> > >Holes can only exist in atomic lattices (i.e., some solids) not in a vacuum. > A vacuum is one humongous hole ;-) Cheers de Gord, VE3EOS -- Gordon L. Hayward, Ph.D., P.Eng., Associate Professor, Biological Engineering, School of Engineering, University of Guelph, Guelph, Ontario, N1G 2W1.