Planetary securityWandering Earth: rocket scientist explains how we could move our planet

By Matteo Ceriotti

In the Chinese science fiction film “The Wandering Earth,” recently released on Netflix, humanity attempts to change the Earth’s orbit using enormous thrusters in order to escape the expanding sun – and prevent a collision with Jupiter.

The scenario may one day come true. In five billion years, the sun will run out of fuel and expand, most likely engulfing the Earth. A more immediate threat is a global warming apocalypse. Moving the Earth to a wider orbit could be a solution – and it is possible in theory.

But how could we go about it and what are the engineering challenges? For the sake of argument, let us assume that we aim to move the Earth from its current orbit to an orbit 50 percent further from the sun, similar to Mars’.

We have been devising techniques to move small bodies – asteroids – from their orbit for many years, mainly to protect our planet from impacts. Some are based on an impulsive, and often destructive, action: a nuclear blast near or on the surface of the asteroid, or a “kinetic impactor”, for example a spacecraft colliding with the asteroid at high velocity. These are clearly not applicable to Earth due to their destructive nature.

Other techniques instead involve a very gentle, continuous push over a long time, provided by a tugboat docked on the surface of the asteroid, or a spacecraft hovering near it (pushing through gravity or other methods). But this would be impossible for the Earth as its mass is enormous compared to even the largest asteroids.

Electric thrusters
We have actually already been moving the Earth from its orbit. Every time a probe leaves the Earth for another planet, it imparts a small impulse to the Earth in the opposite direction, similar to the recoil of a gun. Luckily for us – but unfortunately for the purpose of moving the Earth – this effect is incredibly small.