# What's the most sunsets you could see on Earth in one day?

The childlike fellow from Asteroid B-612 in Antoine de Saint-Exupéry's classic novella, "The Little Prince" (1943), tells the book's narrator that he once saw the sun set 44 times in one day. All the prince had to do to stay ahead of the sun as it set around his tiny space rock was scooch over his chair.

Granted, Earth is much larger than Asteroid B-612, but could any Earthlings top that record? In other words, how many sunsets could you see in person in one day?

Hypothetically, if you started at a location on Earth where the sun was setting and traveled westward at the speed Earth turned to the east, then you could remain in a state of constant sunset. In 2014, an ex-NATO pilot, a photographer and a filmmaker attempted to follow the sunset around the globe, through all 24 time zones, as a publicity campaign for a watch. They didn't quite make it, but their effort provides a look into the science of sunset chasing.

## How to follow a sunset, in theory

At any point in time, a certain swath of Earth is illuminated by sunlight, as if by a lamp, explained Gerd Kortemeyer, ​​an associate professor of physics at Michigan State University. As the planet turns toward the east, a given location passes into, through, and out of that illuminated area, experiencing sunrise, day, and then sunset.

"What you would have to do, if you want to follow the sunrise or you want to follow the sunset, is fly such that you're always just on that borderline" between the area of Earth that's illuminated and the area that is not, Kortemeyer said. That means staying in the same position relative to the sun as the Earth turns underneath you, as if the Earth were a treadmill and the sun a ceiling light. To do that, because Earth rotates toward the east, you would need to fly west at the same speed Earth turns, Kortemeyer explained.

To do that at the equator, where the planet is at its maximum circumference around its axis of rotation, you'd have to fly at 1,000 mph (1,609 km/h), according to HowStuffWorks. That's extremely fast; most commercial airplanes fly at a cruising speed of 460 to 575 mph (740 to 925 km/h), whereas the U.S. Navy’s Blue Angels air display team flies at a maximum speed of 700 mph (1,126 km/h) during air shows. But as you move toward the poles, the circumference around the rotation axis decreases and the speed at which Earth turns — which is the distance covered in a given period of time — decreases accordingly. "The higher your latitude, the slower you're moving," Kortemeyer said.

## "Watch" me try

In 2014, Citizen watches worked with advertising firm Wieden+Kennedy to promote its Eco-Drive Satellite Wave F100 watch and its ability to automatically adjust to time zone changes within seconds, as Fast Company reported. The firm decided to do that by flying through all the time zones and documenting the watch's ability to adjust. The firm assembled a team including ex-NATO pilot Jonathan Nicol, U.K.-based photographer Simon Roberts and filmmaker Tristan Patterson to attempt — and document — the stunt of flying through every time zone at sunset.

They didn't attempt this at the equator. Instead, they flew high in the Arctic at 80 degrees latitude, where Earth rotates at about 180 mph (290 km/h), according to Fast Company. The team took off in Iceland, flew north and east to reach the 80th parallel north and zero degrees longitude (the imaginary line running north-south designating the prime meridian), then turned around to begin the journey west, chasing the sunset across Greenland, then Canada, Roberts told Live Science.

The original plan involved flying over Russia, as well as stopping to refuel in Siberia, according to Patterson, who made a short film for the project. But Russia denied them permission to land, Roberts said. The conflict between Russia and Ukraine had just begun that February, which increased tensions between Russia and the West. These tensions trickled down to the team's project to chase the sunset, according to Roberts and Patterson. Without permission to refuel in Russia, they decided against flying through Russian airspace. Instead, they flew west for only eight hours, passing through Greenland and landing in Resolute Bay, Canada, Patterson said. There, instead of continuing over the Bering Strait and into Russia, they stopped.

In the end, what prevented the team from chasing the sunset around the globe was not a scientific challenge but a political one. "There was so much time and effort put into solving the science or the math equation of how to practically do this thing of staying at sunset for a day, and then the shake up of it is this out-of-nowhere political situation," Patterson told Live Science.

During those eight hours, though, chasing the sunset was thrilling. "There was a kind of general excitement about being in this perpetual state of a sunset," Roberts said. "That sense of dusk and sunset is something extremely romantic. To try and stay in that state for 24 hours was a wonderful idea. In terms of a concept, I think it was quite an extraordinary thing to try and do."

The results of this publicity project included an ad, featuring Roberts' sunset photos, as well as a five-minute film, directed by Patterson.

## Other sunset chasers

Concorde jets, which could reach a speed of 1,354 mph (2,179 km/h), could have kept up with Earth's rotation, even at the equator. But the jets, called supersonic because they flew faster than the speed of sound, stopped flying in 2003. They may not have chased the sunset, but Concorde's flights from London to Dulles International Airport, in Virginia, let passengers catch two sunsets — one as the plane took off in London and another after it landed near D.C. "Concorde was famous for that," Kortemeyer said.

Astronauts at the International Space Station, which orbits Earth once every 90 minutes, can witness 16 sunrises and 16 sunsets per day, as The Atlantic reported.

Saint-Exupéry was an aviator himself. He might have been familiar with the sorts of challenges these sunset chasers faced. Maybe it's no surprise, then, that he imagined the Little Prince chasing the sunset simply by shifting his chair.

Originally published on Live Science.