This is one that has me confused. It seems to be some Rube Goldberg contraption that sets the sprinkler system off to…Push enormous soccer balls with a bulldozer?
It’s about the FIRST Robotics Competition: FIRST Robotics Competition - Wikipedia
It’s a robot that disables the opposing robot by holding a match up the sprinkler system so the water ruins all the electronics.
It had me confused at first too, so I checked the xkcd forums. Apparently it’s a reference to the FIRST robotics competition. This years competition is apparently robot soccer.
The important thing to note is the second to last panel with the opposing team is freaking out because their robot has died.
Apropos of nothing, I competed in the third FIRST* competition in 1994.
*Which sort of reminds me of Third Fifth Bank.
Ahhh, that’s one of the things that confused me. I was wondering why they were dropping a huge block of marble on a wagon.
“Pool on the roof…” is a reference to Hackers.
What are those two structures between the opposing robots (panel 2)?
I assume that’s the stadium dealie the robots are “competing”/soccering in.
The thing about Randall is that his art can be reaaallll subtle. See, the main thrust of the strip was a nod to Don Martin.
THAT part I got. But I am not quite nerdy enough to have gotten the robot reference. Thank you for asking <and explaining> so I didn’t miss out. 
Fifth Third, not that it matters.
I was in it that year, too!
Except for some reason I can’t remember, I was unable to participate in the actual building of the bot, or the competition, just the design portion. (I think that was the year my grandfather died, so I had to travel for the funeral… I know I didn’t drop out, because I got a video of the competition for being part of the team…)
Without the exaggerated tongues and accompanying spittle, I missed it.
I don’t know for certain, but one of the years I did FIRST, there were tall hamper-things on wheels, which were the goals you had to get soccer balls into. So, I’d guess it’s some part of the game they’re playing. Also, FIRST does two-robot teams, so there are two robots on each side.
No, no! The characteristic Don Martin identifier is the hinged feet!
Just because I’m too lazy to look up the numbers, is the equation even close?
Planck Prius Combined
Energy X EPA gas mileage = ∏
Pressure Minimum width
at Earth's of the English
core Channel
The game and the team structure changes every year. Last year there were three robots on each team, and they were sliding around on some low-friction surface. My dad’s team (#33, the Killer Bees) took second place overall one year, and typically places pretty high in the rankings.
I haven’t tried it myself, but from the discussion thread I saw at the xkcd forums, the units cancel out perfectly, and the numbers come out within around a ‘margin of error’ of maybe 15% or so - which is probably reasonable considering how many assumptions even the best guesses are making as far as the pressure at the Earth’s core. 
Link: http://forums.xkcd.com/viewtopic.php?f=7&t=55123&sid=80ace8491ec08e4dda2f1ae9ff97be6c