For some reason it seems I asked this before. Anyobdy know how the Quaternions can be used to rotate objects in three dimensions. I discussed this with my Engineering professor two months ago, he said he never heard of them and does not know how to use them. I kept on wanting to ask but forgot, anybody know how you use them? Interestingly my College has a library that contains the original printing that Hamilton made, very old book. And it is huge too, more than 700 pages only on the Quaternions.