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September 5, 2019 07:00 am

One Number Shows Something Is Fundamentally Wrong With Our Conception of the Universe

Iwastheone shares a report form Space.com: There's a puzzling mystery going on in the universe. Measurements of the rate of cosmic expansion using different methods keep turning up disagreeing results. The situation has been called a "crisis." The problem centers on what's known as the Hubble constant. Named for American astronomer Edwin Hubble, this unit describes how fast the universe is expanding at different distances from Earth. Using data from the European Space Agency's (ESA) Planck satellite, scientists estimate the rate to be 46,200 mph per million light-years (or, using cosmologists' units, 67.4 kilometers/second per megaparsec). But calculations using pulsating stars called Cepheids suggest it is 50,400 mph per million light-years (73.4 km/s/Mpc). If the first number is right, it means scientists have been measuring distances to faraway objects in the universe wrong for many decades. But if the second is correct, then researchers might have to accept the existence of exotic, new physics. Astronomers, understandably, are pretty worked up about this discrepancy. In April, NASA's Hubble Space Telescope confirmed that the Universe is expanding about 9% faster than expected based on its trajectory seen shortly after the big bang. "We are measuring something fundamentally different," said Adam Riess, Bloomberg Distinguished Professor of Physics and Astronomy at The Johns Hopkins University. "One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don't agree, there becomes a very strong likelihood that we're missing something in the cosmological model that connects the two eras."

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