Thanks to gravity, we at least know that dark matter exists. We also know that it is frighteningly abundant, making up about 85 percent of all matter in the universe. But other than that, we know almost nothing. We don’t know what dark matter is or where it comes from, and if it consists of a weakly interacting form of matter, we can’t directly detect even a single particle of it.

Our continued failure to detect dark matter, even with the latest and highly sensitive detection methods, requires rethinking the nature and potential origin of this mysterious substance, according to a theoretical study by two researchers from Colgate University in the US.

Rather than emerging from the Big Bang along with regular baryonic matter, dark matter may have emerged slightly later in its own “Dark Big Bang,” the study authors write. It can now live in the dark sector, which is mostly separated from our visible sector, and interacts with it only through gravity.

Gravity has taught us how little we still know about dark matter. We call this ghost matter dark matter because it does not interact with light or other electromagnetic radiation, making it invisible to us.

However, given its gravitational effect on galaxies and galaxy clusters, as well as other evidence such as its effect on cosmic background radiation, we have strong evidence that dark matter exists. We still know next to nothing about everything else, including what it is and where it comes from.

The search for dark matter has largely focused on Weakly Interacting Massive Particles, or WIMPs. These hypothetical elementary particles interact through two of the four fundamental forces: gravity and the weak nuclear force (but not electromagnetism or the strong nuclear force).

Decades of research have yielded no confirmation of the existence of wimps, somewhat diminishing their appeal and superseding scientific interest in other possible explanations for dark matter.

“As WIMPs continue to evade detection, it becomes increasingly important to look at dark sectors that are strongly separated from the visible sector,” write physicist Cosmin Illier and graduate student Richard Casey, authors of the new study.

In 2023, two other researchers (Katherine Freese and Martin Winkler of the University of Texas at Austin) proposed an intriguing theory: Dark matter may have formed separately from the original cosmic expansion in a second big explosion, which they called the Dark Big Bang.

This challenges many scientists who imagine this pivotal period when all matter and radiation in the universe (including dark matter, whatever it is) came from a single sector of physics.

But according to Freese and Winkler, the dark Big Bang is consistent with the evidence for the existence of dark matter, provided it occurred quickly, about a month after the first Big Bang.

In this scenario, dark matter particles arise from the distortion of a quantum field that interacts only with the dark or hidden sector (a hypothetical set of particles and forces beyond our current knowledge of physics).

The dark Big Bang would cause a first-order cosmological phase transition in the dark sector, comparable to the shift in reality in the visible sector after the first Big Bang, transforming vacuum energy into a hot plasma of radiation and particles.

In their new study, Ilieu and Casey delve deeper into this idea, examining its feasibility and testing a number of different dark big bang scenarios consistent with existing experimental data. Their work helps strengthen Freese and Winkler’s argument; It not only confirms the possibility of the Dark Big Bang, but also comprehensively evaluates various options for the development of such an event.

Among their findings, Ilieu and Casey reveal a number of potential, previously undiscovered parameters regarding the formation of dark matter. They also suggest options for further testing this concept, including the possible existence of detectable signatures such as gravitational waves left behind by these scenarios.

“The detection of gravitational waves produced by the dark Big Bang could provide crucial evidence for a new theory of dark matter,” says Illier.

He notes that although dark matter is unlikely to easily reveal its secrets, there is reason to be optimistic that we will solve this cosmic mystery.

“With modern experiments such as the International Pulsar Timing Array (IPTA) and the Square Kilometer Array (SKA) on the horizon, we may soon have the tools to test this model in unprecedented ways,” says Illier.

For example, in 2023, researchers from the NANOGrav research collaboration, part of IPTA, announced that they had found evidence for the existence of a gravitational wave background in the universe. Illier and Casey say this could help test the dark Big Bang concept and pave the way for further research that could eventually shed some light on dark matter. The research was published in the journal Physical Examination D.