Astronomy is a wonderful field. From History it could be easily seen that Astronomy is the cradle of both Physics and Mathematics. Most of the early phisicists and mathematicians were astronomers too. All astronomical observations from prehistorical times to 1609 were exclusively using naked eye. Those early astronomers had no access to telescopes or cameras or any other sophisticated equipment that we have now. But instead they had access to the most important requirement in Astronomy and that is what we miss now even though we have state of the art equipment: Clear Dark Skies. Astronomy is extremely sensitive to Light Pollution.
In a clear dark sky, one could see around 5600 stars with a maginude of up to 6.0. But in a typical urban environment of today it gets limited to around magnitude 3.0 and the number of visible stars to around 100 or so. Courtsey of Light Pollution.
That is one side of Light Pollution. On the other side we have tremendous amount of energy waste. Studies by US Department of Energy shows that, there are around 52.6 Million Street Lights in US alone. Energy consumption of Street Lights and Parking Lot Lights in the US reaches to around 52 Billion KWh per annum. As far as Carbon Dioxide is concerned, that itself could generate around 40 Million Tonnes of CO2 per year.
Energy Saving Estimates in US (Section 3.2.1)
Lighting Energy Consumption in US (Table Appendix G-5)
Light Pollution has a lot of ecological effects also. Animals, Plants, Insects etc. could get confused by light. Wikipedia has an interesting article on Ecological impact of light pollution.
Ecological Light Pollution on Wikipedia
Do we really need to illuminate the world like this?
Usage of modern street lights became popular more than 100 years before when personal hand-held light sources like flashlights/torches were either unavailable, expensive or inefficient. Modern electronic control systems were also absent at that time. All these technologies could be combined to reduce both energy consumption and light pollution without jeopardizing safety and security.
- Use lower power and higher efficient light sources like Light Emitting Diodes.
Many of the standard street lights use around 150W lamps, by replacing them with higher lumen/Watt LED lamps lot of electricity could be saved. Also LED lamps could be dimmed very easily by controlling individual diodes
- Usage of yellowish higher Color Temperature light sources to reduce scattering and sky glow.
For example whiter Mercury fluorescent light is more scattered than yellow Sodium light. Because of this reasons, Sodium lamps are used near many of the astronomical observatories. Sodium light is more monochromatic so that it could be filtered out very easily. LED lighting could be made with higher Color Temperature to reduce sky glow
- Better fixtures so that light is pointed down where it is required, reducing light leakage
- Limiting the usage of decorative flood lights and illumination by passing required laws and regulations.
They look great, but waste a lot of energy and create a lot more light pollution
- Unlike olden times personal LED flashlights are extremely efficient and ubiquitous, even the el cheapo mobile phones nowadays have LED flashlights, so encourage their usage.
- Context sensitive and intelligent lighting control systems for dimming and controlling light sources.
- Using Thermal imaging and Night Vision devices for safety and security applications so that dependency on visible lighting could be avoided or reduced.
- Efficient usage of Daylight Saving Time
It is proven that aligning business hours with daylight reduces energy usage