Alpha Centauri, the second closest star to Earth, is 4.37 light-years away. That's a tantalizingly close neighbor in an observable universe some 93 billion light-years wide. As we run out of objects to explore in our own solar system, it's among the most tempting places to visit.
Still, even our most ambitious spacecraft could never reach it in our lifetimes. The spacecraft New Horizons, which flew by Pluto last year, flies at around 33,000 miles per hour. That means it would take around 20,000 years to send a craft like it to Alpha Centauri. Humanity itself might not last that long.
So to get there, we'd have to come up with a radical new concept.
Today, Russian billionaire Yuri Milner and super-famous physicist Stephen Hawking announced they have arrived at one: teeny, tiny spacecraft.
They call their initiative the Breakthrough Starshot, and it involves propelling space vessels the size of postage stamps to 100 million miles per hour — 20 percent the speed of light. Facebook's Mark Zuckerberg also serves on the board of the project (Milner is fronting the initial investment).
At that speed, one of these "nanocrafts" can reach Alpha Centauri in 20 years. And because radio communications travel at the speed of light, it would only take an additional 4.37 years for the data from the mission to reach Earth.
"The limit that confronts us now is the great void between us and the stars," Hawking told reporters. "But now we can transcend it."
Milner and Hawking say the nanocrafts can be propelled by an array of lasers on Earth aimed at the craft's solar sails. Here's an animation of the concept. It's wild.
Hawking and Milner think it's possible to design such tiny spaceships because of Moore's law, which dictates microchips will keep getting smaller and more powerful. "This creates the possibility of a gram-scale wafer, carrying cameras, photon thrusters, power supply, navigation and communication equipment, and constituting a fully functional space probe," the Breakthrough Starshot website explains.
What's more, Hawking and Milner claim these "Starchips" will be relatively cheap to manufacture. "Once it is assembled and the technology matures, the cost of each launch is projected to fall to a few hundred thousand dollars," their website states. They won't have to stop at sending one nanocraft to Alpha Centauri — they could send dozens.
But take note: This will not be happening quickly. The New York Times reports Milner says it will take 20 years to get a working nanocraft into Earth's orbit. The Breakthrough Starshot website lists around 20 different engineering hurdles scientists will have to overcome before any of this is possible. For example, they'll need to design a battery to last the whole mission. In total, the project could cost $10 billion. Just getting a proof-of-concept spacecraft could cost $100 million.
Still, it's exciting. And as Hawking warns in a press statement: "Earth is a beautiful place, but it might not last forever. Sooner or later we must look to the stars." We may need to find a new home.