**Future Train Wreck: Mine or Modern Physics talk Next Thursday, Jan. 26**

If you are in Cambridge, MA on Thursday, Jan. 26, you can see me live at MIT in room 3-270 from...

**Holiday Physics Card, 2016**

Just put them in the mail on December 24...It was a fun year of thinking, whether the idea is right...

**Unified Mathematical Field Theory Talk**

I gave a 15 minute talk at a local Americal Physical Society Meeting. Here is the title and...

**Holiday Card 2015**

Here is my holiday card for 2015, a tradition of mine going back to 1990. Enjoy.On the back...

*Z*.]

_{2}**Snarky puzzle**

The only metric that is spherically symmetric and solves the Einstein field equations is the Schwarzschild metric, or so sayith Jørg Tofte Jebsen aka Birkhoff's theorem. [Correction: The theorem applies for a spherically symmetric, non-rotating, and uncharged source for the vacuum field equations.]

This blog will dive into an issue that has bothered me for years, namely that the line assume the only coordinate system that can be used for quaternions are both normal and orthogonal. It is the later property that stumped me, and I made a small step forward I will report on.