A former engineer from NASA discussed the possibility of changing Earth's orbit using massive interstellar comets and asteroids. He said doing so could save the Earth from being completely destroyed by the Sun.
As various scientific reports have confirmed, the Sun will begin to expand and transform into a red giant within around five billion years. Once this happens, its outer layer will consume Earth, burning up the planet and rendering it totally uninhabitable.
Gravity Assist from Asteroids and Comets
According to Mark Adler, a retired project manager and system engineer for NASA's Jet Propulsion Laboratory, the future inhabitants of Earth could prevent this catastrophic event by changing Earth's orbit around the Sun. One way to do this is by using the gravitational pull of massive asteroids and comets to nudge Earth out of its current orbit.
These massive space rocks, which inhabit the Kuiper Belt and Oort Cloud in the Solar System's outer regions, can be diverted to fly next to Earth using fusion bombs or other technological instruments from the future. "One or a few such large Kuiper Belt objects could be diverted to swing by the Earth and then Jupiter," Adler explained on Quora. "They could be put in long-term cycle orbits between the Earth and Jupiter, using Saturn, Uranus, and Neptune as well to return the object."
Escaping the Sun's expansion
Once these giant space rocks have been diverted to orbit Earth repeatedly, their immense gravitational pull could eventually cause Earth's orbit to shift. By doing so, Earth would be pulled away from its orbit around the Sun. Theoretically, by moving away from the Sun, the Earth would be able to escape its expanding outer layer, preventing it from being completely destroyed by the growing red giant.
"Repeated passes by Earth and Jupiter, always on the same side, would transfer angular momentum and energy between the Earth and Jupiter," Adler stated. "You could raise the orbit of Earth significantly, but only lower Jupiter's orbit a tiny amount, where Jupiter is 318 times the mass of Earth."