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Why space mirrors may not be out of this world.

Byline: Steven Cutts

AS countries across the globe suffer heatwaves, is there a high-tech solution to global warming? It's difficult to know if the current heatwave is part and parcel of global warming, but the long term trend seems clear. The world is getting hotter. The ice caps may well melt and global weather patterns seem set to change.

In spite of this, not all the news on the climate front is bad.

Twenty years ago, solar power seemed like an exotic form of energy generation.

Today, solar power is part of the mainstream energy mix with the price of a single panel falling on a regular basis. It's been suggested that by the year 2050, more than a third of the electricity in the world will be generated in this way.

Elsewhere, scientists have seriously considered large scale carbon capture.

In spite of all this, it's not inconceivable that it is already too late. The damage has been done and global temperatures will continue to rise.

When one looks at the full list of potential dangers, it all sounds pretty alarming, but there are far sighted engineers out there that are plotting a potential solution.

We could launch vast mirrors into space and place them between the Earth and the Sun.

These would block out the light from our nearest star and reduce the amount of heat energy hitting our planet. It sounds like science fiction, but quite a few seriously clever people have already investigated this field in depth, partly as an intellectual exercise and partly as a serious attempt to save our species.

The American engineer Lowell Wood has calculated we need only deflect one per cent of the sunlight reaching the Earth in order to counter the effects of global warming.

In practice, heat energy is hitting the Earth from the Sun all day every day and in response, the Earth emits heat energy into outer space.

Providing the second energy flow equals the first, then atmospheric temperatures ought to remain the same. If our temperature increases relative to the icy cold of space, the rate of emission of heat energy from the Earth ought to increase with it.

However, such simple calculations 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 prevent the hot air from rising out of the building. By allowing heat in but restricting its exit, the greenhouse achieves a higher ambient temperature than the rest of the garden.

What then, if the intensity of the Sun's rays were to fall? Well, the temperature of the Earth would fall with it. Wood calculated both the exact size of the mirrors that we would have to assemble in space and their optimum location. The so-called Lagrange Point, also known as L1 appears to be the best.

This kind of idea has already been 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 Worcestershirebased doctor and writer

It sounds like science fiction, but quite a few seriously clever people have already investigated this field

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We could launch mirrors into space between the Earth and the Sun to stem global warming
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Publication:The Birmingham Post (England)
Date:Aug 2, 2018
Words:1044
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