Uploaded June 2025 | Updated September 2026, 2 weeks ago

---

This video proves Birkhoff's Theorem, which states that a spherically symmetric solution to the vacuum #Einsteinfieldequations must necessarily be static. Intuitively, this means that even if our central mass M were radially expanding/contracting with time, the spacetime surface outside that mass will be unchanged.

Questions/requests? Let me know in the comments!

Pre-reqs: Videos before this one in my GR playlist: youtube.com/playlist?list=PLdgVBOaXkb9Dc-vr2nw-UF6PJknfAuJzU
My Tensor Calculus playlist is also essential for this video: youtube.com/playlist?list=PLdgVBOaXkb9D6zw47gsrtE5XqLeRPh27_
Lecture Notes: drive.google.com/file/d/1d07D4Qx68kq0Bwt7yh-bkWrNJY2LdKhG/view?usp=drive_link

Special thanks to my Patrons:
Patapom
Eugene Bulkin
Andy Johnston
Patrick Gibson
Joseph Dubeau
David Johnston