Seems to me like we should’ve easily invented something that lasts indefinitely by now
In: Chemistry
No one has described the physics of how sunscreen works, and there’s a lot of misunderstanding on how sunscreen works in this thread.
Sunscreen gets absorbed into the skin (chemical) or sits on top of the skin (physical) The UV rays have a lot of energy that damages the skin which can lead to cancer, early aging, etc. When the UV rays encounter the sunscreen, the sunscreen absorbs the UV which photodissociates the chemicals in the sunscreen. This breaks the UV rays up into lesser energetic components that do not damage the skin. So by its very nature, sunscreen can’t last indefinitely because it’s not supposed to.
BOTH physical and chemical sunscreens work in this manner. It’s a myth that physical sunscreens reflect light.
Link to the study that shows physical sunscreen absorbs and doesn’t reflect: https://onlinelibrary.wiley.com/doi/10.1111/phpp.12214
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