Universe is Expanding Up To 9% Faster Than We Thought, Say Scientists
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.
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.
Such research has a long history of revision and updates. Einstein’s original calculations for general relativity seemed to predict that the universe was expanding and – in what he is supposed to have described later as his greatest blunder – he confected a cosmological constant to correct what he thought was an error. In 1923, the great American astronomer Edwin Hubble stared through what was then the world’s biggest telescope at what he thought was a nebula – cloud of dust – in the night sky and realised that he was observing another distant star system: the island universe of the Andromeda galaxy. And within two years he had observed the light signature of a receding galaxies, and proposed that everywhere in the universe, galaxies were rushing away each other, the farthest away at a greater rate.
But all astronomical observations depend on being able to calculate distances, and from that make ever more precise estimates of galactic recession. When the Hubble space telescope was first launched in 1990, estimates of the rate of cosmic expansion varied by a factor of two. Continuous observations seemed to narrow the range to ever more precise estimates.
Until 1998, astronomers thought they had got the big picture. The universe was expanding at a steady rate, but it might still be possible that expansion could halt, or even that the universe could contract. A team of astronomers staring at a class of stars called type 1a supernovae across enormous distances realised that the furthest were not just receding at the predicted rate: they were accelerating as if being driven by a mysterious force briefly dubbed “antigravity”.
It was the first hint of what, for want of a better term, is called dark energy: a so-far inexplicable force that is likely to keep the universe expanding forever. And it was at that point that cosmologists began to realise that all the gas, dust, planets, stars, galaxies and black holes they could account for added up to only about 4% of the universe.
It also raised the possibility that, an unimaginable number of years from now, all the other galaxies will have receded over some cosmic horizon, leaving the Milky Way alone in the visible universe, and with no distant objects to provide any evidence at all of accelerating cosmic expansion.
The latest advance on the speed of universal expansion builds on all these elements in a century of cosmological discovery. Riess and colleagues made their discovery by building a better cosmic yardstick to calculate distances. They used the Hubble Space Telescope to measure a particular type of star, known as Cepheid variables – the stars that gave Edwin Hubble and and his colleagues the first hint of an expanding universe – in 19 galaxies beyond our own Milky Way galaxy.
How fast these stars pulse is directly related to how bright they are, which in turn can be used to calculate their distances, much like a 100-watt light bulb appears dimmer the farther away it is. They also used the type 1a supernovae as “standard candles” and it had been this class of objects that had illuminated not just another advance in speed but speculation about dark energy.
The research will be published in an upcoming edition of the Astrophysical Journal.
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