A study of pictures of Earth by night has revealed that artificial light is growing brighter and more extensive every year.
Between 2012 and 2016, the planet's artificially lit outdoor area grew by more than 2% per year.
Scientists say a "loss of night" in many countries is having negative consequences for "flora, fauna, and human well-being".
A team published the findings in the journal Science Advances.
Their study used
.
It showed that changes in brightness over time varied greatly by country. Some of the world's "brightest nations", such as the US and Spain, remained the same. Most nations in South America, Africa and Asia grew brighter.
Only a few countries showed a decrease in brightness, such as Yemen and Syria - both experiencing warfare.
The nocturnal satellite images - of glowing coastlines and spider-like city networks - look quite beautiful but artificial lighting has unintended consequences for human health and the environment.
He and his colleagues had expected to see a decrease in brightness in wealthy cities and industrial areas as they switched from the orange glow of sodium lights to more energy-efficient LEDs; the light sensor on the satellite is not able to measure the bluer part of the spectrum of light that LEDs emit.
"I expected that in wealthy countries - like the US, UK, and Germany - we'd see overall decreases in light, especially in brightly lit areas," he told BBC News. "Instead we see countries like the US staying the same and the UK and Germany becoming increasingly bright."
Since the satellite sensor does not "see" the bluer light that humans can see, the increases in brightness that we experience will be even greater than what the researchers were able to measure.
Prof Kevin Gaston from the University of Exeter told BBC News that humans were "imposing abnormal light regimes on ourselves".