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!)

Wednesday, July 27, 2016

Monday, July 25, 2016

Shhhh...The Heron Is Sleeping

Roger spotted the heron before I did. Its head was hardly visible between the rocks down by the brackish pond. We've seen it in the water here very often, always hunting for little fishes. It took me second to see it. Ahhh, what an interesting perspective. It was standing below the rocky edge.
I took a few photos and then we walked along the path a little further to get a slightly different perspective. It surprised us that it didn't take off. We were really pretty close to it.
As we walked on, it was visible behind the weedy dandelions along the edge of the pond. Still quite calm and unafraid.
That's when I noticed that it was closing its eyes and getting ready for a little nap in the warm afternoon sun. What an interesting thing to see. I was so surprised that its lower lid rises up like this.
Eyes closed and falling asleep. 
We walked on, thanked it for such a nice opportunity for a close up look, and wished it the sweetest dreams.
Nasreen asked a very good question in the first comment here. So, I updated the blog with a photo to show how far we were from the heron. I  had zoomed in at 60X to get these photos.  Click on the pic to see if you can find it! The rocks are a clue.

Wednesday, July 20, 2016

Wordless Wednesday: Prickly Plant Life

Our backyard artichoke
Thistle
Artichoke flowering
Agave
Teasel


Monday, July 18, 2016

River Otter


We had an interesting encounter with a river otter out at the marsh on Sunday. We've seen them out there a couple of times over the years, but this one was definitely not behaving the way we've seen them in the past.
A few days ago we arrived at the marsh and ran into a friend in the parking lot who was just leaving. She said, "There's a mama river otter with her baby in the brackish pond. They've been coming up and going down, swimming around, and carrying on. It's great. Go see them, don't miss it." Well, we headed off in a different direction and planned on looping the brackish pond at the end of the walk as we always do. When we got there only the young otter was around. It was definitely behaving in standard otter fashion, coming up to the surface, looking around, and then heading under the water. I wished I had gotten a photo of it, but it was too busy and hungrily active for a good shot.
Well, we headed back out to the marsh on Sunday. It was quiet out there. So quiet the only photos I had taken by the end of the walk was of thistle flowers. Not much wildlife; the tide was in, and that was that. We did our usual walk, and were heading back to the car when I looked at the small tidal pond where a GIANT transmission tower stands. That's when I saw it. It appeared to be a young-ish (or simply smallish) river otter, just hanging out and not doing its usual exuberant fish hunt.
I took some photos of it and managed to get a short 30 second video. In the video I notice that it closed its eyes for a bit. It was more motionless than I expect a river otter to be. It made eye contact with us, followed our voices and whistles. Now I'm wondering if the creature is not well, hungry, tired, or just young and unsure of humans.


If you make the video full-screen, you can really see its closed eyes. What do you think?

PS-- The water where the otter is swimming is a rather bizarre color because of weird muddy silt that's always there. Also, the patterns on the water are skypools of the windy wavy transmission tower reflection and maybe some clouds.