Geek explosion over at xkcd

First, Randy sucks you in with the Friday comic, a geeky riff on the Drake Equation which calculates the probability of extraterrestrial life. There's even more discussion in the blag.

But then you come upon a newer posting which starts out with a straightforward-seeming explanation of solar sails and why their efficiency is so low (He did, after all, work for NASA.)  But somehow that description mutates from an illustration of that inefficiency (1.21 gigawatts needed to levatate a squirrel by shooting a laser at a mirrored surface) to discussions of how to increase the efficiency with more mirrors, to a suggestion of how the lasers should be solar powered, and how we'd need a Dyson sphere around the sun to capture all the power, and how the sphere would need a hole in it........   you'll see.

Oh, and among the comments to that post is this one:

A lasing medium between the Sun and your sail, you say?  http://laserstars.org/history/mars.html

That URL goes to a rather interesting academic paper describing how the anomalously high levels of long-IR radiation coming from Mars are due to natural lasing effects going on as solar radiation impinges on the CO2 atmosphere.   Hmmm..... Some had wondered if the surprisingly high failure rate of Martian space probes had a common cause, and now we know.  Not only are there Martians, but they're shooting at our incoming missiles with lasers!