Quantitative Research into Light Pollution

Methods:

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Nightly, I used a Sky Quality Meter (produced by Unihedron) to generate a sky brightness reading, while also cross referencing with Air Quality Data provided by the Colorado Government.

Hypothesis:

Filtering Results

Air particulates impact sky glow, via the light scattering off of the particles

Conclusion for this hypothesis

Due to the moon being too bright most nights, or cloud cover impacting the readings I filtered the data I recorded, keeping data from clear and moonless nights.

The results show the beginnings of a statistically significant relationship between higher sky glow and higher air pollution, but a more thorough experiment needs to be conducted to make sure

Results

Issues with the experiment

This graph shows the beginnings of a statistically significant relationship between the amount of particulates in the air, and how dark the sky is.

I simply did not have enough time to conduct a thorough enough experiment. The data displayed on the previous frame was taken from 6-25-19 until 9-10-19.

There were only 14 days in this time frame that were on clear and moonless nights. A full year+ worth of data would be needed to make more definitive statements

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Why does this matter?

The Bounce light is found to be less blue than the LED itself, but it also is found to be contributing to the local light pollution

Bounce Light Analysis

Bounce light is also found to be, on average, 6.3% of the magnitude of the source light

This means that it is more important to shield lights and make sure they are not pointing directly into the sky, but it also tells that the bounce light is still a contributor and is a potential source of light pollution reduction, if remedied.

Focusing on a parking lot light, in the parking lot nearest the Physics Building:

This graph shows the difference in magnitude between the bounce light and the light bulb itself.

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Bounce Light

What is Bounce light?

Bounce light is when a light source is pointed down at a surface, and said surface reflects light back up

What impacts light pollution?

What did I do to quantify this?

Taking multiple different spectrometers around the DU campus, I generated spectra for various light fixtures that were bouncing lots of light off of the surface below them

My research looked into three main potential light pollution contributors:

1: Bounce Light measured by spectrometers

2: Air Quality vs. Sky Brightness

3: Mie Scattering

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Mie Scattering

The Question

When the wavelength of light is close to the diameter of a particle, scattering occurs that is classified as Mie Scattering.

I used Python to run calculations to find the material of particulate that would impact sky glow the most

Before and after the 2003 North East Blackout (Photo from darksky.org)

My research started with the question: "Are there more things contributing to light pollution than just badly aimed light? If there are, how do we quantify them?"

Results for particulates with a 1nm diameter

At this size, water particles scatter blue light (460 nm) the most efficiently, which lends itself to the fact that clouds appear bright at night in an urban area

Overall Results of Mie Scattering

Water particles impact the most at small sizes, but over a much larger range of particulates Soots impact scattering the most. Thus, the conclusion that reducing air pollution from motor vehicles and factories will reduce sky glow is reached.

Results for particulates with a 2.5nm diameter

Quantitative Research into Light Pollution

Propane Soot, Acetylene Soot and Diesel Soot all scatter the most efficiently with blue light (460 nm)

Results for particulates with a 10nm diameter

The same three types of Soot (Diesel, Acetylene, and Propane) still dominate at this size

By: Lincoln Schafer

Overall Conclusion:

Light pollution can be remedied through many ways, but it comes down to individuals to do it.

Shield your outdoor lights, turn them off when not in use.

Limit the air pollution you contribute to.

Be conginsant of if your outdoor lights are simply bouncing back into the night sky.

Most importantly: Just be aware. Too many people do not even consider this issue in their every day lives, and being aware will help tremendously

Light pollution must be combated by people working together, and I hope that you can help this happen