A new study suggests that within a month after the Big Bang, a second explosion may have bestowed the universe with invisible dark matter.
Astrophysicists have proposed in a recent study that the Big Bang may have been accompanied by a shadow, a second explosion that flooded our universe with mysterious dark matter. We might find evidence for this event by studying the ripples in the fabric of spacetime.
Image captured by the Hubble Space Telescope of the galaxy cluster Cl0024+1654, showing small red dots of stars on a blue field of dark matter.
After the Big Bang, most cosmologists believe the universe underwent a period of rapid expansion, notably during its earliest moments, known as inflation. No one knows what caused inflation, but it needs to explain various observations, such as the extreme geometric flatness of the universe on a large scale.
Inflation was likely driven by some strange quantum fields, which are a fundamental entity permeating all of spacetime. When the inflation process ended, that field decayed into a rain of particles and radiation, triggering the “hot Big Bang” that physicists often associate with the beginning of the universe. Those particles went on to combine into the first atoms when the universe was about 12 minutes old and – hundreds of millions of years later – began to coalesce into stars and galaxies.
However, there is another component in the cosmic mix: dark matter. Once again, cosmologists are uncertain about what dark matter is, but they see evidence of its existence through its gravitational influence on ordinary matter.
Scientists did not find any evidence for the existence of dark matter until much later in the evolution of the universe, after this elusive substance had enough time to exert its gravitational influence, so it was not necessary for it to fill the universe during the hot Big Bang alongside ordinary events. Furthermore, since dark matter does not interact with normal matter, it could have its own dark Big Bang, researchers assert.
Dark Big Bang
In their paper, researchers explored what a dark Big Bang would look like. First, they hypothesized the existence of a new quantum field – the so-called “dark field”, necessary to allow dark matter to form completely independently.
In this new scenario, the dark Big Bang only occurs after the inflation process has vanished and the universe has expanded and cooled enough to force the dark field into its own phase transition, where it self-transforms into dark matter particles.
The researchers found that the dark Big Bang must adhere to certain constraints. If it occurs too early, there will be too much dark matter today, and if it occurs too late, there will be too little. However, if the dark Big Bang happens when the universe is less than a month old, it could match all known observations.
Most importantly, the researchers discovered that a dark Big Bang produces a distinct signature in gravitational waves, ripples in spacetime that are still traveling through the universe today. This means that the theory could someday be testable.
