“While it is certainly possible that axions — a hypothetical elementary particle predicted to be among the lightest particles in the universe–make up dark matter, they also may make up a source of “dark radiation” in our universe which we refer to as the Cosmic Axion Background (CaB), analogous to the observed Standard Model radiation, known as the Cosmic Microwave Background,” Jeff Dror, with the Santa Cruz Institute for Particle Physics, told The Daily Galaxy. “Furthermore,” adds Dror, “experiments designed to search for axion dark matter can be repurposed to search for the CaB and potentially lead to the discovery of the axion, which would also teach us a great deal about the history of our universe.”
From our tiny blue dot, the universe appears inconceivably vast. In the grand cosmic scheme of things, all the light in the observable universe provides about as much illumination as a 60-watt bulb seen from 2.5 miles away, says Marco Ajello, an astrophysicist at Clemson University, who led a team in 2018 that has measured all of the starlight ever produced throughout the history of the observable universe.
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“It’s mind-boggling to actually witness material orbiting a massive black hole at 30% of the speed of light,” marveled Oliver Pfuhl, a scientist at the Max Planck Institute for Extraterrestrial Physics.
“The fate of black holes in a quantum theory of gravity is, in my view, the most important problem in theoretical physics,” said Jorge Pullin, the Horace Hearne professor of theoretical physics at LSU.