One of the greatest mysteries in cosmology is the nature and origin of dark matter, the invisible and elusive substance that makes up about 27% of the universe’s mass and energy.
Although 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 formed.
A new study by physicists Katherine Freese of the University of Texas at Austin and her colleagues proposes a radical idea: What if dark matter were created by a second Big Bang that happened when the universe was less than a month old?
This ‘Dark Big Bang’ would have been a separate event from the regular 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 small temperature fluctuations 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 caused by a quantum field that broke down into different types of dark matter particles.
Depending on how rapid 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 various effects on the CMB, such as changing the spectrum or creating distortions in the polarization.
The authors hope that future observations of the CMB and gravitational waves, which are ripples in space-time caused by violent events, can test their theory and shed more light on the nature of dark matter.
They also speculate that there may have been more than one Dark Big Bang, creating a rich diversity of dark matter types in the universe.
Their work is part of a broader shift in cosmology, where instead of assuming a single Big Bang created everything, scientists are exploring the possibility of multiple phase transitions that have shaped the universe over time.
