By the 2140's most of humanity had attained full virtualisation. Almost 100% of the planet's mass, outside of the mantle, had been converted to smart material as a substrate for society's mindstates and the solar energy harvesting systems required to support it.
A few hundred thousand, the New Luddites, refused to leave the flesh they considered to be a divine gift and therefore sacrosanct. Earth had long become uninhabitable as an ecosystem so they resolved to build new arks and sail for the Kepler system, 600 light years away, where Planet 22-b held the promise of being their New Earth.
The arks were driven by vast fusion motors, accelerating the arks to a maximum of just under 0.4C at the midpoint. The voyage was to take over 3000 years, with generations of specially trained navigators and crew awakened for decade-long stints at the helm. The arks held their precious cargo of humans, animals, plants and micro-organisms in outboard hibernation pods. But interstellar space held as yet unknown horrors and the attrition rates of the living cargo were severe.
Pls see also space scene here: www.flickr.com/photos/halfbeak/6529244993