Thursday, July 28, 2016

A Simple Mirage

I remember when I was young and it was summertime, my family would drive to the beach, or out to the country to see my uncle on his 14 acre goat farm. On those roads, where we could see far enough ahead without traffic, we would sometimes see a simple highway mirage. A mirage, just that lovely little illusion of water ahead on the road. We would watch it shimmer and then disappear as the car approached it. I think we kids would shout, "I see a mirage. I see a mirage. Oh no, it's gone."
As I've gotten older and mildly obsessed with atmospheric optics, I've begun to see more than the illusion of water on the road ahead. These crazy "illusions" also seem to "reflect" things like headlights or the car itself as it is driving over them. How is that even possible? It's a mirage, not an actual body of water. So, I began googling around to see what it is I'm actually looking at, when I see a mirage on the road.
Well, I learned on one website that this is not an optical illusion. This is how that site defined an optical illusion:
"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.
Here's a close-up and zoomed in look at a highway mirage. It's been warm and sunny here (for our typically cool coastal foggy weather). Temps have soared into the high 60s (20 C). The pavement is hot and the light rays are bending. I think it's as pretty as an impressionist painting.

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!)

25 comments:

  1. I loved reading this and read a bit to Tom. He told me then that while in eastern Colorado last week he saw a mirage on a dusty gravel road. I had always thought asphalt (or concrete) was a necessary ingredient, so I've learned something new! Also, your final analogy ... wow! Exactly!!

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  3. ^^ sorry, that deleted comment was me. I posted from the wrong account. Anyway, I like this post. I've always liked optical illusions and mirages. However, sometimes the current political activity seems like a hallucinogenic bad trip to me.

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  4. you are my go-to scholar when it comes to optics! Just finished watching the last night of DNC convention. Gotta say, they nailed it. I have issues, you know, but the choice is abundantly clear, right?!

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    1. Clear, absolutely, and it ain't the Trumpkin.

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  5. I've got to copy and keep this explanation of mirages. Thanks for getting into the geeky nitty gritty. :-)
    Re: election, I can't express my displeasure with that buffoon Trump by voting for a candidate with a record of propping up violent thugs in Latin America, so I'm switching to Independent (kma DNC!) and voting for a third party candidate.

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  6. This brings back memories of the long 2-day drive on the hot motorways to our holiday house in Denmark every summer when I was a kid. You bet my father turned it into a science lesson.
    Very impressive pictures, Robin!

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  7. Jennifer-- Mirages can happen in the most interesting places, and there are different kinds of mirages as well. So glad that Tom got to see one on a gravel road. Very cool.

    Dave-- Thank you! I totally own my lifetime of illusions.

    Sharon-- I didn't fall in love with optics until I first saw an iridescent cloud. I was completely knocked out by what I was seeing. That was in 2010, and I've been awestruck and in love ever since. Yes, hallucinatory at times!

    Tara-- You know me, absolutely in love with optics. Foggy days make me boo-hoo all the time. Give me sun and clouds, hot pavement, and ice crystals! The choice is abundantly clear.

    CCorax-- You know me, I've always got to hunt down the geeky nitty gritty of things! I do understand being true to your political convictions, I'm just so afraid of Donald Trump. Here's a link you might appreciate. Interesting it's written by a former student of mine at UC Santa Cruz. I never met him, because he worked on the newspaper at night, but we corresponded via email for a while. He was the first person to tell me about blogging. This is an interview he did in July.
    http://www.vox.com/a/hillary-clinton-interview/the-gap-listener-leadership-quality

    Sabine-- Mirages were the things that kept long summer drives interesting when we were kids. I think I might have liked a science lesson back then, but probably not. Glad you liked the photos!

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  8. I remember being fascinated by those images when I was a kid. Glad you researched them and shared the information.

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  9. Great post all around, Robin Andrea. Thanks!

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  10. Wow, I have never seen reflected lights and trees in a mirage before. What a neat capture. Kind of miss them here for in Ar the roads are too curvy to allow them. Thanks for helping me understand what they are. Love the political reference. Think you are spot on.

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  11. NCmountainwoman-- I was happy to finally take a look at the science behind a mirage.

    Scott-- Glad you liked it!

    Arkansas Patti-- I was so surprised to see lights and cars "reflected" in a mirage. I just had to find out how that happens. Glad you liked the politics. I freely confess my guilt of optical illusions about my party of choice. I wish it were real. Sigh.

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  12. You said they don't bend or reflect, that is certainly true of the Republicans.

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  13. Wonderful post and brilliant clear explanation.

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  14. Steve-- Well, I do think that both parties bend and reflect the needs of big money, but the Dems sometimes do respond to the needs of the many. Glad you liked the post!

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  15. I just had to come back to tell yo---I lied. I took a long trip in Ar today and yes, we do have mirages--I had just not looked for them before as they are VERY brief. But I actually saw headlights in one today. You have such an eye for detail--I tend to see the forest but not the trees. Thanks for making me look.

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  16. Oops, that was supposed to be "you".

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  17. Arkansas Patti-- You just made my day! Thank you for taking a good look around and seeing the mirages on the road. Yay!

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  18. Fear has won big in this election... And that's no mirage. As kids, we saw many road mirages up in Lassen county, vacationing. Thanks for a fun reminder of the simple joys!

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  19. Anne-- True. Fear is not a mirage. I am utterly afraid of Donald Trump. And it is always good to remember the simple joys, especially these days.

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  20. Great post. I have often seen mirages on pavement but don't recall seeing other images in them. Now I will have to look for them. Thanks for taking it one step beyond, Robin, you are a role model for lifelong learning!

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  21. lindaj-- I know you'll see them! Seriously, they are everywhere. And I thank you so much for such kind words.

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  22. We did the same thing as kids. I used to wonder about exactly what a mirage was. Thanks so much for doing all the research.

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  23. Pat-- I was glad to google around and find out just what we are looking at when we see a mirage. Our planet is such a beautiful place!

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