Shocking universe expansion discovery could require totally new physics

25 Apr 2019

Image: © klss777/

Astrophysicists were surprised to discover that the universe is expanding much faster than expected, potentially needing new physics to find an answer.

The Hubble Space Telescope has shed more fascinating light on the universe around us, showing that the cosmos is hurtling away from us at great speed.

In a study published to the Astrophysical Journal Letters, a team of researchers led by Nobel laureate and Johns Hopkins University professor Adam Riess detailed how the universe is expanding 9pc faster than previously thought.

These measurements reduce the chances the large disparity is an accident from one in 3,000 to only one in 100,000, suggesting that new physics may be needed to better understand the cosmos.

“This mismatch has been growing and has now reached a point that is really impossible to dismiss as a fluke. This is not what we expected,” Riess said.

To make the discovery, the team analysed light from 70 stars in our neighbouring galaxy, the Large Magellanic Cloud, with a new method that allowed for capturing quick images of these stars. These Cepheid variable stars brighten and dim predictably, making them excellent for measuring intergalactic distances.

Crucial to the breakthrough was a vastly improved measurement method called Drift and Shift (DASH). Typically, Hubble would only be able to observe one star every 90-mintue orbit around Earth. However, using DASH, the team used Hubble as a ‘point and shoot’ camera to look at up to a dozen groups of Cepheids compared with just one.

These measurements were combined with other observations made by researchers in Chile, the US and Europe that included distance measurements to the Large Magellanic Cloud. This was achieved by observing the dimming of light as one star passes in front of its partner in eclipsing binary star systems.

‘This is not just two experiments disagreeing’

These combined results helped show the team the true Cepheid brightness and ‘tighten the bolts’ of the so-called distance ladder. This is used to determine distances within the universe and calculate the Hubble constant, a value of how fast the cosmos expands over time.

The team’s discovery now significantly contradicts findings made by the European Space Agency’s Planck satellite, which drew on data observed 380,000 years after the Big Bang.

“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.”

With no reason for the discrepancy as of yet, the team is now working to reduce uncertainty from 1.9pc to 1pc. By comparison, in 2001 this uncertainty was 10pc.

Colm Gorey was a senior journalist with Silicon Republic