How Many People Would We Need To Colonize Another Earth?

Various companies are working to settle on other planets. How long would it take and what issues would we face along the way?
Source: DNews
Read more:
Space Future
Space Exploration Books
Spaceships & Rockets
The Future of Mars Exploration
The Future of Moon Exploration
Asteroid Mining
Space Colonization, How Many People Would We Need To Colonize Another Earth

More Posts:

Stephen Hawking - Train Ride To The Future
Imitation Of Flight With SubWing
Sensu Stylus: Paintbrush For iPad
Levitating Graphite Disks Will Lead To A New Light Energy Conversion System (+VIDEO)
The First 3D-Printed Building Will Be Built In 2014
Formula-E Electric Racecars Unveiled
Mab - Finalist Electrolux Design Lab 2013
NASA’s Modular Robotic Vehicle (MRV)
Robots That Can Adapt Like Animals
Scientists Develop Flexible Medical Sensors Using Carbon Nanotube-laced Chewing Gum