Quasar ‘clocks’ suggest the universe was five times slower immediately after the Big Bang


July 03, 2023

(Nanowerk News) Scientists observe for the first time the early universe traveling in extremely slow motion, unlocking one of the mysteries of Einstein’s expanding universe.

Einstein’s general theory of relativity means that we should observe a universe that is far away – and therefore ancient – ​​traveling much more slowly than it does today. However, peering back that far proved elusive. Scientists are now solving the mystery by using quasars as ‘clocks’.

“Looking back to a time when the universe was more than a billion years old, we see that time seemed to flow five times slower,” said the study’s lead author, Professor Geraint Lewis from the School of Physics and Sydney Institute for Astronomy at the University of Sydney. Sydney University.

“If you were there, in this baby universe, a second would feel like a second – but from where we are, more than 12 billion years into the future, that beginning time seems slow.”

This research was published in Natural Astronomy (“Detection of high-redshift quasar cosmological time dilation”).


Video explanation: how quasars worked as standard clocks for the early universe

Professor Lewis and his collaborator, Dr Brendon Brewer of the University of Auckland, used observational data from nearly 200 quasars – hyperactive supermassive black holes at the centers of early galaxies – to analyze this time dilation.

“Thanks to Einstein, we know that space and time are interrelated and, since the beginning of time in the Big Bang singularity, the universe has been expanding,” Professor Lewis said.

“This expansion of space means that our observations of the early universe should appear much slower than the flow of time today.

“In this paper, we assign it to be about a billion years after the Big Bang.”

Previously, astronomers had confirmed this slow-motion universe back to about half the age of the universe by using supernovas – massive exploding stars – as ‘standard clocks’. But even though supernovae are very bright, they are difficult to observe at the enormous distances needed to peer into the early universe.

By observing quasars, this time horizon has been rolled back to only a tenth of the age of the universe, confirming that the universe appears to be accelerating as it ages.

Professor Lewis said: “Where supernovas act like single flashes of light, they are easier to study, quasars are more complex, like an ongoing fireworks display.

“What we have done is reveal the display of these fireworks, showing that quasars can also be used as standard time markers for the early universe.”

Professor Lewis worked with astro-statistician Dr Brewer to examine the details of the 190 quasars observed over the past two decades. Combining observations taken at different colors (or wavelengths) – green light, red light and infrared – they were able to standardize the ‘beats’ of each quasar. Through the application of Bayesian analysis, they found that the expansion of the universe is imprinted on every quasar beat.

“With this extraordinary data, we can chart the ticking of a quasar clock, revealing the effects of expanding space,” said Professor Lewis.

These results further confirm Einstein’s picture of an expanding universe but contrast with previous studies that failed to identify the time dilation of distant quasars.

“This previous study made one wonder whether quasars are really cosmological objects, or even whether the idea of ​​expanding space is true,” said Professor Lewis.

“However, with this new data and analysis, we can find signatures of the elusive quasars and they behave as Einstein’s relativity predicted,” he said.


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