User blog comment:Arbington/The Next Cycle/@comment-2094653-20120803225240/@comment-1221773-20120804183141

That's what my math says. The Reapers did have to move from the Viper Nebula (site of the Alpha Relay) to the Kite's Nest cluster (where the Reapers entered the galaxy). As I remember, the Viper Nebula was located on the very edge of the galaxy, in the same local region that the Kite's Nest would be in. I bet if could compare their locations, they'd be in the ballpark of 1/20 of the width of the galaxy apart, and 1/20 of 100,000 light-years is 5,000 light-years.