George Dvorsky in io9:
A new study suggests that by using the slingshot effect to propel self-replicating probes through interstellar space, an advanced extraterrestrial civilization should be able to visit every corner of the galaxy in a startlingly short amount of time. The Fermi Paradox, it would seem, is alive and well.
Before we get to the new study, let’s quickly review what we mean by self-replicating probes and their relation to the Fermi Paradox.
The hypothetical self-replicating probe (SRP) is an idea that’s been around since the 1940s. Devised by the brilliant mathematician John von Neumann (which is why they’re also called Von Neumann probes), it’s a non-biological system that can replicate itself. Von Neumann wasn’t thinking of space exploration and colonization at the time, but other thinkers, like Freeman Dyson, Eric Drexler, and Robert Freitas, have since extended his idea to exactly that.
Once launched into space, an SRP could travel to a neighboring star system, and through the application of robotics, molecular assembly, and AI, seek out resources to build an exact replica of itself. Really, all it would need to do is find an asteroid with the right material components.