Humans have always been fascinated by death. While the thought of our own mortality frightens us, for some reason we are still compelled by a morbid curiosity to slow down to gawk at a car wreck, knowing that the body under the tarp could be us on any given day. It’s no surprise, then, that we also find ourselves baking up doomsday scenarios that could mean the end not just for us as individuals, but for our entire species. For all our mighty accomplishments, the thought that it could all be ended by a wayward chunk of space rock is both humbling and scary. For three scientists, however, asteroids could in fact be used to save the Earth from the Sun’s inevitable decay into a massive red giant…by literally moving the entire planet out of the Sun’s expansion zone.
The plan is the brainchild of three researchers: Don Korycansky of the University of California-Santa Cruz, Gregory Laughlin of NASA, and Fred Adams of the University of Michigan. It was actually hatched over a decade ago, and I’m kind of amazed I never heard about this one, because it’s what is known in technical circles as “a doozy.” The problem, of course, is that the Sun will eventually expand into a red giant, likely swallowing up the Earth in the process, or at the least charring it into a lifeless cinder. The plan involves the “gravity-assist technique,” sometimes also known as a “slingshot maneuver.” It’s the same technique that was used to allow craft such as the Voyager probes to explore our outer solar system. The idea is to capture a large asteroid and skim it past the Earth, close enough that our planet’s gravity slingshots it around and past us. If the object is large enough – say 62 miles across – its gravity will also pull on the Earth as it passes, slightly altering our planet’s orbit.
The trick is that one such maneuver wouldn’t be enough to save the Earth from the Sun’s expansion. The scientists say it could take as many as a million such attempts to move the planet far enough to keep it safe. And there are other problems. If you get the angle wrong, the asteroid could smack into the Earth rather than zipping around it. These repeated close encounters with asteroids could also mess with the Earth’s rotational speed. The scientists suggest that this could be compensated for by targeting the next asteroid pass to slow the rotation back to normal. If it worked, however, the new orbit could allow the Earth to stay habitable for an extra 5 billion years.
It all sounds like something out of E.E. Doc Smith’s Lensman books, the stuff of space opera rather than science. Nevertheless, Cruz, Laughlin, and Adams describe the plan as “alarmingly feasible” (a phrase which doesn’t inspire enormous amounts of confidence in me). If it were to be undertaken – assuming we haven’t wiped ourselves out in more prosaic ways by then – the project would require unprecedented levels of coordination by the peoples of the Earth. It’s nice to think that by that point we will have evolved to the point where that sort of cooperation is a realistic goal…but the cynic in me says, “We’re boned.”
Then again, if we haven’t figured out interstellar travel by the time the sun begins to die, we probably deserve to get roasted.