I want to eliminate the Earth's axial tilt. How do I do it?

Question

I am an immortal, megalomaniacal supervillain with unlimited resources and patience. I want to slowly eliminate the Earth's axial tilt so that its equatorial plane is coplanar with its orbital plane. How can I achieve this without causing huge numbers of deaths? Assume that I have subjugated the entire planet, and no one will attempt to thwart me. I'm willing to do it slowly over thousands of years so that Earth's life forms have some time to adapt to the lack of seasons.

My first thought is to create some kind of vast, world-spanning magnetically-sensitive rail that will make use of the Earth's magnetic field (or the sun's, or maybe the solar wind?) to create a small asymmetrical rotational force on the planet.

My second idea is to create a space elevator-type structure, with its base on the equator. The tip of the elevator would be a large "sail," comprised of many small panels that could be opened or closed. When closed, the solar wind would push on them, applying a force to them which is transmitted down the elevator stalk to the Earth; when opened, the solar wind would pass through without pushing on them. Thus, the panels would open and close depending on the position of the sail, so that the solar wind would affect it more when it's at a position that decreases Earth's axial tilt, and affect it less when it's at a position that increases Earth's axial tilt.

Answer 1

Earth is already wobbling around in a process known as axial precession on a period of about 26,000 years. The Wikipedia article says that the precession is a gravity induced effect from the Sun and Moon. With unlimited resources (and assuming unlimited energy) the right gravitational pushes could be given to Earth to push the axis of rotation to be perpendicular to Earth's orbital plane. I haven't a clue how much mass it would take or where that mass would sit in relation to the Earth, Sun, and Moon. Orbital mechanics are tricky to get right for small satellites, doing it for a planetoid size mass would be very tricky. Thank goodness for handwaving.

Alternatively, the tilt of the earth could be altered by passing an object with a very large magnetic field through earth's magnetosphere. Again, the math about how to make such an object, position it so that it doesn't affect the orbits of the Moon or Earth and keep the thing in position is far far far beyond me.

Given the timescales involved, throwing big rocks at the right place on earth to alter the spin isn't an option. The biosphere thanks you, Oh Great Leader!

Answer 2

Find a large moon and put it in an orbit that consistently pulls on the equatorial bulge in a way to decrease its tilt. Adjust the moon if it loses sync.

Additional benefit: You can write your name on this second moon as a permanent reminder to the peons!