The arrangement of galaxies across the universe may hold the key to resolving one of cosmology’s biggest mysteries: the Hubble tension. This discrepancy arises from different measurements of the rate at which the universe is expanding, known as the Hubble constant.
Measurements based on early universe features, such as the cosmic microwave background and baryon acoustic oscillations (BAO), suggest a Hubble constant of around 67 kilometers per second per megaparsec. However, those based on closer objects, like Type Ia supernovae and Cepheid variable stars, yield a constant of around 73 kilometers per second per megaparsec.
Cosmologist Indranil Banik proposes that our galaxy may be near the center of a large, local void in space. This could lead to matter being pulled towards higher-density regions, causing the void to expand and objects away from us to appear as if they are moving faster due to local expansion.
BAO measurements suggest that the Milky Way is located within a bubble approximately 2 billion light-years across, which is 20% less dense than average space. However, this explanation remains unproven.
Researchers have reexamined BAO observations over the past 20 years and found a deviation consistent with the distortion caused by a local void. This distortion increases at greater distances, which could be measurable.
The study’s findings indicate that a void model is about one hundred million times more likely than a void-free model. The researchers believe this may hold part of the solution to the Hubble tension, reducing it from 3.3 sigma to 1.1-1.4 sigma. Further testing will be necessary to confirm these results.
Source: https://www.sciencealert.com/sound-of-the-big-bang-suggests-our-galaxy-floats-inside-a-void