Princeton, Save Our Starry Skies

We are all healthier and safer under starry skies. Learn about the adverse effects of light pollution below and help by documenting campus light pollution Here

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What is Light Pollution?

Excessive, misdirected, or obtrusive artificial lighting.

What are the Negative Effects of Light Pollution?

Adverse Health Effects

Artificial light at night can disrupt circadian rhythms and impact human health.

Even dim ambient night-time light is harmful. Note that typical light trespass is much brighter than the light of the full moon. Also note that the light of the full moon is only present for a couple nights out of the month. Student testimonies indicate that light trespass is a significant issue at Princeton.

Light Pollution Effects
Depression Diabetes Obesity Cancer

Health 1 Health 2 Health 3

Wasted Energy

Inefficient lighting wastes electricity and increases carbon footprints.

USA alone wastes $3 billion / year lighting the sky (1/3rd of the annual budget of the NSF, or 1/10th of NASA's budget).

Based on a survey of existing light fixtures on campus, their light levels and their shielding, and the fact that they are on at all times during the night (even when not needed), we estimate that the relevant electric bill of Princeton University could be reduced by 75%.

Light Pollution Effects
Wasted Electricity Increased Carbon Footprint Excessive Cost

Energy 2

Sustainability is one of Princeton's top priorities. Light Pollution is missing from the list.

Energy 1

Hampered Education and Research

Excessive night lighting washes out stars and hinders astronomical research.

AST205 “Planets in the Universe”: 2012 – 2023 Altogether ~1000 students involved.

Strong observational component with telescopes and cameras. About 40 observing sessions per semester.

Alumni return after a decade to our observing sessions (aka star parties). One such event every month.

Strong degradation of sky conditions over a decade. Sky is getting very bright, and very few places remain with no direct glare from fixtures.

Steeply increasing light pollution of Princeton is paralyzing the teaching activities.

Princeton's sky is valued by many other "layers" of our population: alumni, famous visitors, Nobel Prize winners, musicians.

Light Pollution Effects
Skyglow Lost Detail Impaired Observational Data Teaching

Astronomy 1

The roof of Peyton Hall: historically a place for class observations and star parties.

Decline in Safety

The concern is glare.

Overly bright lighting causes glare, hampers vision, and can create a false sense of security.

Light Pollution Effects
Poor Night Vision Pedestrian Hazards Driver Disorientation False Sense of Security

Safety 1 Safety 2 Safety 3 Safety 4

This poor example for glare is on Ivy Lane, next to the EAS construction. The "temporary" lights have been up for over a year. They shine mostly upward and blind pedestrians.

Damaged Ecosystems

Light pollution disrupts wildlife, affecting migration, reproduction, and feeding cycles.

The disruption of ecosystems spans a wide range. A huge number of species are affected (in)directly including insects, birds, and beavers.

Princeton is surrounded by fragile ecosystems: D&R canal park, Stony Brook, Millstone, Lake Carnegie, Wildlife corridors.

Light Pollution Effects
Wildlife Disruption Insect Apocalypse Bird Migration Interference

Ecosystems 1

A recent example: some of our fragile ecosystem was lit up by unshielded "area" lights (Faculty Road). The field across the lake is now constantly illuminated.

Ecosystems 2

Insect apocalypse under way: population dropped to 45% due to light pollution.

Ecosystems 3

Princeton's Situation

Light pollution in Princeton is prevalent. Optimally situated halfway between Philadelphia and New York, Princeton could show starry skies above its campus. Sustainability, park-like night-time aesthetics have always been key considerations in shaping the appearance of our campus, yet the implementation is lagging behind.

Yet, based on our sky background measurements, night-time photography, and satellite data, the sky above Princeton has become about 3-times brighter from 2012 to 2024. The last view of the Milky Way was around 2000, and now we are losing even the brightest stars.

Trend at Princeton over 10 years based on satellite data
Trend at Princeton over 10 years based on satellite data
Simulated night sky above Princeton
Winter Milky Way with no light pollution
Simulations by G. Bakos using Stellarium
Unpolluted dark sky with the winter Milky Way
Night sky in Princeton

Simple estimates show that Princeton could save about 75% of its lighting bill by properly shielded, timer and motion-controlled, dimmable lighting fixtures. A large fraction of AST205 students complain about light trespass in their dorm rooms, disrupting their sleep at night.

Student Testimonials

Do you see a value in Princeton having a starry sky?

Student

Class of 2027

Looking up into a starry night sky on a clear night is a healing experience that cannot be replicated, and a needed respite from a stressful campus. The night sky allows us to see back into eternity, and witness the humbling scale of our own lives on a cosmic level, an experience that many find to be meditative. Taking AST205, a class that heavily emphasizes visual observation of the night sky, I was able to see many incredible sky objects that may no longer be visible due to increasing light pollution in the area. Walking back to my dorm after studying or working is a rare time to reflect, a reflection that is often broken by the harsh campus lighting spilling beyond areas where it is necessary. Princeton is a leader in many environmental fields, including water management and building efficiency, it too should be bold in protecting another natural treasure, the night sky.

Student

Class of 2026

Having a starry sky in Princeton is very important to me; not only did I grow up in Princeton in awe of the sky, it sounds cliche, but looking at the stars at night helped me ground myself in the context of the entire world while also allowing my mind and dreams to reach no bounds. As a student, it is inspiring for me to be able to look up at the sky and reflect on my life, my studies, and what is important to me. I think that recently, it has been increasingly harder to see the stars at night, which has been upsetting since the stars are so important to my mental, academic, and spiritual health.

Student

Class of 2026

Princeton is known, among many things, for its beauty, and a starry sky is a very valuable part of that, especially for our many students that come from populated urban areas where they can't see the stars. I remember the first time my friend from Philadelphia went out to the golf course by Forbes and was amazed at all the stars she could finally see. It's truly so transformative to see. It's also a point of cultural heritage that we should work to preserve. Countless mythologies across cultures around the world are based in the sense of magic held by the stars. They should be preserved as well as any historical or cultural artifact dug up from the ground. Lastly, if the aesthetics and the cultural importance of the aesthetics of a starry sky aren't enough — Princeton is first and foremost a research institution. It was my absolute privilege to get to take a class with Prof. Bakos, a leading scholar in astrophysical sciences. It was incredible to have the opportunity to study under someone who is actively discovering the exoplanets and applying the methods we learn about as a leading researcher in this field. Light pollution on campus actively harms not only the undergraduate (& community auditor) experience in this single class (which is already a shame, because the observation nights, or "star parties," were the highlight of the class), but also ruins opportunities for the extremely talented researchers at Princeton's Department of Astrophysical Sciences to properly execute their research, further the collective knowledge of the field, and contribute to the larger world of astrophysical sciences on Princeton's behalf. Surely it is clear that Princeton has no reason besides ignorance, carelessness, and greed to not include the reduction of light pollution on campus in its list of priorities. We were shown in class possible models of easy fixes to campus light pollution, including models of street lighting that are not only better for the sky, but safer and healthier for students. These models emphasize the reduction of glare when walking, increasing visibility for pedestrians at night, as well as the reduction of excess light shining intrusively into students' dorms and harming our sleep patterns. The solutions already exist and have been thought of in detail. Princeton has no excuse to not implement them if they care about their students, their faculty researchers, and their contribution to the preservation of cultural heritage.

Alumni

Class of 2015

As a student of philosophy, I took seriously Aristotle's exhortation to contemplate the celestial bodies as a part of the good life. So I took astronomy with Professor Bakos, and enjoyed it tremendously. Considering the universe, its stars (and their planets!), is awesome in the most literal sense: it provokes awe, wonderment, and a sublime sense, a humbling perspective, for how small we are. It's a tremendously valuable experience, and one that should be preserved for future generations of Princeton students.

Do you experience light pollution on campus?

Student

Class of 2027

I grew up in a dark place with few sources of artificial light, so attending Princeton was a significant change. I have found my sleep being disrupted by harsh unshielded artificial lighting nearby my dorm room (Forbes College) despite my room shades being fully drawn. As someone who is sensitive to light changes (I wake with a sunrise clock for this reason) this is very challenging, requiring sleep aids such as melatonin and eye masks. While walking around campus at night, I have also found the artificial lighting to often be unnecessary and disruptive, with unused offices, classrooms, and construction sites shining brightly, floodlights lighting up the sides of locked buildings, or casting light directly up into the sky. The sky brightness from artificial lighting has even created a noteworthy haze on some occasions, visible as a purple hue. This is not only a tremendous waste of energy, it is disruptive to the environment (such as to migrating birds) and to student's circadian rhythms, adding to the stresses of a challenging campus. Additionally, I have found it very difficult to see the stars and other astronomical phenomena from most places on campus, another significant change from my home. For instance, when the Aurora Borealis was twice visible from New Jersey for the first time in recent memory, student's enjoyment of the phenomena (a likely once in a lifetime experience) was limited to witnessing color changes in the sky via camera phones, rather than the full dancing lightshow that should have been visible to the naked eye in a less light polluted environment. As a professional astrophotographer and amateur astronomer who is lucky enough to know the difference between a polluted and unpolluted sky, I feel a profound sense of loss being separated from the sky.

Student

Class of 2026

Yes, and it has disturbed me greatly as someone who has lived in Princeton since elementary school-- I find it very agitating that there is so much light and light pollution on campus since it not only messes with my circadian rhythm but also with my actual sleep. I have been a student on campus for three years now, and it has been nearly impossible to fall asleep in all of my dorm rooms because a light has somehow always shone through my window, making it difficult to fall asleep.

Student

Class of 2026

Light pollution has taken away a magical starry sky. Inefficient street lighting often causes glare that actually makes it harder to see when walking at night, the glare of each lamp jarring to the human eye attempting to adjust to a darker environment. The lights by every construction sight pointed inexplicably towards my eyes rather than towards the ground they're actually supposed to illuminate — as well as the ridiculously bright new screen in front of Frist Campus Center — are some of many examples of light pollution on campus. My freshman year dorm had a street lamp outside my window that never allowed the room to be fully dark, which is important for sleep. While I could have resolved this by closing the blinds, the blinds would then block the little sunlight I could get in the morning. Overall, it is clear that Princeton has not prioritized the ability to follow one's natural Circadian rhythms at all, and light pollution is a large part of it. Lastly — the stars are an incredible sight. Everyone deserves to see them. And Princeton has the means to offer everyone not only the opportunity for a top-class education, but also to experience the magic of a starry sky. For people from the city, they may not have seen the stars before, and they deserve to be able to. But also for people from rural areas with starrier skies, seeing the same starry sky can make them feel a little less homesick, which is something that many college students go through. I know that I feel a little better looking at Orion's belt and knowing that it's the same Orion's Belt I can see back home. But there are so many more stars in the sky than the ones we can see. When I took AST205, learning just how many stars are truly in the sky — not absent, but obscured — just made me sad. How much beauty are we missing due to carelessness?

Alumni

Class of 2015

Pollution sullies natural beauty. Light pollution is no exception to this rule. Needless light at night prevents us from gazing at the natural beauty of the cosmos. I remember even ten years ago having some difficulty getting away from the lights of campus. And returning to Princeton since, I've noticed more needless light at night---parking garages floodlit near once-barren spaces we used to go to observe other worlds. Now those worlds are shut off from view, veiled from our eyes of our own doing. This saddens me. I worry that current and future Princeton students won't be able to have the wonderful experiences that I had.

Share Your Photos & Videos

Help us document light pollution on campus by uploading your own photos or videos and tagging their location.

Recent Submissions

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Lewis Library: bright unshielded light

Submitted by: AK

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Unnecessarily bright walkway light between Guyot and Frist

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Lights on inactive construction zone

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Blindingly bright LED in tree near Jones Hall

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Uplighting on new art building

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Whig Hall

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Contrast between two fixtures

Submitted by: Gaspar Bakos

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