You make a very good point, but we can amend (http://paulgraham.com/disagree.html http://paulgraham.com/disagree.html) the GP's argument to say that such macros

You make a very good point, but we can amend (http://paulgraham.com/disagree.html http://paulgraham.com/disagree.html) the GP's argument to say that such macroscopic holes are not very impressive. Now if they were as small as those in balsa, and invisible to the eye... then on a macroscopic level it would appear to be superlight metal. It could also help that the holes are sufficiently small as to not percolate (https://en.wikipedia.org/wiki/Percolation_theory https://en.wikipedia.org/wiki/Percolation_theory).