<p><span style="background-color: rgb(255, 255, 255); color: black;">The collision of high-energy particles in the early Universe can leave detectable correlations in the Cosmic Microwave Background and Large Scale Structure. </span></p><p><span style="background-color: rgb(255, 255, 255); color: black;">I will describe recent efforts to translate scattering theory from particle physics onto expanding spacetimes.</span></p><p><span style="background-color: rgb(255, 255, 255); color: black;">In particular, effective field theory techniques---used to search for new physics at colliders---can now be applied on a quasi-de Sitter background and establish new connections between cosmological observations and the fundamental physics that governs inflation. </span></p><p><br></p>