From building the biggest experiments the world has ever seen to rolling out the latest medical advances on a massive scale and pushing the boundaries of exploration from the deepest ocean to outer space - China's scientific ambitions are immense.Just a few decades ago the nation barely featured in the world science rankings. Now, in terms of research spending and the number of scientific papers published, it stands only behind the US. But despite this rapid progress, China faces a number of challenges. Here are two key science projects that illustrate its enormous strengths, as well as some of its weaknesses, and may help answer the question whether China can become a global leader in research.

At Beijing's science and technology museum children are running around, clambering inside a model of a space station, taking miniature rovers for a test drive and even having a go on a spinning gyroscope. "Space is fun and very cool," one little boy tells me. I ask him about his ambitions, and he pauses for a moment before deciding yes, he would very much like to head into space and become a Chinese astronaut - or taikonaut - when he grows up. China's space programme has certainly captured the imagination here, and there is a sense of national pride in the country's achievements.

Nestling in a vast natural crater, China's giant is about to come alive. A colossal, steeply curved dish glints in the sunlight, surrounded by jagged mountains that cut into the sky. Construction workers, busy putting the finishing touches to this structure, look tiny against the huge backdrop. This is the largest radio telescope ever built, measuring 500m (1,640ft) across.

Prof Peng Bo

"In China, in astronomy, we're far behind the world," says Prof Peng Bo, the deputy project manager of the Five-hundred-metre Aperture Spherical Telescope - or Fast for short.  We used to have to go abroad, to use telescopes outside China. I think it's time for us to build something in China."

Situated in Guizhou Province, in the south-west of the country, Fast dwarfs all other radio telescopes. The former record-holder was the Aricebo Observatory, in Puerto Rico, with a diameter of 305m (1,000ft). The Lovell telescope at Jodrell Bank in the north of England measures 76m (249ft) across. This isn't simply one-upmanship - bigger really is better when it comes to radio astronomy.

While some telescopes, such as the Hubble Space Telescope, use light to see the visible Universe, a radio telescope is more like a giant ear "listening" for radio waves emitted by objects in deepest space. Like light, radio waves are a form of electromagnetic radiation - but they have extremely long wavelengths, ranging from about a millimetre to more than 100km in length. And because these cosmic signals have travelled for great distances in space they are also incredibly weak. This is why radio telescopes need to be big - the larger the dish, the more signals it can collect.

China's new telescope is so large that the team hopes it will pick up radio waves from the far reaches of the cosmos. The telescope will be searching for ancient signals of hydrogen - one of the building blocks of the early Universe - to try to understand how the cosmos evolved. It will also be hunting for new stars - in particular a rapidly rotating and extremely dense type of star called a pulsar - and it will even join the hunt for extraterrestrial life. "The search for extraterrestrial life is a very hot topic for every telescope - and also for the public. I think Fast can make a contribution," Peng says. It took 10 years of trawling through satellite images of the Chinese countryside to find a natural depression big enough to fit the telescope inside. But construction has taken place in record time - just over five years, and it's nearly complete.

The dish is made from 4,450 triangular panels that have been painstakingly lowered into place. While the structure in its entirety is too big to move, each of the panels can be adjusted. It means the telescope's surface can be re-angled to allow scientists to study the parts of the sky they choose.

Professor Nan Rendong

The man masterminding this ambitious project, Prof Nan Rendong of the National Astronomical Observatories at the Chinese Academy of Sciences, says the telescope has been the biggest challenge of his career. "Guizhou is a developing province and our site is remote, in a poor area of countryside," he explains.  

All the heavy parts of the structure we had to transport from an industrial area, thousands of miles away, across these terrible winding roads." Sometimes the problems seemed to be insurmountable, he says, and at times, he wanted to give up. "In the end, though, we found a way."

In ancient times, China was a world leader in science, famed for four great inventions - the compass, papermaking, printing and gunpowder. But over the centuries, as the ruling dynasties placed more focus on the arts, progress stagnated. And in the 1960s, in the turmoil of the Cultural Revolution, things got even worse. Many intellectuals and academics were forced to move to the countryside, and most scientific research came to a halt. But projects like the Fast telescope are powerful symbols of a scientific renaissance. In 2013, China's research and development spending overtook Europe's and it is set to outstrip the US's by 2020. A recent assessment by the journal Nature revealed that in terms of the number of papers being published, China now ranks second in the world behind only the US.

Charlotte Liu, Springer Nature 

"I think in China, there seems to be a sense of urgency. There's a feeling that in the last 100 years, we lost a lot of opportunities because we weren't doing research," says Charlotte Liu, managing director in China for the science publisher, Springer Nature. "And now there is this golden opportunity in terms of funding, in terms of societal recognition, of the role that can be played by science."  

But for those living in the shadow of Fast, the telescope is bringing unwelcome changes. Villages located within 5km (three miles) of the telescope will be subject to a radio quiet zone. Some reports have suggested that thousands of people may be affected. Anything that could interfere with the telescope, such as mobile phones or wireless networks, will be banned, and although the government has offered compensation to those who want to leave, some are unhappy. One woman tells me it will be too difficult to live here, so she'll be moving soon. A man says that while he supports the project, he's unhappy with the amount of compensation being offered. It's not enough money to move to the city, he says, so he's decided to stay put for now.

The scientists say they accept that people are having to make sacrifices, but they hope that the telescope will help the area. "It will attract a lot of scientists and tourists, and it's also a very good model for education, for the next generations, and for Chinese industry," says Nan Rendong. The project is currently on time, ready for completion in September. Only once it's switched on will we see whether it can help China to reclaim its science crown.