Coronavirus latest: locked-down Italians help scientists to measure light pollution

Images and videos of locked-down Italians singing on their balconies to applaud healthcare workers have circulated the world. But last week, thousands of citizens were out for another cause: science. For three evenings, on 23–25 March, 6,000 Italians appeared on their balconies to take part in a citizen-science experiment that has never attempted before to measure light pollution with smartphones.

The project, called Science on the Balcony and launched by the Italian National Research Council, asked participants to turn off all the lights in their apartment and launch an app designed for the study. Then, they were asked to turn their phone screens towards the main light source that can be seen from their windows for example, a streetlight or a sign. Using the phones’ brightness sensors, the app measures the light source’s illuminance, or brightness, in lux units.

Luca Perri, an astrophysicist and science communicator, and Alessandro Farini, a researcher at Italy’s National Institute of Optics, conceived the study. Like many nations, Italy has seen a steady increase in night-time light in recent decades. Such light pollution compromises astronomers’ view of space and presents environmental, economic, safety and public-health problems; it can, for instance, affect the immune system.

But widespread data collection on light pollution requires a significant investment of time and money, and might need researchers or sensors to be placed in homes. And satellites detect only light reflected skywards, meaning they don’t give a full picture. The latest project allowed researchers to measure light inside homes, harnessing the collaboration and enthusiasm of locked-down citizens. Initial data confirm that people in every Italian province participated.

And Farini sees another advantage for science in the project. “This pandemic risks creating doubts about science, because a lot of fake news is circulating,” he says. “With this experiment, we wanted to bring citizens closer to measurement techniques, to let them see the often complex process and allow them to participate in the scientific method.”

Infection-control measures such as national lockdowns in many European countries are reducing the spread of the coronavirus. Across 11 countries, between 21,000 and 120,000 deaths were probably avoided by the end of March, according to a model by a group at Imperial College London.

The study, published by the Imperial College COVID-19 Response Team on 30 March, estimates the effects of non-pharmaceutical interventions, which include closing schools and banning mass gatherings, on the spread of the virus across parts of Europe, including Italy, Spain and the United Kingdom. The authors measured the effects through a change in the virus’s effective reproduction number.

If the effective reproduction number is greater than 1, infections will proliferate and the outbreak will continue to spread. If it is less than 1, the rate of new infections will decrease until the outbreak is under control. The report shows that some of the countries studied including Italy, which implemented stringent lockdown measures three weeks ago might have fallen below this threshold as a result of the interventions. Previous work by other groups has found that the strict lockdowns in China reduced this value to below 1, stemming the tide of the epidemic there.

Because many countries still lack the capacity for widespread testing, the latest model uses reported COVID-19 deaths, rather than infection rates, to track the spread of the virus. Given the lag time between infection and mortality, it could take several weeks for the full effects of the interventions to be felt, especially in countries in the relatively early stages of their epidemics, such as the United Kingdom, according to the report.

The researchers are careful to note that they cannot attribute the transmission reduction to any particular intervention. And it’s too early to know whether the interventions as a whole are having the intended effect in some European countries. But, “if current trends continue, there is reason for optimism”, they write.

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