The article presents an in-depth analysis of epistemic cultures in conflict by exemplifying the epistemic conflict between high energy physics and astronomy which emerged after the discovery of “dark energy” and the accelerating expansion of the universe. It suggests a theoretical framework combining Knorr-Cetina’s concept of epistemic cultures with Whitley’s theory of dependencies in the sciences system, which explains that epistemic conflicts occur, if the strategic and functional dependency of two incommensurable epistemic cultures is suddenly growing. The pre-history of the (...) conflict is discussed on a micro-level for the two research groups involved in the breakthrough. The analysis of the consequent epistemic conflict on a macro-level reveals that it embraces the preferred epistemic strategy, the collaboration style, the instrumental concepts and the question how social legitimacy can be generated. (shrink)