The comic depicts the rendezvous of the Philae lander from the Rosetta probe with comet 67P/Churyumov–Gerasimenko, unfolding in real time and updating on the xkcd site every five or so minutes.
Here’s a flip book of all of them.
ETA: it can be slow loading. Be patient! Server overload, I imagine.
Where’s the kaboom? There was supposed to be an earth shattering kaboom?
Seriously, it’s amazing the things Man has done just in my lifetime.
Hey, it’s a long, long, looooong way away…give it time 
And it appears to have successfully touched town just a few minutes ago.
Yep. It’s a bit of a tense wait until we hear something official.
Darn speed of light! Too slow!
Confirmed! Philae is landed!
SPAAAAACCCEEEE!!
I do love the imagined banter between the probe and lander in the comic, as well as the imagined states of mind for the scientists and whales.
Has anyone tried this before?
Nope.
YAY!
Did something happen with the harpoons? ‘Do harpoons work on comets?’ updated from ‘yes’ to ‘don’t know’ a couple iterations of the comic ago…
They failed to deploy properly: http://www.geek.com/science/esas-philae-lander-successfully-touches-down-on-a-comet-but-harpoons-have-failed-1609299/