Light Pollution

Allen Versfeld's picture

As hinted in an earlier article, Astronomers consider Light Pollution to be the number one threat to civilization, trumping global warming, terrorism and reality TV.  Perhaps our priorities are a little skewed, but there is increasing evidence that light pollution affects all of us, whether or not we care about seeing the stars.


History

It is definitely a new problem.  Before the advent of electricity, everybody who looked up at night saw the sort of breathtaking stellar vista that always astonishes us when we're able to get far out into the country at night.  Before electric light became ubiquitous, the night sky was always like this.  Except that this isn't quite true: a full moon can be as devastating to the night sky as sub-urban light pollution, and our ancestors had just as much of a problem with inconvenient clouds as we do.  But at least they knew that, if the sky was clear and the moon was below the horizon, they could see anything they wanted.  All this began fading away as electric light became more widely available and we started lighting up our world.  Modern humans have an overwhelming fear of the dark, and are always amazed when astronomers claim to be able to see just fine thanks without a torch, so we spend large amounts of money on badly designed light fittings to banish the night forever.  And this causes problems.

Environmental Effects

It's probably no surprise that most creatures on earth live their lives according to a day/night cycle.  Whether nocturnal or diurnal, all creatures from mammals to insects to plants have periods of rest and activity which are synchronised to the Sun.  When you disrupt this natural pattern, living things start to experience strange effects.  A chicken farmer using the battery system knows this well.  The chickens are kept in massive sheds, under conditions that regularly alarm animal rights activists, but the main point of this is to keep them under rigidly controlled environmental conditions.  Chicken farmers are well aware of how an animals circadian rhythms are affected by light, and have expended enormous amounts of money funding research into finding the optimum day/night ratio to maximise the rate at which the birds grow (or lay, depending on their ultimate fate).  It follows that other animals can be quite seriously affected by unnatural light levels.
Many creatures are attracted to light.  Witness the swarms of insects around every street light.  In parts of Switzerland, certain native species of bat have vanished because their food has been concentrated around the street lights, where larger bats prowl.  Since they can't compete, and can't find food away from the lights, they die out.
A more dramatic effect can be found around oil rigs, light-houses, and other intensely bright marine lights.  Sea-birds in their thousands deviate from their normal flight to circle these lights for hours on end, before dropping into the water from exhaustion.
Other birds sing for longer than they should, because of the longer artificial day, and shorter night.  As a result, they feed more, and mate earlier, and begin migration weeks or months early.  Which sounds fine, until they arrive at their destination where it's still too cold for nesting.
To a turtle, searching for a nesting spot at night, the land looks darker than the sea.  It seeks a dark beach, but these are becoming fewer and fewer.  When their young hatch, they head towards the light, since that should lead them to the sea.  Instead, they head away from the sea, and die in their thousands.

Physiological Effects

And these are just some examples.  But what about us?  How are we affected?  According to this article which originally appeared in National Geographic a few years back, darkness is as essential to our biological welfare, to our internal clockwork, as light itself. The regular oscillation of waking and sleep in our lives—one of our circadian rhythms—is nothing less than a biological expression of the regular oscillation of light on Earth. So fundamental are these rhythms to our being that altering them is like altering gravity.
The most obvious effect would be that we don't sleep enough.  And when we do sleep, we don't sleep well.  Too much light interferes with our sleep cycles, but we've all experienced the discomfort of a street-light, or a neighbours security spotlight shining through our windows.  The easiest way to wake somebody up is to simply turn on the lights in their bedroom, and wait a short while.  And now, according to three seperate studies (Meeting report: the role of environmental lighting and circadian disruption in cancer and other diseasesLight at Night Co-distributes with Incident Breast but not Lung Cancer in the Female Population of Israel and Artificial lighting in the industrialized world: circadian disruption and breast cancer), too much light while we sleep can disrupt normal hormonal production, and appears to be linked to an increase in breast cancer.

Causes and Solutions

So what do we do?  We can't ignore the many benefits of electric light, and to propose that lights be banned at night (or after a certain time) like World War Two england is beyond ridiculous.  Lights on roads save countless lights in avoided collisions, lights in our houses and gardens allow us the time to pursue our modern lifestyles, and help keep our homes secure from criminals. 
The answer is to find ways to keep the light where we need it, and away from where we don't.  A typical motion-sensing security light is a great example.  It has two spotlights on a single fitting, mounted in a corner and angled so as to light up the entire area when it is triggered.  But if you look carefully at the beam of light it casts, more than half of that light is beamed up into the sky where you don't want it.  More than half the light you're creating (and therefore more than half the electricity you're paying for) is not only being wasted, but it's adding to the problem of light pollution.
Alternatively, some people install massively powerful floodlights in their gardens, to ensure that burglars will have no place to hide.  Unfortunately, the lights are so incredibly bright that they dazzle anybody who happens to look in their direction, so that the homeowner, concerned neighbours, even passing policemen are discouraged from looking into the area.  And if they do, they're blinded by the bright light shining in their eyes.  End result:  Massive light pollution, and the contradictory effect of having a bright light making it impossible to see the area it's supposed to be revealing.  

So install dimmer lights that illuminate without dazzling.  Position them intelligently, angled downwards so that all their lights shines where it's wanted, and none is wasted.  Many light fittings make this impossible to do, so scrap them and replace with an International Dark Sky approved fitting (available worldwide).  You'll find that not only do you improve your health, environment and security, but you will rediscover the night sky and regain a bit of lost beauty into your life.

Edit:  corrected on 9 March 2010, after a reader working in agricultural research pointed out that I had completely misunderstood battery farming methods. Much appreciated, Alan!


Comments?  Questions?  Why not mail me at uastronomer@gmail.com
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