February 2024
Introduction
Cosmic voids are vast empty regions in the universe that may help solve some of the greatest mysteries in cosmology. In recent years, huge strides have been made in this field, and many scientists believe that studying the empty voids in the universe could provide important clues to help solve the puzzles of dark matter, dark energy, and the nature of the mysterious neutrino particles. Voids have even shown that Einstein’s general theory of relativity works the same way on very large scales as it does locally – something that had not been confirmed before. “Now is the time to use voids” for cosmology, according to David Spergel, former chair of astronomy at Princeton University and current president of the Simons Foundation. Benjamin Wandelt of the Institut Lagrange in Paris echoes this sentiment: “Voids have become a hot topic.”
Discovery of Cosmic Voids
Astronomers discovered cosmic voids in the late 1970s and into the mid-1980s, and these discoveries were shocking to astronomers who were stunned to learn that the universe does not look the way they had always thought. They knew that stars cluster in galaxies and that galaxies often group together in clusters containing dozens or even hundreds of galaxies. But if you zoomed in enough, they thought this clustering would average out: on the largest scales of the universe, the cosmos appears homogeneous. And this was not just an assumption. The cosmic microwave background (CMB) – the electromagnetic radiation released about 380,000 years after the Big Bang – is extremely homogeneous, reflecting the smoothness in the distribution of matter when it was created. And although that was nearly 14 billion years ago, the modern universe is assumed to reflect this structuring.
Voids and Dark Matter and Dark Energy
Dark matter has been an almost confirmed factor in the evolution of the universe from creamy cheese to Swiss cheese. Dark matter is the invisible mass that most astronomers accepted existed only in the 1980s, despite years of compelling evidence from observers like Vera Rubin and Fritz Zwicky. It is estimated to be more than six times the mass of ordinary visible matter. This would make the gravity caused by high-density regions in the early universe stronger than anyone had imagined. Stars and galaxies were supposed to preferentially form in these high-density regions, leaving the low-density areas largely empty.
Voids and Dark Energy
Voids seem like ideal laboratories for understanding the still-mysterious force of dark energy. While galaxies and gas collide in nonlinear, complex interactions in the cosmic web, the voids are quiet enough to allow for the detection of particles that astronomers believe form dark matter. These particles won’t show up directly, as they do not absorb or emit light. But they should sometimes collide, leading to small bursts of gamma rays. They may eventually decay, resulting in the release of gamma rays in the process as well. In the
Source: https://www.scientificamerican.com/article/how-analyzing-cosmic-nothing-might-explain-everything/
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