He explained it to both Mordecai and Twilight in chapter 5.
Sonic: The space colony falling was one of those things. It was known as Space Colony ARK, and it was on a collision course with Earth after my arch-nemesis Dr. Eggman had placed all seven of the Chaos Emeralds in the ARK. That was one of my adventures that involved saving Earth, but I couldn't have done it alone without my friends.
Sonic: The space colony falling was one of those things. It was known as Space Colony ARK, and it was on a collision course with Earth after my arch-nemesis Dr. Eggman had placed all seven of the Chaos Emeralds in the ARK. That was one of my adventures that involved saving Earth, but I couldn't have done it alone without my friends.
ah there we go, sorry bout that missed forgot sonic said that it was eggman's fault sorry