Can you fly an iPhone to the stars?

In an attempt to leapfrog the planets and vault into the interstellar age, a bevy of scientists and other luminaries from Silicon Valley and beyond, led by Yuri Milner, a Russian philanthropist and Internet entrepreneur, announced a plan on Tuesday to send a fleet of robot spacecraft no bigger than iPhones to Alpha Centauri, the nearest star system, 4.37 light-years away.

If it all worked out — a cosmically big “if” that would occur decades and perhaps $10 billion from now — a rocket would deliver a “mother ship” carrying a thousand or so small probes to space. Once in orbit, the probes would unfold thin sails and then, propelled by powerful laser beams from Earth, set off one by one like a flock of migrating butterflies across the universe.

Within two minutes, the probes would be more than 600,000 miles from home — as far as the lasers could maintain a tight beam — and moving at a fifth of the speed of light. But it would still take 20 years for them to get to Alpha Centauri. Those that survived would zip past the star system, making measurements and beaming pictures back to Earth.