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Astronomers merely asking the authorities to make sure that lights shine down, not up. What will the night sky look like at the end of the presen century? We hear a great deal about light pollution, and it is only too evident that the night sky is not so dark as it used to be only a few years ago. City-dwellers barely see the stars at all,a nd in Britain it is hard to find anywhere so isolated that the sky does appear genuinly black. The problem is not confined to industrial areas. At mount Wilson in California, the great 100-inch Hooker reflector - once the most poweful telescope in the world, used by Edwin Hubble to prove that the spiral nebulae really are external galaxies - was mothballe for a while because the sky had become too bright.
But artifical lights are not the only hazards. Commercial radio transmission are interfering with radio astronomy, adn the problem is increaing all the time. Now attention is being brought to aircraft condensation trails, which can dissipate and become indistinguishable from other clouds.
Finally of course we have global warming which is undoubtedly taking place, whether or not we are the cause is a matter for debate.
To know what to do about thiswe have to look at it all one by one. Books have been written about light pollution. There is a great deal of public support, but also a certain amount of opposition, because some people are fondly under the impression that astronomers want to douse all the lights and plunge us into Stygian blacknes. This is far from true. Astronomers are merely asking the appropriate authorities to make sure that lights shine down, not up. The campaign is having a certain amount of success, but there is a long way to go yet, and wecertainly cant be confident that the skies of 2100 will be an inky as those of 1900.
When it comes to radio pollution, the problems are quite different, and relatively recent.
Next on our lists ar contrails. A vivid warning that a threat to astronomy is very serious indeed, If trends in cheap air travel continue then the era of ground astronomy may become to a halt and end much earlier than most have predicted. Global warming is happening at the end of Maunder minimum, the start of the Medieval maximum, and so on. The burning question is, have we anything to do with it, or is the Sun responsible? By 2100 AD we will all be too busy saving our lives to pay much attention to the sky. But assuming that we are still here and that earth remains a subtle place for us, we may have to accept that the night sky is unpleasantly bright, and there is general deterioration in the seeing conditions.
We could control artificial lights, we could ensure that radio pollution was cut, we could reduce the number of trails by reducing the number of flights. Whether we would actually do any of these things is highly debatable, and in any case we cannot control the sun. Global warming is a fact and though in the opinion of many people it is likely to be followed by compensatory period of global cooling, it is something to be discussed.
So in the long term run there is only one answer, to go to space! The hubble space telescope has shown the way. If all goes well we will have observatories on the mon. From Earth we must continue to do well as we can. But are these dire predictions correct.
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