Marie Curie's personal notebooks are kept in a lead-lined box at the Bibliothèque Nationale de France. To read them, you have to sign a liability waiver and wear protective gear. They've been radioactive since she wrote in them, and they'll likely stay that way for another 1,500 years.

Curie handled radium with her bare hands for years. She carried vials of it in her pockets. She kept it in her desk drawer at night because she loved the way it glowed. Nobody in her era understood what radiation actually did to a body over time — the entire field of radiation safety didn't exist yet, because she was one of the people whose work was about to create the need for it.

She died of aplastic anemia, almost certainly caused by decades of exposure to the very element that made her the most celebrated scientist of her generation.

This isn't a story about carelessness — Curie was arguably the most careful, rigorous experimentalist of her era. It's a story about a much harder problem: some consequences don't show up on any timeline you can actually observe while you're living through it. She wasn't ignoring a known risk. The risk hadn't been discovered yet, because she was the one discovering it, in real time, with her own body as part of the data.

The uncomfortable, useful version of this lesson: the fact that something hasn't hurt you yet is not the same as evidence that it won't. Some of the costs we're least prepared for aren't the ones we ignored — they're the ones that genuinely couldn't be known yet, which is exactly why they're worth staying a little humble about, even when everything currently looks fine.