If an asteroid were heading for earth, could we knock it off course? We’re about to find out
Lesson summary
Hi there I’m Jeff and this is Plain English, where we help you upgrade your English with current events and trending topics. Today is lesson number 515, so that means JR, our producer, has uploaded the full lesson content to PlainEnglish.com/515.
Back during the early days of the COVID-19 pandemic, I considered doing a lesson on all the other terrible things that might happen to humanity—things that have a low probability of happening, but which still might cause mass chaos. I decided not to write that because it was too depressing to even contemplate. But one of those possible risks was an asteroid hitting earth. It’s a very, very low probability event—but hey, it has happened before and it could happen again.
So given that, NASA is starting to plan ahead, thinking about what to do if the earth were threatened by an asteroid. And on today’s lesson, you’ll hear about a recent test for just that situation.
In the second half of the lesson, I’ll show you what it means to “set something off” and we have a song of the week. Let’s dive in.
Trial attempt to knock an asteroid off course
About 66 million years ago, a 10-kilometer-wide asteroid struck the earth near what is today the Yucatán Peninsula of Mexico. The impact was so strong that it killed three-quarters of the plant and animal species on earth, including all the dinosaurs.
Scientists now believe the event also caused an earthquake that was felt for weeks and months after the impact. You might remember the earthquake in the Indian Ocean in 2004; it was the third-largest earthquake ever recorded. Scientists believe the earthquake that hit after the asteroid impact was 50,000 times more intense than that. It was enough to kill most animal and plant life on the whole planet.
Could it happen again? Moviegoers have long contemplated this doomsday scenario, as asteroid impacts have been featured on the big screen for decades. In the 1998 movie Armageddon, an asteroid the size of Texas, or over 1,000 kilometers wide, is on a collision course with the earth. NASA, America’s space agency, has just 18 days to stop it. They send a team of underground drillers to land on the asteroid, to drill a hole in it, and set off a nuclear bomb to destroy the asteroid. They do it; the world is saved. There’s also a romantic subplot.
You don’t need me to tell you that this is unrealistic. Astronomers would have decades, if not centuries, of warning of a large asteroid heading our way. But even a small asteroid could do significant damage if it hit the earth; a very small one could still wipe out the population of a city.
But with enough notice, humans wouldn’t have to destroy an asteroid to avoid a collision. If the asteroid is still far away, a small nudge of just a few centimeters in one direction would be enough to push the asteroid off course.
And toward that end, NASA sent a device into space to collide into an asteroid on a practice run to save humanity.
Dimorphus is a 160-meter-wide asteroid about seven million miles away. It’s not now, and never will be, anywhere near earth. It orbits another, larger asteroid. It poses no danger to anyone.
But in November 2021, NASA launched something called DART—it stands for Double Asteroid Redirection Test. The purpose of DART was to crash into Dimorphus at a high speed and to change Dimorphus’s trajectory, even a little. The idea is a proof of concept: NASA wants to know if it can launch a device into space and change the trajectory of an asteroid. That way, if a small asteroid ever is coming our way, NASA will know how to save humanity—or at least avoid a potentially catastrophic impact.
The mission had two challenges: first, it had to hit its target; and second, it had to alter the asteroid’s trajectory. Last month, the DART successfully hit its target. And now, the James Webb Telescope , among others , will study the asteroid’s post-collision course to see if the DART did change the orbit of the asteroid.
We’re not talking about a big change. The forces of gravity will still apply and Dimorphous will still orbit the larger asteroid. But NASA calculated that Dimorphous made a full rotation around the larger asteroid once every 11 hours and 55 minutes. DART was designed to crash into Dimorphous and move it slightly closer to the big asteroid. The mission will be a success if Dimorphous makes a complete circuit in 11 hours and 45 minutes, just a ten-minute difference. This would be the first time humans intervened to change the arrangement of objects in the universe, even if it’s just by a little.
DART was equipped with a camera so that NASA astronomers—and the world—could watch as the spacecraft got closer and closer to its target. For much of its journey from earth, DART could be controlled remotely to fine-tune its trajectory.
But in the last few minutes, there was nothing to do but watch. NASA scientists watched the live camera feed as the asteroid got bigger and bigger and bigger on the screen—until it went blank, meaning that the crash happened as intended.
In a few months, the data on Dimorphous’s new trajectory will be in—and we’ll know if the mission was a success.
Which is worse?
So let me ask you, what’s scarier? Getting 18 days’ notice that the world would end, or getting like 100 years’ notice? I mean, if like in Armageddon, you have just 18 days until the end of the world, you wouldn’t be living with the dread for a long time.
Yes, it would be nice to have, say , a two-century lead time to destroy an oncoming asteroid. But that would be multiple generations full of worry.
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