Evacuate Earth

I saw this program of Nat Geo. It deals with a cosmic collision of Earth and humans having 75 years before it comes. It had a lot of scientists and experts from all fields to discuss the scenarios and pros and cons with each one. The best scenario they decide upon is building a circular ship that could house around 200,000 people. The go through all the issues that would come into play to make that ship and evacuation happen (ie getting world governments to work together, building the ship, supplying the ship, picking the evacuees, private vs government efforts, etc) as well as what would happen to those left back on Earth (radiation, meteors, civil wars, violence, etc) since there are 7 billion people and only space for 200,000 on the ship. It was made as a documentary and while nothing has ever been attempted like this before (and hopefully never will need to be) it was pretty realistic in that they used what we basically know today and not what we could know in the future. It was a very interesting and sobering program. I don't see myself getting a spot on-board the ship or that I would go even if I could (of course no one knows for certain how they would react until placed in that situation.) This program goes beyond a normal "Hollywood" space disaster movie and tries to show all sides, the good and the bad, in dealing with a collision that would destroy Earth. All the questions on how to save whatever we can (people, animals, artifacts, etc) are raised.