False moon: Could China really light up the night sky?

A Chinese company has announced ambitious plans to create a "false moon" in space to illuminate the night sky.

According to the People's Daily newspaper, officials from a Chengdu private aerospace institute wish to launch this "lighting satellite" in orbit by 2020 and claim that it will be bright enough to replace public lighting.

The news straight out of science fiction has sparked fascination, skepticism on the part of scientists, many questions and outright derision.

What do we know about this project?

Not much – and the little information available is somewhat contradictory.

The People's Daily reported it for the first time last week, citing comments made at a conference on innovation by Wu Chunfeng, chairman of the aptly named Institute of Aerospace Sciences Chengdu Institute of Microelectronics Research Systems, Co., Ltd.

Wu said the idea had been under test for a few years and that the technology was now in place to get there, with a launch scheduled for 2020.

According to China Daily, Wu said three "big mirrors" could be launched by 2022.

None of the reports can tell if this project has official support.

How could a "false moon" work?

According to the China Daily, the artificial moon would function as a mirror reflecting sunlight on Earth.

It would gravitate around the Earth for 500 km – about the same height as the International Space Station. The Moon orbits on average about 380,000 km from the Earth.

The reports gave no details about the appearance of the false moon, but Wu said it would reflect sunlight over an area between 10 km and 80 km with a brightness "eight times" higher to that of the real moon.

According to Wu, the accuracy and intensity of the light would be controllable.

But why?

Save money. This may sound ridiculous, but Chengdu aerospace officials believe that installing a fake moon in space might prove less onerous than paying for it. 39, public lighting.

According to the China Daily, Wu would have lit up an area of ​​50 square kilometers to save up to 1.2 billion yuan ($ 173 million) a year in electricity charges.

It could also "illuminate hidden areas" after, for example, a natural disaster such as an earthquake.

"Consider this as a kind of investment," Dr. Matteo Ceriotti, a lecturer in space systems engineering at the University of Glasgow, told the BBC.

"The electricity at night is very expensive, so if you could say that you have free lighting for up to 15 years, it could work better economically in the long run."

OK but is it possible?

Scientifically, it is viable, says Dr. Ceriotti.

But to reach its goal, the false moon should be permanently in orbit over Chengdu, a relatively tiny area when you look at the Earth from space.

This would mean that it should be in geostationary orbit, about 37,000 km from the Earth.

"The only problem is that at this distance the satellite's pointing direction would have to be extremely precise," said Dr. Ceriotti.

"If you want to illuminate an area with a 10 km error, even if you miss a hundredth of a degree, you will have the light directed to another place."

And to make an impact of this distance, the mirror should be really huge.

What impact would this have on the environment?

Kang Weimin, director of the Harbin Institute of Technology, told People's Daily that the light from the satellite would be similar to a "glow similar to that of twilight" and "should not affect the routines of animals".

But social media users in China have concerns.

Some said it would surely confuse nocturnal animals, while others claimed that many cities in China were already suffering from light pollution.

"The moon would dramatically increase the nighttime brightness of a city already polluted by light, creating problems for Chengdu residents who can not filter out unwanted light," said John Barentine, director of public policy at the University of California. 39, Dark Sky International Association. Forbes press point.

Dr. Ceriotti told the BBC that if the light was too strong "it would disrupt the night cycle of nature and this could possibly affect animals".

"But conversely, if the light is so dim, the question is, what is its interest?"

Is it a first?

No, a space mirror to create daylight at night had already been tried before.

In 1993, Russian scientists took out a reflector 20 meters wide from a supply ship heading for the Mir space station, which was in orbit between 200 and 420 km.

Znamya 2 briefly transmitted a light point about 5 km in diameter to the Earth. The light crossed Europe at 8 km / h, before the satellite caught fire on his return.

Attempts to build a larger model of Znamya failed in the late 1990s, leading the BBC's science editor at the time to say that he had "there" no chance for the Earth to be surrounded by space mirrors in the near future. "