How many people do we need for a viable space colony?

Someday, either because of curiosity, necessity, or both, the human species will need to leave planet Earth and travel to the stars. But we must consider several important factors before we begin our journey. For example, how fast can we get to the planets we want to colonize, and how many people will we need to put on starships to make that happen? Although a previous study in 2002 stated that only 150 people would be needed, a new study by John Moore at the University of Florida estimates that the number is closer to 10,000, or even possibly 40,000 will be necessary.

So why so many people? The first thing to look at is that even the nearest star system, Proxima Centauri, is over four light-years away from Earth. At our current technology level, it would take us thousands of years to get there. This means we’d need to have a starship where generations are born and then die without ever seeing the planet that will eventually be colonized, not to mention the planet that they came from. 150 people could probably handle that, but there would be very little genetic diversity, which could increase susceptibility to genetic diseases. In Moore’s study, a larger number — at least 10,000 people — would ensure viable diversity in the human gene pool.