system
Given the following post, respond as if you're commenting on Reddit:
human
[ELI5] How does the flash in cameras damage paintings in museums?
gpt
Flashes used to emit a lot of UV which damages dyes and paint. Flashes no longer emit UV so they don’t do any damage. 

Museums have kept this rule for two reasons: 
1. Flashes are really annoying for everyone else.
2. They have a higher chance of selling their book to you if you can’t take good photos yourself.