If Chinese news outlets are to be believed, there might be quite a story in the offing as far as science goes. State-owned portal China Daily reported online that China is in the process of designing a huge space mirror which they wish to launch into orbit and help reflect sunlight onto the earth.
In Chengdu, a city in southwestern Sichuan province, the "illumination satellites" are being rigorously tested. The construction is intended to shine eight times brighter than the moon if everything goes without a hitch. They are scheduled for launch before the end of this year from the Xichang Satellite Launch Center in Sichuan province.
According to Wu Chunfeng, head of Tianfu New Area Science Society and the company responsible for the project, the three huge mirrors will supposedly split the 360 degree orbital plane – enabling them to continuously illuminate an area for 24 hours.
There are hopes that these artificial moons will help cut down on the cost of energy utilisation – with the long term aim being to replace streetlights in urban areas. Organisers say the city could save an average of 1.2 billion yuan ($170 million, €149 million) a year when illuminating an area of 50 square kilometres. The first launch is scheduled to be a test launch, with the 2022 launch “being the real deal with great civic and commercial potential.”
Such an effort has been attempted before in the history of astronomy, with the Russians in 1990 failing at it after not adjusting their illumination angles. Scott Manley, physicist and astronomist tells German news outlet DW that, “They created a bright spot on the earth that would move along at seven kilometers per second, so you had to chase it if you wanted to get sustained brightness. Otherwise you would just see a flash of light for a second.”
Manley also criticises the Chinese project by saying that their calculations do not make sense. “They talk about the spacecraft being 500 kilometers away [roughly 300 miles], which is fine — that's a low Earth orbit,” he says, “But then they talk about providing light for an extended period of time. And the problem with that is, at 500 kilometers up, satellites are moving very quickly. If you see a satellite, it moves across the sky in a few minutes. So they would only be able to direct light at a single point for a few minutes at a time. And that means if you really want to give light to a city, you need multiple satellites, and the satellites also need to be able to track the location on the ground.”
The satellite could be put on a geostationary orbit – an orbit which is directly above the equator and thus an object put there appears to be motionless and stationary to an observer on Earth. This property could theoretically help illuminate a large area continuously.
However, Manley thinks there are issues there too. “The problem is, as you go further and further out, you need to make your mirror larger and larger.” At the geostationary orbit – with an altitude of 36,000 kilometres, the mirror itself has to be hundreds of metres across and this would naturally increase the area that is covered on earth by the artificial light to more than just a single city. Moreover, in the geostationary orbit, the mirrors will also reflect the sun. And sunlight also exerts pressure. Manley sees another potential hurdle where the pressure exerted by sunlight would eventually force the satellites to change orbits.
Another potential pitfall is that it could alter the ecosystem and the biological processes of a lot of organisms which rely on the normal circadian rhythm and natural processes like night and day for their own self-regulation.
The Chinese flirtation with the idea of artificial moonlight is not new and it may be the closest humanity gets to actual attempt and achievement of this technology. But right now, from a mathematical, physical and a biological standpoint, there are a lot of factors that go against it and it may well remain science fiction for the time being rather than actual scientific achievement.