To Fly

Natural History Magazine

by Neil deGrasse Tyson

From Natural History Magazine, April 1998

In ancient days two aviators procured to themselves wings. Daedalus flew safely through the middle air, and was duly honoured in his landing. Icarus soared upwards to the sun till the wax melted which bound his wings and his flight ended in a fiasco. In weighing their achievements perhaps there is something to be said for Icarus. The classic authorities tell us, of course, that he was only 'doing a stunt'; but I prefer to think of him as the man who brought to light a serious constructional defect in the flying-machines of his day [and] we may at least hope to learn from his journey some hints to build a better machine.

Sir Arthur Eddington, astrophysicist
Stars & Atoms (1927)

For millennia the idea of being able to fly preoccupied human dreams and fantasies. Waddling around on Earth's surface as majestic birds flew overhead, perhaps we developed a form of wing-envy. One might even call it wing worship. You needn't look far. The United States adopted a flying predator as a symbol of its strength—the bald eagle appears on the back of the dollar bill, the quarter, the Kennedy half dollar, the Susan B. Anthony dollar, and the Eisenhower dollar. There's also one on the floor of the Oval Office in the White House. Our most famous superhero, Superman, can fly, upon donning blue panty hose and a red cape. When you die, if you qualify, you might just become an angel—and everybody knows that angels (at least those with wings) can fly. Then there is Peter Pan and his fairy sidekick Tinkerbell, the winged horse Pegasus, the wing-footed Mercury, and the aerodynamically unlikely Cupid. And for most of the history of broadcast television in America, when a station signed off for the night, it didn't show somebody walking erect and bidding farewell, it instead would play the Star Spangled Banner and show things that fly, like soaring bald eagles or some Air Force jets whooshing by.

In textbook comparisons of human biological features to those of other species in the animal kingdom, our inability to fly often goes unmentioned, although we are quick to use the word flightless as a synonym for hapless. Birds such as the ostrich, the kiwi, and the penguin tend to find themselves at the wrong end of evolutionary jokes told by humans. In our own defense, we ultimately learned to fly due to the technological ingenuity of our human brains. And of course, while birds can fly, they are stuck with bird brains. But this self-aggrandizing line of reasoning is somewhat flawed because it ignores the thousands of years that preceded the twentieth century, when we had not yet figured out how to fly and thus could not have make such a comparison.

I remember as a student in junior high school reading an essay, published near the turn of the nineteenth century, that argued the impossibility of flight by any device that was heavier than air. This was clearly a myopic prediction, but one didn't have waited for the first airplanes to be invented to refute premise of the essay. One only needed to look at birds, which have no trouble flying and, last I checked, are all heavier than air. If something is not forbidden by the laws of physics then it is, in principle, technologically possible, regardless of the limits of your foresight. The speed of sound though air falls anywhere from 700 to 800 miles per hour, depending on the atmospheric temperature. There's no law of physics that prevents objects from going faster than Mach 1, the speed of sound. But before the sound barrier was broken in 1947 by the Major Charles E. (Chuck) Yeager piloting the Bell XS-1 (a U.S. Army rocket plane) there was much claptrap written about the impossibility of objects moving faster than the speed of sound. Meanwhile, bullets fired by high-powered rifles had been breaking the sound barrier for over a century. And the crack of a whip, or the sound of snapping somebody's rear end with a wet towel in the locker room is the mini sonic boom created by the tiny tips moving though the air faster than the speed of sound. Any limits to breaking the sound barrier were purely psychological and technological.

The fastest winged aircraft is incontestably the Space Shuttle, which, when emerging from orbit, slows down from speeds in excess of Mach 20. When I now tell you that you can never travel faster than the speed of light, I speak not from a naiveté about technology's future. I speak from a platform built from the universal laws of physics. The Apollo astronauts who went to the Moon are credited attaining with the fastest speeds at which humans have ever flown: about seven miles per second at the end of the rocket burn that lifted their craft beyond Earth's orbit. This is a paltry 1/250th of one percent of the speed of light. Actually, the real problem is not the moat that separates these two speeds but the laws of physics that prevent any physical object from ever achieving the speed of light, no matter how inventive your technology. The sound barrier and the light barrier are not equivalent limits on invention.

The Wright Brothers of Ohio are, of course, generally credited with being first in flight, as North Carolina's automobile license plate slogan is quick to remind you. But this claim needs to be further delineated. Wilbur and Orville Wright were the first to fly a heavier-than-air, engine-powered vehicle that carried a human being—Orville, in this case—and that did not land at a lower elevation than its takeoff point. Previously, people had flown in balloon gondolas, in gliders, and had executed controlled descents from cliffsides, but none of these efforts would make a bird jealous. Actually, Wilbur and Orville's first trip would not have turned bird-heads either. At 10:35 AM eastern time, on December 17, 1903, the first of their four flights on that historic day lasted 12 seconds, at an average ground speed of 6.8 miles per hour, against an air speed of 30 miles per hour.

The Wright Flyer, as it was called, had traveled 120 feet, a little more than length of one wing on a Boeing 747 jumbo jet. Surprisingly, even after the Wright brother's achievement was widely known, the media took little notice of this and other aviation firsts. As late at 1933, H. Gordon Garbedian ignored airplanes in the otherwise-prescient introduction to his book Major Mysteries of Science:

Present day life is dominated by science as never before. You pick up a telephone and within a few minutes you are talking with a friend in Paris. You can travel under sea in a submarine, or circumnavigate the globe by air in a Zeppelin. The radio carries your voice to all parts of the earth with the speed of light. Soon, television will enable you to see the world's greatest spectacles as you sit in the comfort of your living room.

But some journalists did pay attention to the way flight might change civilization. After the Frenchman Louis Bleriot crossed the English Channel from Calais to Dover on July 25, 1909, an article on page three of the New York Times, was headlined Frenchman Proves Aeroplane No Toy. The article went on to observe England's reaction to the event:

Editorials in the London Newspapers buzzed about the new world where Great Britain's insular strength is no longer unchallenged; that the aeroplane is not a toy but a possible instrument of warfare, which must be taken into account by soldiers and statesmen, and that it was the one thing needed to wake up the English people to the importance of the science of aviation.

The guy was right. Thirty-five years later, not only had airplanes been used as fighters and bombers in warfare, the Germans took the concept a notch further and invented the V2 which wreaked havoc on London in 1943. This vehicle was significant in many ways. First, it was not an airplane, it was an unprecedentedly large missile. Second, it was launched like a rocket from five hundred miles away in Germany. Third, its modern-looking, pointy, bullet-shaped body with large fins at the base influenced an entire generation of images in science fiction stories of space travel. And lastly, for its entire airborne journey after launch, it moved under the influence of gravity alone. In other words, it was a sub-orbital ballistic missile, the fastest way to deliver a bomb from one location on Earth to another. Cold War advances on the design of ballistic missiles enabled cities halfway around the world to be targeted. The flight time? About a half an hour.

Colloquial usage of the term notwithstanding, if something goes ballistic, its trajectory is simply no longer controlled by rockets or fins or wings. Where it goes (and where it lands) is controlled by the laws of gravity alone, although fins can add stability to its flight. All falling objects, all satellites (including the Hubble Space Telescope), and all interplanetary spacecraft go ballistic after they are launched.

While we can say they're traveling ballistically, do we have the right to declare missiles to be flying? Are falling objects in flight? Is Earth flying in orbit around the Sun? By Wright Brothers' rules, a person must be on board the craft and it must move under its own power. But there is no rule that says we cannot change the rules. If flight includes space travel, then the sky is the limit. Knowing that orbital technology was within reach with the V2 rocket, people were getting impatient. An article dated 22 March 1952, and titled What Are We Waiting For? was written by the editors of Collier's Magazine, a popular, family-oriented magazine that especially flourished in the post war period. The article was conceived and written after two Collier's journalists had visited New York City's Hayden Planetarium on Columbus Day of 1951 for a seminal Space Travel Symposium, attended by engineers, scientists, and visionaries. The Collier's editors commented on the need and value of a space station serving as a watchful eye over a divided world:

In the hands of the West a space station, permanently established beyond the atmosphere, would be the greatest hope for peace the world has ever known. No nation could undertake preparations for war without the certain knowledge that it was being observed by the ever-watching eyes aboard the sentinel in space. It would be the end of the Iron Curtains wherever they might be.

We didn't build a space station, but we went to the Moon. In this effort, human bird-worship continued. Never mind that on the Moon, where there is no air and where wings are completely useless, our astronauts landed in a spacecraft named after a bird. A mere 65 years, 7 months, 3 days, 5 hours, and 43 minutes after Orville left the ground, Neil Armstrong gave his first statement from the Moon's surface, Houston, Tranquillity Base here. The Eagle has landed.

The human record for altitude does not go to anybody for having walked on the Moon. It goes to the astronauts of the ill-fated Apollo 13. Knowing they could not land on the Moon after the explosion in their oxygen tank, knowing that they did not have enough fuel to just stop, turn around, and head back, they executed a single figure '8' ballistic trajectory around the Moon, which swung them back towards Earth. But the Moon just happened to be near apogee, its farthest point from Earth in its oval-shaped elliptical orbit. No other Apollo mission (before or after) went to the Moon during apogee, which granted the Apollo 13 astronauts the human altitude record. When I calculated that they must have reached about 245,000 miles above Earth's surface, including the orbital distance from the Moon's surface, I asked Apollo 13 commander Jim Lovell, when he was visiting the Museum recently, Who was on the far side of the command module as it rounded the Moon? That single person would hold the altitude record. He refused to tell.

In my opinion, the crowning achievement of flight was not Wilbur and Orville's airplane, nor Chuck Yeager's breaking of the sound barrier, nor the Apollo 11 lunar landing. For me, it was the launch of Voyager 2 , which ballistically toured the solar system's outer planets. During the flybys, its slingshot trajectories stole some of Jupiter and Saturn's orbital energy for its rapid exit from the solar system. Upon passing Jupiter in 1979, Voyager's speed exceeded 40,000 miles per hour, sufficient to escape the gravitational attraction of the Sun. Voyager passed the orbit of Pluto in 1993, entering the realm of interstellar space. Nobody happens to be on board the craft, but it does contain a gold phonograph record attached to its side and etched with the earthly sounds of, among many things, the human heartbeat. So with our heart, if not our souls, we continue to fly farther and faster than ever before.

Neil deGrasse Tyson, an astrophysicist, is the Frederick P. Rose Director of New York City’s Hayden Planetarium and a visiting research scientist at Princeton University.