Using a giant set of lasers to catapult thousands of miniature spacecraft 25 trillion miles to the Alpha Centauri star system may sound like the stuff of science fiction.

But Internet entrepreneur and science philanthropist Yuri Milner, in collaboration with renowned cosmologist Stephen Hawking and Facebook CEO Mark Zuckerberg, is placing a $100-million bet that he can turn this into science reality within a generation.

Milner announced on Tuesday the creation of "Breakthrough Starshot," a research project meant to prove that it's possible to propel nanoscale spacecraft at one-fifth the speed of light. (See animation below.)

That's equal to 60 million meters per second, or 134 million miles per hour. At this speed, the craft would reach our nearest star system in about 20 years, or more than a thousand times quicker than today’s fastest spacecraft, Milner says.

On top of that, each spacecraft would weigh no more than 20 grams -- roughly equivalent to a toothbrush.

While the main body of the spacecraft is likely to be smaller than the size of a credit card, it would contain cameras, photon thrusters and a power supply, plus navigation and communication equipment, Milner told The Huffington Post. The craft would be propelled by beaming Earth-based lasers at an onboard "lightsail" that would be a few meters tall but no more than a few hundred atoms thick.

The concept of a lightsail is not new. Milner said the first person to have discussed the idea was German astronomer Johannes Kepler, who in 1608 wrote a letter to Italian astronomer Galileo Galilei, predicting that a space sail could capture sunlight the way a boat uses the wind.

"For thousands of years, people have been looking up at the stars and thinking about how we get there," he said. "It’s an interesting circle that so much of the exploration in ancient times was done with the sail and the wind, and we are now using the same approach."

According to Milner, advances in technology mean that most of the knowledge needed to build nano-spacecraft is already available or likely to be attainable in the near future. He credits three major developments in the past 15 years that make it conceivable to break out of our solar system: One is that sophisticated electronic devices can be made much smaller and more cheaply than ever before. The second is that we can produce very thin and lightweight materials. The third is that it is now possible to link together a number of lasers.

"If one of those developments would not happen, we could not be talking about this project," he said. "There are engineering challenges ahead, but we know that, in principle, it can be done."

So much of the exploration in ancient times was done with the sail and the wind, and we are now using the same approach. Yuri Milner

Opening up a new era in space exploration is the latest stage in Milner’s ambitious "Breakthrough" project to search for life in the universe. Last year, the early Facebook and Twitter investor said he committed $100 million for "Breakthrough Listen" to search for signs of intelligent life beyond Earth, and launched "Breakthrough Message," an international competition to generate messages that might one day be sent to alien civilizations.

The public should not worry that sending the nanocraft outside our solar system would alert potentially hostile extraterrestrial life to our existence, Milner said.

Astronomers say there is a reasonable chance that an Earthlike planet exists in the "habitable zones" of Alpha Centauri’s three-star system. But Milner said initial research had shown that while simple life forms might exist there, it's highly unlikely that the system harbors intelligent life. By the time the nanocraft are ready to launch, Milner says we will know a lot more about that region of the universe.

Wikimedia Commons: Skatebiker In this photo, the two bright stars are Alpha Centauri (left) and Beta Centauri (right), and the faint red star in the center of the red circle is Proxima Centauri. It could be just a couple of decades before we're able to spend spacecraft to explore them, says entrepreneur Yuri Milner.

Besides looking for the first signs of extraterrestrial life, Milner said, Breakthrough Starshot would provide valuable information about our galaxy and give early warning about meteors that might be on a collision course with Earth.

Hawking suggested that the project could also help identify planets that human beings could colonize, if his worst fears come true that humanity could destroy itself in the next 100 years.

He said in a statement that "Earth is a wonderful place, but it might not last forever. Sooner or later, we must look to the stars. Breakthrough Starshot is a very exciting first step on that journey.”

Milner envisions releasing thousands of nanocraft from a high-flying mother ship, dwarfed by the roughly kilometer-wide laser launch system needed to speed them on their way. Essentially an array of lasers, this "light beamer" would need to generate 100 gigawatts to get the spacecraft up to the necessary speed, he said.

Ivan Alvarado / Reuters A view of the radio telescopes that make up the Atacama Large Millimeter Array, or ALMA, in Chile's Atacama desert on March 12, 2013.

According to Milner, the beamer would ideally be built in space, but it would be prohibitively expensive to do so. What's more, he said, "having a big generator of power in space is not acceptable from a policy standpoint," even though it would not have a destructive capability.

Milner instead proposes building the laser system at high altitude and in a dry climate, like Chile's Atacama Desert. The driest non-polar desert in the world, it's already home to many of the world’s biggest telescopes.

The laser array would need to be powered up for just a few minutes and would create about the amount of energy that's needed for a NASA space shuttle's liftoff.

If Milner and his team can prove the feasibility of Breakthrough Starshot, he says it will require international cooperation on the scale of CERN, the European Organization for Nuclear Research, to make the project a reality. The world's largest physics laboratory, CERN spent about $13.5 billion to discover the Higgs boson subatomic particle, and Milner says a similar amount of money would be needed to scale up Breakthrough Starshot.

Once Milner's new venture is up and running, he says, the cost of launches would become progressively cheaper. The body of the craft could be mass-produced at the same cost of an iPhone, and the light beamer can easily be modified over time to save money. Once it is assembled and the technology matures, he expects the cost of each launch to fall to a few hundred thousand dollars.

The public should not worry that sending the nanocraft outside our solar system would alert potentially hostile extraterrestrial life to our existence, Milner said.

Milner, who was named after Yuri Gagarin, the Soviet cosmonaut who became the first human to journey into outer space in 1961, says the Breakthrough Starshot project has been a lifelong dream of his.

"Every time someone calls me Yuri, I get reminded that I was named after someone who was the first man in space," he told HuffPost. "There was a lot of excitement at the time, and I carry a part of that excitement in my name."

Now is the first time in history that it's really possible to reach for the stars, he said. "Many people have dreamed about this and made films about it, but for the first time ever, we can actually do it within one generation ... To think that it can actually be done -- not in the way you would see in Star Wars, where there are huge spaceships going through wormholes, but by sending small robots that represent us -- this is very exciting."

Still, Milner played down any comparison with President John F. Kennedy’s 1961 moonshot speech, in which he called for America to put a man on the moon by the end of that decade.

"I don’t really make that type of comparison," Milner said. "I think every generation should have its own challenges, and sometimes they will be achieved and sometimes not achieved. But if it is something in principle which is achievable, we should be trying to do that."

Scroll through the timeline below for a look at the history of spaceflight.