Context
- Recently, the global scientific community has raised alarms over the rapid degradation of the world’s clearest skies due to urban sprawl and industrial development. Even remote locations like the Atacama Desert in Chile—the future site of the $1.5 billion Extremely Large Telescope (ELT)—are facing unprecedented light trespass.
- This issue is particularly relevant as India recently inaugurated its first Dark Sky Reserve in Hanle, Ladakh, marking a shift toward recognizing “darkness” as a natural resource that requires urgent legislative protection.
1. Defining Light Pollution (ALAN)
Light pollution, or Artificial Light at Night (ALAN), is the alteration of outdoor light levels through man-made sources. It is not merely an aesthetic issue but a significant environmental pollutant.
- Components of Light Pollution:
- Skyglow: The brightening of the night sky over inhabited areas (the most common form).
- Glare: Excessive brightness that decreases visibility and causes visual discomfort.
- Light Trespass: Light falling where it is not intended or needed.
- Clutter: Bright, confusing, and excessive groupings of light sources.
2. The Scientific Metric: The Bortle Scale
To quantify the impact of light pollution, astronomers use the Bortle Scale, which ranks the darkness of a location from 1 to 9.
- Class 1: Pristine dark-sky site (ideal for professional observatories).
- Class 9: Inner-city sky (only the brightest celestial objects are visible).
3. The Atacama Desert and the ELT Project
The Atacama Desert is uniquely suited for astronomy due to its “Photon Valley”—a corridor of high-altitude observatories.
- The ELT (Extremely Large Telescope): Managed by the European Southern Observatory (ESO), it features a 39-meter main mirror.
- Comparative Advantage: Once completed in 2030, it will be 20 times more powerful than current leading telescopes and 15 times sharper than the Hubble Space Telescope.
- Geographic Factors: High altitude (>3,000m), low humidity, and historically minimal light interference.
4. Impact on Biodiversity and Human Health
- Ecological Disruption: Many species, including sea turtles and migratory birds, rely on natural light cues. Artificial light disorients them, leading to increased mortality.
- Melatonin Suppression: In humans, blue-rich LED light suppresses melatonin, the hormone responsible for the Circadian Rhythm, potentially leading to sleep disorders and metabolic issues.
- The Rebound Effect: Ironically, the adoption of energy-efficient LEDs has led to cheaper lighting, causing people to install more lights, which has increased global light pollution by roughly 2% per year.
5. Important Indian Sites and Initiatives
- Hanle Dark Sky Reserve (HDSR): Located in Ladakh, it is India’s first dark sky reserve. It is protected by strict regulations on light usage to facilitate research at the Indian Astronomical Observatory (IAO).
- Pench Tiger Reserve: Located in Maharashtra, it recently became India’s first Dark Sky Park, emphasizing the link between darkness and wildlife conservation.
Q. With reference to the impact of Light Pollution, consider the following statements:
1. The Bortle Scale is used to measure the transparency of the atmosphere for radio telescopes.
2. The "Rebound Effect" describes a situation where increased lighting efficiency leads to higher overall light consumption.
3. The Hanle Dark Sky Reserve in India is situated within the Changthang Wildlife Sanctuary.
Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 3 only
(d) 1, 2, and 3
Answer: (b)
Solution:
• STATEMENT 1 IS INCORRECT: The Bortle Scale measures the brightness (light pollution) of the night sky for optical observations, not radio telescope transparency.
• STATEMENT 2 IS CORRECT: The "Rebound Effect" occurs when the cost-savings from energy-efficient LEDs encourage the installation of more light fixtures, worsening light pollution.
• STATEMENT 3 IS CORRECT: The Hanle Dark Sky Reserve is indeed located in the high-altitude region of Ladakh within the Changthang Wildlife Sanctuary.
