Space Rocks and Banana Peels on Staircases

Nothing in this world is permanent. The world itself is not permanent: civilization far less so. The odds favor civilization getting through the next 100 years, but there is a small risk it won’t. The risk of disasters – natural and anthropogenic – occurring that don’t threaten civilization but nonetheless kill millions is so high as to approach certainty, e.g. the Spanish flu of 1918-19 and the Asian flu of 1957-58, the latter of which was as deadly as COVID-19 though the public response at the time was pretty casual.
 
Back in 2008 the Future of Humanity Institute at Oxford took a stab at calculating odds of human-caused catastrophic global events prior to 2100. The researches divided risks into three categories: events causing at least 1 million deaths, events causing at least 1 billion deaths, and extinction events. The chance of extinction from a genetically engineered virus was given at 2% by 2100. The existential risk from Artificial Intelligence was estimated at 5%. The extinction risk from war came in at 4%. The total risk of extinction from any and all anthropogenic causes combined by 2100 came in at 19%. FHI focused on human-caused disasters, but natural phenomena have in the past caused and will again cause global mass extinctions. An outburst of vulcanism on a scale that formed the Deccan and Siberian traps could do it. So could gamma ray bursts from a close enough supernova: one such may have caused the Devonian extinction.  Asteroid impacts are not just the stuff of science fiction.
 
Current estimates are that some 2000 asteroids large enough to threaten civilization have orbits that cross earth’s orbit. Most are unidentified despite ongoing cataloging efforts by NASA and other space agencies. Many times that number are too small to be globally catastrophic but still large enough to obliterate a city. This was demonstrated on many a dashcam in Chelyabinsk Russia back in 2013 when a 20-meter diameter meteor vaporized with an explosive force estimated at 500 kilotons. (This is about equivalent to the W88 thermonuclear warhead carried by some US and British Trident missiles; the Hiroshima bomb was 15 kilotons.) Fortunately the rock exploded at an altitude of over 25 kilometers, which limited damage on the ground though 1000 people were still injured by flying glass from the shock wave. A rock about this size enters earth’s atmosphere every few decades, mostly over the ocean. Near misses by far bigger ones occur with similar frequency.

Chelyabinsk meteor

 
In 2029 the large asteroid Apophis will pass inside the orbit of geosynchronous communications satellites. It will be visible to the naked eye from the ground. The odds of it striking earth are vanishingly small on that pass, but when it returns in 2068 the odds, while still small, are not vanishingly so. It is impossible to calculate all the possible perturbations to an asteroid’s orbit from gravitational interactions and small impacts, so there is always some degree of uncertainty to these predictions. The most dangerous rocks of all, of course, are the ones that no one sees until they arrive. Sooner or later a big one will.
 
The good news is that (probably) nothing so earth-shattering will happen within the lifetime of anyone alive today. Individually, we are much more likely to be done in by mundane events than by anything celestial or geologic. Leaving aside death by natural causes, which all of us who live long enough will face, ordinary accidents pose a non-negligible risk. According to the Insurance Information Institute the lifetime risk of accidental fatal poisoning is 1 in 63 (1 in 4990 in any one year). The lifetime risk of dying by automobile accident is 1 in 107. Falling down stairs is 1 in 1652. The chance of death by firearm is 1 in 289. The total lifetime risk of dying by an accident of any type is 1 in 17 (1 in 1306 in any one year). Those are still pretty good odds that our own klutziness won’t kill us. Most of us will get to live out our 4000 weeks.

4000 Weeks is the title of a book by Oliver Burkeman, long time columnist on psychology for The Guardian. He believes that calculating in weeks rather than years improves our sense of just how fleeting life is. He does this not to be depressing but to nudge us into focusing on what is important to make that limited span better. He reminds us that every activity will have a “last time,” and we do well to treat each one with the reverence we would show if we knew for a fact it was the last: “there will be a last time we visit our childhood home, or swim in the ocean, or make love, or have a deep conversation with a certain close friend.” And that is without a rock falling on us from space. By and large, Burkeman makes good points, but in a world filled with office hours, quarterly taxes, and monthly bills that impose from the outside an order on our time, his advice is easier to give than to follow.

R.E.M – It’s the End of the World