Tuesday, February 11, 2025
Two videos on how we figured out our solar system just based on obversations alone, long before we left the surly bonds of Earth
The video “Terence Tao on how we measure the cosmos” was very interesting to watch, as Terence goes into depth on how people in the past, and by past, I mean the distant past, figured out the earth was a sphere, how big that sphere was, and even reasoned that the earth went around the sun, long before the Christian Church even existed! And the method that Kepler used to figure out the orbits of Earth and the planets, when at the time we didn't quite know the distance to them, and all we had were positions in the sky to go by.
Incredible.
Also, a second video on how the moons of Jupiter (yes, it's not at all about Pluto despite the title) revealed much about how our solar system works. It even revealed that light had a finite speed.
I think if these methods were more widely known, how we figured out the shape of the Earth, the size of the moon and sun, and how orbits worked, then people wouldn't have the mistaken belief of a flat earth holding up the firmaments.
I never got the memo on “copyover servers”
There’s only so much you can do with builder rights on someone else’s MUD. To really change the game, you needed to be able to code, and most MUDs were written “real languages” like C. We’d managed to get a copy of Visual C++ 6 and the CircleMUD source code, and started messing about. But the development cycle was pretty frustrating — for every change, you had to recompile the server, shut it down (dropping everyone’s connections), bring it back up, and wait for everyone to log back in.
Some MUDs used a very cool trick to avoid this, called “copyover” or “hotboot”. It’s an idiom that lets a stateful server replace itself while retaining its PID and open connections. It seemed like magic back then: you recompiled the server, sent the right command, everything froze for a few seconds, and (if you were lucky) it came back to life running the latest code. The trick is simple but I can’t find a detailed write-up, so I wanted to write it out while I thought of it.
Via Lobsters, How Copyover MUD Servers Worked | Blog | jackkelly.name
Somehow, in all my years of programming (and the few years I was looking into the source code of various MUDs back in the early 90s) I never came across this method of starting an updated version of a server without losing any network connections. In hindsite, it's an obvious solution—it just never occured to me to do this.
