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Cosmic magnifying glasses yield independent measure of universe's expansion:
A team of astronomers using NASA's Hubble Space Telescope has measured the universe's expansion rate using a technique that is completely independent of any previous method.
Knowing the precise value for how fast the universe expands is important for determining the age, size, and fate of the cosmos. Unraveling this mystery has been one of the greatest challenges in astrophysics in recent years. The new study adds evidence to the idea that new theories may be needed to explain what scientists are finding.
The researchers' result further strengthens a troubling discrepancy between the expansion rate, called the Hubble constant, calculated from measurements of the local universe and the rate as predicted from background radiation in the early universe, a time before galaxies and stars even existed.
This latest value represents the most precise measurement yet using the gravitational lensing method, where the gravity of a foreground galaxy acts like a giant magnifying lens, amplifying and distorting light from background objects. This latest study did not rely on the traditional "cosmic distance ladder" technique to measure accurate distances to galaxies by using various types of stars as "milepost markers." Instead, the researchers employed the exotic physics of gravitational lensing to calculate the universe's expansion rate.
The astronomy team that made the new Hubble constant measurements is dubbed H0LiCOW (H0 Lenses in COSMOGRAIL's Wellspring). COSMOGRAIL is the acronym for Cosmological Monitoring of Gravitational Lenses, a large international project whose goal is monitoring gravitational lenses. "Wellspring" refers to the abundant supply of quasar lensing systems.
The research team derived the H0LiCOW value for the Hubble constant through observing and analysis techniques that have been greatly refined over the past two decades.
H0LiCOW and other recent measurements suggest a faster expansion rate in the local universe than was expected based on observations by the European Space Agency's Planck satellite of how the cosmos behaved more than 13 billion years ago.
The gulf between the two values has important implications for understanding the universe's underlying physical parameters and may require new physics to account for the mismatch.
"If these results do not agree, it may be a hint that we do not yet fully understand how matter and energy evolved over time, particularly at early times," said H0LiCOW team leader Sherry Suyu of the Max Planck Institute for Astrophysics in Germany, the Technical University of Munich, and the Academia Sinica Institute of Astronomy and Astrophysics in Taipei, Taiwan.
More information: Kenneth C. Wong, et al. H0LiCOW XIII. A 2.4% measurement of H0 from lensed quasars: 5.3σ tension between early and late-Universe probes. arXiv:1907.04869v2 [astro-ph.CO]: arxiv.org/abs/1907.04869
Previously: New Measurement of Hubble Constant Adds to Cosmic Mystery
(Score: 2) by PiMuNu on Tuesday January 21 2020, @04:51PM
> But we only see stuff far away and we assume that things behave as we expect from our local experiments
I disagree.
We assume that there exist a set of physics principles (call them "laws of physics" if you like) which apply to stuff "over there" and also to stuff "over here". We then attempt to deduce a consistent set of principles based on observation. That is not quite what you said; things can be radically different "over there"; but there is an assumption that there is some physical principle which does apply "over there" and "over here" at the same time.
For example, matter moving near to a black hole behaves very differently to matter moving around on earth. But based on observations of matter moving on earth, and in our galaxy, and in nearby galaxies, we deduce a set of principles that can explain *all visible phenomena*. This is the standard model of physics, and it does a pretty good job.