In 1994, Los Angeles was hit by an earthquake at 4.31am causing a city wide blackout. Upon leaving their houses, members of the city were shocked to find a strange silvery cloud overhead. Panicking at the sight, many called the local observatory and some reports say others even phoned the police!

What they were seeing were stars, a sight they had never before witnessed, due to light pollution!


What is Light Pollution?

Artificial lights are important to towns and cities, allowing for safety, security and for activities such as sports to be done later in the evenings and nights, but it is not always necessary. The quantity and quality of the light given out by streetlights and other outside fittings are large contributors of inappropriate and excessive light, otherwise known as light pollution.



Light pollution is most noticeable, like in the example above, when looking up at the stars, but it also has many other effects on the natural environment. The lack of visible stars can effect birds navigation, and the disruptions of the day and night cycle has been seen to be affecting animal’s communication, foraging and reproduction.


What can we do?

We can all do our part in reducing light pollution, starting with our own homes. Clearly, the easiest thing we can do is switching off unnecessary lights. Having our lights only running when needed prevents obtrusive light while, at the same time, saving money. For outside lights, we can turn them off at the mains for lights that are seldom used, but for security lights we can also use a PIR or Microwave sensor, meaning the lights come on only when needed.

We must also consider, how lights that we can’t easily or safely switch on and off, such as street lights. These lights are everywhere in our modern society, and are some of the biggest contributors to light pollution. Older designs of these lights tended to allow light to be scattered in all directions and not just towards the ground where it is needed. Newer designs have started using the more directional light of LEDs.


Benefits and limitations of LEDs

When used correctly, LEDs are can have a great impact on reducing light pollution by using a narrower beam angle, directing light towards the ground and not into the sky. Often, however, the LEDs are brighter than necessary causing glare to drivers and with shorter wavelengths can scatter a lot further.

Due to the coolness of early LEDs, many theorised that the light, even reflecting off the ground, would penetrate further through the atmosphere. This would actually contribute more to light pollution. As LED technology has gotten better and better over the years, we are now able to produce any colour temperature and filter out the short wave UV and blue light.

Evidence, from a study in Swedish schools, has suggested that cooler lights increase focus. This, applied to roads, could lead to less accidents due to tiredness at night. LEDs also have much lower running costs, meaning cities could save significant money on street lighting. Looking forward, this could mean that we can have cheaper lights that will increase safety and reduce light pollution.

Of course, changing street lights is not a cheap task. This is, of course, the main opposing argument to upgrading. Many lighting schemes are already installing LED streetlight as standard on new roads and on new streets and, when older lights are reaching the end of their cycle, outdated technology is being replaced with newer models.

We are making steps towards reducing light pollution in our towns and cities. We can all do our bit by preventing unnecessary light, just switching off our external lighting or utilising PIR and microwave technology. With constant improvements in LEDs, both in efficiency and colours, we will be able to save money and allow our sky to be more visible.

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