Humanity has been travelling the stars for a good 120 years now. Each new Earth-like planet they find they make peace with and trade resources to make sure humanity never goes hungry. When they find the planet that holds Equestria, they are met with an over-protective ruler who has seen Equestria burn because foreigners have arrived in hopes that they could conquer it. She will not let it happen again.
This is a one shot inspired by other stories constantly depicting Celestia as a ruler so protective that she is willing to shun humanity completely because they might want to conquer Equestria. I will not be continuing this story past the possible beginning.