i hope someday we construct a collider that spans the entire circumference of the earth. But we'd probably have to build one that spans the circumference of the moon first, and then maybe mars, since the oceans are going to be a bit of a doozie to work around that we don't have the technology for, whereas the interior of a collider is supposed to be evacuated, so, the moon almost kinda already handles that for us. heat might be an issue of course, but if we can figure out thermal radiator panels that can dump the heat straight into space, maybe we could pull it off...

mars would address the heat issues, but those dust storms are no joke and the dust itself is microscopic toxic/caustic razors and it'll try to get in everywhere and ruin fine instruments it touches. Moon dust is also really bad but there's no wind to kick it up on the moon obviously...

but damn. DAMN. imagine the fucking science we could get done with a LUNAR-SCALE PARTICLE COLLIDER!!!