system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How are big firework shows (NYE, Independence Day, etc) implemented? Obviously, there are no trial runs before the big show, so how do they know how it will look like, and guarantee that everything is in place and will work as intended?

Happy new year everyone!
gpt
The expense of a massive, nationally-televised fireworks display buys a lot of professional experience, reliable technology, and redundancy. Just like surgeons don't "practice" surgery on a patient before they cut them open, but they don't need to. They've done it so many times that they're prepared for any eventuality. Any highly-skilled professional brings the same skillset to their job.

Also, in many cases, you won't know if something did go wrong. Let's say that eight fireworks pop instead of ten for a given frame. Well, that's okay, because you won't likely miss the other two. It's like if a politican skips a line in a speech, you probably wouldn't know unless they react to their own mistake. The devices are also pretty reliable, provided they're dry and high-quality. Experts know how they work down to the grain.

Finally, unit tests help. By ensuring that each charge fires as expected in isolated shots (probably in isolated areas, too) these guys make sure everything will go according to plan.