Science & Technology

How can we illuminate our city and still see the night sky?

The night sky is part of humanity’s natural heritage. Looking up at heaven is a unified act performed by almost all human beings who have ever lived. Didn’t you look up at the night sky and feel it ignite your mysterious sensations?

However, the night sky is not very visible in modern cities.And the majority of humans Live in the city now. How can I regain my heritage? Can quiet contemplation be revived?

It may be possible, and a team of researchers from Spain, Portugal, and Italy tackled the problem. In their new treatise, “Can we illuminate our city and see the stars (yet)?The team outlines how to not only keep the city bright at night, but also allow you to ponder the night sky. This paper is available on the preprint site

NS Dark sky movement A global effort to reduce light pollution and change the way cities are illuminated. Its supporters argue that our city is too bright, not only bad for humans and circadian rhythms, but also bad for nocturnal animals. They also say that we waste too much energy to illuminate our city, and much of the light is unplannedly directed into the sky for no good reason.It creates a phenomenon called SkyglowThis is not only a quiet contemplation, but also an obstacle to scientific astronomical observations.

The authors show that their treatise shows how even in the heart of a metropolitan area, a reasonably dark sky can be created by controlling both emission levels and direct glare. Insist. “These results adopt a science-based democratic public decision on the use of light in our municipalities, with the aim of regaining the possibility of thinking of the night sky throughout our planet. You may support it, “they write.

A glittering night map of Europe. Most of the lights in this image are street lights and account for most of the light pollution. The atmosphere scatters light and creates Skyglow. Image of NASA Earth Observatory by Joshua Stevens using Suomi NPPVIIRS data from Miguel Román, NASA’s Goddard Space Flight Center

The Dark Sky Movement has fought defensive battles for the most part. They are trying to preserve the dark sky areas that already exist, especially in our urban areas. They have been working to limit light pollution in places such as city parks and popular star observation spots in light-polluted areas. And those efforts helped.

But that’s not enough. Not for the future, not for the author of this treatise. “Nevertheless, a purely defensive and responsive stance seems to be inadequate today to ensure the future of the dark nights on Earth,” they write. “Radance and the sustained increase in illuminated surface gradually erode dark areas, reducing their size and natural values.”

The authors are worried that there will be no enough dark skies to defend in the future. “The dark areas of defense become smaller and more fragmented, often breaking the continuity of nocturnal ecosystems.
“Corridor” is written.

For some, the battle is already lost. Some believe that the current emission levels in our urban areas are inevitable. Some argue that roads must be as bright as they are today, in order for streetlights to produce most of the light, for safety, to prevent crime, or to promote our compulsive consumption. However, the author states that these are “old truths” and there is no good reason to keep things going as they are today. “… a compelling reason to support actual road lighting recommendations in the name that modern research has not further demonstrated the benefits of traffic safety, increased compulsive consumption, or increased photon density. Finding has failed many times. Avoid some actions … “

That’s all we can get involved with. But this is a scientific treatise, and the author digs deeper.

“The results strongly suggest that even in our metropolitan area, the complete loss of starry nights is not an unavoidable fate.”

From “Can we illuminate our city and see the stars (yet)?”

According to researchers, two questions arise naturally. What is the maximum level of luminescence compatible with the dark urban sky? What are the compromises and balances?

The ability to see the stars in the night sky depends on several factors. The type and amount of light from the background and stars, the difference in human vision, and even the skills and experience of individual observers. Researchers say that all of this can be included in a single number called the Luminance Contrast Threshold. Basically, it states that as the background brightness increases, so does the brightness of the observed object, depending on several factors.

The night sky will never be completely dark. Nature itself can provide enough background light, even on moonless nights, which helps reduce contrast and make the stars less visible. But the natural background light coming from the Milky Way and other unresolved stars from other sources is part of what we want to see. The problem is artificial light.

The author has come up with a simplified situation that captures and analyzes the physics of the problem.

This evening image of Mexico City shows the power of Skyglow. Imagine trying to see a star in this setting. By Fernando Tomás in Zaragoza, Spain-Flickr, CC BY 2.0, https: // curid = 348732
This evening image of Mexico City shows the power of Skyglow. Imagine trying to see a star in this setting. Fernando Tomás in Zaragoza, Spain – Flickr, CC BY 2.0, https: // curid = 348732

Imagine being in a small city park with a radius of about 200 meters (656 feet). The small park is in the center of a metropolitan area where there is no spatially uniform light, a particularly dominant directional light source. There are no annoying light sources in the park itself, but the paths are bright. Due to the canopy, the pathway lights are not aimed at the sky or the observer’s eyes. Did you take it? The author describes in much more detail the formulas accepted to calculate these variables that interested readers can dig into. But for the rest of us, imagine a park. Imagine that most cities would look like this.

There are a huge number of variables in the author’s calculations, but they think they have simplified them for this task. Atmosphere changes significantly from season to season and from place to place on Earth. Buildings and obstacles of various heights affect the night sky. Wealthy cities produce more light and more. However, the researchers have come to some conclusions.

“What a night in our city should look like is a social and political decision.”

From “Can we illuminate our city and see the stars (yet)?”

They say that we can improve the darkness of our urban night sky by making smarter decisions about what and how much we illuminate. That probably sounds obvious, but now there’s data to help support and explain it.

“The darkness of the sky in our city is the area to be illuminated.
“The average spatial density of urban luminescence,” they write in the conclusion of the treatise. “The simplified equations derived in this paper can be used to gain quantitative insights into the trade-off between emissions and the starry sky. The result is that even in our metropolitan areas, the starry sky. It strongly suggests that the complete loss of night is not an unavoidable fate. “

Obviously, we need to illuminate our city at night. But how much is it? We want more and more light and seem to use more and more energy. What are its benefits? Are you well thought out? Or is it recursive?

“What a night in our city should look like is a social and political decision,” they write. “The use of artificial light sources creates a new reality that is different from natural light. Artificial nightscapes need to be collectively determined by their key characteristics before choosing a technical solution to achieve these goals. I have.”

The author says it’s time to control how we illuminate our city. According to researchers, there is no good reason to keep things going like we do. It’s not well thought out and we’re losing our legacy. They emphasize that the conservation of the night sky is an important issue. Millions of children in the world do not have the opportunity to fully look at the power of nature and wonder about themselves and humanity.

What if we don’t even see heaven if we don’t understand that we are part of nature? Are we courting disasters in a bright city?


How can we illuminate our city and still see the night sky? How can we illuminate our city and still see the night sky?

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