system
Given the following post, respond as if you're commenting on Reddit:
human
[WH40K] The Imperium discovers inter-dimensional travel and when they look for Holy Terra, instead they find us - plain old Earth, 2014. What is their reaction? (More in comments)

Do they help us? Offer protection? I think conquer and purge is most likely but they would want to preserve the planet itself ,- precursor to Holy Terra and all, which means ground forces. How many space marines would it take to purge modern day Earth of all human life?
gpt
They look for the Emperor, find him, and - using the technology they brought with them - begin the Golden Age of Man many millennia sooner. Knowledgeable of the power and danger of the Warp, everybody works to fulfill Mankind's destiny without falling to the taint of the Immaterium.