Fasten your starship seatbelt: although cosmic inflation is well known for resolving some important mysteries about the structure and evolution of the universe, other very different theories can also explain these mysteries. In some of the theories, the state of the universe preceding the Big Bang – the so-called primordial universe – was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.
The beauty of the Universe is that there’s always a mystery. Scientists might have an explanation for the existence of an especially cold region in the afterglow, known as the CMB Cold Spot. Its origin has been a mystery so far but might be attributed to the largest absence of galaxies ever discovered.
“In the end, the most improbable and hence the most puzzling aspect of space is its very existence. The simple fact that we live in an apparently smooth and regular three dimensional world represents one of the greatest challenges to the developing quantum theory of gravity,” wrote physicist Lee Smolin in Three Roads To Quantum Gravity. “If you look around at the world seeking mystery, you may reflect that one of the biggest mysteries is that we live in a world in which it is possible to look around, and see as far as we like. The great triumph of the quantum theory of gravity may be that it will explain to us why this is so.”
“The Hubble tension between the early and late universe may be the most exciting development in cosmology in decades,” says Nobel laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University. New Hubble Space Telescope data suggests a faster expansion rate in the modern universe than expected based on how the universe appeared more than 13 billion years ago, strengthening the case that new theories may be needed to explain the dark energy forces that have shaped the cosmos.