How fast is the universe expanding? It’s one of the greatest puzzles of modern physics. But now a team of researchers claims to have cracked it, and their answer could hold the clue to the fate of our galaxy – and every other.
Cosmologists working as part of the H0LiCOW collaboration (yes, really) have been observing how light from distant quasars – super bright galaxy cores – is bent around the many galaxies in the middle-distance.
Using the Hubble telescope, the scientists were able to measure over time how long it took for different bursts of the quasars’ light to reach Earth, or at least the low-orbit in which Hubble sits.
The longer the delays between each burst, which are just a flicker when they reach Hubble, the longer the path. This measurement is directly related to the speed of the universe’s expansion, the Hubble Constant.
With some pretty complicated maths, the scientists came to the conclusion that the universe was expanding at 72 kilometres a second per megaparsec.
That’s really, really fast.
Each megaparsec is equivalent to about 3 million light years, so every 3 million light years out, the universe is expanding 72 kilometres/s faster, which converts to around 161,000 mph.
It’s also faster than an established estimate based on cosmic microwave background radiation from the start of history, which, critically, fits our current understanding of the universe.
But the H0LiCOW team claims their lensing technique is a more accurate representation of the speed of expansion now.
“Our method is the most simple and direct way to measure the Hubble constant as it only uses geometry and General Relativity, no other assumptions,” said co-lead Frédéric Courbin from EPFL, Switzerland.
Significantly, the figure also chimes with other recent estimates of the rate of expansion drawn from observations of the local universe.
Sherry Suyu, leader of the research team, said this could have a profound impact on our understanding of cosmology.
“The expansion rate of the Universe is now starting to be measured in different ways with such high precision that actual discrepancies may possibly point towards new physics beyond our current knowledge of the universe,” Suyu added.
Speaking on Radio 4’s PM show, Karen Masters, an astronomer at Portsmouth University, said the measurements could have major implications for our understanding of how dark energy works together with dark matter to force the universe apart at an accelerating rate.
At the moment, both those forces are hypothetical, but Masters said they could have a very real impacts on the future of the universe: “The expansion will get strong enough to rip apart galaxies and even solar systems, but we’re talking trillions of years in the future.”
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