While we can observe its gravitational effects on normal matter, such as galaxies and clusters, we still don’t know what it is made of or how it came to be.
A new study by physicists Katherine Freese from the University of Texas at Austin and her colleagues proposes a radical idea: what if dark matter was created by a second Big Bang that occurred when the universe was less than one month old?
This “Dark Big Bang” would have been a separate event from the ordinary Big Bang that gave rise to the matter and radiation we see today.
The researchers base their idea on recent observations of the cosmic microwave background (CMB), the faint afterglow of the first light in the universe.
The CMB contains tiny fluctuations in temperature and polarization that reveal information about the early history of the cosmos. By analyzing these fluctuations, cosmologists can infer the properties of dark matter, such as its mass and interaction strength.
Freese and her team suggest that the Dark Big Bang was triggered by a quantum field that decayed into different types of dark matter particles.
Depending on how fast and violent this decay was, it could have produced either very heavy “darkzillas” or lighter “dark cannibals” that would consume each other over time. These particles would have different effects on the CMB, such as altering its spectrum or creating distortions in its polarization.
The authors hope that future observations of the CMB and gravitational waves, which are ripples in space-time caused by violent events, could test their theory and shed more light on the nature of dark matter.
They also speculate that there could have been more than one Dark Big Bang, creating a rich diversity of dark matter species in the universe.
Their work is part of a broader shift in cosmology, where instead of assuming a single Big Bang that created everything, scientists are exploring the possibility of multiple phase transitions that shaped the universe over time.