Once upon a time, time flowed more slowly, that’s for sure

In the early universe, when matter is highly concentrated, time should flow slower than later, the general theory of relativity says. However, access to reliable clocks is limited. Quasars are proving to be helpful.

[Photo: ESO/M. Kornmesser, CC BY 4.0, via Wikimedia Commons]

Quasars, or extremely bright galactic nuclei, got their name from the fact that at first glance they resemble stars (quasar: quasi stellar object), but on closer inspection they turn out to be quite different from them. First of all, they emit light in almost the entire range of radiation, unlike stars, which emit light in a specific range corresponding to their temperature.

Their light comes from heated gas falling on a supermassive black hole at the center of the galaxy in which they are located. They are some of the brightest cosmic objects we know of. No wonder we use them to study the origins of the Universe.

[Photo: NOIRLab/NSF/AURA/J. da Silva, CC BY 4.0, via Wikimedia Commons]

Geraint Lewis of the University of Sydney, together with Brendon Brewer of the University of Auckland, collected observations of nearly 200 quasars scattered across the sky. Through statistical analysis, they were able to show that when the Universe was a billion years old, time flowed five times slower…