Comment Why space mirrors may not be out of this world
don’t factor in the greenhouse effect. If you wander through a garden on a summer’s day, you may be conscious of the ambient temperature.
However, if you enter a greenhouse, you suddenly become aware of a much higher temperature.
A greenhouse itself isn’t being actively heated, but the glass panels forming the roof will allow heat energy from the sun into the room.
As the ground beneath it heats up, the air heats with it, but the glass examined by science fiction writers who suggested that in the future, the planet Venus might be cooled by an even more elaborate system of mirrors. In turn, this would allow the surface temperatures to fall far enough to allow human colonisation.
The surface temperature on Venus is hot enough to melt lead. If someone is seriously suggesting that we could fix this problem using space mirrors, surely the challenge of correcting global warming here on our own much cooler planet ought to be relatively straight forward?
The problems arise when we start to look at the sheer scale of the challenge involved.
Provisional calculations suggest that the mirror, or collection of mirrors, would need to have the cross sectional surface area of Greenland, a not insignificant land mass.
The location of L1 would allow the mirror to appear relatively stable in the sky and make its impact quite predictable.
Assembly in outer space would also allow us to use materials and techniques that would be unthinkable here on Earth and a mirror that is, in effect, a mass of tin foil would be entirely acceptable.
Given the current speed of development in robotics, such a structure could be built with minimal human interference.
Better still, the tin foil could be less than one per cent of the thickness of the stuff you might find in your kitchen. Even allowing for such niceties, the entire construct would still be incredibly heavy.
A mirror that is 1,600,000km squared might best be constructed using raw materials extracted on the moon or smelted from the kind of rocks we might reasonably find in near Earth asteroids.
Mining raw materials in outer space has been under discussion for many years and sounds far more credible than it did in the past.
Even so, we should not forget just how vast a challenge this project would be.
The massive infrastructure needed to embark on such an adventure does not yet exist.
No human explorers have visited the Moon since 1972 and under current plans, the next manned expedition won’t not orbit before the Moon in 2022.
To some, space mirrors are a distraction. They provide some of our politicians with a get out jail free card for the issue of global warming and divert attention from more realistic policies such as preserving the rainforests, planting more trees and industrialised carbon capture.
However, given the extreme threat that global warming now represents, it is not unreasonable to suggest that we should leave no stone unturned.
The provisional work on space mirrors tells us that the technical challenges involved exceed our current capability – but technology is advancing all the time and it is important that governments become aware of this option, no matter how fantastical it may appear. Steven Cutts is a Worcestershire
based doctor and writer
It sounds like science fiction, but quite a few seriously clever people have already investigated this field