relativity was first suggested in the 1960s and 1970s to try to work out what kinds of gravitational waves (ripples in the fabric of spacetime) would be emitted if black holes collided and merged. This is an extreme scenario for which it is impossible to solve Einstein’s equations with paper and pen alone–sophisticated computer code and numerical approximations are required. Its development received renewed focus when the LIGO experiment was proposed in the 80s, although the problem was only solved in this way in 2005, raising hopes that the method could also be successfully applied to other puzzles.

“You can search around the lamppost, but you can’t go far beyond the lamppost, where it’s dark–you just can’t solve those equations. Numerical relativity allows you to explore regions away from the lamppost,” says Eugene Lim.

One longstanding puzzle that Lim is particularly excited about is cosmic inflation, a period of extremely rapid expansion in the early universe. Inflation was initially proposed to explain why the universe looks the way it does today, stretching out an initially small patch, so that the universe looks similar across a vast expanse. “If you don’t have inflation, a lot of things fall apart,” explains Lim. But while inflation helps explain the state of the universe today, nobody has been able to explain how or why the baby universe had this sudden, short-lived growth spurt.

The trouble is, to probe this using Einstein’s equations, cosmologists have to assume that the universe was homogeneous and isotropic in the first place–something which inflation was meant to explain. If you instead assume it started out in another state, then “you don’t have the symmetry to write down your equations easily,” explains Lim.

But numerical relativity could help us get around this problem, allowing radically different starting conditions. It isn’t a simple puzzle to solve, though, as there’s an infinite number of ways spacetime could have been before inflation. Lim is therefore hoping to use numerical relativity to test the predictions coming from more fundamental theories that generate inflation, such as string theory.

Cosmic Strings, Colliding Universes

There are other exciting prospects, too. Physicists could use numerical relativity to try to work out what kind of gravitational waves could be generated by hypothetical objects called cosmic strings–long, thin “scars” in spacetime–potentially helping to confirm their existence. They might also be able to predict signatures, or “bruises,” on the sky from our universe colliding with neighboring universes (if they even exist), which could help us verify the multiverse theory.

Excitingly, numerical relativity could also help reveal whether there was a universe before the Big Bang. Perhaps the cosmos is cyclic and undergoes “bounces” from old universes into new ones, experiencing repeated rebirths, big bangs, and big crunches. That’s a very hard problem to solve analytically. “Bouncing universes are an excellent example, because they reach strong gravity where you can’t rely on your symmetries,” says Lim. “Several groups are already working on them–it used to be that nobody was.”

Numerical relativity simulations are so complex that they require supercomputers to run. As the technology of these machines improves, we might expect significant improvement in our understanding of the universe. Lim is hoping the team’s new paper, which outlines the methods and benefits of numerical relativity, can ultimately help get researchers across different areas up to speed.

“We hope to actually develop that overlap between cosmology and numerical relativity so that numerical relativists who are interested in using their techniques to explore cosmological problems can go ahead and do it,” Lim says, adding, “and cosmologists who are interested in solving some of the questions they cannot solve, can use numerical relativity.”

Reference: “Cosmology using numerical relativity” by Josu C. Aurrekoetxea, Katy Clough and Eugene A. Lim, 23 June 2025, Living Reviews in Relativity.
DOI: 10.1007/s41114-025-00058-z

Never miss a breakthrough: Join the SciTechDaily newsletter.

When NASA’s Dawn mission arrived at Ceres in 2015, scientists and the general public got their first detailed look at this strange and beautiful planetoid. As the largest object in the Main Asteroid Belt, accounting for more than 39% of its total mass, Ceres is the only object in the Belt that has undergone hydrostatic equilibrium (aka. became round under the influence of its own gravity). The data Dawn obtained between 2015 and 2018, when the mission ran out of fuel, revealed some very interesting things about this mysterious, icy planetoid.

Like Jupiter’s moon Europa, and Saturn’s moons Titan and Enceladus, scientists have speculated that Ceres could be an “Ocean World,” meaning that it could have a liquid water interior that could support life. Dawn’s findings indicated that the planetoid is too cold in its interior to prevent water from freezing, and any liquid it contains is likely to be concentrated brines. But according to new research by NASA scientists, Ceres may have had the right conditions to support single-celled lifeforms about 2.5 to 4 billion years ago.

The study was led by Samuel W. Courville, a Planetary and Earth Scientist from the School of Earth and Space Exploration (SESE) at Arizona State University (ASU), who conducted it while interning at NASA’s Jet Propulsion Laboratory (JPL). He was joined by multiple researchers from SESE and JPL, the School of Molecular Sciences at ASU, and the Department of Genome Sciences at the University of Washington. The paper summarizing their findings was published on August 20th in Science Advances.

This illustration depicts the interior of dwarf planet Ceres, including the transfer of water and gases from the rocky core to a reservoir of salty water. Credit: NASA/JPL-Caltech

According to Dawn’s data, scientists concluded Ceres has insufficient heat in its core from the decay of radioactive elements to maintain an interior ocean. Unlike Europa, Enceladus, and other “Ocean Worlds,” it does not have the benefit of tidal heating caused by the gravitational influence of a massive planet. Data obtained by the Dawn mission previously suggested that the bright, reflective patches on Ceres’ surface were largely composed of salts left over from liquid water that percolated up from a massive reservoir beneath the surface. Other research found evidence of organic carbon-bearing molecules on its surface.

For their study, the authors created thermal and chemical models that mimic the temperature and composition of Ceres’ interior over time. They found that 2.5 to 4 billion years ago (roughly 500 million to 2 billion years after it formed), Ceres’ subsurface region may have had a steady hot water supply. This water was heated by the decay of radioactive elements in Cere’s rocky, metallic core when the planetoid was still young. Their analysis also showed that this water contained dissolved gases bubbling up from metamorphosed rocks at the core-mantle boundary.

These results indicate that Ceres had the third and final element needed for life in the past, and they have implications for other water-rich objects in the Solar System. Many planetoids comparable in size to Ceres (~940 km; 585 mi) also don’t have sufficient internal heating mechanisms caused by radioactive decay or the gravitational influence of giant planets. These findings essentially state that while these bodies may not be habitable today, they may have been in the past. Said Courville in a NASA press release:

On Earth, when hot water from deep underground mixes with the ocean, the result is often a buffet for microbes — a feast of chemical energy. So it could have big implications if we could determine whether Ceres’ ocean had an influx of hydrothermal fluid in the past.

Further Reading: NASA JPL, Science Advances