Thank you for expanding on this -- I agree with all of these points. There is a real and tangible, albeit in this case indirect, value to have highly skilled people try to push that boundaries of what is possible technologically. It is easy to forget that the world-wide-web itself had its inception in at CERN -- an institution whose focus is particle physics.

In my opinion, another important reason to support of keeping these large accelerators alive is there is a very real chance that the expertise to build these kind of devices could atrophy or be lost entirely given the long timescales involved. Even if one is opposed to building this specific collider, I think the prospect of losing this kind of institutional knowledge is concerning (though if one finds these things useless, you might care less if we lost that capability).

Oh yes, good point about the Web. I know there’s a lot of cutting edge research on storage and computing distributed across the world to handle the sheer amount of data coming out of the LHC. It’s not implausible that this could help improve the Internet’s architecture.

I entirely agree with your second point. I’ll add that it is also important to keep these people (from highly specialised technicians and physicists to diplomats and support staff) employed in positions where they can keep their skills sharp. Some of them then go back to their countries of origin to apply this experience and knowledge to help improve research and policy at home, whilst retaining personal links with their counterparts abroad.

In the grand scheme of things, the expenditure is a rounding error anyway.

It was lost in the US after the supercollider project was cancelled in the 90s.

That's the same argument as weapon developers use, and weapon development contributed much more to fundamental physics than particle accelerators. The majority of funds after the WWII flowed to physics thanks to the nuclear arms race.

So what's your point? The weapon developers are correct of course. But the difference between weapons and super colliders is that super colliders are designer to help humanity instead of destroy it.

I can assure you weapon developers also think they benefit society. They usually say: WWIII did not happen only because of nuclear weapons. The question here is, what would benefit society more, spending said $21B on virology research or on a collider? Or maybe if you spend $21B on AI research, the computer will solve all the remaining theoretical problems of string theory in 0.21 s.

Of course weapons benefit society. I didn't say they didn't...