My novel is coming together rather rapidly, but I've left some pretty big holes in my descriptions of the setting. It takes place on a generational ship traveling from Earth to a New hypothetically hospitable planet. Essentially I would like to know the amount of time that has passed on both Earth and the golden ship when the story takes place. Imagine catastrophe hits in 20 years time. Economic collapse, multiple international wars, the works. Nasa spots a planet way off in the distance which passes every test they throw at it in terms of the substance of its atmosphere and surface, and they are essentially convinced that it could be hospitable to humans. So with the guise of producing mining endeavors in the astroid belt of our solar system, they begin carving out an asteroid and build a ship in secret. The ship is tube like, and it is filled with all types of Earth material. The finished product has lakes and rivers and mountains and cities all living inside safely. News gets out of this and the US is attacked. 10,000 lucky citizens are sent off to board the ship and it takes off. Somewhere during the trip the society of generational colonists develop newer and faster technologies that begin to increase the momentum of the ship drastically. It reaches near light speed travel. Being science fiction, I merely allude to a large nuclear force, since I do not need to necessarily explain everything mathematically. So here's what I'm wondering. The total amount of time for the trip aboard the ship should be 200 to 500 years, depending on what sort of celestial bodies exist that far off (any opinion on this matter?) Say 200 years have passed on this ship. How many times has planet Earth circled the sun, in other words, how much time would have passed on our calanders as we continue our lives and the lives of the people on the ship have reached year 200? Thanks in advance!