In the first years of powered flight planes had no cockpit instruments, nothing telling pilots how fast and how high and in what direction they were flying. They didn’t even have a cockpit. Pilots sat in front, the air whipping their faces letting them know when their machine was rolling fast enough over the grass field to take to the sky. At forty miles an hour, typical flight speeds for the earliest aircraft, sitting up front with a good pair of goggles and a warm leather coat wasn’t so bad.
But soon planes were flying faster and higher than leather, goggles and guesswork could handle. Pilots needed cockpits and planes needed instruments.
I am not overreaching by claiming that without the gyroscope, the history of the twentieth century would have looked very different. No ship, submarine, plane or spacecraft could have sailed, submerged, flown or navigated safely without it.
The first gyroscopes appeared in the early 1800s. They are direct descendants of the spinning top, the child’s toy that has been around for over five thousand years. Inventors and scientists – and children – knew that until its spinning slowed, a top would remain upright and motionless as it twirled. At its core the gyroscope is that same spinning top, except surrounded by a thin metal frame. But while they were fascinating to kids, no adult could identify a real use for them.
That changed in the 1850s when French physicist Léon Foucault was searching for a foolproof way to demonstrate to the masses that the earth rotated. The Paris-born Foucault had originally trained as a doctor, but an intense fear of blood unavoidably forced his educational pursuits to be directed elsewhere. He became a prolific inventor and is best known today as the creator of the Foucault Pendulum, something we are all taught about in middle-school science class.
This might sound familiar from back then. In 1851 Foucault hung a 62 lb brass ball under a 220-foot wire and set it swinging in a long sweeping arc. It was so heavy and its swing so pure that as it silently swished back and forth in place, the earth turned under it. If you stood directly in front of it as it swung, first making certain the brass ball didn’t clock you, within a few minutes it would no longer be swinging at you. You, and the earth under you, had moved while the swinging ball remained in place. Its position in space didn’t change – yours did. You had witnessed the earth rotating.
Not satisfied with one proof the earth rotates, in 1852 Foucault saw in the gyroscope the possibility of a second. While working with it he not only invented the modern version of the gyroscope, he coined its name, which roughly translated from Greek means see rotation.
Many of us remember gyroscopes, how if you wound the string that came with it around its axle and then pulled with all your might, the center wheel would spin furiously and the thing would balance perfectly on one of its thin feet, standing as erect as a toy soldier.
Place the spinning gyroscope on top of a book you held parallel with the floor, and it would dutifully stay where you put it, spinning merrily, its axle pointing directly at the ceiling. Now here is the interesting part: if you moved the book, tilting it this way and that, the gyroscope would remain pointing at the ceiling. No matter how you angled the book in your hand, the gyroscope’s axle would continue pointing straight up.
Thinking big, Foucault realized a spinning gyroscope was not really pointing at the ceiling. Instead, it was actually utterly immobile in three dimensions. It remained precisely where it was placed, continuing to point at whatever it was pointing to, regardless of what the world around it was doing. Put differently, just like his pendulum swinging in space, a gyroscope was maintaining its position in space.4
Foucault presumed if he suspended his gyroscope properly – meaning with no friction or as close to ‘no friction’ as he could come in 1852, with nothing to stop it from maintaining its place in space – as the earth rotated, he could show that rotation against the immobile gyroscope.
Practical electric motors didn’t exist in 1852, so Foucault built a crank-and-gears contraption that got his gyroscope spinning at a remarkable 12,000 revolutions per minute. [FIGURE 1] Once spinning, he focused a microscope on a point on the gyroscope and, as he expected, soon saw movement. The microscope was drifting away from the gyroscope. Exactly like with the pendulum, while the gyroscope held steady everything else moved: Foucault, his microscope, the table it sat on and the earth beneath all of them had shifted together. As the name said, he was ‘seeing rotation.’
Why do we care? Because a gyroscope’s stability in space means if you point it at ‘up’ it will keep pointing at ‘up’ while you and the vehicle you are flying in turn, climb, roll, descend, or loop. Go into outer space and point it at the earth, and while your spaceship swings around the back side of the moon you will always know how to find home. Foucault’s pendulum was also stable in space, but it would not fit inside a space capsule or a plane cockpit, and it needed gravity to work.
Very few of us will ever get to outer space, but we can hop into a small plane to watch a gyroscope in action. Start the engine, take off, and climb to a safe altitude. Start your gyroscope spinning and place it upright on the glareshield (in a car that would be the top of the dashboard). It will stay there spinning and pointing straight up. [FIGURES 2, 3]
If you bank the plane the gyroscope will appear to you, sitting in the pilot’s seat, to be leaning the opposite way. Bank the plane left and the gyroscope will look like it is leaning right. Banking right will make the gyroscope look like it is leaning left. That is because while the plane has tilted, the gyroscope continues pointing straight up. [FIGURE 4]
If you push your plane into a dive, the gyroscope will look like it is leaning towards you. Same reason as before: you’ve tilted earthward, not the gyroscope. If you climb, it will appear to be leaning away from you. [FIGURE 5]
Pilots don’t look at gyroscopes while flying. They look at instruments connected to gyroscopes. But first someone had to invent those instruments.
That is where the father and son team of Elmer and Lawrence Sperry come in.