Free online courseCosmology

Course Description

Cosmology is the story of everything: how space and time began, how matter gathered into galaxies, and why the universe’s expansion appears to be speeding up. This free online course is a guided tour through the big ideas and the real observations that shaped modern astronomy, helping you build an intuitive, evidence-based view of the cosmos—from the first fractions of a second to the largest structures we can map today.

You will connect classic questions such as what happened at the Big Bang or how far the universe extends with the measurements scientists actually use to answer them. Along the way, you’ll see why the cosmic microwave background matters, what inflation tries to explain about the early universe, and how cosmologists test competing explanations rather than relying on speculation. The lessons are designed to make complex concepts feel grounded, using clear explanations that emphasize what we know, what we infer, and what remains genuinely mysterious.

The course also highlights how discovery happens in practice through major instruments and surveys. You’ll encounter the Dark Energy Survey and learn why mapping billions of light years can reveal clues about dark energy and the growth of cosmic structure. You’ll also explore how advanced telescope cameras—built for extremely precise measurements—help researchers track subtle signals in the sky, from patterns imprinted soon after the universe became transparent to the explosive counterparts of gravitational wave events.

Modern cosmology is not only about distant galaxies; it also sits at the intersection of particle physics and gravity. The course introduces the puzzle of quantum gravity, explains why gravity is treated differently from the forces in the Standard Model, and shows how ideas about dark matter and dark energy emerged from observations that didn’t fit ordinary matter alone. Short exercises reinforce key takeaways, so you can check your understanding as you go and leave with a sharper sense of how today’s best evidence supports the leading cosmological model—without glossing over its open questions.