It's said the earth is approaching the sun. Can we push it away little by little?
Although we can emit rocket towards the sun, but it's too expensive to make a rocket:
So I think maybe we can recycle the rocket, at first, the rocket is send out with a very fast speed, so give back a big force to the earth. And then, we let the rocket slowly comes back to the earth, and re-send it again:
Well, this solution sounds a little inefficient. Still I don't know if it works. Better ideas?
EDIT
Umm.. It seems the earth is leaving the sun. That's ok. Then, the question is how can we push the earth towards the sun, i.e., correct the orbit by human force? Even if the sun turns into a red giant someday, we may finally find a way to put the earth at a safe position far enough from heat.
Best Answer
The Earth is pretty heavy. No rocket that we can currently make is going to have much effect on it's motion.
The only remotely feasible suggestion I've seen is to divert asteroids from the asteroid belt so they pass close to the Earth in a slingshot orbit. The idea is to accelerate the asteroid and decelerate the Earth, which causes the Earth to move into a larger orbit. Any one asteroid isn't going to have a big effect, but there are a lot of asteroids out there so you would do it repeatedly.
There are potential problems of course. You still need a fair bit of energy to divert the asteroid, though you could do it with a solar sail if you had enough time. Also you'd need to be pretty sure you could divert the asteroid accurately as an error in the asteroids trajectory could prove embarrassing.
Anyhow, who told you the Earth is approaching the Sun? As far as I know it isn't, though because the Earth's orbit is an ellipse the Earth-Sun distance does decrease for for six months then increase again for the next six months.