Mystery of the Universe's Expansion Rate Widens with New Hubble Data

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Scientist Adam Riess has stated that the mismatch has been growing and has now reached the point where it's "really impossible" to dismiss as a fluke. But that's usually a slow task to do precisely, with the Hubble able to precisely measure just one distant cepheid at a time.

More recently, a team of researchers led by Adam Riess, a professor of physics and astronomy at The Johns Hopkins University in Baltimore and a laureate of the 2011 Nobel Prize for physics, found an even higher rate for the Hubble Constant.

There are a number of ways to derive the Hubble Constant.

The universe is expanding faster than expected, scientists have claimed after reviewing new measurements from NASA's Hubble Space Telescope.

Hubble's measurements of today's expansion rate do not match the rate that was expected based on how the Universe appeared shortly after the Big Bang over 13 billion years ago. All the steps involve building a strong "cosmic distance ladder", by starting with measuring accurate distances to nearby galaxies and then moving to galaxies farther and farther away. "It's going to break everything.' Now they are saying, 'we actually could do this, '" Riess said.

As the team's measurements have become more precise, their calculation of the Hubble constant has remained inconsistent with the expected value derived from observations of the early Universe's expansion made by the European Space Agency's Planck satellite. 'We are measuring something fundamentally different.

The researchers relied on the same tool that astronomer Edwin Hubble used to show that the universe was expanding back in 1929: a class of pulsing stars called cepheids.

Readers might remember the team from Johns Hopkins University and the Space Telescope Science Institute, led by Nobel Laureate Adam Riess, came up with the difference a year ago as the gang worked to refine the Hubble Constant (how fast the universe expands with time) following results from the European Space Agency's (ESA) Planck observatory.

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Our universe is expanding much faster than previously thought. Cepheids vary their brightness in such a dependable and regular way that they have become an important "cosmic distance ladder" to aid scientists determine how far away things are in the Universe.

The history of the measurement of Hubble's Constant has been always fraught with challenges and unexpected revelations. Riess's team reduced the uncertainty in their Hubble constant value to 1.9% from an earlier estimate of 2.2%. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding.

The new estimate of the Hubble constant is 74 kilometers (46 miles) per second per megaparsec. The fact the two values differ indicates that something is missing in the current model.

So, what could explain this discrepancy? Or perhaps dark energy, an unknown form of energy that pervades space, is responsible for accelerating the expansion of the Universe.

Another hypothesis is that dark radiation is present in the universe. The new theory suggests that there was a third dark-energy episode not long after the big bang, which expanded the universe faster than astronomers had predicted.

Another idea is that the universe contains a new subatomic particle that travels close to the speed of light.

The goal is to get this uncertainty down to 1 per cent. But like Riofrio, there are others who postulate that a changing speed of light cannot only account for a simplified explanation of an expanding Universe without invoking the need for dark energy, it can explain many other cosmological phenomena too.

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