In the year 1054, Chinese astronomers of the Song Dynasty recorded a star in the sky so bright that it was visible to the naked eye even during daytime for several weeks.
China was the world's leading scientific power at that time. But its people also saw astronomical events as omens of earthly affairs. And so the astronomers carefully recorded the location of the star and the time it was visible.
Now fast-forward to the present day. China has just built the world's largest radio telescope. Known as the Five-hundred-meter Aperture Spherical Telescope, or FAST, it looks like a giant silver dish, nestled among the jagged, green mountains of southwest China's Guizhou Province.
The exploding star or supernova seen in 1054 has become another kind of star, a pulsar, which emits not light but radio waves that are picked up by China's new telescope. China is investing heavily in huge projects like the telescope to reclaim the leading position in science that it held throughout much of history.
"Accurate records of astronomical observations may still be useful a thousand years later," says the telescope project's lead scientist, Zhu Ming, who hopes to leave similar records for posterity.
"I expect that we will discover many new things," he says. Among them, Zhu says, the telescope will help discover thousands of new galaxies and will observe the hydrogen clouds from which stars and planets are born.
That's awhile off. For now, Zhu and his team must perform thousands of tests to calibrate and focus the telescope to maximize its sensitivity.
Zhu showed me the telescope, which cost a reported $180 million to build, on a recent visit.
"The circular beam we're looking at is a support structure," he said, as we stood on the rim of the huge dish. "It supports a network of more than 2,000 cables. The cables are covered with more than 4,450 panels. The cables can be pulled to adjust the shape of the dish."
This allows the telescope to focus on an object and track it across the sky for up to six hours, as the earth turns.
Scientists used satellites to scour the country for just the right location for the dish, Zhu says.
"You've got a town just two or three miles from here," Zhu explains, "and the signals from the cell phones, microwave ovens, cars, cameras and digital devices there would all be too great, if not for these mountains."
In other words, the province's karst mountains serve as a sort of natural egg cup, surrounding the telescope and blocking out interference — which Zhu points out is thousands of times stronger than the faint radio signals coming from the far reaches of the universe.
Next, we drive down a spiraling road that leads to the bottom of the dish, where there is a receiver module, suspended by cables above the dish to pick up signals. Then it's lowered to the bottom for maintenance.
The dish's aluminum panels are full of holes. When the wind blows through them, it generates an eerie, buzzing roar that seems straight out of a sci-fi soundtrack.
Not far from the dish is its control center. Here, clusters of supercomputers surrounding the main control room process the data – millions of gigabytes each day, representing the radio traffic of the universe that is picked up by the telescope.
"We're looking out into space about nine or 10 billion years back into the history of the universe," says Peter Quinn, Director of the International Centre for Radio Astronomy Research at the University of Western Australia, which helped build the telescope's receivers and data processing systems.
As the universe is about 13.7 billion years old, that means the telescope will be able to see back almost to the universe's beginnings. "It's obviously a very large eyeball," Quinn says.
He and other foreign scientists will have access to some of the project's data.
Quinn says telescope-building has recently entered a golden age, producing tools that are many times more powerful than those of a generation or so ago. But he adds that making scientific breakthroughs requires more than just technology. It also takes human curiosity and a good bit of luck.
"The most enduring characteristic of telescopes, over the history of people building telescopes, seems to be that they always find things we don't expect," he says.
One unexpected consequence is that in order to scan the heavens, the local government had to move about 9,000 people here on Earth.
Farmer Shen Minghua lives in a village just outside the entrance to the telescope.
He says the local government is giving residents the lowest possible compensation for their land. Some who did not cooperate were beaten or jailed, he says. The farmers are challenging their relocation in court.
"Our ancestors have lived here for generations," Shen says. "Now, they've built this observatory here. It's good for the nation, but not for us ordinary folks. Folks have to move elsewhere, they have no homes and no way to live."