Ben Cox writes in his blog about visualizing IPv4 address space use by mapping the whole IPv4 Internet with Hilbert curves [benjojo.co.uk]. While the IPv4 address space is quite large it is still small enough to be able to send a packet to each and every IP address. He goes a little into the background of the maths involved and then makes a comparison to the IPv4 address space back in 2012 using data from the Carna botnet [soylentnews.org].
Earlier on SN: Vint Cerf's Dream Do-Over: 2 Ways He'd Make the Internet Different [soylentnews.org]