If climate change escalates, and we are unable to mitigate its effects, humanity is going to need a plan B to planet Earth. Some scientists think our next best option is a 1000-year space mission to save future generations from extinction.

Their target is a planet called Proxima Centauri b, an exoplanet in a habitable zone of a star similar to our sun. This means that theoretically water could exist in liquid form there and, the thinking goes, thus it could support human life. We don’t know what the atmosphere is like, or whether the planet’s surface is too hot or too cold to sustain living organisms as we know them.

A program founded by science philanthropist Yuri Milner and the late Stephen Hawking is building a spacecraft weighing only a few grams that would be propelled by a 100-billion-watt laser fired at it from earth. The craft would take 20 years to reach the Alpha Centauri solar system, where Proxima Centauri b is located. It’s a step toward building a new kind of spacecraft, one big enough to transport us deep into space on a 1,000-year journey to reach humanity’s new home.