Quasar 'Clocks' Show the Universe Was Five Times Slower Soon After the Big Bang

Scientists have achieved a breakthrough by observing the early universe in extreme slow motion, confirming Einstein's theory of an expanding universe. The research is published in Nature Astronomy. Phys.Org reports: Einstein's general theory of relativity means that we should observe the distant -- and hence ancient -- universe running much slower than the present day. However, peering back that far in time has proven elusive. Scientists have now cracked that mystery by using quasars as "clocks." "Looking back to a time when the universe was just over a billion years old, we see time appearing to flow five times slower," said lead author of the study, Professor Geraint Lewis from the School of Physics and Sydney Institute for Astronomy at the University of Sydney. "If you were there, in this infant universe, one second would seem like one second -- but from our position, more than 12 billion years into the future, that early time appears to drag." Professor Lewis and his collaborator, Dr. Brendon Brewer from the University of Auckland, used observed data from nearly 200 quasars -- hyperactive supermassive black holes at the centers of early galaxies -- to analyze this time dilation. Previously, astronomers have confirmed this slow-motion universe back to about half the age of the universe using supernovae -- massive exploding stars -- as "standard clocks." But while supernovae are exceedingly bright, they are difficult to observe at the immense distances needed to peer into the early universe. By observing quasars, this time horizon has been rolled back to just a tenth the age of the universe, confirming that the universe appears to speed up as it ages. Professor Lewis worked with astro-statistician Dr. Brewer to examine details of 190 quasars observed over two decades. Combining the observations taken at different colors (or wavelengths) -- green light, red light and into the infrared -- they were able to standardize the "ticking" of each quasar. Through the application of Bayesian analysis, they found the expansion of the universe imprinted on each quasar's ticking. "With these exquisite data, we were able to chart the tick of the quasar clocks, revealing the influence of expanding space," Professor Lewis said. These results further confirm Einstein's picture of an expanding universe but contrast earlier studies that had failed to identify the time dilation of distant quasars.

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