Cooper: We used to look up at the sky and wonder at our place in the stars, now we just look down and worry about our place in the dirt.
Cooper: Mankind was born on Earth. It was never meant to die here.
CASE: This is not possible.
Cooper: No. It's necessary.
Doyle: You can't just think about your family. You have to think bigger than that.
Cooper: I'm thinking about my family and millions of other families.
Dr. Brand: Do not go gentle into that good night; Old age should burn and rave at close of day. Rage, rage against the dying of the light.
Answer: I am not exactly sure what kind of propulsion system is used, however; you must consider that although in our galaxy even the closest planets to Earth take years to travel to, in this alternate universe, the planets may be arranged in a closer formation.