Sep 5, 2023 04:14 PM
https://www.universetoday.com/163026/its...e-tension/
INTRO: Our best understanding of the Universe is rooted in a cosmological model known as LCDM. The CDM stands for Cold Dark Matter, where most of the matter in the universe isn’t stars and planets, but a strange form of matter that is dark and nearly invisible. The L, or Lambda, represents dark energy. It is the symbol used in the equations of general relativity to describe the Hubble parameter, or the rate of cosmic expansion. Although the LCDM model matches our observations incredibly well, it isn’t perfect. And the more data we gather on the early Universe, the less perfect it seems to be.
A central difficulty is the fact that increasingly our various measures of the Hubble parameter aren’t lining up. For example, if we use fluctuations in the cosmic microwave background to calculate the parameter, we get a value of about 68 km/s per megaparsec. If we look at distant supernova to measure it, we get a value of around 73 km/s per megaparsec. In the past, the uncertainty of these values was large enough that they overlapped, but we’ve now measured them with such precision that they truly disagree. This is known as the Hubble Tension problem, and it’s one of the deepest mysteries of cosmology at the moment.
Much of the effort to solve this mystery has focused on better understanding the nature of dark energy. In Einstein’s early model, cosmic expansion is an inherent part of the structure of space and time. A cosmological constant that expands the Universe at a steady rate. But perhaps dark energy is an exotic scalar field, one that would allow a variable expansion rate or even an expansion that varies slightly depending on which direction you look. Maybe the rate was greater in the period of early galaxies, then slowed down, hence the different observations. We know so little about dark energy that there are lots of theoretical possibilities.
Perhaps tweaking dark energy will solve Hubble Tension, but Sunny Vagnozzi doesn’t think so. In a recent article, he outlines seven reasons to suspect dark energy won’t be enough to solve the problem. It’s an alphabetical list of data that shows just how deep this cosmological mystery is... (MORE - details)
INTRO: Our best understanding of the Universe is rooted in a cosmological model known as LCDM. The CDM stands for Cold Dark Matter, where most of the matter in the universe isn’t stars and planets, but a strange form of matter that is dark and nearly invisible. The L, or Lambda, represents dark energy. It is the symbol used in the equations of general relativity to describe the Hubble parameter, or the rate of cosmic expansion. Although the LCDM model matches our observations incredibly well, it isn’t perfect. And the more data we gather on the early Universe, the less perfect it seems to be.
A central difficulty is the fact that increasingly our various measures of the Hubble parameter aren’t lining up. For example, if we use fluctuations in the cosmic microwave background to calculate the parameter, we get a value of about 68 km/s per megaparsec. If we look at distant supernova to measure it, we get a value of around 73 km/s per megaparsec. In the past, the uncertainty of these values was large enough that they overlapped, but we’ve now measured them with such precision that they truly disagree. This is known as the Hubble Tension problem, and it’s one of the deepest mysteries of cosmology at the moment.
Much of the effort to solve this mystery has focused on better understanding the nature of dark energy. In Einstein’s early model, cosmic expansion is an inherent part of the structure of space and time. A cosmological constant that expands the Universe at a steady rate. But perhaps dark energy is an exotic scalar field, one that would allow a variable expansion rate or even an expansion that varies slightly depending on which direction you look. Maybe the rate was greater in the period of early galaxies, then slowed down, hence the different observations. We know so little about dark energy that there are lots of theoretical possibilities.
Perhaps tweaking dark energy will solve Hubble Tension, but Sunny Vagnozzi doesn’t think so. In a recent article, he outlines seven reasons to suspect dark energy won’t be enough to solve the problem. It’s an alphabetical list of data that shows just how deep this cosmological mystery is... (MORE - details)