The “bright nights” are a phenomenon also known as “Night Sun”, an occurrence already identified at least since the time of the Romans. Subsequently, these nights began to be described as an inexplicable glow that occurred at night. Scientists at York University in Canada now claim to have discovered a possible explanation for this rare event. The study was published earlier this month in the journal Geophysical Research Letters.
After using data collected by satellites, two scientists from Toronto, who are dedicated to the study of the atmosphere, have suggested that bright nights are not due to the sun or meteors but to the result of the convergence of “local waves” in the atmosphere Planet.
“There have been very few occasions when this event was recorded”.
In the first century AD, Pliny the Elder saw a brilliant night and described this event as an apparition of the day at night.” In the years 1783 and 1908, two more events were recorded.
At present times, we live in the age of artificial light and the opportunities to watch the Night Sun are smaller. Gordon Shepherd, one of the authors of the study, regretted having yet to witness any brilliant night.
It was Shepherd who, in 1991, built a satellite with the ability to measure atmospheric luminescence, or airglow, that occurs when ultraviolet radiation from the sun separates the oxygen molecules into individual atoms. The atoms recombine overnight, releasing energy that emits a green hue.
His investigations began after other scientists reported that luminescence sometimes could not simply be seen with the naked eye.
Together with Young-Min Cho of York University, Shepherd conducted an analysis (for two years) of data collected by the satellite. He eventually discovered that the wavelengths of the upper atmosphere were in some cases superimposed on one another, thus producing light in the airflow.
The study also found that “Night Sun” phenomena occurred mostly in high altitude areas and were almost always circumscribed to an area that is the size of Europe.
Even now, the chances of seeing this phenomenon are remote, since the levels of light pollution in the air do not allow it.
“If we go back to Roman times, they lived in an environment without artificial light. Now almost everyone lives in artificial light”, as quoted by The Guardian.
Still, scientists say that, despite being difficult to see with the naked eye, bright nights can still be seen through satellites.