It is 1966, and astronaut Buzz Aldrin is on the Gemini 12 mission into space when the electronics fail. He saves the mission and makes the rendezvous with another spacecraft by using an instrument that mariners have used for centuries.

In 1970, Apollo 13 lost all power, calling “Houston, we’ve had a problem.” Commander Jim Lovell used that same instrument to navigate the stricken spacecraft back to Earth. What was it? 

A sextant.

The sextant has been the essential tool for celestial navigation since long before John Paul Jones sailed into battle or Shackleton crossed Antarctica. And celestial navigation using a classic sextant was taught at the U.S. Naval Academy in Annapolis for more than a century.

Until 1998.

That was when there were enough satellites in the sky that the GPS navigation system was considered perfect. Why would naval officers struggle to capture a star reflected on a tiny mirror aboard a rolling ship when they could push a button on a GPS unit and instantly know their position within a few feet? And so the Navy eventually dumped celestial navigation as being out-of-date.

Flash forward to the present and, 18 years after deciding that computers could do a better job, the U.S. Navy has reinstated celestial navigation at Annapolis. But this isn’t about nostalgia, or even teaching midshipmen about maritime history. 

It’s because you can’t hack a sextant.

In this digital age, nothing is secure from determined hackers and cyber attacks have successfully targeted everyone from international banks to the White House and even the head of the CIA. Nothing is sacred, and that includes GPS, although GPS hasn’t been attacked. Yet.

There is also the possibility that the U.S. might be the hacker, bringing the GPS system down so enemies can’t use it. Until 2000, the GPS signals had “Selective Availability,” which meant the government degraded the signals to the public, while reserving the most accuracy for the military.

But should GPS go black, one naval officer noted, “There is no backup!” And so the Navy has reinstituted teaching middies an ancient technique to wage modern wars. 

I’m delighted because I love stars. They’re my friends. I remember my father helping me learn the stars, and then teaching me celestial navigation. And every time I look at the stars, they remind me of him.

When war came, he was a young merchant seaman and, because he knew celestial navigation, he quickly became an aircraft navigator. 

This was when radio direction finding was as scratchy and vague as a 78-rpm Victrola record. Aircraft in the 1940s were capable of flying thousands of miles across empty oceans, but they had outpaced the navigation tools. A sextant (or, rather, the aircraft version called an octant) was much the same device that navigators used when boats were wood and sails were canvas.

Somewhere a thousand miles from land, everyone in the aircraft knew that their fate depended on his skills to find a tiny pinpoint of an island somewhere in the vast wasteland of an ocean. Whether it was named Midway or the Azores, it was called Life.

My father, and all those like him, would take that fragile instrument into a tiny dome atop the aircraft. With luck, they were above the clouds and he could pick out stars he needed for a fix. Then he would climb down to his little nav station, work the numbers, put a mark on a chart, and lean into the cockpit. “Come right, two degrees.”

My father later put those skills to use as a navigator on ocean racing yachts, this time doing his magic and then leaning into a darkened sailboat cockpit. “A couple of points to starboard is the finish line.”

When I was learning to use a sextant, I traveled to some wonderful places. Though I was standing in our Southern California backyard, I visited Utah and Hawaii and San Francisco, with one completely inexplicable trip to Morocco. But I persevered and finally reached a point where I could pencil a spot on a chart that was within my own county. 

She Who Must Be Obeyed and I are headed for the British Virgin Islands for a bareboat charter soon, and I’ll be tucking a plastic Davis sextant into my duffel bag with an almanac and some tables. Perhaps I’ll see if the BVIs are where they’re supposed to be.

Just lying on the forward trampoline of a catamaran anchored in the BVI with that giant black dome overhead, pierced with billions of stars never seen in the light pollution of cities is magic. 

Looking up at this incredible array, I wonder what these stars have seen. Pirates and buccaneers, Spanish galleons laden with gold, perhaps a German U-boat or two. All of them navigating by the stars.

On a boat, I sleep like a combat infantryman, with one eye open and one ear cocked. My senses are attuned to what isn’t right—a change in motion, an odd clunk, whatever. She Who Must Be Obeyed knows that I get up at all hours, just to check the anchor, take a visual bearing on land and, what she doesn’t know, to look at the stars. 

In the darkness, I can sometimes see tiny satellites move across the sky because this is, of course, the modern world. Sometimes I’ll see a meteor, but mostly I’ll see all my friends: Cassiopeia, Orion, Polaris, Castor, Arcturus. The very names are magical and I always think of the legions of navigators who also looked at them and were comforted by knowing how to find their way home.

Today, a new generation of naval officers will add celestial navigation to their skill set once again and I can only think that, far at sea on a dark night, they’ll look to the sky and see their friends also.

You’ll probably never save a space mission or cross Antarctica on foot, but you might enjoy celestial navigation. It’s challenging but if a 19-year-old midshipman can do it, so can you.

Besides, you never know when the GPS will go black.