Clicker Training

After a a few weeks of settling in, I thought I’d give some clicker training a go with Lucy, Destroyer of (Laptop) Mice.

In a word, astounding.

I’m only peripherally familiar with operand conditioning, but I bought and am following Karen Pryor‘s Clicker Training for Cats book. I started on Sunday with loading the click with chicken liver treats. After 5 clicks she had cottoned on and 10 clicks later she was targetting a biro with her nose and I could lead her around the room with it. 5 more clicks and she was giving me high fives in the air with her paws. This all took less than five minutes!

Now it’s Wednesday and she’s quite reliably giving high fives, coming when called, sitting and staying on her spot and getting down from the table on command.

For some obscure reason teaching her to switch the light off on command and to play the piano are high on the list…

General Relativity

Why is General Relativity so damned difficult and inaccessible? Because of tensor fields.

So what’s this about tensors? Well, caclulus might be abstruse enough already, but tensor calculus takes abstrusity (?) to a whole new level. A tensor is a multidimensional generalisation of scalars and vectors, to n-dimensions. So, a scalar quantity such as mass, having one dimension, can also be thought of as a tensor of rank zero. A vector quantity such as velocity can be thought of as a rank one tensor. Things become complicated when dealing with more complex quantities, such as elasticity, a rank four tensor in materials science.

Performing calculus with tensors becomes useful when considering quantities with two or more dimensions. The great benefit is that it allows you to treat quantities with as many dimensions as you need with the same notational convenience.

A tensor field is a tensor quantity that varies across all points in space. A magnetic field, denoted B, is a vector field, and so can be treated as a tensor field of rank one. The space in which the field is mapped may be the standard Euclidiean 3-space, but might well be some other space, like gee, how about a 4-dimensional spacetime? And I haven’t even mentioned Riemannian manifolds yet.