The traditional realm of astronomy is the observation and study of the largest objects in the Universe, while the traditional domain of high-energy physics (HEP) is the study of the smallest things in nature. But these two sciences concerned with opposite ends of the size spectrum are, in Muir's words, bound fast by a thousand invisible cords that cannot be broken. In this essay I propose that collaborations of astronomers and high-energy physicists on common problems are beneficial for both fields, and that both astronomy and HEP can advance by this close and still growing relationship. Dark matter and dark energy are two of the binding cords I will use to illustrate how collaborations of astronomers and high-energy physicists on large astronomical projects can be good for astronomy, and how discoveries in astronomy can guide high-energy physicists in their quest for understanding nature on the smallest scales. Of course, the fields have some different intellectual and collaborative traditions, neither of which is ideal. The cultures of the different fields cannot be judged to be right or wrong; they either work or they do not. When astronomers and high-energy physicists work together, the binding cords can either encourage or choke creativity. The challenge facing the astronomy and HEP communities is to adopt the best traditions of both fields. It is up to us to choose wisely.

When we try to pick out anything by itself we find that it is bound fast, by a thousand invisible cords that cannot be broken, to everything in the Universe.
John Muir¹