Shadows of convex bodies
  It is proved that if $C$ is a convex body in ${\Bbb R}^n$ then $C$ has an affine image $\widetilde C$ (of non-zero volume) so that if $P$ is any 1-codimensional orthogonal projection,   $$|P\widetilde C| \ge |\widetilde C|^{n-1\over n}.$$   It is also shown that there is a pathological body, $K$, all of whose orthogonal projections have volume about $\sqrt{n}$ times as large as $|K|^{n-1\over n}$. 
Keith Ball