Far out cosmology: Hubble tension and more (Introduction)

by David Turell , Saturday, October 29, 2022, 16:47 (754 days ago) @ David Turell

Our different ways of studying the universe reach conflicting results:

https://bigthink.com/starts-with-a-bang/new-anomaly-universe/?utm_source=mailchimp&...

"Early relics and late-time objects give incompatible results for the expanding Universe. This independent anomaly intensifies the problem.

"The most puzzling, unexplained anomaly in all of cosmology is the Hubble tension: the difference in the measured expansion rate depending on which method is used. However, a second, less-publicized anomaly is also extremely puzzling: a difference in our observed motion through the Universe and how different things appear in various directionsConsider the cosmic microwave background (CMB): leftover radiation from the Big Bang.. We have many different methods of estimating how the Universe differs in different directions, and they're not all consistent with one another. That's a real, unsolved, but important problem!

"The largest anomaly is the Hubble tension. Two expansion rate measurement methods yield incompatible values. The early relic method, via cosmic imperfections, yields 67 km/s/Mpc. The distance ladder method, from individually measured objects, yields 73 km/s/Mpc.

"But another cosmic imperfection anomaly is similarly puzzling. Although mostly uniform, one direction is ~3.3 millikelvin hotter while the opposite is similarly cooler. This “CMB dipole” reflects our Sun’s relative motion to the CMB: of ~370 km/s. (look at the article to see the illustration) Our Local Group moves much faster: ~620 km/s. This should be due to cosmic, gravitational imperfections tugging on us. Nearby galaxy motions consistently support this picture. However, more distant motion tracers conflict with it. Plasmas within clusters indicate smaller overall motions: below ~260 km/s. The brightest cluster galaxies, however, reveal larger motions: ~689 km/s. Cluster scaling relations reveal giant, wrong-directional motions of ~900 km/s. And anisotropies in galaxy counts reveal more than double the expected effect. Radio galaxy counts are even worse: four times the expected amplitude. Quasar counts from WISE [NASA’s Wide-field Infrared Survey Explorer] possess the same problem. Larger-scale, upcoming surveys could robustly confirm this second “Hubble tension.'”

Comment: That we measure the Hubble rate of expansion in two ways, and they don't agree tells us we still haven't defined the universe's properties in a reliable way. Download the article to see more explanations and illustrations