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Michael Hartl’s Substack is currently focused on math and math learning, including announcements about Tau Day and The Tau Manifesto. Posts include discussions of select mathematical topics (including proofs) as well as curated recommendations for books and YouTube channels.

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Subscribe to Michael Hartl’s Substack

Currently focused on math and math learning, with additional subjects likely in the future. Posts include announcements related to Tau Day and The Tau Manifesto, as well as a variety of math topics and curated book and YouTube recommendations.


Physicist, educator, and entrepreneur. Founder of Tau Day, author of The Tau Manifesto. Formerly of Learn Enough and the Rails Tutorial. “Hartl understands physics deeply… and like Feynman he is an outstanding pedagogue.” —Kip Thorne