deletions | additions       diff --git a/can_we_map_full_skeleton.tex b/can_we_map_full_skeleton.tex  index 900f8df..161a3dc 100644  --- a/can_we_map_full_skeleton.tex  +++ b/can_we_map_full_skeleton.tex 
...
Carry out the following thought experiment. Draw a rough plan of a spiral galaxy on a very flat piece of paper. Position a vantage point a tiny distance (a few hundredths of an inch) above that piece of paper, about two-thirds of the way out from the center of the galaxy. Now give the observer at that vantage point super-sharp eyesight and ask if the observer can separate the spiral arm features you drew, as they observe them. They can--if and only if the spiral you drew has very narrow features defining its arms. If the observer were exactly {\it in} the piece of paper (living in Flatland), separating the arms would be impossible, regardless of their width. We are, like your observer, are at a tiny, tiny, elevation off of a spiral galaxy, and our vision is good enough to separate very skinny arm-like features.  So, how might we use out vantage point above the Plane to map out more of the Milky Way's skeleton? It turns out that Nessie is located in a place where seeing a very long IRDC projected parallel to the Galactic Plane should bejust about the  easiest, so it is not surprising (and in fact is re-assuring)  that we found it first. Look again at Figure \ref{fig:topview}, and consider Nessie's placement there. According to the current (data-based cartoon) view of the Milky Way shown in Figure \ref{fig:topview}, Nessie is in the closest major spiral arm (Scutum-Centaurus) to us, along a direction toward, but not exactly toward, the (confusing) Galactic Center. Nessie's placement there means that it will have a bright background illumination as seen from futhrer out in the Galaxy (e.g. from the Sun), and that it will have a long extent on the Sky as compared with more distant or less perpendicular-to-our-line-of-sight objects. To find more `Nessies,' if such narrow features are in fact typical in spiral arms, we need to be clever about where and how we look. Our current understanding of the Milky Way's spatial and velocity structure will allow us to draw more velocity-encoded lines like the ones shown in Figure \ref{fig:coloredlines} on the Sky, mapping out the whole Galaxy as seen from the Sun's vantage point. Once this drawing is done, we should design algorithms to look for dust clouds elongated (roughly) along those lines, and then we should examine the velocity structure of the elongated features, as we do in \S \ref{3D}, above. Of course, we need to be flexible in which features we accept as possible other ``bones," remembering that the model we will use to draw the expected features on the Sky is the same one we seek to refine! It is likely that a Bayesian approach, using the extant Milky Way model as a prior, will succeeed in this way.