"Technically, the term optical illusion refers to a broad class of phenomena, all of which happen entirely inside your head. With an illusion, your eye-brain system is being tricked by geometry or color."When I googled mirage, I found that it is also not a hallucination (YAY!):
"In contrast to a hallucination, a mirage is a real optical phenomenon that can be captured on camera, since light rays are actually refracted to form the false image at the observer's location. What the image appears to represent, however, is determined by the interpretive faculties of the human mind. For example, inferior images on land are very easily mistaken for the reflections from a small body of water."Okay, then, what are we actually seeing when we see a mirage? I liked this explanation:
In a mirage, light rays are changing direction not because of reflection (which is what a mirror does). They’re changing direction because of refraction (which is what a temperature gradient does). The speed of light depends on what it’s going through. In the vacuum of space, that speed is exactly 299,792,458 meters/second (about 186,000 miles/second). But light moves 0.0008% slower in air, and slower still through cooler air (which is more dense). The bottom line is: a temperature gradient in air causes light to veer toward the cooler air. Air near the pavement can be 10-20 degrees hotter than air farther up. This temperature gradient “bends” the light rays that would otherwise hit the pavement, and directs them to your eyes. So you see blue sky (water), extra headlights, and upside-down tree trunks on the road.
So, as I've been typing this post, my country is getting ready to watch the last night of the Democratic Convention. It's interesting to consider politics through the lens of optical effects. I know that neither major party is as good as a mirage, because they do not really bend, reflect or refract the light. They are more like an optical illusion, appearing to their constituents like an image created between their hearts and their brains. Ah, now I get it! (PS-- I'm a total, dyed in the wool Democrat and plan to vote accordingly. But I do acknowledge my illusions!)