The Atlantic has a great piece on the E.T.-hunting radio telescope that China just built (it’s twice the size of Arecibo) with a little input from China’s greatest living science fiction author, Liu Cixin:
In some ways, it’s no surprise that Liu was invited to see the dish. He has an outsize voice on cosmic affairs in China, and the government’s aerospace agency sometimes asks him to consult on science missions. Liu is the patriarch of the country’s science-fiction scene. Other Chinese writers I met attached the honorific Da, meaning “Big,” to his surname. In years past, the academy’s engineers sent Liu illustrated updates on the dish’s construction, along with notes saying how he’d inspired their work.
But in other ways Liu is a strange choice to visit the dish. He has written a great deal about the risks of first contact. He has warned that the “appearance of this Other” might be imminent, and that it might result in our extinction. “Perhaps in ten thousand years, the starry sky that humankind gazes upon will remain empty and silent,” he writes in the postscript to one of his books. “But perhaps tomorrow we’ll wake up and find an alien spaceship the size of the Moon parked in orbit.”
Even without federal funding in the United States, seti is now in the midst of a global renaissance. Today’s telescopes have brought the distant stars nearer, and in their orbits we can see planets. The next generation of observatories is now clicking on, and with them we will zoom into these planets’ atmospheres. seti researchers have been preparing for this moment. In their exile, they have become philosophers of the future. They have tried to imagine what technologies an advanced civilization might use, and what imprints those technologies would make on the observable universe. They have figured out how to spot the chemical traces of artificial pollutants from afar. They know how to scan dense star fields for giant structures designed to shield planets from a supernova’s shock waves.
In 2015, the Russian billionaire Yuri Milner poured $100 million of his own cash into a new seti program led by scientists at UC Berkeley. The team performs more seti observations in a single day than took place during entire years just a decade ago. In 2016, Milner sank another $100 million into an interstellar-probe mission. A beam from a giant laser array, to be built in the Chilean high desert, will wallop dozens of wafer-thin probes more than four light-years to the Alpha Centauri system, to get a closer look at its planets. Milner told me the probes’ cameras might be able to make out individual continents. The Alpha Centauri team modeled the radiation that such a beam would send out into space, and noticed striking similarities to the mysterious “fast radio bursts” that Earth’s astronomers keep detecting, which suggests the possibility that they are caused by similar giant beams, powering similar probes elsewhere in the cosmos.
Andrew Siemion, the leader of Milner’s seti team, is actively looking into this possibility. He visited the Chinese dish while it was still under construction, to lay the groundwork for joint observations and to help welcome the Chinese team into a growing network of radio observatories that will cooperate on seti research, including new facilities in Australia, New Zealand, and South Africa. When I joined Siemion for overnight seti observations at a radio observatory in West Virginia last fall, he gushed about the Chinese dish. He said it was the world’s most sensitive telescope in the part of the radio spectrum that is “classically considered to be the most probable place for an extraterrestrial transmitter.”
Before I left for China, Siemion warned me that the roads around the observatory were difficult to navigate, but he said I’d know I was close when my phone reception went wobbly.
The collective energy of all the radio waves caught by Earth’s observatories in a year is less than the kinetic energy released when a single snowflake comes softly to rest on bare soil. Collecting these ethereal signals requires technological silence. That’s why China plans to one day put a radio observatory on the dark side of the moon, a place more technologically silent than anywhere on Earth. It’s why, over the course of the past century, radio observatories have sprouted, like cool white mushrooms, in the blank spots between this planet’s glittering cities. And it’s why Nan went looking for a dish site in the remote Karst mountains. Tall, jagged, and covered in subtropical vegetation, these limestone mountains rise up abruptly from the planet’s crust, forming barriers that can protect an observatory’s sensitive ear from wind and radio noise.
Siemion told me he’s especially excited to survey dense star fields at the center of the galaxy. “It’s a very interesting place for an advanced civilization to situate itself,” he said. The sheer number of stars and the presence of a supermassive black hole make for ideal conditions “if you want to slingshot a bunch of probes around the galaxy.” Siemion’s receiver will train its sensitive algorithms on billions of wavelengths, across billions of stars, looking for a beacon.
Liu Cixin told me he doubts the dish will find one. In a dark-forest cosmos like the one he imagines, no civilization would ever send a beacon unless it were a “death monument,” a powerful broadcast announcing the sender’s impending extinction. If a civilization were about to be invaded by another, or incinerated by a gamma-ray burst, or killed off by some other natural cause, it might use the last of its energy reserves to beam out a dying cry to the most life-friendly planets in its vicinity.
Even if Liu is right, and the Chinese dish has no hope of detecting a beacon, it is still sensitive enough to hear a civilization’s fainter radio whispers, the ones that aren’t meant to be overheard, like the aircraft-radar waves that constantly waft off Earth’s surface. If civilizations are indeed silent hunters, we might be wise to hone in on this “leakage” radiation. Many of the night sky’s stars might be surrounded by faint halos of leakage, each a fading artifact of a civilization’s first blush with radio technology, before it recognized the risk and turned off its detectable transmitters.
Plenty more at the link. I encourage you to read the whole thing.
[via Mme Boyer]