“We Exist in a Cyclical Universe” –Chinese Scientists Measure Cosmic Expansion With a ‘Magic Ruler’

 

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“What it means is that dark energy, which causes cosmic expansion, might not be a vacuum energy with a constant density, like many scientists previously believed, but rather an energy field with certain dynamic properties,” said Zhao Gongbo, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences.


There’s a giant “ruler” hidden among millions of galaxies in the universe that scientists can use to measure how fast the universe is expanding, which allows them to explore dark energy, the mysterious power behind cosmic expansion. Chinese astronomers recently used this "ruler" to reconstruct the evolution of dark energy based on the observation of over a million galaxies. 

 

The research result made by a team led by Zhao was recently published on the academic journal, Nature Astronomy. "Dark energy determines the universe’s destiny," he said. “If dark energy is indeed a vacuum energy, the universe will keep on expanding until it ends with a ‘big rip’. But if dark energy is dynamic, the universe might go through expansion, contraction and then expansion again – a cyclical universe.” According to Zhao, scientists measure such a vast universe with a "magic ruler" – baryon acoustic oscillations (Image below E.M. Huff, the SDSS-III team, and the South Pole Telescope team; graphic by Zosia Rostomian).

 

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The early universe consisted of a hot, dense plasma of electrons, baryons (protons and neutrons) and photons, like a pot of porridge. The primordial disturbances from cosmic creation transmitted through the “porridge,” causing periodic changes to its density, temperature and pressure on the chronological sequence. This transmission mechanism is similar to sound waves transmission, so it is called baryon acoustic oscillations (BAO) by scientists.

About 380,000 years after the Big Bang, the cooled-down universe became transparent. The transmission of BAOs stopped, and the information of those oscillations was frozen in space-time. But the great power of it influenced the distribution of galaxies in the universe.

 

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In 2005, the BAO signal was discovered for the first time, providing cosmologists with the “standard ruler” they dreamed of, in order to measure the universe and determine if it’s flat or curved, and how fast it’s expanding.

Since 2012, Zhao’s team has been making observations with the Sloan telescope at the Apache Point Observatory in New Mexico, where based on the observation of galaxies and quasars, they obtained high-precision BAO signal.

“The observation of BAOs is becoming more precise. Previous observations focussed on a short period of the universe, but we adopted a new method. Like doing a CT scan for a more remote universe, we get to know more about the history of cosmic evolution,” said Zhao.

Based on the measurement with the ruler, astronomers will be able to draft a three-dimensional map of the universe where billions of years flew by, galaxies took shape and the universe evolved. “With the help of China’s Tianhe supercomputer as well as foreign supercomputers, we simulated approximately 2,000 universes for analytic purposes,” said Zhao.

The image at the top of the page is the first realistic virtual universe using a computer simulation called “Illustris.” Illustris can recreate 13 billion years of cosmic evolution in a cube 350 million light-years on a side with unprecedented resolution. “Until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously,” says lead author Mark Vogelsberger (MIT/Harvard-Smithsonian Center for Astrophysics), who conducted the work in collaboration with researchers at several institutions, including the Heidelberg Institute for Theoretical Studies in Germany.

The Daily Galaxy via XINHUA Beijing

Image credit: NASA

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