Harrison Farm

for now, the only thing we're growing on this farm is kids - not the goat variety

Month: March 2017

My shadow project

[A little introduction by Marathon: ]

We were talking about solar eclipse phenomena recently. I told the kids about my memories from eclipses that I experienced as a boy, especially about how all the leaves of a tree would take on the shape of the eclipse.

After the conversation, I did some image searches so I could show them what I remembered.

I was stunned to find that the truth was nothing like I remembered it!

Instead, there are thousands of images showing pinhole-camera effects. That is, the light from the sun passes through tight squeezes between the leaves and casts itself on the ground as an inversion of the sun's distorted shape. Here is a typical example (Photo by torbakhopper):

backwards in time -- leaves as a natural pinhole camera during solar eclipse : san francisco (2012)

I couldn't find a single picture to support what I remembered!

But I couldn't seem to let go of it either. Without being able to explain very well why, it just seemed to me that there would be an eclipse shadow effect separate from the well-known pinhole effect.

I muttered something to the effect of, "We'd need some fancy lighting or a computer program to know if there was any truth to what I was thinking."

Little did I know that wheels had been set in motion...

Over the past week, I have been working on a project. A coding project.

Sometimes we would play games with light during supper, when the light from the sun would reflect off glass buildings. I noticed that the shadows were almost perfectly crisp, even though our shadows fell on a wall that was 15-20 feet away.

That isn't the case when the light is coming straight from the sun.

In the morning's direct sunlight, the shadows are all fuzzy, and they would do all kinds of crazy stuff, like jumping over to other shadows, or some shadow that is a lot thinner than it should be...

A week ago, I had a realization about why shadows seem to warp sometimes.

I had always assumed that it was from the light of the sun bending, slightly.

But that isn't the case. I realized that if you have a small slit letting sunlight through, there will be a light spot on the ground that is a good bit wider than the small slit. I realized this was because of the light from the right side of the sun shining through to the left of the slit, and vice versa.

During an eclipse, also, a tree shows many mini eclipses on the ground, on it's shadow. This, we found out, is due to the pinhole effect.

Marathon still felt that a normal object, without a pinhole might also give an eclipse-like shadow. We made this big sketch, we kept messing up, but finally, we were pretty sure that any object would give a slightly eclipse-like shape.

It would take a long time to explain it all in writing. It's pretty complicated.

So, instead, I did this coding project to make it easier to understand:

https://www.khanacademy.org/computer-programming/eclipses-shadow/5898189205209088

I consider ~150 inches from the ground to be the best distance for seeing the eclipse-like shadow.

Hope you like it!

[Marathon: So, thanks to Doodle's javascript program, we can see how a shadow of basically anything leaf-sized, that is positioned around 12 feet above the ground, gets distorted by parallax effects to look vaguely like the crescent of the eclipse.

Here's a leaf-like shape's shadow at 10 inches above the ground during an ~80% solar eclipse:

Now here's the same shape's shadow at the same moment if it was 12 feet off the ground:

Totally different!

Even the staple shape, that already is a crescent of sorts, will bend to roughly become a crescent in the opposite direction! Try it for yourself.

Here's another neat effect we found. If you set the moon's size to be slightly smaller than the sun so that it allows for a "ring of fire" at the point of complete eclipse, here's what the shadow of a ping-pong sized ball looks like.

Another symmetrical shape that gets bent into a crescent:

 

 

 

Andinismo

Doodle is quite the enthusiastic outdoorsman

 

The locals use the word "Andinismo" to mean "exploring the Andes Mountains". So far our experience of the Andes has been limited to areas in close proximity to civilization.

I felt it was time to do something more, and summer was almost gone.

Following a two day scouting trip by Doodle and I a few weeks ago, Sudoku joined us this past Sunday for a three day attempt to reach the La Paloma glacier, the lesser of the two glaciers visible from downtown Santiago.

streams through needle-like tundra grass

We picked the warmest sequence of days we could find, but the temperature still dropped below freezing at night where we slept.

The 20 km trail toward the glacier was quite busy on Sunday afternoon, but once night came at our base camp around 9000 feet, it would not be until midday Tuesday that we would see another human being.

It's safe to drink the water at certain places along the hike. Here's a little log of that for those interested:

  • At 1.5 hours of ascent, you'll cross the potable Agua Larga, marked with a wooden sign.
  • At four hours, you'll reach La Lata, a marshy pasture area with horses. The water here is said to be safe to drink, but I didn't trust it because of the presence of horse and hiker feces in the area. However, just above La Lata, there is a stream much like Agua Larga which shows none of the copper/ sulfur discoloration indicative of the non-potable waterways. We took water at that stream.
  • At six hours, you'll reach Las Cascadas, where two major waterways join, but none of the water in that area is considered potable due to the high concentration of metals.
  • At seven hours, Piedra Carvajal appears to be a former glacier lake, but now filled with tundra and very clear streams of water running through it. This water is said to be safe, and it's your last chance for water before the glacier. [Sudoku: The grass here was so tough that some spots of blood appeared on my hand when I touched it!]

The hike was hot and dusty and we had some boot problems and other difficulties with our cobbled-together gear. Fortunately, the three of us are all fairly close on shoe size right now, so we were able to swap around to mitigate the effects of boot irritations.

[Sudoku: My toes only came within about 2.5" of the end of Dad's boots, but they were pretty comfortable.]

By the time we reached our intended overnight spot, La Lata, the air had grown noticeably thin.

The peaks ahead of us were amazing under light of sunset. The stars would have been great (Doodle saw five shooting stars on our scouting trip), but we had a dusk that seemed to last forever and a full moon.

Here in Chile, we've grown quite accustomed to having grazing animals around us when we slept outside in the countryside. Nonetheless, it was a bit unnerving to have horses nonchalantly grazing right up against our tent all through the night.

[Sudoku: I woke up several times to hear Dad shooing the horses away from our tent again.]

We woke feeling good on Monday morning and went for the glacier. It was clear and dry. (there was no dew on the tent.) I couldn't keep up with the kids, so I stopped about an hour short of the glacier's scree-field base and they went to the glacier without me. (And I had the camera with me. Hence no actual pictures of Paloma glacier. Sorry! Here are some.)

camping with grazing animals

On the way down we had the thrill of watching a pair of soaring/gliding condors -- practically stationary in the air just above us -- as we approached one of the steepest sections of the trail.

I never saw a mouse, but I did see a hole in a bag of cheese left inside a backpack we hid in the rocks back at the camp site.

the enchanted tundra field at Casa Piedra Carvajal

Here are some of my takeaways regarding Andinismo:

  • we form a route by connecting water points like camels in the desert and those water points are often glorious
  • the tremendous scale of everything boggles the mind, and the lack of vegetation makes it very difficult to tell how far way things are because there is no reference object
  • managing the sun and the cold is difficult but doable, even for lightly-equipped folk like us
  • appreciating the tenacious plants and sometimes invisible mountain creatures

a wall of ice, but not actually as vertical as it appears

 

The animals we saw over 3 days: Horses, cows, snakes, lizards, mice, foxes, toads, and condors.

[Sudoku: The boys did a great job making sure we had everything we needed for the trip. They have short hair though, and weren't able to warn me about the big tangle I had by the end of our trip!]

[Doodle: Once, when we were hanging out around some small pools of red water, I noticed that it wasn't the water that was red, but that there were hundreds of tiny, red bugs, all crawling over each other.]

© 2017 Harrison Farm

Theme by Anders NorenUp ↑