Buckle up, folks. Our understanding of the universe may be turned upside down.
The most precise measurement ever made of the current rate of expansion of the universe has produced a number that appears incompatible with the measurements of radiation left over from the Big Bang. In other words, if the findings are confirmed, the laws of cosmology may have to be rewritten.
What’s more, it might mean that dark energy — the unknown force that is believed to be responsible for the observed acceleration of the universe’s expansion — has increased in strength since the universe’s birth.
“I think that there is something in the standard cosmological model that we don't understand,” astrophysicist Adam Riess, a physicist at Johns Hopkins University in Baltimore, Maryland, who co-discovered dark energy in 1998 and led the latest study, said in a news release.
In the current model of cosmology, the universe evolved mostly through the competing action between dark matter and dark energy. Dark matter acts to slow cosmic expansion, while dark energy pushes in the opposite direction, making it accelerate. But dark energy’s strength has been thought of as constant throughout the history of the universe.
What scientists know about the contributions of dark matter and dark energy actually comes from the radiation left behind from the Big Bang, called the Cosmic Microwave Background (CMB). In fact, neither dark energy nor dark matter have been directly observed.
While dark matter is thought to make up 27 percent of the Universe, and visible matter — what we see — just 5 percent, dark energy is estimated to make up a staggering 68 percent of the known universe.
The most detailed study of the universe was recently completed by the European Space Agency’s Planck observatory, and based on Planck’s measurements, cosmologists can predict how the universe will evolve, including how fast it expands at any point in time.
“For years, those predictions have disagreed with direct measurements of the current rate of cosmic expansion - also known as the Hubble constant,” wrote Davide Castelvecchi at Nature. “But until now the error margins in this constant were large enough that the disagreement could be ignored.”
However, Reiss and his colleagues found a new way to measure the rate of expansion: using the brightness of certain types of stars and supernovae, known as standard candles. According to Kelly Dickerson at Mic.com, standard candles are believed to emit the exact same level of brightness at all times, meaning physicists can use them as markers to measure how fast the universe is expanding.
Riess’s team analyzed 18 standard candles using hundreds of hours of data from the Hubble Space Telescope, and calculated that the speed of expansion is about 8 percent faster than Planck’s measurements predicted.
“If this new measurement is accurate - and our maps of the CMB are also accurate - then something about our fundamental understanding of the Universe is wrong,” explained Dickerson.
Recently, we have been hearing a lot about new research findings regarding our universe that are questioning the laws of physics. For example, astronomers discovered a binary star that is tumbling through our Milky Way galaxy with speeds that challenge current theories on dark matter.
However, for now we are going to have to wait for the results to be either confirmed or disproved, but it sure is an exciting time to be a physicist.
The paper has been published on the arXiv.org website.