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New Hubble Space Telescope data indicates that the universe is expanding 9% faster than previously predicted. [phys.org]

The data reflects a discrepancy between the trajectory of the Universe 13 billion years ago and today based on early universe measurements by the European Space Agency's Planck satellite and Hubble.

"The Hubble tension between the early and late universe may be the most exciting development in cosmology in decades," said lead researcher and Nobel laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in Baltimore, Maryland. "This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke. This disparity could not plausibly occur just by chance."

The new measurements by the Hubble Space Telescope reduce the likelihood of the discrepancy being a statistical fluke (pegged at around 1 in 3000 in earlier readings) to 1 in 100,000.

These most precise Hubble measurements to date bolster the idea that new physics may be needed to explain the mismatch.

"This is not just two experiments disagreeing," Riess explained. "We are measuring something fundamentally different. 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."

The estimate of the Hubble Constant is now 1,233.3 Ice Hockey Rinks (74 Kilometers) per second per megaparsec, up from the Planck's predicted 1,116.6 IHRs (67 Kilometers) per second per megaparsec.

One explanation for the mismatch involves an unexpected appearance of dark energy in the young universe, which is thought to now comprise 70% of the universe's contents. Proposed by astronomers at Johns Hopkins, the theory is dubbed "early dark energy," and suggests that the universe evolved like a three-act play.

Another idea is that the universe contains a new subatomic particle that travels close to the speed of light. Such speedy particles are collectively called "dark radiation" and include previously known particles like neutrinos, which are created in nuclear reactions and radioactive decays.

Yet another attractive possibility is that dark matter (an invisible form of matter not made up of protons, neutrons, and electrons) interacts more strongly with normal matter or radiation than previously assumed.

Which of these possibilities is the explanation, or if it is something completely different, remains an open question.

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