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Hubble Measurements Show The Universe Is Expanding 9 Percent Faster Than Expected

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It's a widely accepted knowledge that the universe is continuously expanding, spreading outward with the space between galaxies getting bigger and bigger.

The question is, how fast is it growing? About 9 percent faster than expected, according to new research.

A Mismatch Between Modern And Ancient Universe Expansion Rates

NASA reports that new measurements from the Hubble Space Telescope show a faster expansion rate in the modern universe than astronomers previously predicted. The old predictions were based on measurements of the early universe after the Big Bang using the European Space Agency's Planck satellite.

It's a disparity that has been observed in the past few years, but astronomers were not certain whether the difference is due to errors of measurement techniques or unlucky measurements.

Astronomers previously estimated that the chances that the discrepancy is a fluke is about 1 in 3,000, but the new, more precise data reveal that the possibility of a fluke is only 1 in 100,000.

In a study published in the Astrophysical Journal, researchers suggest that these revelations highlight the need for new knowledge and theories to understand the changing cosmos.

Measuring The Expansion Rate Of The Universe

Astronomers measure the rate of the universe's expansion — also known as the Hubble constant — by finding out how far a certain star is and then how fast it's getting farther and farther away from Earth.

For the new study, the team trained their sights on 70 stars called Cepheid variables in the Large Magellanic Cloud.

Data from their observations, which has become increasingly more precise, produced a Hubble constant that are at odds with the number produced by previous measurements of the early universe. The earlier Hubble constant was derived by analyzing the cosmic microwave background, which is relic radiation that lingers from the early stages of the universe.

The new Hubble constant estimate is 46 miles (74 kilometers) per second per megaparsec, which is 9 percent faster than the Planck estimate from the early universe at 41.6 miles (67 kilometers) per second per megaparsec.

"To use an analogy, let's look at a two-year-old and see how tall they are, and then try to figure out how tall they are going to be when they grow up. Then we could actually wait until they grow up and measure them," explains study lead author Adam Riess to National Geographic. "If they far exceed that [extrapolation], we'd have a real mystery on our hands. Something isn't right in our understanding of how this person grew."

For now, astronomers don't have an explanation for the changing expansion rate, although many have mused about dark energy, dark matter, a new subatomic particle, and other possibilities.

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