According to Linden Lab's official blog, Second Life's physics engine is at last getting a tune-up, after a couple years' unfulfilled promises.

Tony Walsh's Clickable Culture blog has plenty of excellent detail on the change - Second Life has been running on the Havok 1 physics engine since 2003, and it will now be updated to run on the more recent Havok 4 engine, improving the performance and capabilities of the virtual world.

The Havok 4-powered Second Life is currently in public beta. From Linden Lab's blog:

"This project is all about improving sim stability and reliability, reducing lag in the physics engine, and fixing some bugs that could not be fixed under Havok1. In other words, there are no new features in the Havok4 project, despite the fact that there has been significant work done 'under the hood'".

Among some of the improvements Linden hopes to see from the engine upgrade are reduced simulator crashes, less lag, stacked objects that behave dynamically (reacting when supporting objects are removed) and improved management of how in-world people and objects react when they collide.

There are still some bugs, according to the blog, but once the physics engine completes beta testing and rolls out across the grid, Linden will presumably begin actual work on Havok 4 features. the heels of frequent snarking about Second Life being "over the hill," it's expected that this facelift will help it stay current.