Manifest Destiny is an achievement present in Spore. This achievement can be earned when the player has found the Earth planet in Sol solar system. It can be earned in the Space Stage.
Tips and Tricks
The location of Earth is the same in every game, for directions, go here.
The coordinates are shown below. The first number is the angle, the second is the distance from the Galactic Core.
Manifest Destiny is the belief that USA was destined to expand from the Atlantic seaboard to the Pacific Ocean (making reference to colony expansion) and to conquer all of North America (reference to conquering other empires).
The phrase is normally used to advocate and justify other territorial acquisitions.
Advocates of Manifest Destiny believed that expansion was not only good, but that it was obvious ("manifest") and certain ("destiny").
In relationship to the game, given on the hardship and commitment of locating Earth, it is to say that the player is destined to colonize the rest of the Galaxy.