The World Without Us

DURING THE 1890s, a Serbian immigrant to America, Nikola Tesla, and an Italian, Guglielmo Marconi, each patented devices capable of sending wireless signals. In 1897, Tesla demonstrated sending ship-to-shore pulses across bodies of water in New York, even as Marconi was doing the same among various British isles—and, in 1901, across the Atlantic. Eventually they sued each other over the claim, and the royalties, to the invention of radio. No matter who was right, by then transmission across seas and continents was routine.

And beyond: Electromagnetic radio waves—waves much longer than poisonous gamma radiation or ultraviolet sunlight—emanate at the speed of light in an expanding sphere. As they move outward, their intensity drops by a factor of one over the distance squared, meaning that at 100 million miles from Earth, the signal strength is one-fourth what it was at 50 million miles. Nevertheless, it is still there. As the sphere of a transmission’s surface expands through the Milky Way, galactic dust absorbs some of the radio radiation, attenuating the signal further. Still, it keeps going.

In 1974, Frank Drake beamed a three-minute radio greeting from the largest radio dish on Earth, the 1,000- foot, half-million-watt Arecibo Radio Telescope in Puerto Rico. The message consisted of a series of binary pulses that an extraterrestrial mathematician might recognize as representing a crude graphical arrangement, depicting the sequence 1 through 10, the hydrogen atom, DNA, our solar system, and a human-shaped stick figure.

The signal, Drake later explained, was about a million times stronger than a typical TV transmission, and was aimed at a star cluster in the constellation Hercules, where it wouldn’t arrive for 22,800 years. Even so, due to the subsequent outcry over possibly having revealed Earth’s whereabouts to superior, predatory alien intelligences, members of the international community of radio astronomers agreed to never unilaterally expose the planet to such a risk again. In 2002, that accord was ignored by Canadian scientists who directed lasers heavenward. But as Drake’s broadcast has yet to elicit a response, let alone an attack, the chance that anything might cross their tight beams can’t be meaningfully computed.

Besides, the cat may long be out of the bag. For more than a half-century, we’ve been sending signals that by now would take a very large or very sensitive receiver to collect—yet, considering the size of the intellect that we imagine might be out there, it’s not impossible.

In 1955, a little more than four years after leaving a TV studio in Hollywood, signals bearing the first sound and images of the I Love Lucy show passed Proxima Centauri, the nearest star to our sun. A half-century later, a scene with Lucy disguised as a clown sneaking into Ricky’s Tropicana Night Club was 50-plus light-years, or about 300 trillion miles, away. Since the Milky Way is 100,000 light-years across and 1,000 light-years thick, and our solar system is near the middle of the galactic plane, this means in about AD 2450 the expanding sphere of radio waves bearing Lucy, Ricky, and their neighbors the Mertzes will emerge from the top and bottom of our galaxy and enter intergalactic space.

Before them will lie billions of other galaxies, over distances we can quantify but can’t really comprehend. By the time I Love Lucy reaches them, it’s unclear how anything out there would be able to make much sense of it, either. Distant galaxies, from our perspective, are moving away from each other, and the farther away they are, the faster they move—an astronomical quirk that appears to define the very fabric of space itself. The farther radio waves go, the weaker they become, and the longer they appear. Out at the universe’s edge, 10 billion-plus light-years away from now, light from our galaxy seen by some superintelligent race would appear shifted to the red end of the spectrum, where the longest wavelengths lie.

Massive galaxies in their path would further distort radio waves bearing the news that in 1953, a baby boy was born to Lucille Ball and Desi Arnaz. It would also increasingly compete with the background noise from the Big Bang, the original birth cry of the universe, which a consensus of scientists dates to at least 13.7 billion years ago. Just like Lucy’s broadcast shenanigans, that sound has been expanding at the speed of light ever since, and thus pervades everything. At some point, radio signals become even weaker than that cosmic background static.

But however fragmented, Lucy would be there, even fortified by the far more robust ultrahigh-frequency broadcasts of her reruns. And Marconi and Tesla, the most gossamer of electronic ghosts by now, would have preceded her, and Frank Drake after them. Radio waves, like light, keep expanding. To the limits of our universe and our knowledge, they are immortal, and broadcast images of our world and our times and memory are there with them.

As the Voyagers and Pioneers erode away to Stardust, in the end our radio waves, bearing sounds and images that record barely more than a single century of human existence, will be all the universe holds of us. It’s hardly an instant, even in human terms, but a remarkably fruitful—if convulsive— one. Whoever awaits our news at the edge of time will get an earful. They may not understand Lucy, but they will hear us laugh.

CHAPTER 19 The Sea Cradle

THE SHARKS HAVE never seen humans before. And few humans present have ever seen so many sharks.

Except for moonlight, the sharks have also never seen the equatorial night be anything other than dark and deep. Nor have the eel fish, which resemble 5-foot silver ribbons with fins and needle snouts as they skitter up to the research vessel White Holly’s steel hull, entranced by shafts of color drilled into the night sea by spotlights from the captain’s deck. Too late, they notice that the waters here are boiling with dozens of white-tipped, black-tipped, and gray reef sharks racing in delirious circles that scream hunger.

A quick squall comes and goes, blowing a curtain of warm rain across the lagoon where the ship is anchored and drenching the remains of a deckside chicken dinner eaten over a plastic tarp stretched across the dive master’s table. Still, the scientists linger at the White Holly’s railing, fascinated by thousands of pounds of sharks—sharks proving that they rule the food pyramid here by snatching eel fish in mid-flight as they leap between swells. Twice a day for the past four days, these people have swum among such sleek predators, counting them and everything else alive in the water, from swirling rainbows of reef fish to iridescent coral forests; from giant clams lined with velvety, multihued algae down to microbes and viruses.

This is Kingman Reef, one of the hardest places to reach on Earth. To the naked eye, it barely exists: a change from cobalt blue to aquamarine is the main clue that a nine-mile-long coral boomerang lies submerged 15 meters below the surface of the Pacific, 1,000 miles southwest of Oahu. At low tide two islets rise barely a meter above the water, mere slivers consisting of giant clamshell rubble heaped by storms against the reef. During World War II, the U.S. Army designated Kingman a way-station anchorage between Hawaii and Samoa, but never used it.

^{Gray reef shark. Carcharhinus amblyrhynchos. Kingman Reef.}

^{J. E. MARAGOS, U.S. FISH AND WILDLIFE SERVICE.}

Two dozen scientists aboard the White Holly and their sponsor, Scripps Institution of Oceanography, have come to this water-world-without-people to glimpse what a coral reef looked like before human beings appeared on Earth. Without such a baseline, there can be little agreement on what constitutes a healthy reef, let alone on how to help nurse these aquatic equivalents of rain forest diversity back to whatever that might be. Although months of sifting data lie ahead, already these researchers have found evidence that contradicts convention, and seems counterintuitive even to themselves. But there it is, thrashing just off starboard.

Between these sharks and an omnipresent species of 25-pound red snappers equipped with noticeable fangs—one of which sampled a photographer’s ear—it appears that big carnivores account for more total biomass than anything else here. If so, that would mean that at Kingman Reef, the conventional notion of a food pyramid is standing on its pointy head.

^{Two-spot red snapper. Lutjanus bohar, Palmyra}