Quaternions in recent years

[robinlandseadel at comcast.net]

While googling around this morning, hoping to find some text 
involving Quarterninions from the the years when Thomas Pynchon 
taught chemistry at Trinity, ran across this current Wikipedia
listing for that now obscure branch of science. I did not know that 
the use of Quaternions was revived by computer graphics:


Recent years
Quaternions are often used in computer graphics (and associated 
geometric analysis) to represent rotations (see quaternions and 
spatial rotation) and orientations of objects in three-dimensional 
space. Certain fractals can plot in quaternion coordinates. They 
are smaller than other representations such as matrices, and 
operations on them such as composition can be computed more 
efficiently. Quaternions also see use in control theory, signal 
processing, attitude control, physics, bioinformatics (see: Root 
mean square deviation (bioinformatics)), and orbital mechanics, 
mainly for representing rotations/orientations in three dimensions. 
For example, it is common for spacecraft attitude-control systems 
to be commanded in terms of quaternions, which are also used to 
telemeter their current attitude. The rationale is that combining 
many quaternion transformations is more numerically stable than 
combining many matrix transformations. There is also less 
overhead in using quaternions compared to using rotation matrices, 
because a quaternion has only four components instead of nine, 
so the multiplication algorithms to combine successive rotations 
are faster, and the result is much easier to renormalize afterwards.

Since 1989, the Department of Mathematics of the National 
University of Ireland, Maynooth has organized a pilgrimage, 
where scientists (including physicists Murray Gell-Mann in 2002 and 
Steven Weinberg in 2005 and mathematician Andrew Wiles in 2003) 
take a walk from Dunsink Observatory to the Royal Canal bridge 
where, unfortunately, no trace of Hamilton's carving remains.

http://en.wikipedia.org/wiki/Quarternions