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Is the universe expanding faster than we thought?

New data from the Hubble Space Telescope seems to indicate that the universe is expanding up to nine percent faster than expected.

Illustration demonstrating the steps the team took to measure the Hubble Constant.

NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU)

A new study could change how we examine the universe. Using Hubble data, a team of researchers led by Nobel Laureate Adam Riess has recalculated the expansion rate of the universe, finding that it could be as much as nine percent faster than previous calculations indicated.

To calculate the universe's rate of expansion, known as the Hubble Constant, the team measured the movements of 2,400 stars and 300 supernovas. These precise measurements gave a Hubble Constant of 73.2 kilometres per second per megaparsec.

At the new rate of expansion, the distances between cosmic objects would be expected to double in 9.8 billion years. However, getting a consensus on the Hubble Constant is not an easy task.

The problem with the new Hubble Constant is that it is inconsistent with NASA's Wilkinson Microwave Anisotropy Probe and Planck data about the rate of the universe's expansion just after the big bang.

"If we know the initial amounts of stuff in the universe, such as dark energy and dark matter, and we have the physics correct, then you can go from a measurement at the time shortly after the big bang and use that understanding to predict how fast the universe should be expanding today," Riess said in a statement.

"However, if this discrepancy holds up, it appears we may not have the right understanding."

The team proposed several hypothetical reasons for the discrepancy. One was that dark energy, already shown to be accelerating the universe's expansion, could be doing so with increasing strength. Another was that a new type of subatomic particle, like a neutrino, travelling at near light-speed in the early universe, affected the universe's expansion rate.

One thing, however, is certain. More work needs to be done in order to reconcile the new study with previous research.

"We should be sceptical about comparisons of this result with Planck's," cautioned Jeremy Mould, who has conducted important research into the Hubble Constant.

"The Planck folks have found support for the standard model of particle physics with three kinds of neutrino. Concluding that there's a fourth such relativistic particle is an extraordinary result which requires an extraordinary standard of proof. It's not there yet in my opinion. But the work is ongoing. It can only get better, as long as the Hubble survives."