Resharing:
How much does a rainbow weigh?
— Not much. It’s pretty light.
@erkhyan Actually, how much *does* a rainbow weigh? Gonna take that joke and go pedantic instead, as one does.
It's not the weight of the droplets, since there's no rainbow without the added near-parallel light source. It's just the optical properties.
A rainbow redirects some light upwards, exerting force downwards on the supporting air. So it's a bit like asking how much a reflection weighs.
@erkhyan
🥁