p.s.  alx, I am going to go with the fact that all particles, ie, the summation of life form and planet and star, have spin.<br/><br/>A chronitron with a negative spin goes backwards in time.  Positive, forward in time.  Since we are talking particles that only exist in the traversing of time, they only exist if they are moving forward or backward in time.<br/><br/>This is kinda based on Shroedinger's cat on his theoretical premise that either the cat is dead or isnt based on the spin of a as of yet undiscovered particle.  The birth of quantum physics.<br/><br/>Photons only exist if they are moving, therefore, chronitrons only exist if they are moving forwards or backwards in time.  If they cant move, they cease to exist, like a proton.<br/><br/>And that, ladies and germs, is where the McNair's shields come in.