via reddit.com
Arguably, since Pope Emeritus Benedict XVI lives in a disused convent in a corner of Vatican City the papal density of the Vatican is actually 4.54 P/km².
what if we accelerated both popes to a substantial fraction of lightspeed and collided them together, that would reveal valuable information about their internal structure
The God Particle
They tried that a couple of times in the middle ages, but all they got was a schism and a standard pope-antipope pair