The universe is expanding faster than anyone had previously measured or calculated from theory. This is a discovery that could test part of Albert Einstein’s theory of relativity, a pillar of cosmology that has withstood challenges for a century.
Nasa and the European Space Agency jointly announced the universe is expanding 5% to 9% faster than predicted, a finding they reached after using the Hubble space telescope to measure the distance to stars in 19 galaxies beyond theMilky Way.
The rate of expansion did not match predictions based on measurements of radiation left over from the Big Bang that gave rise to the known universe 13.8bn years ago.
Physicist and lead author Adam Riess said: “You start at two ends, and you expect to meet in the middle if all of your drawings are right and your measurements are right.
“But now the ends are not quite meeting in the middle and we want to know why.”
The researchers arrived at a new expansion rate of 73.2 kilometres per second per megaparsec. A megaparsec is 3.26 million light years. The consequence of this adjustment in difficult-to-imagine speeds over unthinkable distances is that the distance between cosmic objects will double in another 9.8 billion years. The catch is that such speeds do not match predictions for an expansion rate from other observations made by Nasa’s Wilkinson microwave anisotropy Probe, or the European Space Agency’s Planck satellite. Both went into orbit to study the afterglow of the Big Bang, in which time, space and matter were created. And both delivered lower – and in each case slightly different – predictions for cosmic expansion, the first 5% and the second 9% lower.
The latest discovery also stirs hypotheses about what fills the 95% of the cosmos that emits no light and no radiation, scientists said on Thursday.
One possibility for the discrepancy is that the universe has unknown subatomic particles, similar to neutrinos, that travel nearly as fast as the speed of light, about 186,000 miles (300,000km) per second.
Hubble is used to measure the distances to stars called Cepheid variables. Their brightness means they can be used as cosmic yardsticks to measure distances to galaxies. Astronomers then look for galaxies that contain Cepheids (centre) and Type Ia supernovae, and determine their distance. They then look for supernovae in more remote galaxies. The brightness of distant supernovae are compared to measure out to the distance where the expansion of the universe can be seen (right). Those measurements are compared with how light from the supernovae is stretched by the expansion of space
Another idea is that so-called “dark energy”, a mysterious, anti-gravity force discovered in 1998, may be shoving galaxies away from one another more powerfully than originally estimated.
“This may be an important clue to understanding those parts of the universe that make up 95% of everything and that don’t emit light, such as dark energy, dark matter and dark radiation,” said Riess, with the Space Telescope Science Institute in Baltimore, Maryland.
Riess shared the 2011 Nobel prize in physics for the discovery that the expansion of the universe was speeding up.
The speedier universe also raises the possibility that Einstein’s general theory of relativity, which serves as the mathematical scaffolding for calculating how the basic building blocks of matter interact, is slightly wrong, or at least incomplete.
“We know so little about the dark parts of the universe, it’s important to measure how they push and pull on space over cosmic history”, said one of the team, Lucas Macri of Texas A&M University.
Source: The Guardian