As the largest encyclopedia in the world, it is not surprising that Wikipedia reflects the state of scientific knowledge. However, Wikipedia is also one of the most accessed websites in the world, including by scientists, which suggests that it also has the potential to shape science. This paper shows that it does.Incorporating ideas into a Wikipedia article leads to those ideas being used more in the scientific literature. This paper documents this in two ways: correlationally across thousands of articles in Wikipedia and causally through a randomized experiment where we added new scientific content to Wikipedia. We find that fully a third of the correlational relationship is causal, implying that Wikipedia has a strong shaping effect on science.Our findings speak not only to the influence of Wikipedia, but more broadly to the influence of repositories of scientific knowledge. The results suggest that increased provision of information in accessible repositories is a very cost-effective way to advance science. We also find that such gains are equity-improving, disproportionately benefitting those without traditional access to scientific information.