One of the riddles of Einstein's expanding cosmos has been solved when
scientists for the first time witnessed the early universe growing in
extremely slow motion. The study has been released in Nature
Astronomy.
According to Einstein's general theory of relativity, the cosmos in the
past should have moved far more slowly than it does now. Looking back that
far in time has been difficult, though. The enigma has finally been solved
by scientists utilizing quasars as "clocks."
Lead researcher Professor Geraint Lewis from the School of Physics and
Sydney Institute for Astronomy at the University of Sydney stated, "Looking
back to a time when the universe was just over a billion years old, we see
time appearing to flow five times slower."
One second might feel like one second if you were there, in this young
cosmos, but from our vantage point more than 12 billion years in the future,
that early period seems to linger.
In order to study this temporal dilation, Professor Lewis and his
University of Auckland coauthor Dr. Brendon Brewer used observational data
from over 200 quasars, which are hyperactive supermassive black holes in the
cores of early galaxies.
We now understand, according to Einstein, that space and time are
interconnected, and that the universe has been expanding ever since the Big
Bang, at the beginning of time.
"Due to the expansion of space, time should appear to move considerably
more slowly in the early cosmos than it does now, according to our
measurements.
We have demonstrated in this study that this dates back to around a billion
years after the Big Bang.
Previously, scientists used supernovae, or large exploding stars, as
"standard clocks" to validate this slow-motion cosmos back to roughly half
the age of the universe. Supernovae are incredibly brilliant, yet given the
vast distances required to view the early cosmos, it is challenging to
observe them.
This time horizon has been pushed back by observing quasars to barely a
tenth of the age of the universe, proving that the cosmos appears to
accelerate with age.
Supernovae behave like a single burst of light, making them simpler to
examine, while quasars are more complicated, acting like a continuous
fireworks display, according to Professor Lewis.
What we have done is disassemble this fireworks display, demonstrating that
quasars may also serve as accepted chronometers for the early cosmos.
Astrostatistician Dr. Brewer and Professor Lewis examined the specifics of
190 quasars spotted during a two-decade period. They were able to
standardize the "ticking" of each quasar by combining the data made at
different colors (or wavelengths)—green light, red light, and into the
infrared. They discovered the universe's expansion was imprinted on each
quasar's ticking by using Bayesian analysis.
Professor Lewis remarked, "With this fine data, we were able to record the
tick of the quasar clocks, indicating the impact of expanding space.
These findings support Einstein's theory of an expanding universe even
more, in contrast to prior research that was unable to detect the time
dilation of far-off quasars.
The validity of the notion that space is expanding was also questioned as a
result of these previous research, according to Professor Lewis.
"With these new data and analysis, however, we've been able to find the
elusive tick of the quasars and they behave just as Einstein's relativity
predicts," the scientist added.
