Picking a higher density of the material just means the one gram would occupy less volume, it doesn’t affect how much energy that gram is equivalent to in terms of E=mc2. For that calculation, as the equation implies, only the mass matters; a gram of feathers is equivalent to the same amount of energy as a gram of lead for that equation. Now, this equation is in fact a simplified assumption; if you launch your feather at relativistic speed, then we’re talking
I’m sorry but you can totally control the margin size in LaTeX if you learn the right incantation
backslash UsEpAcKaGe letterpaper H-maaaaaaargin point seventy-niiiiiine inch brackets GEOOOOOMETRY
then you spread the entrails slightly and stab towards the sky. Really don’t see what the big fuss is all about.