Today you may have noticed Earth wasn’t torn apart and everything we know and love vaporized.

I notice that almost every day! But in this case there’s a reason it didn’t happen. Well, a lot of reasons, but one specific one I want to talk about.

I was poking around on some planetarium software (Sky Safari, the one I use most often) and noticed the Sun will be close in the sky to the center of the galaxy on today’s date, December 18. That gave me a slow, sly smile, reminding me of a time not too long ago when I was spending much of my efforts debunking yet another clot of pseudoscientific fetidness.

This would be the Maya apocalypse, the chuckleheaded claim that the world would end on December 21, 2012.

Remember that? It was all the rage in the media, ranging from breathless claims of Maya prophecy in some seedier corners of the internet to more bog-standard misuse of science without mentioning the super goofy stuff in mainstream media. It was based on the erroneous idea that the ancient Maya calendar ended on that date, and they knew that would bring the end of the world. Shocker: this was wrong, both in its interpretation and in the fact that the Maya calendar didn’t actually end on that date (like ours, it was cyclical, so it just rolled over every cycle just as ours does on December 31).

I wrote several articles about this at the time. It happened while I was still writing for Slate, and I put together a deep debunking of the claims to post a few days before the non-event (that’s behind a paywall, but SYFY has it up for free), as well as another for when I was at SYFY when the idea was inevitably rehashed by more opportunistic grifters in 2020. Most of the claims were the usual illucid nonsense, but one that I thought was particularly funny was straight-up astronomy based: the Sun would align with the black hole in the center of our galaxy, causing a gravitational summation that would lead to our summary execution.

Before you panic: again, yeah, this didn’t and cannot happen. But there’s a sliver of truth here, a small iota of fact, which is then wildly extrapolated into goofball territory.

Here’s the deal. Earth orbits the Sun once per year. From the Sun’s point of view, Earth moves across the sky slowly, taking a year to circle it once, moving against the background stars as it does so. But we live on Earth, so from our point of view it’s the Sun that slowly slides through the background stars. As it does so it passes through the zodiac constellations, like Gemini, Aries, Taurus, and so forth. It passes through them at pretty much the same time of the year, so, for example, the Sun is in Sagittarius in December.

Now, at the same time, we are inside the Milky Way Galaxy, a flattened disk 120,000 light-years across with a central bulge of stars. From our point of view out in the galatic suburbs, that section of the galactic downtown is in the constellation of Sagittarius, so the Sun passes through that part of the sky every December.

As it happens, there is also a supermassive black hole in the exact center of our galaxy, which we call Sgr A* (for “Sagittarius A-star” or “Saj A star” for short). It has about 4 million times the mass of the Sun, which is a lot. It has extremely powerful gravity, which dominates the central volume of the Milky Way.

And hey, the Sun dominates the gravity of our solar system. If the Sun passes by that black hole in the sky, their gravity will add together, and that spells doom. DOOOOOOOMMMMM!

Or not. I mean, this was the claim, though specifics like math and physics, oddly enough, were never mentioned. But it turns out they’re important.

4 million solar masses is a load, but it’s also 26,000 light-years away. The gravitational force of an object does depend on its mass, but it also depends on the distance. The square of the distance, in fact, so that dominates for far-away objects. Sure, it has four million times the Sun’s mass, but it’s also 1.7 billion times farther away than the Sun. Even before squaring that number you can see it has no effect on us. But doing the math you find it has a force that is about a trillionth the strength of the Sun’s. Literally, the effect of Mercury’s gravity on Earth is stronger.

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