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    Re: Spacecraft Attitude Determination and Control
    From: Aubrey O?Callaghan
    Date: 2003 Feb 14, 08:39 +0000

    William Rowan Hamilton was Irish studied at Trinity College Dublin.... I'm
    quite proud of having read Engineering there. Our Maths Prof. never allowed
    us forget Hamilton !
    Just did a quick google search, as I never followed up much on this before:
    http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Hamilton.html
    
    Aubrey.
    
    
    At 03:20 14-02-03, you wrote:
    >On Thursday, February 13, 2003, at 05:20 PM, Robert Eno wrote:
    >
    >>What is a quaternion?
    >
    >In the world of mathematics there are a variety of numbers:
    >
    >* scalars
    >     - single numbers (3.14, 58)
    >* complex numbers
    >     - pairs of numbers like x,y points (1,2)
    >     - also written as real + imaginary (1+2i)
    >     - a set of arithmetic operations are defined such that
    >       the square root of -1 is an imaginary number called i
    >* vectors
    >     - several numbers (often 2-4) grouped together (1,2,3)
    >     - often used to represent dimensions of space and time
    >     - special operations like dot and cross product defined
    >     - used in navigation, i.e., a 2D vector is distance & course
    >* tensors
    >     - a matrix of numbers used in advanced physics & relativity
    >[(1,2,3)(4,5,6)]
    >     - a generalization of vectors
    >* quaternions
    >     - 4 numbers grouped together (q1,q2,q3,q4)
    >     - used in rigid body rotations and computer graphics
    >     - invented by Sir William Rowan Hamilton, circa 1866.
    >     - allows multiple rotations be to computed with fewer operations
    >     - think of them as a cross between a 3D vector and a complex number
    >     - shares some properties of both vectors and complex numbers
    >
    >http://www.cs.berkeley.edu/~laura/cs184/quat/quaternion.html for more.
    >
    >Dan
    
    
    

       
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