> Earth is such a tiny speck in the vast emptiness of space, that unless galaxy colonising aliens are capable of traveling in spaceships at FTL (faster than lig

> Earth is such a tiny speck in the vast emptiness of space, that unless galaxy colonising aliens are capable of traveling in spaceships at FTL (faster than light) speeds, it may indeed take them hundreds or thousands or millions of years to pass by Earth again on their next sweep through the Goldilocks planets in their terraforming list in this corner of the Universe. This is why it makes sense that we haven't planned for that too occur. And really, if they do have FTL capability it's very unlikely we would have any tech that would be of any danger to them anyway. It makes for nice SciFi B-movies but I don't think it's a realistic scenario.