Confirmation

It turns out that Charles was right. Here is an e-mail that was sent to someone in the Harvard Society of Physics Students:

———- Forwarded message ———-
From: Randall Munroe
Date: Tue, Dec 15, 2009 at 12:25 PM
Subject: Re: the harvard physicists are on to you: (was: Fwd:
[sps-open] xkcd and galactic rotation curves)
To: Jacob Rus

It’s a coincidence, but I swear I’ve seen that graph before. I
remember wishing I could see the error bars and data points.

Best,
Randall