Free online course Cosmology Fundamentals: Hubble’s Law, FLRW Models, Inflationand Structure Formation

About the free online course

Turn big cosmological ideas into concepts you can calculate and explain. This free online astronomy course builds a clear path from the discovery of cosmic expansion to the models that describe our universe on the largest scales. You will develop intuition for what observations actually measure, why galaxies appear to recede, and how the language of modern cosmology connects distances, time and the geometry of space.

You begin with the practical foundations needed to talk about the universe with precision: units, dimensions and the meaning of key measurable quantities. From there, Hubble’s law becomes more than a historical statement, helping you relate recession velocity to distance and interpret what expansion implies rather than assume it. With a Newtonian approach as a bridge, you see how a dust-filled universe can already suggest the basic dynamics of cosmic evolution.

Next, the course moves into the relativistic framework that underpins contemporary cosmology. You will review the essential ideas of general relativity and then work with the FLRW metric, the central tool for describing a homogeneous and isotropic universe. This is where expansion histories, matter versus radiation domination, and special cases such as the Milne universe become coherent stories about how different ingredients shape cosmic time.

Observational cosmology takes center stage as you connect theory to data. You will learn how redshift relates to the scale factor, how horizons constrain what can be observed, and how conformal diagrams clarify causal structure. You will also build understanding of distance measures, angular sizes, luminosity, number counts and what these observations reveal about composition and the thermal history of the universe.

Finally, you will explore the early universe and the origin of structure. Inflation is treated as a physical idea with consequences you can reason through, alongside a glimpse of modified gravity via f(R) models. You then examine gravitational instability in both Newtonian terms and within general relativity, linking tiny primordial inhomogeneities to the large-scale structure seen today. By the end, you will be able to read popular explanations more critically and follow technical discussions with far greater confidence.