I work at the Four Seasons in Philadelphia, which gives me a view that can be wonderfully distracting. One thing I’ve noticed is that the building lights closer to the airport seem to twinkle more than the ones farther away. The buildings themselves are doing their usual excellent impression of staying put, but their lights can look restless. Once you notice that shimmer, it becomes difficult to stop looking for it. Apparently, my brain sees an illuminated skyline and decides we should also have a small physics investigation.
That observation belongs beside a question most of us first encountered in a nursery rhyme: why do stars twinkle? The answer connects those distant points above us with much nearer lights across the city. Light travels through air that is changing in temperature and density, and those changes can alter what reaches our eyes. A star may be shining steadily while its light appears to flicker here. A distant building light can do something similar, even though its journey began with wiring rather than nuclear fusion.
The airport detail is my observation, rather than proof that airports automatically make nearby buildings sparkle. The distance to each light, its height, the air along the viewing path and the light itself all matter. Still, I love that something I notice at work can open a door into astronomy. The sky becomes easier to understand when we realize that part of its apparent behavior is happening in the air immediately around our own planet.
The atmosphere keeps changing the view
The technical term for rapid fluctuations in a star’s apparent brightness is scintillation. Earth’s atmosphere contains regions with slightly different refractive properties, influenced by temperature, density and other conditions. As this uneven air moves and changes, it distorts the incoming light. The amount reaching a small receiving area, including the pupil of an eye, fluctuates. We see a point brighten, fade or flash. The star doesn’t have to change its output for that to happen.
Refraction is familiar even when we don’t call it that. A spoon can seem bent where it enters a glass of water because light changes direction at the boundary between different materials. Air is subtler: variations within it can also bend light. The shimmering view above hot pavement is another everyday example of temperature differences affecting an image. You don’t have to see the air directly to recognize that it has started interfering with the view.
For starlight, a useful picture is an ever-changing optical surface between the source and the observer. It redirects and redistributes incoming light as conditions shift. The full physics involves how light waves propagate through that uneven medium, so “the wind blows the light around” is an oversimplification. Wind can carry regions of differing refractive index across the line of sight; temperature and density variations help create the optical differences. Air is transparent without being optically uniform.
Why a light across the city can sparkle too
A distant lamp can occupy a very small angle in our view, much as a star does. Along a long path through the lower atmosphere, its light encounters changing air above roofs, roads and other surfaces. If the refractive conditions vary enough, the light can shimmer or fluctuate. Buildings don’t need to be moving, and their electrical supply doesn’t need to be faltering. Part of the apparent motion can belong to the air between the building and the person watching.
That is the connection I think about when I look out from the Four Seasons. The lights on the buildings closer to the airport appear livelier to me than those farther from it. That makes a plausible starting point for questions about the air along those particular sightlines. It doesn’t establish a rule about the airport’s distance. A building nearer the airport might also be farther from me, lower in my view or seen across a different mixture of surfaces.
Those details are easy to collapse into one impression when you’re looking at a skyline. The eye sees a pattern; explaining it takes more information. I can describe what I notice without pretending I’ve placed instruments on every roof in Philadelphia. Tempting, certainly, but I suspect the equipment request would raise questions. The satisfying part is that ordinary observation gives us something specific to investigate: which lights fluctuate, under what conditions, and whether the same ones do it again.
What an airport study can and cannot tell us
There is research connecting aviation turbulence with optical measurements. A study published in Boundary-Layer Meteorology examined a scintillometer installed alongside a runway at Amsterdam’s Schiphol Airport. The instrument transmitted light across a measured path and recorded fluctuations. Under sufficiently stable nighttime conditions, researchers could detect signals associated with aircraft wake vortices. During daytime conditions, background atmospheric turbulence could overwhelm those signatures. The result depended on the conditions and the instrument’s viewing path.
That is fascinating support for the broader idea that changes in air can reveal themselves through light. It is not evidence that a particular flight causes the building lights I see from work to twinkle. The experiment involved a specific runway installation, with timing and wind information that I don’t have for my view. Heat released by surfaces and local air movements are also possible contributors to optical turbulence. Sorting out their relative roles would require measurements.
I like leaving that question open. An observation can be interesting before it has a complete explanation attached. In this case, the established connection is between uneven air and fluctuating light; the explanation for the stronger shimmer in one part of my view remains a hypothesis. That distinction makes the story more useful. It lets me keep the experience that prompted the question while giving the science enough room to tell us which explanation actually fits.
Stars look small because they are so far away
Stars are enormous physical objects, but the stars in our night sky are so distant that their apparent disks are usually unresolved in ordinary viewing. To the unaided eye, they behave much like points of light. That small apparent size makes atmospheric fluctuations conspicuous. Think of how little averaging is possible when nearly all the light we perceive as one star arrives from an extremely narrow direction. The shifting atmosphere can make that single point look remarkably animated.
Planets generally present a larger apparent disk, even when our eyes can’t resolve its shape. Light arrives from different parts of that disk through slightly different paths, and the fluctuations tend to average together. This usually makes a bright planet look steadier than a nearby star. The distinction concerns angular size: how large the object appears from where we stand. Being physically large somewhere in space is different from presenting a large enough image in our sky to smooth out the fluctuations.
The familiar instruction that stars twinkle and planets don’t is a useful first clue, with exceptions. Planets can twinkle, especially low in the sky or through particularly disturbed air. A steady bright point is therefore a candidate for a planet, rather than a complete identification. Its position and a reliable sky chart help settle the question. I appreciate any astronomy rule that gets a beginner looking up, provided we don’t make it promise more certainty than the atmosphere intends to provide.
The horizon gives light a longer route through air
Stars low in the sky generally twinkle more noticeably because their light passes through a longer atmospheric path before reaching us. Look nearly overhead and you’re looking through a comparatively shorter section of the atmosphere. Look toward the horizon and the route becomes more oblique. That geometry gives the incoming light more opportunity to encounter varying conditions. The same star can therefore look different as it moves higher or lower during the night.
Brightness and the observer matter as well. A bright flickering point is easier to notice than a faint one, and a dramatic low star can draw attention away from the rest of the sky. It can even seem to flash different colors. Atmospheric refraction depends on wavelength, so the colors in starlight are not all affected identically. Those rapid apparent changes shouldn’t be confused with a star repeatedly changing its surface temperature while we watch it from the sidewalk.
A calm evening at street level doesn’t guarantee smooth air along the entire path. Higher layers can have different conditions from the air beside your face. Equally, a breezy night doesn’t translate into one fixed amount of twinkling everywhere. This is why I’d resist using a single sparkling star as a precise weather forecast. The view carries information about the atmosphere, but interpreting it requires more care than matching one visual impression to one guaranteed outcome.
A telescope has to look through the same air
Astronomers use the word seeing for the atmospheric effects that limit an image’s sharpness. A telescope may show a star image dancing or spreading, and fine planetary detail can appear unstable. Scintillation and image blur are related consequences of optical turbulence, though they describe different aspects of the observation. A sky that looks beautifully sparkly to someone enjoying the evening can be an irritating place to try to measure a faint detail precisely.
Large observatories address this with technologies such as adaptive optics. These systems sense distortions in arriving light and adjust a deformable mirror to reduce their effect on the image. Some use laser-created guide stars as references. ESO’s work shows how much engineering can go into compensating for the air we ordinarily look straight through. The telescope has collected the light; the next challenge is recovering a sharper view from what happened to it on the way down.
A home telescope won’t remove the atmosphere, but it can make observing enjoyable. If you’re considering the beginner telescope linked in my original article, check its current specifications, mount and included accessories before choosing it. I’m no longer attaching a fixed under-$100 price to that suggestion, because prices and packages change. A phone adapter can help attach a camera when included, but it doesn’t turn every flickering point into a detailed stellar portrait. Most stars will still appear as points.
Above the air, stars can still change
A telescope in space avoids Earth’s atmospheric distortion. That is one reason an observatory such as Hubble can produce sharp images without the same ground-level seeing problem. It doesn’t mean every star becomes permanently constant once viewed from orbit. A star can have genuine changes in brightness, and an object passing in front of it can also change the light received. Removing the atmospheric contribution makes those other signals easier to study.
NASA’s accounts of stellar oscillations describe how space telescopes measure small brightness variations associated with waves inside stars. Those variations can help researchers infer properties of the stars themselves. Variable stars also include objects that pulsate and systems in which one companion eclipses another. The important question is where the change originates: in the source or its system, in the intervening path, or in the measurement. A flicker by itself doesn’t answer all of that.
That distinction changes the poetry of the subject for me. A twinkle can tell us about our own air; a carefully measured variation can tell us about a distant star. Both arrive through the same sense, yet they belong to different stories. I find that far more interesting than imagining every change we see must come from the star itself. Sometimes the universe is doing something extraordinary. Sometimes Earth has added a flourish to an otherwise steady message.
Watching carefully is a skill with a long history
People have been reading patterns in the sky long before modern observatories. Specific traditions deserve specific accounts, rather than a vague claim that every culture assigned the same meaning to a star. Research by Duane Hamacher, John Barsa, Segar Passi and Alo Tapim combines archival work with fieldwork in Australia’s Torres Strait. It documents Meriam knowledge of changes in stellar appearance as indicators of weather and seasonal conditions, and discusses related knowledge among Northern Dene communities.
That work offers a richer perspective than reducing sky knowledge to either superstition or a single romantic sentence about ancestors. Observations are made within places, languages and accumulated experience. Their interpretation can be sophisticated without resembling the layout of a contemporary laboratory notebook. I’d rather name the researchers and communities accurately, then leave readers a source to explore, than borrow a generalized spiritual meaning because it sounds beautiful at the end of a paragraph.
My own skyline observation is much smaller in scope, but it reminds me how curiosity begins: something looks different, and we wonder why. The useful next step is to notice more carefully. For those building lights, I’d want to compare the same locations on different nights, noting weather and viewing conditions. That would still be an informal record, not a controlled airport study. It would, however, give the next question something firmer to stand on.
Making a little room for the night sky
Light pollution adds another layer to what we can see. Artificial light scattered through the atmosphere brightens the background sky, making faint stars harder to distinguish. That is a contrast problem, rather than the same process as scintillation. A city can have lights that shimmer beautifully while its sky reveals fewer stars. Loving a skyline and wanting better conditions for stargazing can coexist. I don’t think Philadelphia needs to choose between being visible and remembering there is a universe above it.
For a simple comparison, find a safe place away from immediate glare and look at a bright star low in the sky, then one higher up. If a known planet is visible, compare it too. Allow your eyes time to adjust and keep bright phone screens out of the way. You don’t need to buy anything to begin noticing the differences. I’d definately start with the eyes I already own before deciding that curiosity requires another box arriving at the front door.
I’ll keep noticing the building lights from the Four Seasons, especially the ones nearer the airport that first caught my attention. Now they give me another way to think about the stars. Between a light and the person seeing it lies a whole stretch of changing air, shaping an appearance we might otherwise attribute entirely to the source. The building stays where it is. The star carries on. And for a moment, the atmosphere lets us see something of its own restless life.
Related Reads
The Quiet Terror of the Cosmos: Unseen Forces and Forgotten Corners
The Sun Isn’t Yellow: A Mind-Bending Dive into Light, Space, and the Lies Our Atmosphere Tells
The Science of Nostalgia: Why We Long for Summers That Never Really Existed
The Sky Isn’t Blue: The Lie We Were Taught About Color and Light
Make Plantable Seed Paper From Junk Mail: A Crafty Way to Grow Beauty from Trash
The Emotional Lives of Fish: What Science Knows, and What We Ignore
Sources
Hong Kong Observatory — temperature variations and refraction
NASA/JPL — atmospheric propagation, scintillation and image distortion
Boundary-Layer Meteorology — runway scintillometer study at Schiphol
Hamacher, Barsa, Passi and Tapim — Indigenous use of stellar scintillation
Updated October 21, 2026. Images are AI-generated editorial scenes, not photographs from the Four Seasons, measured airport effects, astronomical observations or the linked telescope.
