Ryan E. Johnson

Associate Professor




Campus Box 0405


Masters Hall
Room 205
300 North Washington St.
Gettysburg, PA 17325-1400


BS University of New Mexico, 2001
PhD Dartmouth College, 2011

Academic Focus

Observational astronomy, multiwavelength observations and interpretations of galaxy clusters, Data Science

I am an observational astrophysicist and cosmologist and am currently employed as an assistant professor of physics at Gettysburg College.  The question that drives my research is this: what is the true nature of gravity?  The 20th century showed, among other things, that our model for gravity, the Newtonian model, was just a specific case of a more general theory for gravity developed by Einstein.  Einstein's General Theory of Relativity, as it is called, predicts that what we see as gravity is actually the manifestation of a 4-dimenstional curvature in space.  In the extreme limits of this model, this curvature can affect how all matter, and even light, moves through that space.  


I study galaxy clusters and, in particular, when galaxy clusters collide with one another.  These collisions represent one of the most extreme environments within which we can examine whether the gravitational force as we know it on smaller spatial scales (like the size of our solar system or even our galaxy), does an acceptable job of predicting galaxy motions on the largest scales.  In this way, I am using observations to constrain our theory for gravity with the hope of revealing something deeper in its nature.


I am also very interested in undergraduate education, particularly astronomy education.  I have seen astronomy inspire students to creatively think through questions moreso than any other discipline.  Astronomy thrives off curiosity, and it is my goal, more than any other, to inspire curiosity in my students.  For those already curious, I try to instill in them the critical thinking and reasoning skills to dissemintate and contextualize the vast array of information available, so that they may incorporate that information into their world view and beyond.  

Courses Taught