Update: How cold is the LHC right now? What about now?
As CERN's Large Hadron Collider is gradually chilled to its operating temperature of 1.9 degrees Kelvin -- colder than the vacuum of outer space -- you can follow along at this Web site. It shows the temperature of each of the machine's eight sectors in real time, or pretty close to it. Thanks to Bad Astronomy for pointing this out.
Why so cold? Check out this post from Monday.