About Open Cosmology
Open Cosmology is a free, non-commercial, complete university programme in physics that leads to cosmology: a four-year bachelor's core and a fifth, graduate year. Every lecture of every course is covered, following MIT's undergraduate physics curriculum (and, in Year V, two MIT graduate courses: 8.902 Astrophysics II and 8.962 General Relativity) and, inside each course, MIT's own lecture order. Cosmology is the destination and the largest part, and the earlier courses show where each idea is used in cosmology.
The site owner's personal reflections on faith and the beginning, separate from the course material: Wonder.
Sources
- Pages are rewritten in our own words from MIT OpenCourseWare lectures and course notes, which MIT publishes under CC BY-NC-SA 4.0. Every page credits the course, the instructors and the lecture it follows, and every displayed formula links to its source.
- Material MIT marks “All rights reserved” is never reused; we draw our own diagrams instead. “Courtesy of …” credits are kept wherever such material is referenced.
- David Tong's lecture notes and the Feynman Lectures on Physics are used only to fact-check, never copied. OpenStax and LibreTexts content is not used.
- Interactive simulations on early pages are by PhET Interactive Simulations, University of Colorado Boulder, licensed under CC BY-NC 4.0 (non-commercial use only), and are credited where they appear. They run from this site as unmodified copies of PhET's own files, with the version given on each simulation.
Offline use
Courses can be saved on your device and read without an internet connection: use “Save this course for offline” on a course page, or “Save the whole site” in Reading options (the “Aa” button). Pages you have opened are also kept for offline reading. Everything stays on your device; use “Remove offline copies” in Reading options to delete it.
How the pages are made and checked
The pages are written with the help of an AI assistant (Anthropic's Claude), working from MIT's transcripts, slides and notes. Each page is then compared against its MIT lecture notes, slides and transcript by a separate checking pass, which records every difference in a review file; the page is published only after all findings are resolved. In addition, every number in a worked example, caption or quiz answer is recomputed automatically, and the key formulas are tested directly. Mistakes can still slip through: if you find one, please use the “Report a mistake” link at the end of the lesson.
Accessibility
The site aims to meet the Web Content Accessibility Guidelines (WCAG) 2.2 at level AA, and to go further where it can.
- Reading options (the “Aa” button at the top of every page): text size from 90% to 200%, relaxed or wide spacing, an easy-to-read font (Atkinson Hyperlegible) or a dyslexia-friendly font (Lexend), high contrast, shorter lines, highlighted links and stopping all animations. Your choices are remembered in this browser.
- Listening: every page, section, worked example or selected text can be read aloud, maths included, with a choice of voices and speeds.
- Keyboard: everything works without a mouse, with a visible focus outline. Press ? for shortcuts, such as / to search and n / p for the next or previous lesson.
- Screen readers: pages use proper headings and landmarks, formulas are also provided as MathML, and every graph has a “Show values as a table” button that gives its numbers as a data table.
- Colour and contrast: text meets the 4.5:1 contrast standard in light and dark modes, controls have a 3:1 visible border, and information is never shown by colour alone.
- Your browser's own settings are respected: zoom, dark mode and “reduce motion”.
If something is hard to use for you, please open an issue on GitHub so it can be fixed.
Privacy
No accounts, cookies, advertising or tracking: what the site remembers for you stays in your browser. Details on the privacy page.
Licence
The site's content — the lessons, quizzes, diagrams, symbol glossary and review files — is released under Creative Commons Attribution-NonCommercial-ShareAlike 4.0, as MIT's licence requires. You may share and adapt it for non-commercial purposes, with attribution, under the same licence. The software that builds the site is released under the MIT License, so anyone may reuse it. There are no paid features on MIT-based content. MIT and the course instructors do not endorse this site.