The Big Bang may not be one. The emergence of all particles and radiation in the universe may have been combined with another Big Bang that flooded our universe with dark matter particles. And maybe we can find it. According to the standard cosmological picture, the early universe was a very exotic place. Perhaps the most important event occurring in our universe is inflation, which caused our universe to undergo an extremely rapid expansion in the very early period after the Big Bang.

When the inflation ceased, the exotic quantum fields that caused the event disappeared and became a stream of particles and radiation that persists today. When our universe was less than 20 minutes old, these particles began to form the first protons and neutrons in what we call the Big Bang nucleosynthesis.

Big Bang nucleosynthesis is the foundation of modern cosmology because the calculations behind it accurately predict the amount of hydrogen and helium in the universe. However, despite the success of our early universe picture, we still don’t understand dark matter, the mysterious and invisible form of matter that makes up the vast majority of mass in the cosmos. A standard assumption in Big Bang models is that whatever process produced the particles and radiation also produced dark matter. And after that, dark matter hung around, ignoring everyone else.

But a group of researchers suggested a new idea. They suggest that our eras of inflation and Big Bang nucleosynthesis are not the same. Dark matter can evolve along an entirely separate orbit. In this scenario, when inflation ended, it still filled the universe with particles and radiation. But not dark matter. Instead, some quantum field remained intact. As the universe expanded and cooled, this additional quantum field eventually transformed, giving rise to dark matter.

The advantage of this approach is that it separates the evolution of dark matter from normal matter, so that while dark matter evolves separately, Big Bang nucleosynthesis can occur in the way we currently understand it. This approach also opens avenues for exploring a wide variety of theoretical models of dark matter, since it now has a different evolutionary path so it can be more easily tracked in calculations to see how it compares to observations.

For example, the team of the paper’s authors were able to determine that if there was a so-called Dark Big Bang, it must have happened when our universe was less than a month old. The study also found that the emergence of the Dark Big Bang gave rise to very unique signatures of powerful gravitational waves that persist throughout the modern universe. Ongoing experiments such as pulsar timing probes should detect these gravitational waves, if any. We don’t know yet if there is a Dark Big Bang, but this study provides a clear path to test the idea.