Elon Musk wants to build a transit system that lets humans tour the entire Solar System

Elon Musk today announced plans for a giant rocket and spaceship that will theoretically be capable of sending humans to Mars. The theory, according to him, is that we could find a way to colonize Mars in just a century or two. In typical Musk fashion, he wasn't done there. During the latter stages of his presentation, the SpaceX CEO explained why he decided on Twitter a few weeks ago to rename the Mars Colonial Transporter to the "Interplanetary Transport System" — he wants the ITS to go so much farther beyond Mars. With a proposed 77-meter-tall rocket acting as a "javelin" for the massive ITS spaceship, Musk teased the idea of SpaceX spending centuries helping humans explore the outer reaches of the Solar System.

Musk said he settled...