Twinkle, twinkle, little star, How I wonder what where you are! Up above the world so high, Like a diamond in the sky Yes, there is a change, apologies to the creators. While children in Delhi and other cities have learnt their Twinkle, twinkle, little star like generations before them, they have not really had a chance to see a real star.“A child today, say a child under six in Delhi, is unlikely or probably has never seen the Pole Star or the Orion,” said Raghu Kalra, general secretary, Amateur Astronomers Association (AAA) Delhi. This hobby club with its mix of seasoned astronomers and enthusiastic star gazers has been around since 1986.“In the mid-80s when there was a power cut, one could see the Milky Way. Now, for one, we don’t have power cuts, the generators kick in, but even so, since the beginning of this millennium one sees fewer and fewer stars in the sky.” Kalra said he doesn’t lament that there are no power cuts, just that you see stars in the night sky.“Compared to say 10 years ago, the number of stars has reduced in the sky over Delhi,” said Ajay Talwar, vice-president of the AAA. Where have all the stars gone? Ask around, and the most likely answer is: air pollution. The smog and haze makes it difficult to see the stars.“There is a thick blanket in the atmosphere because of the smog. Dust from more than 2,000 high rise-buildings in Gurugram Noida , and smoke from various open gas plants in Delhi create this layer of smog. Visibility of stars has dropped by an average of 5% every year over the last 30 years or so,” said Monica Sangwan of Science Popularization Association of Communicators and Educators ( SPACE ), a non-governmental organisation focusing on popularising science.Air pollution it turns out is an important contributor but not the main villain obscuring the stars in our sky. “The main culprit is light pollution,” explained Dr N Rathnasree, director of the Nehru Planetarium. Light pollution refers to excessive and inappropriate artificial light that escapes into the atmosphere and is reflected back. It occurs mostly because of bad lighting design that allows artificial light to shine outward and upward into the sky, where it’s not wanted, instead of focusing it downward, where it is required.It takes the form of urban sky glow or the brightening of the night sky over inhabited areas; light trespass that is light falling where it is not intended, wanted, or needed; glare — excessive brightness and clutter — bright, confusing, and excessive groupings of light sources common in urban areas. “What we have is a uniform umbrella of lights over our heads that masks everything else,” said Rathnasree.Air pollution exacerbates the adverse effects of light pollution. Aerosols, which are solid particles or liquid droplets suspended in air such as soot, dust and sulfur dioxide particles, scatter the light in the atmosphere, and it is refracted back to earth. “The bright orangish hue of the night sky is because of the aerosol,” said Rathnasree.Light pollution, said Kalra, is the easiest pollution to address. While it does require better lighting systems, and urban design, there is a simple immediate remedy that can alleviate the situation. Just switch off the lights you don’t need. “It is a small step but it can make a difference,” said Kalra.India has no lighting standards. So even if someone wanted to ensure there was appropriate lighting or no pollution or wastage, there are no guidelines. “Take the street lights, how high should the pole be, what should be the inclination of the mount to prevent upwards dispersing of light, there are no standards for these,” said an expert working in the area of sustainable habitats.Experts stressed that lighting standards is something that the Bureau of India Standards, which framed the National Building Code, needs to develop. Especially as India urbanises, and builds its smart cities. Among the building ratings system, LEED is the only one that takes cognisance of light pollution. The CII-sponsored Indian Green Building Council too gives passing recognition to the problem of light pollution.As experts and policy makers develop standards for lighting to limit excessive and wasteful use of lights, there are some measures that can be taken immediately. Streetlights need to be adjusted. Instead of being turned on at some arbitrarily set time, they need to be calibrated to natural light levels. “I don’t understand why the streetlights are on at six in the evening during the summer months. There is ample daylight,” says TM Prakash, a long time south Delhi resident.Experts say there is need for better planning around use of lights. Ensuring better spread of business and residences to prevent clustering of use of light is another immediate step. “People think of light pollution as an aesthetic issue, you know about seeing the stars. But light pollution has impact on our health, nature. But think of this, preventing excessive use of lights will mean consuming less energy. It avoids energy wastage. That is a good thing in the age of climate change.”