New measurement may resolve cosmological crisis

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"Astronomers have now provided many different estimates of the universe's expansion, some of which agree and some which don't. Each team is striving for the best accuracy they can provide, Birrer said, and sorting out which might contain the ultimate answer is still unclear. "

"Freedman agreed, saying that she and her colleagues have recently been approved to use the upcoming James Webb Space Telescope to look at both Cepheids and red giants. Those observations should help clear up some of the remaining systematic uncertainties and hopefully get closer to the true value of the Hubble constant."
 

rod

Oct 22, 2019
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The space.com reports "It's landing in the same place, just shy of 70 [km/s/Mpc] with an uncertainty of just over 2%," Freedman said of the new Hubble constant estimate from the red giant stars. "If we compare those results to the CMB, we wouldn't say there's an issue."

H0 is critical to measuring the age of the universe and size of the universe too for objects reported with different redshifts or z values, size of the universe when these objects formed compared to the present size some 93 billion light years diameter where CMBR z ~ 1100 today. Here are some cosmology calculators I use.

https://ned.ipac.caltech.edu/help/cosmology_calc.html, https://www.kempner.net/cosmic.php

H0 values 67 to 72 km/s/Mpc can show dramatic differences.

The age of the universe can vary based upon different input parameters like for H0 using the cosmology calculators. A good example is the kempner.net calculator. Using H0 = 70 km/s/Mpc, the age of the universe is “age of the Universe at z = 13.2451 Gyr” when z = 0 and H0 = 70 km/s/Mpc. Thus some stars can still be dated older than the universe beginning using BB cosmology calculators. This was a problem when H0 = 500 km/s/Mpc in the early days of redshift surveys with the universe age near 2 billion years old. Using cosmology calculator I, H0 = 70 km/s/Mpc and z = 0, the universe age is "It is now 13.642 Gyr since the Big Bang. The age at redshift z was 13.642 Gyr." Using cosmology calculator II with H0 = 70 km/s/Mpc z =0, universe age is "Age of the universe: 13.4112 Gyr, which is 100% of the age of the universe today. Lookback time: 0 Gyr." The Hubble time for age of the universe in the expanding universe model for the BB is very sensitive to input parameter changes.

The list of 5 very old stars in the S&T report is also a good example of what can happen with the age of the universe calculated using different values for H0. There will be stars older than the BB event or at least older than when the CMBR formed, about 380,000 years after the BB :)

IN SEARCH OF ANCIENT SUNS, https://skyandtelescope.org/astronomy-news/in-search-of-ancient-suns/, May 2021.
 
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