Knowing where you are

You can get turn-by-turn directions.  What more do you need?

Last month there was a pretty sight in the evening sky: the Moon passed close by Venus.  This sort of thing happens often, but this time there was much clear weather over populated places, they were both high in the sky and bright, and the approach was particularly close.  Our astronomer saw many postings of pictures of the event, many–even most–from non-astronomers.  He found he could tell much about his correspondents from details of the pictures.  He could follow the approach of the Moon through the time zones, tell something of the latitude of the picture-taker from the horizon, a bit about the local time.  The pictures from his friends in the Southern Hemisphere were obviously different, in expected ways.

Of course there was no need to analyze pictures of the sky to know where his correspondents were.  He has mailing addresses of almost all of them (however unnecessary they are in the post-mail age), and when they travel most post mid-trip pictures.  The celestial details are there, nonetheless.

It’s still summer here by the Potomac, still warm and humid weather in which air conditioners are important.  But he can tell, in his routine travels, that the Sun is lower in the sky than it was this time last month.  The shadows come at different angles.  There is a bit of practical application of this: he can advise our photographer when the light is likely to be just so on a particular building or scene.  In principle, some patience on the part of the photographer would be just about as useful, but it’s efficient to be able to predict things.

Being aware of the sky has other uses.  If he’s out in the morning hours, often he’ll pick out the last-quarter Moon in the daytime sky.  Few people notice it.  He can imagine that there is the point where Earth will be in its orbit around the Sun in just a few hours’ time.  With a bit more effort he can imagine the various circles that map out our little section of the universe.

Overall, though, this celestial navigation is unnecessary.  You can get wherever you want to go through turn-by-turn directions on your smartphone.  Even working out which direction is which, when emerging from an unfamiliar Metro station, is easier through the phone than by noticing the angle of the Sun, and more accurate.  Why bother?

It has something to do with placing oneself in the universe.  It’s something about knowing where you are, in a sense that’s not easy to put into words.  Maps are different from a list of directions, as we’ve noted before.  They involve a different way of thinking of the world.  It’s a way we want to hang on to.