In a 1610 correspondence to Galileo Galilei, Johannes Kepler noted, “Ships and sails proper for the heavenly air should be fashioned. Then, there will also be people, who do not shrink from the dreary vastness of space.” Now, more than four centuries later, the Russian venture capitalist Yuri Milner is applying these principles to modern day space exploration.

Human travel to our nearest star system, Alpha Centauri, will not be possible for many years, if ever. However, in the near future, robots might be able to make the trip in an inexpensive and scalable way. Using a solar sail, a nearly weightless spaceship and a powerful beam of light, probes could travel the 4 light years to Alpha Centauri in only 20 years. The most expensive piece of equipment, the beam of light, will stay on the planet, and each spaceship will cost only as much as a smartphone. With this scalable model, our earthly civilization might someday become truly galactic.