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A new study reveals that the time in the universe when it was 1 billion years old was five times slower than the present time. Image: NASA.
This discovery reinforced Albert Einstein’s theory of relativity, which posits that the universe moved much slower in the past. Given the vast scale of the universe, studying its early days is akin to looking back into the past. Dim light from distant galaxies is still traveling through space to reach Earth, so the farthest reaches of the universe that scientists can observe are from the past.
However, peering into the ancient universe, formed by the Big Bang roughly 13.8 billion years ago, presents an immensely challenging task. The range of modern astronomical instruments, capable of observing different wavelengths of light, has been expanding across the universe. As a result, scientists have focused on a phenomenon that serves as a cosmic clock: quasars.
Quasars, or supermassive black holes, are highly active in the centers of newly formed galaxies, shining more brightly than our Milky Way galaxy by a factor of 100. This light acts as a cosmic stopwatch that researchers can use to track time in the universe.
Observing quasars over time enables the team of astronomers to understand how the universe has been accelerating as it ages. The results of their study were published in the journal Nature Astronomy on July 3rd.
“Looking back to a time when the universe was only about 1 billion years old, we observed time apparently passing five times slower,” said Geraint Lewis, the lead researcher and Professor of Astrophysics at the Sydney Institute for Astronomy and the University of Sydney.
The research indicates that the universe is expanding and accelerating at a gradually increasing rate, a phenomenon that scientists are striving to explain. Decoding what transpired in the early days of the universe may help scientists unravel the greatest mysteries about its origins, evolution, and future.
“Thanks to Einstein, we know that time and space are linked together from the singularity of the Big Bang, and the universe is expanding,” Professor Lewis remarked.