In last Friday’s Scientific American article that I wrote for my Universe column, I talked about the roundest objects we know of in the Universe. What I didn’t say specifically is that these were natural objects like Venus and the Sun.

What about artificial ones? What are the most spherical human-made objects?

Back in the early 2000s I worked with a group at Sonoma State University creating educational materials for some high-energy NASA astronomical observatories like Swift and Fermi. Another mission that was being built around that same time was called Gravity Probe-B (or just GPB for short). It was designed to test a weird prediction of Einstein’s General Relativity: a rotating mass will drag the fabric of spacetime along with it, like a twirling fork in spaghetti noodles. This is called frame dragging.

Because it’s so weird and hard to explain, we came up with a demo kids can do in school: pour some honey onto a paper plate. Cut a rubber ball in half and place the flat side down in the center. Then take a few peppercorns and place them in a line starting at the ball and moving outwards. Now carefully (so you don’t get all sticky) spin the ball around. After a few spins you’ll see the inner peppercorn was dragged around a bit by the honey, and the farther out you go the less the peppercorns are moved. That’s analogous to frame dragging. 

Another outcome of frame dragging is called the Lense-Thirring Effect. It’s complicated, but in essence if you put a gyroscope near a spinning massive object, the axis of the gyroscope will precess, itself spinning around. This is the same sort of a thing a spinning top will do; the axis rotates due to friction with the surface it’s on. The Earth does this as well due to the gravitational tugs of the Sun and Moon.

The denser the object and the faster it spins the easier it is to measure this effect, making black holes the best places to observe it. But (perhaps happily) there are no black holes around to test this directly. But Earth is spinning, and kinda sorta massive. It does drag spacetime around with it, but only at a very low rate. 

But it’s measurable! GPB was a spacecraft in low-Earth orbit that had gyroscopes on it, and used precise measurements to watch them precess. The rotors of the gyroscopes were 3-centimeter-wide ball bearings, but very, very special ones: they were made of fused quartz and plated in niobium, and were created so perfectly they were only a few atoms in thickness off from being perfect spheres. They’ve been credited as the most perfect spheres ever made, which is the point of this whole thing I’m writing here. Pretty cool.

The spheres spun at about 4,000 rpm, and as Earth rotated below GPB the axes of the spheres’ spins precessed, which could be measured. In the end they got rates that matched predictions made using Einstein’s equations very well indeed, again showing relativity is correct.

I’ll add that the effect was actually measured elsewhere before GPB’s results were finalized, and while this didn’t negate the need for GPB, it did make the announcement a lot less dramatic. The mission was also plagued with problems that wound up delaying its launch and data collection, and it ran over budget as well. That happens in science sometimes when you try doing cutting-edge work; if it takes too long or is harder than you thought with your rig, someone else might come along and scoop you.

Anyway, that’s the tale of the most spherical artificial objects ever made. I wanted to talk about it in my SciAm article, but as you can see there was way too much to say, so I decided to leave it for the newsletter. It has some bearing, after all.

If you’ve been a BANner for a while, you may remember I left Twitter in September 2023. Musk’s cozying up to Nazis and far-right figures was final enough for me, and I stopped posting. I left my account active because I had a lot of history there, and I figured why bother deleting everything? I also didn’t want to deactivate my account, lest some ne’er-do-well hijack my handle and use it for nefarious purposes.

But then in the past couple of weeks two things happened. One is that Musk really went Full Lickspittle for Trump. That actually didn’t change my opinion much, since it’s been pretty clear he’s been fascist friendly for a while. But the real game changer was when I found out that any and all tweets on the site would be fed into his abominable AI called Grok as a learning database. 

I wrote favorably about AI back in BAN 533 (with some caveats), but things have changed since then. I learned how huge an energy hog these things are, and they went from a curiosity to being used for outright evil purposes pretty danged quick (like, people using them to plagiarize books and grabbing up a huge amount of copyrighted material without permission). So I’m not a fan, to be polite.

And with Elon Musk behind one? Yeah, I wouldn’t trust it to do simple math. His posts on Xitter^* have shown he’s totally in the tank for Trump, and his past actions have shown he cannot be trusted not to fiddle with the algorithm over there to force right-wing propaganda on readers. There is no way I will allow what I have written to even have a chance of being a part of that. 

So I decided to delete all my tweets (to prevent them from being used without my permission; I used this free code to do so) and deactivated my account. My presence on the former Twitter, and all history of it, is gone.

At this point I didn’t hesitate to do this, nor shed any tears. A year ago I was pretty unhappy to leave it, since it was like turning my back on all my friends, colleagues, and more. But I’ve been on Bluesky since May 2023, and it’s far better. It’s very old-Twitter like, but you can set it to simply show you posts from people you follow in reverse chronological order, with no algorithm screwing things up. Perfect!

There has been a huge exodus from Xitter the past few weeks (people are calling it Xit, which I love) and a lot of them are finding a new home on Bluesky. If you’ve had enough of other social media sites (I left Facebook ages ago), then come on over. I’m easy to find, and finding others is easy, too.

* Pronounced using the Maya X.

You can email me at [email protected] (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!