Take Me to Your Leader: Perspectives on Your First Alien Encounter by Neil deGrasse Tyson - 5

No science achieves maturity without a system of measurement.

—LOGAN CLENDENING 1

Aliens might find it hilarious that human cultures have deeply influenced our measurements of things. One could fill an anthropological museum with efforts to establish quantities with precision that today we take for granted. A unit of measure is the thing that allows the measured number to have meaning. In response to the question, how fast were you driving, you would not reply to the police officer, “Fifty-five cents.” Or if someone asked, “How tall are you?” you know not to reply, “Seventy-five degrees Fahrenheit.” Units need to make sense in the context of what’s being measured. Only then can you compare one quantity with another. And only then might sixteen ounces of prevention equal a pound of cure.

That there was ever an official unit of length called Feet is itself laughable. Then there’s the Mile, which obviously has 5,280 feet in it. We (still) measure the height of horses in Hands. But let’s not stop there. We’ve had Cups and Pints and Gallons. We’ve had Bales and Bushels, Leagues and Fathoms, and Shiploads—itself a unit that’s easy to mishear. The Second of time, at one point, was officially defined to be exactly 1/31,556,925.9747th of the year 1900, measured by the Sun returning to its position on the sky at year’s end. Even in the metric system, the Meter was defined by the French in 1789 to be one ten-millionth the distance from Earth’s North Pole to the Equator along a line passing through the Paris Observatory.

For all we know, units of measure used by Alien scientists are equally as obtuse. But there’s a place to meet that we might call common ground. The universe happens to reveal what we call universal constants. They’re all important, but at the top of a hallowed list we find (1) the speed of light: “ c ,” (2) Planck’s constant: “ h ,” and (3) the constant of gravitation: “ G ,” sometimes called “big G.” The speed of light is fast. Very fast. And it’s the same no matter when, where, or how you measure it, checking in at exactly 299,792,458 meters per second—a quantity so well measured and so fundamental that any modifications or updates to the speed will force a change in the definition of the length of the meter itself. Planck’s constant, discovered in 1899 by German physicist Max Planck, is fundamental to our understanding of quantum physics. And big G comes from Newton’s law of gravitation.

The universe is exquisitely shaped by the value of these constants. For example, in a calculation typically done during one’s first year of graduate astrophysics, you can show that if the constant of gravitation were a mere 10 percent larger, the Sun’s luminosity would double, along with that of all stars in the universe. More importantly, they’d all live half as long. If that were actually the case, the Sun would be dying right now, and all life on Earth would be going extinct.

We fully expect Alien scientists to have discovered all physical constants, especially the big three, which would make an important conversation starter for your first encounter. How? Turns out, you can combine these three constants to create units of measure that make no reference to body parts or Earth years or French people. Max Planck first conducted this exercise in 1899, and gave us:

Planck Length: L =

Planck Mass: M =

Planck Time: T =

Whether or not you’re comfortable with those equations, the takeaway is that the units are based on universal physical constants and would, in principle, be known by Alien scientists across the universe. Planck himself was feeling Alien-adjacent when he wrote:

It is possible to set up units… which are independent of special bodies or substances, necessarily retaining their meaning for all times and for all civilizations, including extraterrestrial and non-human ones, which can be called “natural units of measure.” 2

Many other units of measure can be derived from these three. For example, the unit of volume would simply be the Planck length cubed. The unit of speed would be the Planck length divided by the Planck time.

These quantities happen to be astronomically small by normal human metrics and all have seriously negative exponents. The Planck length is 1.6 x 10 –35 meters. The Planck mass is 6.14 x 10 –9 kilograms. And the Planck time is 5.4 x 10 –44 seconds. For context, that Planck length is one one-hundred-quintillionth the diameter of the proton. But the absolute scale of these quantities is irrelevant. What matters is that Planck gave us a means to measure the universe, right alongside Alien scientists.

Shared units of measure notwithstanding, practically every pop culture portrayal of intelligent Aliens leaves us far behind their technologically superior abilities. But this was not always the case. In an extreme extrapolation of “They’re just like us,” the Dutch polymath Christiaan Huygens wrote the playfully speculative book Cosmotheoros: Or Conjectures Concerning the Inhabitants of the Planets , posthumously published in 1698. When imagining life on Jupiter and Saturn, Huygens will stop at nothing to deduce they must be just like us:

If their Globe is divided like ours, between Sea and Land, as it’s evident it is (else whence could all those Vapors in Jupiter proceed?) we have great reason to allow them the Art of Navigation, and not proudly ingross so great, so useful a thing to our selves.… And what a troop of other things follow from this allowance?

Huygens is on a roll:

If they have Ships, they must have Sails and Anchors, Ropes, Pullies, and Rudders, which are of particular use in directing a Ship’s Course against the Wind.… And perhaps they may not be without the use of the Compass too.… But there’s no doubt but that they must have the Mechanical Arts and Astronomy, without which Navigation can no more subsist, than they can without Geometry. 3

Whatever mastery of technology the Aliens may wield, their machines and inventions must still obey the universal laws of physics. In his quaint way, Huygens hypothesized it. But in modern times we declare it as an objective truth.

There’s good reason to be skeptical of this claim. When taking cues from our own history, many declared we would never fly, that we would never break the sound barrier, and that we would never reach the Moon. Here are some especially boneheaded negative predictions made by people who should have known better:

It’s scarcely possible that the twentieth-century will witness improvements in transportation that will be as great as were those in the nineteenth-century.

—GEORGE H. DANIELS, NEW YORK CENTRAL RAILROAD,IN THE BROOKLYN DAILY EAGLE , DECEMBER 30, 1900

Man will not fly for 50 years.

—WILBUR WRIGHT TO HIS BROTHER, ORVILLE, 1901

No flying machine will ever fly from New York to Paris.

—ORVILLE WRIGHT, 1908

Landing and moving around on the moon offer so many serious problems for human beings that it may take science another 200 years to lick them.

—SCIENCE DIGEST , 1948

Man will never reach the moon, regardless of all future scientific advances.

—LEE DE FOREST, RADIO PIONEER, 1957

What these predictions have in common is an absence of vision for what the future of technology would bring, even though the last two quotes explicitly (and wrongly) blame the limits of science. Fact is, no law of physics prevented any of those achievements, at any time. What’s on display is a lack of imagination I .

The term “universal” is commonly misapplied by Earth humans. Having not checked standards of beauty on other planets, the winner of the Miss Universe pageants should have always been named “Miss Earth.” The opening sequence for Universal Pictures, with full cinematic fanfare, shows—you guessed it—planet Earth. And how many times have we heard various human behaviors described as “universal”? Once again, that’s our ego run amok.

Anything truly universal should apply on Earth as in the heavens. That’s precisely what makes laws of physics universal, and it’s what allows us to set limits not only on Alien technology but on Alien physiology as well.

The justified audacity of this claim comes from simple reasoning: there is no understanding of biology without chemistry, and there is no understanding of chemistry without physics. And while it’s not obvious that this should be true, the laws of physics happen to manifest across all of space. For example, the spectra of stars and galaxies reveal, among other features, the chemical elements that comprise them. These spectra match precisely what we observe in Earth’s laboratories, telling us that quantum physics, which accounts for the formation of spectra, is indeed universal. Meanwhile, Newton’s laws of motion and gravity, as well as Einstein’s relativity, manifest everywhere we’ve looked in the universe, from nearby binary orbiting stars to distant galaxy clusters. These are not assumptions we make about the universe, they are experimentally and observationally verified objective truths.

Remarkably, the laws of physics discovered on Earth also apply across all of time, from present day back to the Big Bang itself. As we look out into space, we see the universe not as it is but as it once was, back when the light we observe was emitted. Indeed, the cosmos is a veritable time machine. Light travels about one foot per nanosecond—twelve inches every billionth of a second. So everything we see exists in our past. The person seated across the table from you is actually two- or three-billionths of a second older than what you observe. The Moon, 1.3 seconds older. The Sun, eight minutes and twenty seconds older. The Sun’s nearest neighbor, Proxima Centauri, four years and three months older. We observe the Milky Way’s neighbor, the Andromeda Galaxy, as it was 2.5 million years ago. The Cosmic Microwave Background hails from 13.8 billion years in our past. At every distance—at every cosmic time—the laws of physics manifest just as they do on Earth. It’s why science works at all.

All this leaves me saddened to report that smooth, rotating flying saucers are not a thing. They violate the conservation of angular momentum, which is physics-speak for declaring they cannot spontaneously spin up and spin down without some other thing to counter the rotational momentum. That’s why helicopters have tail rotors. Damage it and the chopper spins out of control. Helicopters designed without a tail rotor otherwise sport two counter-rotating main rotor blades, to compensate for each other’s angular momentum. You can also spin up via sideways jets that spew forth any kind of mass. Turn those same jets around by 180 degrees and they will slow down your rotation.

And how is it that flying saucers rotate, yet views out their front window do not show the outside swirling by? If you see a flying saucer approach with two counter-rotating disks, or with edge jets, then there’s a better chance you’re about to have an authentic Alien encounter.

As for sleek, aerodynamic spaceships, they look cool, but their only value is if you plan to travel supersonically through the air. Empty space makes no such demands on your design. An advanced spaceship coming upon Earth would never have to travel fast through our atmosphere. It could gently descend without the thermal drama of a reentry shield. If our own spaceships used fuel instead of aerobraking to slow down from orbit, we could descend gently as well.

Of course, when Aliens come to visit, we can be sure their technology will be greater, more advanced, and more sophisticated than anything we’ve dreamt of. They came from deep space. Whereas we cheer fellow humans who have ascended one hundred kilometers above Earth’s surface—the Kármán line II —and we call them astronauts. For reference, if Earth were shrunk to the size of a schoolroom globe, those twenty-first-century spacefaring tourists would have merely ascended the thickness of two dimes above Earth’s surface.

A common “wow” feature of UFO reports is their sudden and rapid acceleration across the sky, typically defying all known means of propulsion. Zero to a thousand miles per hour in just a second. Changing directions instantly. Cool. In that case, their ships would indeed require a sleek, aerodynamic design for rapid maneuvers within an atmosphere.

In physics, an acceleration is a change in speed and/or a change in your direction of motion. And unless the acceleration is mild, you’ll know it when it’s happening to you. Speed up and you feel pressure against your seat back. Slow down and you lean forward against the seat belt you should be wearing. Turn left and your body leans right. Turn right and your body leans left. At any constant speed and direction, your body feels nothing. In the 2014 “Speed” issue of Car and Driver magazine, I contributed an article that made the case for “I can’t wait to accelerate!” which had no hope of replacing the Top Gun (1986) aphorism “I feel the need for speed!” but I tried.

According to Newton’s famous equation relating force to acceleration, III practically any acceleration is possible if you apply a high-enough force. The high speeds of Alien craft, even if mysterious to twenty-first-century human technologists, is not the problem here. In most lethal accidents that involve motion, what kills you is the acceleration. Colloquially, what we call deceleration is simply a negative acceleration. So a high-enough acceleration will damage your internal organs and break your bones. This occurs regardless of whether you are rapidly slowing down, rapidly speeding up, or rapidly changing your direction of motion.

To reduce acceleration, you want to increase how long it takes you to change your speed or direction. That’s why high jumpers and pole vaulters don’t typically land on cement. Instead, they land on soft cushions, greatly slowing their change in speed, allowing the athletes to survive the fall for another attempt.

At the 2001 Daytona 500 car race, NASCAR legend Dale Earnhardt died in the final lap, during an abrupt collision with the track’s wall after a mild collision with another car. His body went from 160 miles per hour to zero in a fraction of a second. No tumbling wreckage. No spinning tires bouncing down the track. No explosive fire. Just a negative acceleration that amounted to about 60 times the acceleration of gravity, or “60-Gs.” We can calculate how much kinetic energy the car and driver carry at 160 miles per hour. Whatever it is, we know that at zero miles per hour, the kinetic energy is zero. Where did the energy go? It crumpled the car and broke the molecular bonds that keep a driver’s and passenger’s body whole and functioning.

In head-on collisions, the person’s torso is decelerated by the seat belt, which is attached to the car. Drivers of racecars typically use five-point harnesses—one above each shoulder, on each side of the hip, and one between the upper thighs. But the driver’s head maintains full forward velocity until it’s decelerated by the neck. Dale Earnhardt’s cause of death was a basilar skull fracture when his head separated from the top of his shoulders, which killed him instantly. 4

As evidence that people generally don’t think of such abrupt collisions as lethal or even dangerous, multiple YouTube compilations feature spectacular racecar accidents in which cars tumble down the track as they break apart and burst into flames. The tagline for the videos? “And They Walked Away.” What’s missing in their analysis is that the cars took extra time to come to a stop, greatly reducing the deceleration, greatly reducing the risk of death.

I know someone who became religious after he fell asleep at the wheel, careened off the road, and rolled his car before coming to a stop. The highway trooper, upon arriving at the scene, noticed the car’s wrecked condition, and declared, “It’s a miracle you survived!” Sometimes, not knowing the laws of physics can masquerade as divine intervention.

Back to our accelerating Aliens with their mysterious, high-force engines. Happy to grant them propulsion systems we don’t yet know how to make. If the Aliens are composed of biological tissue and not steel or some other rigid substance, and if the pilot and passengers accelerated from zero to one thousand miles per hour in a second, everyone on board will have experienced upward of 50-Gs, squashing them into a pile of goo for each impressive maneuver in our skies.

Why can a physicist make this claim? There are only four forces in the universe: the “strong nuclear force,” which holds atomic nuclei and nuclear particles together; the “weak nuclear force,” which mitigates radioactive decay; the “electromagnetic force,” which controls all interactions of atoms, molecules, and light energy in the universe; and, of course, the force of gravity. All molecules in the universe are assembled from atoms and held together by chemical bonds enabled by the electromagnetic force. Chemical bonds have thresholds of strength, above which they simply break. Typically, the larger the molecule, the more bonds it contains and the more susceptible it will be to an assault. Sink enough energy of any kind into a pool of molecules and you will break apart 100 percent of them into their constituent atoms. High acceleration of animate or inanimate matter is a means of spontaneously pumping energy into a system.

Eyewitnesses to UFO accelerations commonly describe them as silent. We don’t know how to do that yet. Our accelerations are quite noisy, although over the decades, thanks to the efforts of acoustic engineers, our cars, buses, trucks, commercial aviation engines, and most loud things have gotten steadily quieter. Old-timers may remember that when an airplane flew overhead, you had to pause conversations in the street until it passed. So loud were airplanes that in 1969, during the home World Series games played between the New York Mets and the Baltimore Orioles at Shea Stadium, Mayor John V. Lindsay requested that nearby LaGuardia Airport redirect their planes to not take off and land over the Stadium, lest announcers get frequently and frustratingly drowned out by engine noise.

What silently accelerating Aliens can’t circumvent is the sonic boom created upon crossing the sound barrier—Mach 1 IV . When moving slower than the speed of sound, air molecules gladly part for you. Exceed the speed of sound and the molecules cannot move out of your way fast enough, requiring your fuselage have a pointy nose and sleek wings to cleave its way through the air, creating a shock wave. That’s why all supersonic planes look badass. In Earth’s lower atmosphere, the speed of sound is around 750 miles per hour, depending on the air temperature. So, if you witness sudden acceleration that reaches high speeds in a fraction of a second with no sonic boom, you are likely misinterpreting what you see. But if there’s an accompanying sonic boom, it’s an actual craft moving through our actual atmosphere, and there may be actual dead Aliens on board.

For Aliens to arrive on Earth, they must traverse the vast distances of space. Space is mostly empty. How empty? Again, scale everything to a schoolroom globe: The International Space Station orbits 0.4 inches (1 centimeter) above the surface. The Moon orbits 10 feet away (3 meters). Mars, a mile away (1.6 kilometers). That’s why it takes human-made rockets eight minutes to reach Earth orbit, three days to reach the Moon, and nine months to reach Mars. Restoring Earth back to its actual size, consider the Asteroid Belt, “crowded” with large chunky rocks. There, however, the average distance between known asteroids is 600,000 miles. To visit us, Aliens need the technological ways and means to traverse long distances in presumably short time frames, and they need to know where they’re going, lest they become lost in space.

The twentieth-century Italian-American physicist Enrico Fermi thought about this problem (after creating the world’s first artificial nuclear reactor). He performed a simple “back of the envelope” calculation to assess whether Aliens should have visited us by now. We know the age of the Milky Way Galaxy—at least 13 billion years. We know how big it is—about 100,000 light-years across. We know approximately how many stars populate it—hundreds of billions. And let’s imagine that every star has at least one habitable planet. If Aliens are hell-bent on colonizing the Galaxy, and they’re technologically proficient, then, from their home planet, they might send a Mayflower -style mission to a nearby planet. The pilgrim Aliens would arrive, build a rocket factory, and send two more Mayflower -style missions to other nearby planets. If every mission creates two more missions then the number of Galactic colonies will grow exponentially. By this method you could populate 100 percent of the Galaxy’s habitable planets in a mere thirty-seven steps. V What about the travel time? If humans straddled our fastest-ever rocket out of the solar system—NASA’s New Horizons mission to Pluto at ten miles per second VI —to reach the Alpha Centauri system, a mere 4.2 light-years away, would take eighty thousand years. That duration is somewhat longer than our life expectancy, requiring us to send a generational ship, populated by a batch of fertile astronauts, while condemning the unborn to complete the mission set forth by the first generation that started it all. Two thousand generations later the ship arrives at a new planet. To cross the entire Galaxy, planet by planet, would take billions of years.

But we’re not talking about humans here. We’re talking about high-tech Aliens. Let’s say they figured out how to travel a modest 20 percent the speed of light. They could move among the stars in years, not billennia. At those speeds, the entire Galaxy could be populated within a few million years, rather than a few billion years. Still sounds like a long time, however a few million years is a mere 0.02 percent the age of the Galaxy. By this measure, the Aliens should have colonized every planet by now, including Earth. But all life on Earth has common DNA and common origin. No outsiders among us. Soooo, where are the Aliens? That is the essence of Fermi’s argument, which has come to be known as Fermi’s Paradox.

Since we already have the answer—they’re not here—it’s easy to invent all manner of excuses for why. The English physicist Stephen Webb, in a book titled If the Universe Is Teeming with Aliens… Where Is Everybody? , 5 proposes seventy-five solutions to that paradox. Here are a few:

Any one of those would explain why they’re not here. In combination, we have good reason to feel safe from an Alien invasion. But if you are sure they’re already here, masquerading as humans or as some other life-form, then there’s still a problem. Fundamental to the premise of the Fermi Paradox is that the Aliens arrive, set up shop, and send forth two more space missions in search of more planets. I think somebody would notice if that happened.

My favorite explanation, however, is called the Cosmic Quarantine Hypothesis, 7 developed by my Museum colleague Steven Soter in 2005. He explored the plausible fate of colonistically hungry life-forms. They have come to be called “grabby Aliens” 8 for whom finding and colonizing planets sits deeply in their urges, and they can’t stop themselves. We presume these Aliens have also mastered the science and technology that enables these ambitions.

As the wave of colonization continues across the Galaxy, spreading like mold in a petri dish, fewer and fewer habitable planets come available. But grabby Aliens always want more, more, more. Not all habitable planets are equally desirable, so conflict within the Alien species is inevitable as they fight each other for the fewer and fewer planets that remain. They might even fight each other over already settled planets. Rather than “I want a planet,” that’s a case of “I want YOUR planet.” The conflict reaches a tipping point when the entire race of Aliens is at war with itself, causing this exercise in Galactic colonization to implode.

Sounds far-fetched. But that’s exactly what happened on Earth with the great seafaring colonizing powers of England, France, Spain, Portugal, and the Netherlands. Add to that list the Japanese Empire, the Mongols, the Polynesians, and the Ottoman Empire and you have a single species of life carving up all desirable areas of Earth’s surface. That works until two colonizing powers confront each other, ultimately waging war between themselves for control over land of common interest. That grabby-Alien scenario across the Galaxy would surely be us, if our technology enabled it.

One of the great triumphs of modern science is the Periodic Table of Elements. Failed attempts to organize the elements, beginning with alchemists of centuries past, Isaac Newton included, finally succumbed, in 1869, to the genius of Russian chemist Dmitri Mendeleev. It’s more than just a list of the then sixty-three known elements. In tabular form, it reveals repeating properties of otherwise disparate elements. And where holes existed in the Table, new elements awaited discovery. The Table’s columns and rows capture properties that convey deep insight into the chemical behavior of atoms, in spite of it preceding by thirty years the discovery of the electron, which is responsible for all chemical reactions between elements.

A full understanding of why chemical periodicities existed at all in the Table would elude science until the discovery of quantum physics in the 1920s. Currently, we are rising through 118 known elements and there are no gaps. Ninety-two of these elements occur naturally in the environment and across the universe. From hydrogen, with one proton in its nucleus, through uranium, with ninety-two. We manufacture elements heavier than uranium in laboratories.

Well, then, if the Alien has any understanding at all of the chemical elements in the universe, it would (or should?) recognize the Periodic Table of Elements for the amount of information it condenses and organizes. So keep one of those in your pocket as well. Right next to the Pythagorean triangle. And that antimatter test coin. The Alien won’t recognize the chemical symbols we use, especially when many derive from Latin roots that don’t match the element’s common name, like Ag for silver, Au for gold, and Pb for lead. VII But the Table itself should be immediately recognizable, since we and the Alien live in the same universe, with access to the same elements, across time and space.

By now the Alien should be impressed with us. And if we’re lucky, it might want to teach us a thing or two about its own science and technology. That would be good, because if the Aliens are evil and want to harm us, our guns and missiles and bombs and baseball bats and tiki torches will likely be useless against them. If we fire upon Aliens, it will probably just piss them off, at which point we should, perhaps, run and hide.

The intent of Alien weaponry will be no different from anything millennia of human warfare has created. What all weapons have in common is the desire to take energy from here and put it over there. From the kinetic energy of your fist, to arrows shot by bows, to bullets shot by guns, to guided missiles, to electromagnetic ray guns. Most importantly, you want to ensure that the energy you transfer to your target exceeds the energy that protects or holds together the target you want to disable or destroy.

As already contemplated, more terrifying than an Alien who threatens to kill you with a ray gun might be an Alien who instead threatens to eat you. Many of the great fairy tales contain storylines where children are at risk of getting eaten—from “Little Red Riding Hood” to “Goldilocks and the Three Bears” to “Hansel and Gretel” to “Jack and the Beanstalk.” The threat reaches deep into our childhood fears. In yet another classic episode of The Twilight Zone called “To Serve Man” 9 a race of nine-foot-tall Aliens called the Kanamits land on Earth and teach us advanced crop sciences that greatly increase the yields of our farm production. Worldwide hunger is eradicated and everybody is well-fed. And all wars over limited resources end. The Kanamits then invite curious and interested humans to visit their home planet aboard their spaceship. People line up eagerly to embark on the voyage. We later learn from cryptographers that a book the Kanamits had accidentally left behind, titled To Serve Man , was not a primer on how to help humanity. Instead, it was… a cookbook.

The persistent portrayal of evil Aliens with advanced science, tools, and weaponry derives from how we suppose they will behave toward us. But maybe it’s unwittingly based on the actual evidence of how we know we have behaved against ourselves in the history of civilization. Encounters between humans wielding advanced technology and humans who don’t has never ended well for the humans who don’t. Colonization and slavery come to mind. But so does outright genocide.

H. G. Wells made this point in the first chapter of The War of the Worlds , attempting to engender understanding, if not sympathy for the invading Martians: 10

And before we judge of them too harshly we must remember what ruthless and utter destruction our own species has wrought.… The Tasmanians, in spite of their human likeness, were entirely swept out of existence VIII in a war of extermination waged by European immigrants, in the space of fifty years. Are we such apostles of mercy as to complain if the Martians warred in the same spirit?

So, space Aliens could be the most peaceful creatures in the universe, accompanied by a moral code exceeding anything yet attained by human civilization. But our storytelling has mirrored upon them the worst behaviors of humanity. We’ve seen the enemy, and it’s ourselves.