What is an object, anyway?

And now for the second inanimate object of the new year is something that is definitely inanimate, but may not actually be an object.

Now there are lots of things that are definitely objects in this picture.  I'm sure we'll get to all of those at some point.  The thing I'm interested in is the rainbow, which has some properties of an object but lacks others.  The definition of an object is:

1a: something material that may be perceived by the senses

So it's definitely something that can be perceived by the senses, but it isn't really material.  Wikipedia comes down pretty squarely on the side of "not an object":

A rainbow is not located at a specific distance from the observer, but comes from an optical illusion caused by any water droplets viewed from a certain angle relative to a light source. Thus, a rainbow is not an object and cannot be physically approached. Indeed, it is impossible for an observer to see a rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the light source. Even if an observer sees another observer who seems "under" or "at the end of" a rainbow, the second observer will see a different rainbow—farther off—at the same angle as seen by the first observer.

 Mostly because I like this picture and think it's pretty, I'm going to argue that the rainbow is an object.  In an effort to dispel the commonly-held 15th century notion that rainbows are unicorn tractor beams ¹ , scientists tirelessly worked to explain what really causes rainbows.  After years of work and dozens of successful grants, science finally decided that rainbows are caused by sunlight bouncing off the inside of a raindrop, coupled with the natural dispersion of light in water.

This explains why rainbows always appear opposite to the sun.  Of course, the rainbow is just some special reflected light, which means it's arguably not an object.  All that other stuff in the picture is just reflected light, too, just without all the fancy dispersion.  So if the Hancock Tower gets to be an object, so does the rainbow.  It's just that the rainbow is really a bunch of raindrops in the sky somewhere over Boston.

An interesting aside about this particular rainbow (or that particular bunch of raindrops) is that it occurred just before the World Series game between the Red Sox and Dodgers was about to start.  All the local sports fans took this as a sign that the Red Sox would win (which they did). 

¹ Another common misconception about rainbows is that leprechauns hide their pots of gold at the end of rainbows.  Leprechauns abandoned the gold standard after the establishment of the Bretton Woods system in 1944.