[unification_fan]

> You still have to cope with failures from cosmic rays

Much like you have to cope with hash or GUID collisions... that is, you don't, because it statistically never happens. Unless you're speedrunning super mario or something.

Besides if you have a program that's formally verified, you just need to do what NASA did for its Apollo missions and make all the logic redundant and gate it behind a consensus algorithm.

You can argue that all 4 computers might get hit by a cosmic ray in just the right place and at just the right time... But it will never ever happen in the history of ever.

So my point is that the real world is messy. But the systems we design as engineers are not necessarily as messy. And the interface between the real world and our systems can be managed, and the proof of it is that we wouldn't be chatting across an entire ocean by modulating light itself if that weren't the case.

[AlotOfReading]

I've definitely dealt with hash/GUID collisions in the context of safety critical systems before. It's not a particularly uncommon requirement either.

"just" is pulling a lot of weight in your comment. Redundant consensus is difficult and expensive, all to address very particular error models (like the one you're assuming). If we expand our error model from localized error sources like cosmic rays to say, EMI, there are entire categories of fault injection attacks well-known to work against modern redundant systems.

That's assuming your specification is comprehensive and correct in the first place of course. My experience is that all specifications have holes related to their assumptions about the real world, and many of them have bugs or unintended behavior as well.