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Starry Night by Vincent Van Gogh

The Case of the Disappearing Night: Where Did the Stars Go?

Change is often imperceptible. It happens day by day so that we don’t see apparent differences. But over the past 1,460 nights, while you’ve been sleeping, the world has become 8.8% brighter. That brightness is from two sources:

  1. Over the past four years, the amount of land covered by artificial light has increased by 2.2% annually; and
  2. The actual light intensity of the areas already lit four years ago has also increased by 2.2% a year!

Anyone who has driven out of darkness toward a town or city would be familiar with the orb of light pollution that hangs above the population. That light pollution is often visible 50 kilometres or more away from large cities.

The 2.2% annual increase in lit acreage is a direct result of population growth and urbanization. But energy efficient LED public lighting is also a two edged sword. It reduces CO2 pollution but, globe for globe, increases light pollution. The result is brighter cities and suburbs and a night sky that is rapidly becoming invisible for many of us.

Gif: Earth Science and Remote Sensing Unit/Johnson Space Center/NASA These photos from 2010 and 2015 show changes in outdoor lighting in Calgary, Canada. In the 2015 photo, many new areas on the edge of Calgary are lit up. Some neighborhoods have also switched from orange sodium lamps to white LED lamps.
These photos from 2010 and 2015 show changes in outdoor lighting in Calgary, Canada. In the 2015 photo, many new areas on the edge of Calgary are lit up. Some neighborhoods have also switched from orange sodium lamps to white LED lamps.    Gif: Earth Science and Remote Sensing Unit/Johnson Space Center/NASA

A 2016 study found that 60% of Europeans and a whopping 80% of Americans can no longer see the Milky Way from their homes! The study did not include countries like Australia with extremely high urban populations but it is likely that Aussies are at least up with the 80% of night-sky deprived Americans.

Another study indicates strongly that the high levels of artificial lighting that most of us experience, is injurious to our well being. Quite simply, it is mucking up our circadian rhythm leading to poor quality sleep.

This image shows the extraordinary extent of light pollution in the USA. It's stretches way beyond the cities.
This image shows the extraordinary extent of light pollution in the USA. It stretches way beyond the cities.

Man and Beast
Naturalists have also found that artificial lights affect animals including insects, bats, and sea turtles. And a UK study suggests that even trees and other plants, including vegetable crops, are being effected!

Prior to October, 2011, photos from military weather satellite photos were used to measure the global extent of artificial lighting, but those cameras were not calibrated to measure brightness. They were also prone to changes in sensitivity.

A NOAA (National Oceanic and Atmospheric Administration) satellite launched in October, 2011 carries a Visible Infrared Imaging Radiometer Suite—a set of instruments that includes a sensor calibrated to measure night-time radiance at wavelengths from 500 to 900 nanometers. While that sensor’s primary role is to collect data for short-term weather forecasts, analysis of that well-calibrated data allows the measurement of changes in the brightness and extent of artificial lighting at night.

Chart reflecting changes in artificially lit surface of Earth at night.
Image: Carla Schaffer/AAASMost of the world is getting brighter, even when measured by instruments that do not account for the blue component of outdoor LED lighting. The few exceptions include countries with ongoing wars.

The bottom line is that it’s getting harder to see that gorgeous night sky at the rate of 2.2% a year! That means that it’s getting harder for most of humanity to experience the sky that Van Gogh saw. Our world is brighter but the stars have become visually dimmer or even invisible.

Starry Night by Vincent Van Gogh
Starry Night by Vincent Van Gogh

Think you still see the night sky? Perhaps this video will enlighten you (pun intended). Light pollution is so pervasive that most of us no longer question what we can or can’t see. Based on the Bortle scale, a measure of the brightness of the night sky and how well the stars can be seen, from 1 (excellent dark sky) to 9 (inner-city sky) it compares nine locations.

Perhaps it’s time to dig out that tent and spend a night or three gazing up in wonder! At the very least, it will help put some perspective back into our place in this infinite universe.

 

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