http://www.space.com/scienceastronomy/planetearth/earth_move_010207.htmlIf the sun is heating Earth too much we can just move the planet out a bit. We are going to have to do it anyway in the next billion years so we might as well get started now.
Here's what you do:
* Using humans or robotic spacecraft, attach retrorockets -- like those that maneuver spacecraft -- to the rock. Alter its course of so that it passes near Earth. The planet then steals some of the space rock's orbital energy and uses it to move into an orbit slightly farther from the Sun. (NASA employs a similar technique to propel spacecraft, sending them around a planet in order to boost them into new trajectories at higher speeds.)
* Send the comet or asteroid back out around Jupiter and Saturn, where it will regain orbital energy by robbing it from the giant planets. (In effect, Earth is ultimately getting its orbital boost from Jupiter and Saturn.) Make the rock continue on a long, elliptical orbit that goes way the heck out there -- 325 times the distance from Earth to the Sun.
* Bring the rock back around Earth every 6,000 years or so, and each time the planet will creep outward a few more miles. The goal: An ultimate retreat of several million miles (kilometers).
Well it would be easier than getting people to give up their SUV's.