A Milky Way Shadow at Loch Ard Gorge via
Unlike some animal species, humans aren't equipped to navigate by the stars. It's something we have to learn, and it doesn't always go well. But if our GPS ever stops working, the stars are our main fallback.
The dung beetle is one of the species that does have a natural propensity for celestial navigation. Sunlight is highly polarized, shining through the atmosphere in a particular pattern, and it’s one that dung beetles can see. They, like many insects, have specialized photoreceptors in their eyes that detect it. Dung beetles follow the virtual map sunlight creates in the sky as they roll their dung balls along, intending to draw a mate.
If they get lost, they climb on top of the dung ball to reorient themselves. They can also do the same with diffused moonlight and light from the Milky Way. Researchers recently showed this by putting little caps on beetles and observing their circular and haphazard movements. Without some light source, they couldn’t find their way.
Yes, that's a dung beetle wearing a hat.
Humans lack the photoreceptors that let us see diffusing sunlight as a map in the sky. We can use the Sun during daylight hours, but at night the stars are, like the dung beetles’, our chief ally. But we, usually pilots and sailors, have to learn them. Aids like the Nautical Almanac and Air Almanac help, annual publications that describe the precise positions and movements of celestial bodies at specific times and dates for different regions. Needless to say this task is much easier for pilots who can fly above cloud cover.
On the morning of October 27, 1962, at the height of the Cuban Missile Crisis, Charles Maultsby was flying a U-2 towards the North Pole. He was on an atmospheric sampling mission – testing the air for evidence of a Soviet atomic bomb test – using the stars as his guide. But he hadn’t anticipated the Northern Lights, the beautiful atmospheric phenomenon that blocked out the starlight, causing him to get lost over Soviet airspace. MiGs were scrambled, leading to a chain of events that nearly started the third world war. As Maultsby's case shows, dung beetles have us beat when it comes to instinctive celestial navigation.
In addition to the Sun, Moon, and planets, there are 57 standard stars that serve as a baseline for celestial navigation. They are all bright stars, second magnitude or brighter though there are a few dimmer stars on the list. They are all easy to identify, and far enough apart to give the navigator a sense of place anywhere in the whole sky. Interestingly, the North Star isn’t on the list; it’s too perfectly over the North Pole to be strictly useful.
Pilots start by measuring the altitude of one of these baseline stars above the horizon at twilight, when both the star and horizon are visible. This gives what’s called a "circle of position" on the Earth's globe. A pilot must be somewhere on this circle to see the star at a certain altitude at a given time. Beginning with a different star gives a different circle of position. Where they intersect is the pilot’s location. Things get a little easier if you know where you are and where you're going relative to the stars. In this case, celestial navigation becomes a matter of keeping a certain star or constellation in the same spot to maintain a straight path.
A map of the equatorial stars; a little more complicated than a roadmap. via
Of course, this means a navigator has to be familiar enough with the night sky to recognize the stars, or at least know how to look them up in an almanac. But it’s a useful skill that’s gotten a number of pilots out of tight spots. Like Wally Schirra. On his Sigma 7 flight, the Mercury astronaut was supposed to manually align his capsule for reentry using landmarks on Earth. But cloud cover left him basically blind. So he tapped into his past learning celestial navigation with the Navy and used the stars to line up his capsule for a perfect reentry. A clever solution – and totally badass.
With asteroids buzzing the planet from time to time, some closer to the Earth than our GPS satellites, I wonder what we would do if we lost the computer-based network that tells us all how to get where we’re going. We’d still have maps and marked interstates, but the handful of people who can actually navigate by the stars like the dung beetle would be tasked with guiding the masses around the world.
Maybe we should all start looking up a little more often.