Speaking about symmetry, look out our window, and you may see a cardinal attacking its reflection in the window. The cardinal is the only bird we have who often does this. If it has a nest nearby, the cardinal thinks there is another cardinal trying to invade its territory. It never realizes it is attacking its own reflection. Cardinals don't know much about mirror symmetry!
![Speaking about symmetry, look out our window, and you may see a cardinal attacking its reflection in the window. The cardinal is the only bird we have who often does this. If it has a nest nearby, the cardinal thinks](http://cdn.quoteddaily.com/images/martin-gardner/speaking-about-symmetry-look-out-our-window-and-you-may-see-a-cardinal-attacking-its-reflection-in-the-window-the.jpg)