At its top speed of 16.26 km/s (36,400 mph) New Horizons would take over 80,000 years to reach Alpha Centauri (the nearest star system). There’s a redaction here: My bad: Have aliens ever visited Earth?) It has been proposed that aliens may have a technology that would allow them to travel faster than light (FTL). If aliens have been to Earth, they’ve been suspiciously cool about it. Perhaps it’s also worth mentioning that when aliens actually arrived at Earth after such a trip, our civilization would have changed dramatically from the time they departed.