Coherence, Comets in Cinema, and the Real 3I/ATLAS

In 2013, director James Ward Byrkit shot a science fiction film in his own living room over five nights, with no script, no crew, and a budget of $50,000. The result — Coherence — became one of the most acclaimed indie sci-fi films of the decade, built entirely around a single premise: a comet passes overhead, and reality fractures.

With 3I/ATLAS currently crossing our solar system as the third confirmed interstellar object, the film's central idea feels more resonant than ever. Comets have always occupied a strange space in human culture — somewhere between wonder and dread — and cinema has exploited that tension for decades. Here is how Coherence fits into the long tradition of comet stories, and what happens when fiction meets a real interstellar visitor.

Coherence: The Comet That Broke Reality

The setup of Coherence is deceptively simple. Eight friends gather for a dinner party on the night a comet is passing close to Earth. The power goes out. Phones crack. When two guests walk down the street to find the only other house with lights on, they discover it is their house — with another version of themselves inside.

The film's genius is in its restraint. Director James Ward Byrkit spent nearly a year before production creating elaborate charts, maps, and diagrams tracking the fractured realities his characters would navigate. But the actors knew almost nothing. They were given basic character outlines and motivations each night, and improvised their dialogue. The surprises — the power outage, the knocks at the door, the discovery of the other house — were real to them.

The science, such as it is, draws loosely on quantum decoherence and the many-worlds interpretation of quantum mechanics. In the film, a physicist character's notes explain that the passing comet has caused normally separate realities to overlap, allowing people to wander between versions of their lives. It is not rigorous physics — the film knows this and does not pretend otherwise — but it provides an elegant framework for a story about identity, choice, and the unsettling possibility that you might not be the best version of yourself.

Coherence earned a 88% on Rotten Tomatoes and became a cult favourite precisely because it took a cosmic event — a comet flyby — and made it personal. The comet never appears as a special effect. You never see it destroy anything. Its power is entirely psychological: the knowledge that something is passing overhead, that the rules have changed, and that you cannot trust what you see.

Centuries of Comet Dread

Coherence taps into something ancient. For most of human history, comets were objects of visceral fear — uninvited visitors that disrupted the orderly heavens and seemed to herald catastrophe.

The earliest recorded comet observations date to the third millennium BCE in Mesopotamia, where they were interpreted as messages from the gods. Almost universally, the message was bad. In ancient China, comets were called "broom stars" and associated with war, famine, and the fall of dynasties. In Mongolia, they were "the daughter of the devil." In medieval Europe, comets were considered the "heavy hand of God" — divine warnings of floods, earthquakes, and plague.

The fear was not abstract. In 1456, Pope Callixtus III reportedly excommunicated Halley's Comet, declaring it an instrument of the devil. In 1528, the French surgeon Ambroise Paré described a comet "the colour of blood" with an apparition so terrifying that "some died of fear." When Halley's Comet returned in 1910 and astronomers announced Earth would pass through its tail, charlatans sold "comet pills" and gas masks while panicked Americans boarded up their homes against imagined cyanide poisoning.

Even in the modern era, the dread persists in subtler forms. In 1997, thirty-nine members of the Heaven's Gate cult took their own lives during the appearance of Comet Hale-Bopp, believing the comet concealed a spacecraft that would carry them to a higher plane of existence.

This history is the cultural soil in which every comet film grows. When Coherence places a comet overhead and lets reality unravel, it is drawing on millennia of human anxiety about these unpredictable celestial visitors.

Hollywood's Comet Obsession

Cinema has explored comets from nearly every angle — as extinction-level threats, as catalysts for the supernatural, and as metaphors for human psychology.

The disaster film tradition reached its peak in the summer of 1998, when two comet-impact blockbusters arrived within weeks of each other. Deep Impact took the thoughtful route: a 7-mile-wide comet on a collision course with Earth, with the story focused on how individuals, families, and governments prepare for potential extinction. Armageddon went the opposite direction, sending Bruce Willis and a team of oil drillers to land on an asteroid and blow it apart with nuclear weapons. Together, they defined the two poles of comet cinema — quiet dread versus spectacular action.

Lars von Trier's Melancholia (2011) used an approaching rogue planet as a metaphor for depression itself. The film's protagonist, played by Kirsten Dunst, finds a strange peace as the world ends, while the "healthy" characters around her unravel. It remains perhaps the most psychologically honest depiction of an impending cosmic collision ever filmed.

Night of the Comet (1984) went full B-movie: Earth passes through a comet's tail and most of humanity is reduced to red dust or turned into zombies, leaving two Valley Girl sisters to survive the apocalypse. It became a cult classic that perfectly captured 1980s pop culture mixed with Cold War-era nuclear anxiety.

And then there is Don't Look Up (2021), Adam McKay's satirical take on a comet heading for Earth while politicians, media, and the public argue about whether to take it seriously — a thinly veiled allegory for climate change denial.

Each of these films treats the comet as a plot device — a catalyst that reveals something about human nature. But Coherence stands apart because it is the only one where the comet's effect is not destruction but distortion. The world does not end; it multiplies.

Why Coherence Gets Comets Right (Emotionally)

What makes Coherence the most interesting comet film from an astronomical perspective is not its physics — which is, of course, entirely fictional — but its emotional accuracy about what it feels like to watch something unknown pass through your sky.

The film captures three feelings that real comet observers know intimately:

The sense that something is happening overhead that you cannot control. In Coherence, the characters cannot stop the comet or its effects. They can only react. This mirrors the real experience of watching a comet — you are a spectator to something vast, indifferent, and temporary. The comet does not care that you are watching.

The collapse of the familiar. The dinner party in Coherence starts as something completely normal — friends, food, wine, conversation — and slowly becomes alien. Real comets do something similar to the night sky. A familiar constellation suddenly has an intruder: a fuzzy smudge that was not there last week, moving against the fixed stars. It is a reminder that the sky is not a ceiling but an open window.

The brevity. The comet in Coherence passes in a single night, and when it is gone, the fractures close. Real comets are similarly fleeting. They brighten, peak, and fade over weeks or months. You either see them or you do not. There are no replays.

These emotional truths are why the film resonates with anyone who has stood outside and watched a real comet crawl across the sky.

The Real Thing: 3I/ATLAS Is Stranger Than Fiction

No screenwriter would dare pitch the story of 3I/ATLAS. An object formed around an unknown star, possibly billions of years ago, ejected into interstellar space, drifting for aeons through the galaxy, and arriving in our solar system at 58 kilometres per second on a trajectory tilted almost exactly backwards relative to the planets. It passed inside the orbit of Mars, developed a tail of alien ice sublimating in our Sun's heat, and is now heading back out past Jupiter toward the void — never to return.

Every comet film uses the comet as a metaphor for something else: extinction, depression, societal failure, fractured identity. But 3I/ATLAS does not need a metaphor. It is genuinely, factually a visitor from another star. The ices in its tail formed in a protoplanetary disc around a distant sun. The dust grains it sheds have never been touched by our solar radiation before. When astronomers point spectrographs at 3I/ATLAS, they are reading the chemical fingerprint of another planetary system.

Coherence imagined a comet that allowed you to glimpse parallel versions of your own life. In a poetic sense, 3I/ATLAS does something similar for astronomers: it offers a glimpse of a parallel planetary system — one we can never visit but whose material is, briefly, passing through our neighbourhood.

The key difference between cinema comets and real ones is the ending. In films, the comet's passage resolves something — the reality fractures close, the asteroid is destroyed, the world ends or is saved. Real comets simply leave. 3I/ATLAS will fade from our telescopes by mid-2026, and the data collected during its passage will be studied for decades. There is no dramatic resolution, only the slow, patient work of science.

Watch the Real Comet, Then Watch the Film

If Coherence is the best comet film for capturing the emotional truth of a flyby, then 3I/ATLAS is the best real comet for living it. The interstellar visitor is still observable through telescopes, fading as it heads outward — check our observing guide for current coordinates and equipment recommendations.

There is something uniquely satisfying about watching Coherence on the same night you have been outside with a telescope, tracking a real comet. The film's central anxiety — that something is passing overhead, something beyond your understanding, something that will be gone by morning — maps directly onto the experience of observing 3I/ATLAS. Except in reality, the comet does not fracture your identity. It just reminds you how small your corner of the galaxy is, and how much is passing through it that you will never see.

For more on the real science of 3I/ATLAS, explore our science page. To see where the comet is right now, visit the orbit viewer. And to see what other observers have captured, browse our media gallery.

Then queue up Coherence. It pairs well with comets.