Spaceships pushed by LIGHT – the future of space travel?

I was at a TED talk yesterday and Hawkin announced he was working with a few others to design a ship that will travel 1/5 of the speed of light to Alpha Centuri. It's probe only a few mm across propelled by lasers from a whole field of transmitters at a giant sail. Supposedly it shouldn't be that long away and in theory the younger generation may be alive when the ship finally reaches its destination and transmits back. Incredible what the minds of today can create.