A HALF CENTURY ago astronomers designed a map that might point to Earth from anywhere within the galaxy. Then they sent it into space, reasoning that any aliens smart enough to intercept a spacecraft could decode the map and uncover its origin. Many movies & television shows have used variations on this theme as a plot point, but we didn’t borrow it from fantasy . It’s reality.
Truth is, this tale has been a part of my family’s lore since before i used to be born. Growing up, I’d heard stories about the map and seen its depiction on multiple interstellar spacecraft, and a number of other years ago, I found the real , penciled-in pathway to Earth where my parents had stashed it.
That was an exciting find! Then came the buzzkill: This original map won’t be good for for much longer , cosmically speaking. The signposts it uses will disappear within tens of many million years, and albeit they don’t, the map would point toward our home for less than a fraction of the 200 to 250 million years it takes the sun and other nearby stars to spin once round the Milky Way .
Sure, the probabilities of aliens intercepting the map are astronomically improbable—but if that did happen, an outdated map would be useless instead of helpful. which wasn’t the goal.
Why on Earth does this map even exist?
It was December 1971, and NASA was preparing to launch Pioneer 10, a spacecraft that might sweep by Jupiter and make the primary reconnaissance of the solar system’s biggest planet. More stunningly, though, Pioneer 10’s brush by Jupiter would sling it onto an interstellar trajectory, making it the 1st ever human-made object destined to go away the solar system .
With a small help from his friends, the astronomer Carl Sagan decided that the craft need to carry a greeting from humanity—a message identifying and commemorating Pioneer’s makers that might be interpretable by anyone who found it. NASA agreed and gave Carl but a month to style the message.
This is when Carl’s friend, the astronomer Frank Drake, enters the story. Frank also my dad, and among other notable accomplishments, he’s credited with conducting the primary scientific look for noisy aliens and with formalizing a framework for estimating the amount of detectable alien civilizations within the Milky Way galaxy.
Carl asked Dad for help crafting the message while the 2 of them were in San Juan, Puerto Rico, for a gathering of the American Astronomical Society. Dad recalls that, within the lobby of the San Gerónimo Hilton, he and Carl quickly came up with ideas about what to include: line drawings depicting humans, a rendering of the spacecraft—and then, “in subsequent moment, we hit on the thought of a galactic map that might pinpoint the situation of Earth in space.”
Dad designed that map, and in 1972 it flew into space aboard Pioneer 10. subsequent year Pioneer 11 launched, ultimately carrying the map past Saturn and now on to the celebs . Then in 1977 both Voyager spacecraft left Earth carrying Dad’s guide to finding our planet, which is etched onto the duvet of the “golden record.” The way Dad designed the map means it points back to Earth both in space and in time, making it a galactic positioning system (a different quite GPS) in 4-dimensions.
At the time, Dad and Carl didn’t really worry that the aliens who found their message inbottle could be of the more malevolent variety.
How the map was made
Our galactic neighborhood has no obvious street signs, and crafting a map pointing to at least one planet among the billions (and billions) of worlds populating the Milky Way is not any simple feat.
Finding Earth means finding solar system , and therefore the sun is quite unremarkable. There’s really no way to distinguish it from the opposite several 100 billion stars in galaxy, each of which is tracing its own path round the galactic center and slowly shifting in location relative to its neighbors. That stellar jostling means the constellations spangling Earth’s skies won’t be an equivalent in our near future—nor do the celebs align within the same recognizable configurations from anywhere aside from the solar neighborhood. In fact, in about 2,000 years, Polaris will not longer be the Polaris , even as it had been not the polestar for ancient Egyptian, Babylonian, and Chinese sky-watchers.
So, what to do? Though normal stars with churning nuclear engines in their cores won’t have distinctive fingerprints, Dad realized that pulsars—the corpses of stars that when were much larger than the sun—are potentially uniquely identifiable. Discovered in 1967, pulsars spin very rapidly, often 100 times per sec. Using powerful radio telescopes, astronomers can measure with extreme precision how quickly pulsars rotate, meaning that every of those spinning stellar relics writes its own signature in space. Dad selected 14 pulsars that would triangulate Earth’s position, and he coded information about their rotation rates into the map.
It’s not your typical map
Appropriately, Dad’s pulsar map seems like a flowery asterisk, a radial explosion of hatched lines that intersect at our solar system’s location. Briefly, here’s how his map works:
Each of the lines connect Earth to a pulsar. The hatch marks are binary numbers that reveal the pulsar’s rotation rate (at the time the map was designed), & line lengths are roughly proportional to distance. a number of the pulsars parked on Dad’s map—for ex, the Crab and Vela—sit in centers of lovely nebulae created during the pulsars’ violent formations. Presumably, any civilizations sharp enough to detect and snare a quiet interstellar spacecraft would realize pulsars. And by matching the rotation periods on the map with stellar signposts within the sky, aliens could find their ways to Earth relatively easily.
In addition, because the energy we see from pulsars comes from their spin and that they hamper over time, Dad’s map also points to Earth within the time . By calculating the difference between the observed and coded rotation periods—a difference which will be apparent after 1000 of years—aliens could find out how way back the map was made.
Perhaps somewhat surprisingly, Dad’s map became lodged in popular imagination and is now commonly found on everything from T-shirts to tattoos. i assume there’s something captivating about always having the ability to seek out your way home, even within the most cosmic sense imaginable.
Keeping it in family
Several years ago, 2 significant things happened. I found the real , penciled-in pulsar map, folded away and casually tucked into a tomato box up my parents’ closet. and that i linked up with a cragsman named Scott Ransom, one among the world’s more prolific pulsar astronomers.
Scott had been brooding about the Voyagers, the “golden record,” and therefore the pulsar map since he was a 10-year-old in Mansfield, Ohio, watching Carl’s Cosmos television program . Some years and an astronomy Ph.D. later, he realized that Dad’s map features a near-future expiration date. Its Achilles’ heel is that the same property that lets it pinpoint Earth in time: Pulsars hamper , and therefore the ones Dad had chosen would fade and disappear within several million years, give or take a couple of millennia.
Coincidentally, Scott had began to form a new , more precise, and longer-lived pulsar map even before we moved in together and portmanteau’d ourselves into the Dranksomes. Now I write the words that tell our stories, and Scott does the important cartographic stuff like choosing pulsars and deriving their binary codes. He occasionally drafts some text passages, but you’ll never catch me committing academic acts of astronomy.
A newer, better map to Earth
Scott’s new map may be a GPS for the ages. It navigates to Earth using pulsars both inside and out of doors the Milky Way , with a twist.
Instead of the more ordinary pulsars Dad selected, the new map employs millisecond pulsars that spin faster, last longer, and have also-dead orbital companions. These binary pulsars afford a second set of identifiers: the orbital period of the system, which doesn’t change over billions of years. And, crucially, millisecond pulsars age far more slowly than those in Dad’s map, meaning that it takes 1000 of times longer for spins to become unrecognizable.
In addition, Scott included another layer of signposts: pulsars in globular clusters orbiting the Milky Way . Ancient clumps of stars that predate the Milky Way , globular clusters are gorgeous and mysterious, and that they are veritable millisecond pulsar factories.
By including signposts in these hard-to-miss stellar globs outside the galaxy, Scott’s map allows Earth to be discoverable for billions of years, even after the Milky Way’s stars have trekked round the galactic core multiple times, shuffling their positions and obliterating constellations.
And Dad, for the record, thinks that’s spectacular.
But first, someone has got to read it
Dad’s map, of course, remains out there—but likelihood is that slim to zero that the Pioneers or Voyagers carrying it’ll be intercepted. Though all 4 spacecraft are on interstellar trajectories, space is big, and therefore the next stellar systems on the horizon are many 1000 of years away. Plus, the spacecraft are tiny and can be completely quiet within subsequent few decades, making them extremely hard to detect.
As for sending the new map: There’s no Voyager-like space guided probe scheduled for launch anytime soon. But if this map did hitch a ride beyond our system , and if it got scooped up by intelligent space aliens, the map should be quite easy for them to read and follow.
That raises all kinds of questions: Would aliens at those distances have the means to succeed to reach Earth? If so and that they head our way, what if they don’t are available peace? What if they’re hangry? And what if they’re not vegetarians?
Here’s the elemental question that didn’t stop Carl and Dad: Is it an honest idea to randomly send our address into the cosmos? Today, some folks would haven’t any reservations, as long as earthly transmissions already are leaking into space and, traveling at the speed of light , are detectable by anyone with an honest radio reflector living within 100 light-years folks . folks , perhaps more cautiously, would hold off on announcing our presence until we all know if ETs have honorable intentions.
As for the Dranksomes: We’d gladly send the new map to Earth, as a bid to make sure that our presence as a species would survive in some form. If that message in bottle were finally picked up, after bobbing and drifting through the galactic ocean for millions or billions of years, someone would know that Earthlings did exist—or, with luck, still do.