Friday Fabulousity: The Endless Entertainment of Electromagnets

For all your walking on the ceiling needs, see Hackaday: http://hackaday.com/2014/05/23/electromagnetic-boots-for-all-your-upside-down-needs/

The craftsmanship seems to be at a high level, although I am not trained in the use of power tools.  But all the pieces fit neatly together and the all the connections are tidy, just like a good piece of clothing.  I like watching craftspeople at work.   I might need some ceiling walking in my training exercises.

Here's the main making-of video from the Hackaday site:



As Oersted, Ampere, and Maxwell said  
$$\nabla \times \mathbf{B} = \frac{4\pi}{c}\mathbf{J} +\frac{1}{c} \frac{\partial \mathbf{E}}{\partial t}$$ That is, the magnetic field B generated around a wire (the curl $\nabla \times \mathbf{B}$) is proportional to the sum of the current density J and to the change in time of the electric field E!  This equation encapsulates a whole boatload of exciting math, as well as being almost unbelievably beautiful and tidy!   We have no a priori reason to believe that the universe is (sometimes) so tidy, but sometimes it is.   Oh, and if you have enough J you can walk on the ceiling!   (The $\partial \mathbf{E}/\partial t$ effect is usually pretty small compared to gravity on Earth.)