Don’t Look Up is fiction. Here’s the real science of that doomsday scenario

Two low-level astronomers discover a “planet killer” comet hurtling toward Earth but struggle to get anyone to pay attention in Don’t Look Up, a new satirical sci-fi from Netflix. Directed by Adam McKay (The Big Short), it’s a mostly amusing, star-studded confection that ably skewers science denial and cynical politicking even in the face of almost certain annihilation.

(Mildest of spoilers for the film below.)

Per the film’s official synopsis:

Kate Dibiasky (Jennifer Lawrence), an astronomy grad student, and her professor Dr. Randall Mindy (Leonardo DiCaprio) make an astounding discovery of a comet orbiting within the solar system. The problem—it’s on a direct collision course with Earth. The other problem? No one really seems to care. Turns out warning mankind about a planet-killer the size of Mount Everest is an inconvenient fact to navigate. With the help of Dr. Oglethorpe (Rob Morgan), Kate and Randall embark on a media tour that takes them from the office of an indifferent President Orlean (Meryl Streep) and her sycophantic son and Chief of Staff, Jason (Jonah Hill), to the airwaves of The Daily Rip, an upbeat morning show hosted by Brie (Cate Blanchett) and Jack (Tyler Perry). With only six months until the comet makes impact, managing the 24-hour news cycle and gaining the attention of the social media obsessed public before it’s too late proves shockingly comical—what will it take to get the world to just look up?!

The cast also includes Mark Rylance, Timothée Chalamet, Kid Cudi, Ariana Grande, Ron Perlman, Michael Chiklis, Robert Joy, Sarah Silverman, Chris Evans, Himesh Patel, Paul Guilfoyle, and Liev Schrieber.

Near-Earth objects do exist, and astronomers track them diligently, even though the real-world likelihood of a planet-killing comet or asteroid colliding with Earth is vanishingly small. Naturally, when McKay needed scientific input for his doomsday scenario, he turned to NASA. The space agency recommended Amy Mainzer, an astronomer at the University of Arizona’s Lunar and Planetary Laboratory. Mainzer studies asteroids and comets for a living, particularly those whose orbits might pass close to Earth, and is the principal investigator for both the NEOWISE project and the Near-Earth Object Surveyor space telescope mission. Ars sat down with Mainzer to learn more.

Ars Technica: Is there a real-life inspiration for the comet that threatens humanity in the film?

Amy Mainzer: This is absolutely a science fiction movie. One of the great things about science fiction is that it lets us explore what-if scenarios. The comet in this story is really an allegory for other types of disasters that people face, both natural and human caused. It’s a broader allegory for the role of science in society and whether we make decisions as a society based on science or not.

In real life, we don’t know of anything that’s headed our way that poses any sort imminent impact threat. However, I did loosely base the comet on Comet NEOWISE, which we discovered last year. We do see these long-period comets that come from the outer parts of the Solar System. They pop up without a lot of warning because they move with incredible velocities relative to the Earth. Fortunately for us, space is really, really big, so most of the time, there’s absolutely no chance of an impact whatsoever.

Ars Technica: Scientifically, what’s the difference between a comet and an asteroid?

Amy Mainzer: Composition-wise, we now think that asteroids and comets represent a spectrum rather than being two completely different categories. Asteroids are rockier with less ice on their surfaces. We think they formed in the warmer parts of the inner Solar System. So they’ve been exposed to more sunlight, and that tends to fry any ice off of the surface. On the other end of the extreme, you have comets, which are generally thought to have formed in the more distant parts of the Solar System, so they have more icy surfaces.

But there’s also a whole new class of objects that look like normal asteroids in terms of their orbits. They just go around the Sun peacefully between Mars and Jupiter. They’ve been there forever and will probably stay there forever. Sometimes they sprout tails like a comet. And sometimes we see near-Earth objects that have wacky comet-like orbits, but they show no signs of activity at all. They never sprout a tail.

In terms of their dynamics, these objects can be very different. The asteroids are the most hazardous with the greatest chance of intersecting with the Earth, because they tend to have Earth-like orbits. Their relative velocities are lower than comets, but they still travel at tens of thousands of miles per hour. That’s why a tiny little piece of sand can make a brilliant light in the night sky; it’s just moving so fast. Comets move even faster. With Comet NEOWISE, we first discovered it in March, and by July, it had already made its closest pass to the Sun.

Ars Technica: Just how close are we talking about?

Amy Mainzer: It really depends on the size of the object. Tiny things come close to the Earth all the time. Every day, roughly 100 tons of material from asteroids and comets bombard our Earth. It’s mostly in the form of teeny-tiny little sand-grain-sized pieces that are perfectly harmless. They make a beautiful, bright light of shooting stars in the sky, but that’s about it. As we get to larger sizes, those impacts become much less frequent.

When we talk about close approaches, what’s important is how much we know about the orbit of an individual asteroid. When we first find something, we know almost nothing about it. Usually we just have a handful of snapshots. That’s not a lot to go on. So then the race is on to gather more information about it. When we call something a near-Earth object, what we mean is that it comes within about 1.3 times the Earth/Sun distance. That doesn’t mean it has any significant chance of impacting the Earth. But we have to figure out exactly how close does it get. The process depends upon collecting more observations over time and then gradually refining those orbit estimates.