Far out cosmology: two expansion rates (Introduction)

by David Turell , Sunday, December 26, 2021, 14:37 (854 days ago) @ David Turell

Conflict not resolved:

https://www.nationalgeographic.com/science/article/the-universe-is-expanding-faster-tha...

"It’s one of the biggest puzzles in modern astronomy: Based on multiple observations of stars and galaxies, the universe seems to be flying apart faster than our best models of the cosmos predict it should. Evidence of this conundrum has been accumulating for years, causing some researchers to call it a looming crisis in cosmology.

"Now a group of researchers using the Hubble Space Telescope has compiled a massive new dataset, and they’ve found a-million-to-one odds that the discrepancy is a statistical fluke. In other words, it’s looking even more likely that there’s some fundamental ingredient of the cosmos—or some unexpected effect of the known ingredients—that astronomers have yet to pin down.

***

"Researchers have tried to measure the universe’s current rate of expansion in two primary ways: by measuring distances to nearby stars, and by mapping a faint glow dating back to the infant universe. These dual approaches provide a way to test our understanding of the universe across more than 13 billion years of cosmic history. The research has also uncovered some key cosmic ingredients, such as “dark energy,” the mysterious force thought to be driving the universe’s accelerating expansion.

"But these two methods disagree on the universe’s current expansion rate by about 8 percent. That difference might not sound like much, but if this discrepancy is real, it means the universe is now expanding faster than even dark energy can explain—implying some breakdown in our accounting of the cosmos.

"The researchers’ findings, described in several studies submitted last week to The Astrophysical Journal, use specific types of stars and stellar explosions to measure the distance between us and nearby galaxies. The dataset includes observations of 42 different stellar explosions, more than double the next-biggest analysis of its kind. According to the team’s work, the tension between their new analysis and results from measurements of the early cosmos has reached five sigma, the statistical threshold used in particle physics to confirm the existence of new particles."

Comment: this is an astronomy problem, but doesn't negate that the universe is in constant expansion. Apparently since the origin expansion is an unexplained requirement.