Posted on 02/17/2019 8:54:27 AM PST by ETL
Measurements of gravitational waves from approximately 50 binary neutron stars over the next decade will definitively resolve an intense debate about how quickly our universe is expanding, according to findings from an international team that includes University College London (UCL) and Flatiron Institute cosmologists.
When neutron stars collide, they emit light and gravitational waves, as seen in this artist's illustration. By comparing the timing of the two emissions
from many different neutron star mergers, researchers can measure how fast the universe is expanding. Credit: R. Hurt/Caltech-JPL
The cosmos has been expanding for 13.8 billion years. Its present rate of expansion, known as "the Hubble constant," gives the time elapsed since the Big Bang.
However, the two best methods used to measure the Hubble constant have conflicting results, which suggests that our understanding of the structure and history of the universe—the "standard cosmological model"—may be incorrect.
The study, published today in Physical Review Letters, shows how new independent data from gravitational waves emitted by binary neutron stars called "standard sirens" will break the deadlock between the conflicting measurements once and for all.
"We've calculated that by observing 50 binary neutron stars over the next decade, we will have sufficient gravitational wave data to independently determine the best measurement of the Hubble constant," said lead author Dr. Stephen Feeney of the Center for Computational Astrophysics at the Flatiron Institute in New York City. "We should be able to detect enough mergers to answer this question within five to 10 years."
The Hubble constant, the product of work by Edwin Hubble and Georges Lemaître in the 1920s, is one of the most important numbers in cosmology. The constant "is essential for estimating the curvature of space and the age of the universe, as well as exploring its fate," said study co-author UCL Professor of Physics & Astronomy Hiranya Peiris.
"We can measure the Hubble constant by using two methods—one observing Cepheid stars and supernovae in the local universe, and a second using measurements of cosmic background radiation from the early universe—but these methods don't give the same values, which means our standard cosmological model might be flawed."
Feeney, Peiris and colleagues developed a universally applicable technique that calculates how gravitational wave data will resolve the issue.
Gravitational waves are emitted when binary neutron stars spiral toward each other before colliding in a bright flash of light that can be detected by telescopes. UCL researchers were involved in detecting the first light from a gravitational wave event in August 2017.
Binary neutron star events are rare, but they are invaluable in providing another route to track how the universe is expanding. The gravitational waves they emit cause ripples in space-time that can be detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo experiments, giving a precise measurement of the system's distance from Earth.
By additionally detecting the light from the accompanying explosion, astronomers can determine the system's velocity, and hence calculate the Hubble constant using Hubble's law.
For this study, the researchers modelled how many such observations would be needed to resolve the issue of measuring the Hubble constant accurately.
"This in turn will lead to the most accurate picture of how the universe is expanding and help us improve the standard cosmological model," concluded Professor Peiris.
Explore further: Could gravitational waves reveal how fast our universe is expanding?
More information: Stephen M. Feeney, Hiranya V. Peiris, Andrew R. Williamson, Samaya M. Nissanke, Daniel J. Mortlock, Justin Alsing and Dan Scolnic, 'Prospects for resolving the Hubble constant tension with standard sirens' will be published in Physical Review Letters on Thursday 14th February 2019.
Journal reference: Physical Review Letters
Everything can be explained by invoking Dark Matter.
Something Is Not Quite Right In the Universe, Ultraprecise New Measurement Reveals
Space.com ^ | February 9, 2019 | Mara Johnson-Groh, Live Science Contributor
Posted on 2/9/2019, 12:49:05 PM by ETL
https://www.freerepublic.com/focus/f-chat/3726592/posts
Thank goodness.
Everyone was getting tired of those bloody knife fights in the faculty lounge.
Gravity is a constant.
Zwicky was the first to propose the existence of dark matter based on the rotational velocity of galaxies. Galaxies are rotating too quickly for gravity from observable stars to hold them together. Black holes don’t work, because if the matter were concentrated at the center the outside would rotate more slowly than the inside, just as Pluto orbits the sun more slowly than Mercury. Zwicky concluded that if Newtonian mechanics explained the structure of galaxies there must be some unseen matter more or less uniformly distributed throughout the galaxy holding them together that did not show up in telescopes. Hence the term, dark matter.
The nature of dark matter is not known, no compelling evidence for any particular form exists, although neutrinos and failed stars (super Jupiters) has been ruled out.
Regardless, dark matter does not explain the discrepancy between estimates of the Hubble constant resulting from different measurement techniques.
“Unbelievably (IMO),”
You don’t believe?
Once they settle the question of the Universe’s expansion, and after dozens of learned papers are read, after readers are completely astounded and flummoxed, there will appear a slight niggle, which, after further intense study, will need some very expensive equipment to uncover the truth - wherein they will find out that gravitational waves are not what they thought they were and everything will go back to square one: namely we know less than nothing about the true nature of the Universe and are not likely to uncover that truth for some millions of years - supposing the human race lasts that long ...
How do you like that for one sentence?
In the history of modern physics has there been a more productive instrument than the interferometer?
Curious: how fast do they propagate?
I would have to say that in my many years of lonely, obsessive, near-ceaseless research the disgronificator has played an even larger role.
So, does the force of gravity travel faster that light or not?
Is that the Washington state site?
There is also one in Louisiana.
Signals found by both sites indicate that gravity waves travel at the speed of light.
That is not the only mathematical “constant” in the standard model that might be a big error.
I think the next twenty years will produce an exlosion of findings that will explode the standard model. I think that model has included a greater than actual role for gravity and a lesser than actual role for other forces in the universe. One of the lesser understood and lesser admitted role is that of “charge” (as in the positive & negative electromagnetic charge) on the large scale, as applies to solar systems, star formations and the entire cosmos.
“Gravity is a constant.”?
Relative to what? Relative to an object at a point in space? Over time?
The instrumentation to detect gravity waves puts Rube Goldberg to shame. Detecting neutrinos was easy in comparison.
Unless the gravitational wave method gives them... A THIRD SOLUTION for the Hubble constant!
Totally cool!!
Thanks for forwarding on.
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