Last month, Russian billionaire Yuri Milner, joined by Stephen Hawking and other esteemed scientists, announced a plan that still sounds impossibly brazen: They want to send a fleet of tiny probes to Alpha Centauri, the nearest star to our own. The $100 million Breakthrough Starshot initiative would beam lasers from Earth onto a few hundred metal sails, accelerating them to one-fifth the speed of light. If all went well, the probes would only need two decades to reach Alpha Centauri, and another 4 years to beam back images of any planets orbiting the system.
The plan is audacious, to say the least. But if it worked, we might be able to do more than send wisps of metal to another star. The laser that sent them packing would also be the biggest lighthouse in the cosmos—that we know of—and we could use it to let other civilizations know we’re here. Its beam could travel well beyond Alpha Centauri, to any planet orbiting any star in the observable universe, says Philip Lubin of the University of California, Santa Barbara.He studies directed energy for propulsion, and his research, which is funded by NASA, is the driving force behind Breakthrough Starshot. Like using a garden hose to roll a soccer ball, directed energy from a laser pushes and steers a spacecraft. Lubin says he realized that this same intense energy source could also be used as a lighthouse, or rather, an interstellar flare gun of sorts.
“We’ve reached the point that we can project our presence throughout the universe. We’ve never been able to make that statement before,” Lubin says. “We’ve evolved technologically to the point that another civilization like us, anywhere in the universe, could detect us. And vice versa is, of course, much more interesting.”
We already broadcast radio waves constantly, but we haven't intentionally sent out messages of our own, apart from a few short-lived, quixotic projects. Astronomers have proposed building optical or radio-wave lighthouses for some time, however—and in recent years, they have studied how we might search the cosmos for someone else’s beacon. Recent leaps forward in laser technology and optics, which are advancing at roughly the breakneck pace of semiconductors, mean these signals could soon become powerful enough to reach the whole observable cosmos, Lubin says.
He studies directed energy for propulsion, and his research, which is funded by NASA, is the driving force behind Breakthrough Starshot. Like using a garden hose to roll a soccer ball, directed energy from a laser pushes and steers a spacecraft. Lubin says he realized that this same intense energy source could also be used as a lighthouse, or rather, an interstellar flare gun of sorts.