It is one thing to draw up a map of the United States or even Earth.
But the entire universe?
That's the ambitious plan of an international team of scientists from 11 countries, who are planning to use the largest telescope ever built to complete a massive survey that will scan huge swaths of the universe and will provide much more detail than ever before on how it has evolved over 14 billion years.
In a series of papers on astrophysics website arXiv.org, the scientists said the experiment will combine signals from hundreds of radio dishes and receivers spread out across South Africa and Western Australia. Known as the Square Kilometer Array (SKA), it will cover an area the size of 15 soccer pitches and produce more data in one day than several times the daily traffic of the entire Internet.
Until now, the idea of mapping the entire universe seemed impractical.
Currently, researchers map galaxies by detecting the faint radio signals from many individual galaxies and then studying them for long enough to measure properties like their distance. Though time consuming, this method is the most accurate, allowing highly detailed 3D maps of the matter distribution to be made. In the coming decades, researchers hope this method allows them to find almost a billion galaxies.
Still, there has to be a faster way and that is where SKA comes in. It allows scientists to rapidly scan the telescopes across the sky, sacrificing accuracy but surveying a much larger area in a short period of time.
"This will only give us a low-resolution map," said Mario Santos of the University of the Western Cape. "But that's already enough to start answering some serious questions about the geometry of the universe and the nature of gravity."
"It will be like making a movie of the universe from a young age, when it was only about 2 billion years old, until today when it is about 14 billion years old," SKA Cosmology Working Group Chair Roy Maartens, from the University of the Western Cape in South Africa, said. "The movie will be low resolution but enough to test the fundamentals of cosmology."
The hope is that this network will be able to detect the faint radio emissions from hydrogen gas, which is key to mapping the cosmos.
"Hydrogen is the most common element in the universe, so we see it everywhere" said Phil Bull, from the University of Oslo in Norway. "This makes it ideal for tracing the way matter is distributed throughout space."
SKA should be competed by 2020 and the first survey by 2022. A second phase, due in 2025, will be ten times larger.
Along with mapping the universe, researchers hope to answers some fundamental questions about the universe that have dogged astronomers for eons. Among them are the mysteries of dark matter, which is completely invisible to telescopes, but can be detected through its gravitational pull on other objects, like hydrogen-containing galaxies.
"The SKA will allow the most precise investigations of dark energy to date," said Alvise Raccanelli, from Johns Hopkins University. "By using 3D maps of the distribution of galaxies, we can study dark energy and test Einstein's general theory of relativity better than any experiment so far."
Gongbo Zhao, of the National Astronomical Observatories of China, said he also was hoping the survey would shed light on Einstein's theory, adding that it might answer whether there is a "5th force of nature."
There is also interest in better understanding what may have happened just after the Big Bang.
"What happens on ultra-large distance scales tells us something about how the newborn universe behaved when it was only a tiny fraction of a second old," said Stefano Camera, at the Jodrell Bank Center for Astrophysics in the United Kingdom. "The measurements will allow researchers to more closely scrutinize 'cosmic inflation,' the process that is believed to have sown the seeds of structures like galaxies and super clusters that we see today."
Others are hoping that scientists gain a better insight into how the universe functions by studying a billion galaxies, ten years apart.
"SKA will be able to measure the expansion of the universe directly," said Hans-Rainer Klöckner from the Max-Planck Institute for Radioastronomy in Germany.
Because cosmic expansion happens relatively slowly, Klöckner said that performing a direct measurement like this "would be a major technical achievement."
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