Negative Effects of Sky Glow

Sky glow is the orange light that we get at night above a town or city. Although light in the right place, makes urban areas safer and more pleasant to be after dark, if not designed properly, it can also have negative effects.

What Causes Sky Glow

Sky glow occurs when artificial light which shines upwards, reflects off clouds and atmospheric particles such as dust and water, causing a ‘scattering’ effect.

It can be caused by any artificial lighting such as street lamps, flood lights, security lighting, illuminated buildings, lights left on in office buildings at night, airport landing lights and so on.

Invisible Stars

One of the negative effects of sky glow is that we are now growing up in a world where star-gazing is an impossible thing for millions of people. It’s not that our stars have disappeared, but that our eyes cannot pick out the distant stars due to the ‘glare’ of nearby ambient light. In fact, approximately one fifth of the world’s population are not able to see The Milky Way – one a common sight.

In ideal conditions, it should be possible to see four or five thousand stars.

Astronomers understandably, therefore find sky glow extremely frustrating as it means they are much less able to observe the stars at night.


There is also abundant evidence that sky glow is impacting on our wildlife.

It stands to reason that the presence of light at night will have a huge effect on nocturnal creatures but it is also being seen to disrupt the activities of a wide range of species including insects, reptiles, birds, and amphibians. Scientists have observed that a number of basic functions are being affected and that light plays an important part in how many animals communicate, forage for food, migrate, and select mates.

For instance, there are many examples of birds which migrate at night and use the stars to navigate, being confused by the bright lights of towns and colliding with buildings, losing any sense of direction, and dropping from exhaustion.

Similarly turtles which hatch on the sand and need to find their way to the sea at night will also become disoriented by any nearby lights. All sea turtles in Florida are now endangered and experts believe sky glow to be one of the main contributing factors.


It’s not just animals who might suffer the negative effects of sky glow. Research shows that humans too, need a certain amount of darkness for optimum health.

It is during the night, in the dark, that our bodies ‘regulate’ our body clock and release hormones that help to calibrate our bio-rhythms. Some scientists are now beginning to link an inability to do this, and a lack of the hormone melatonin, with the development of certain types of breast cancer.

Reducing Sky Glow

Fortunately, a lot can be done to reduce the negative effects of sky glow and most of them are very simple.

The majority of sky glow is caused by badly designed lighting which is defusing light upwards into the atmosphere where it does little good and wastes a lot of energy, rather than down, where it is needed.

Examples of things you can do yourself to help bring the stars back are:

  • Switch off lights at night.
  • Make sure you buy downward lighting with no ‘seepage’ upwards.
  • Consider removing or reducing security lighting – there is little evidence that it reduces crime and some to show it may actually increase it.
  • Lobby your local council to review public lighting design and effects.
  • Visit your local astronomy group and be amazed again by the stars.