NEW YORK (AP) – Far away, ancient stars are giving scientists some clues that a mysterious force called dark energy may not be what they thought.
Astronomers know that the universe is splitting apart at a rapid rate and have been wondering for decades about what could be causing everything to move so fast. They argue that there is a powerful, ever-present force at work, that fits perfectly with the grand mathematical model that explains how things in the universe work. But they don’t see it and don’t know where it comes from, so they call it dark energy.
It’s so big that it’s estimated to make up about 70% of the universe – while ordinary things like all the stars and planets and humans only make up 5%.
But the findings published earlier this year by an international research consortium of more than 900 scientists from around the world gave a big surprise. When scientists studied how galaxies move, they found that the force pushing or pulling them in all directions seemed to be constant. And the same group released a new, broader set of tests on Tuesday that yielded a similar result.
“I didn’t think such an effect would happen in my lifetime,” said Mustapha Ishak-Boushaki, a cosmologist at the University of Texas at Dallas who is part of the collaboration.
Called the Dark Energy Spectroscopic Instrument, it uses a telescope in Tucson, Arizona to create a three-dimensional map of the 11 billion-year history of the sky to see how galaxies have assembled throughout time and space. This gives scientists information about how the universe has evolved, and where it may be going.
The map they are building would not make sense if dark energy was a permanent force, as it is thought to be. Instead, the power seems to be changing or weakening over time. If this is true, it will enhance the cosmological model of astronomers. It could mean that dark energy is a lot different than science thought – or there could be something else entirely going on.
“It’s a time of great excitement, and then head-scratching and confusion,” said Bhuvnesh Jain, a cosmologist at the University of Pennsylvania who was not involved in the study.
The current correlation points to a possible explanation from an ancient theory: that over the billions of years of cosmic history, the universe expanded and galaxies clustered together as predicted by Einstein’s correlation.
The new findings are inconclusive. Astronomers say they need more information to overturn the theory that seemed so consistent. They hope observations from other telescopes and new analyzes of the new data over the next few years will show whether the current view of dark energy holds up or collapses.
“The significance of the results right now is interesting,” said Robert Caldwell, a physicist at Dartmouth College who was not involved in the research, “but it’s not like a gold-plated standard.”
There is much more to the answer. Because dark energy is a large part of the universe, its behavior determines the future of the planet, explained David Spergel, an astrophysicist and president of the Simons Foundation. If dark energy continues to exist, the universe will continue to expand, become colder and more empty. If it is growing in energy, the universe will grow so fast that it will destroy itself which astronomers call the Big Rip.
“Don’t panic. If that is what is happening, it will not happen for billions of years,” he said. “But we want to know about it.”
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Associated Press video reporter Mary Conlon reported from New York.
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