How to colonize the galaxy by using very slow crafts? There is the possibility that we ever can make things like FTL (Faster-Than-Light) technology. But there is another way to travel between stars. And that technology is called "generation ships". Those crafts would reach about 1-20% of the speed of light. And that thing means that travel to the nearest solar systems takes even thousands of years. In that version, generations will change inside the craft. And when the journey ends to Alpha Centauri or Bernard Star the people inside that craft are forgetting the Earth. And they might think of their craft as home. Those generation ships require lots of genetic material. For denying the genetic matter degeneration. The degeneration predisposes the organism to hereditary diseases. So the crew must modify the genomes of the next generations. So that the variation of the DNA is high enough. That craft could be a giant O'Neill cylinder. And when that cylinder travels in