Most people only ever encounter rubidium as the purple color in fireworks, but the obscure metal has helped two University of Chicago scientists propose a theory of how the moon may have formed.
![](https://scx1.b-cdn.net/csz/news/tmb/2019/nasamoonrock.jpg)
Source:
https://phys.org/news/2019-10-nasa-moon-picture-early-earth.html