Hi Monique,
I love the pictures! What he did was quite novel.
Here is a simplified explanation of how the internet works (if anyone cares).
When you do a trace route, the locations that you see are where backbone providers have their gateways & access routers (POP's-points of presence).
The paths taken are determined by several factors. Your internet provider either owns a "backbone" or leases bandwidth from someone who does. The routing will be determined by the peering arrangements that the backbone provider has to the end user's address that you are doing the trace to. If you and the other location are on different backbones, they have to hand off to one another at either private or public peering points. A peering point is a physical location where 2 or more companies with backbones hand off traffic to each other.
The handoff is usually what we call "hot potato" routing. Let's say you use ISP A and want to hit a site that has ISP B. ISP A will search for the closest point that it can hand the traffic off to ISP B. When the traffic returns to you, ISP B will search for the closest point that it can handoff to ISP A. So, the route to and from A & B will usually differ.
Also, the routes are dynamic so the route taken between identical endpoints can be affected by congestion and equipment or network failures.
So, what he did was map the particular trace routes he ran, but it is not actually an accurate depiction of the "internet".