Tag: shadows

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Yes, it turns out a colander *does* make a fun instrument for observing a solar eclipse! Also, thinking about how common eclipses actually are.

Circular shadow on the sidewalk, with lots of bright crescents inside, all facing the same direction.

For a lot of reasons, we didn’t arrange another road trip to see today’s total eclipse like we did in 2017 (which was amazing, by the way!). It was only partial out here in California, and not even with as high a magnitude as the one last October.

But we had clear skies, so we broke out the eclipse glasses from 2017 again. After testing them first by looking directly as a bright indoor lamp to make sure there were no scratches. And I’d heard that colanders make interesting patterns (each hole works as a pinhole camera) much like overlapping leaves do, so I brought that out — as you can see, it worked quite well!

I do kind of regret not being able to get out to see this one as total. Partial eclipses can be really cool, especially if you have multiple ways to observe them, but XKCD has a point. There really isn’t any comparison to experiencing totality, and it doesn’t come through very well in photos.

I bet northern Spain is already booked for 2026.

It is interesting to think that solar eclipses happen every year — usually twice! — but they’re not always total, and they’re only visible from a small part of the planet at a time. And sometimes that’s a slice of, say, Antarctica or Siberia or out in the middle of the ocean. Not rare for the planet, but definitely rare for any given location.

On one hand, it’s no wonder people used to see them as omens. With travel and communication slow (and in many cases impossible) in the ancient world, if you’re only going on what’s been seen in your area, it seems super-rare and unpredictable. On the other hand, cultures with sophisticated enough astronomy like the ancient Babylonians were able to calculate the eclipse cycle thousands of years ago!

One bit of funny timing: We’ve been catching up on the last season of The Magicians. Today we got up to an episode that…well, let’s just say the moon figures very prominently in it!

Update: Axios posted a nice map last week showing how fully booked AirBnBs are for the day in different parts of the US…which shows the path of totality *very* clearly!

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Umbrella shadows and reflection

Late afternoon sun reflecting off a decorated window into the shadow of an umbrella.

We went out for frozen yogurt yesterday to celebrate finally putting all the Christmas decorations away, only to find that the shop still had their Halloween decorations up. I didn’t feel quite so bad after that!

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While driving around lunchtime, I saw an airplane pass overhead, its contrail casting a shadow on the thin cloud layer below. I had my camera handy, and was stopped at an intersection, so I snapped a couple of shots. As often seems to happen, the first, haphazard one was the best.

The diagonal line extending down from the sun is, I believe, a sun pillar-like effect in the trails left by the windshield wipers. Also: Unless I’m mistaken, you can just barely see the edge of a halo in the feathery clouds at bottom center. It’s the slight reddening.

A few hours earlier, I saw this:

I glanced out the window while changing lanes on the freeway this morning & noticed the bottom edge of this halo. By the time I had a chance to stop the car and really look, the lower arc seemed to have disappeared, but the left side was sharply visible – as was a sundog. I rolled down the window and snapped a couple of photos while waiting for the light to change. Unfortunately, I couldn’t position anything to block the sun, so the exposure isn’t all that great.

By the time I reached my destination and parked, it had all faded except for a slightly bright patch in the clouds to the left.

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Yesterday morning while driving to work, I looked up from the road and saw two parallel lines in the sky: One white, one dark blue. They were, of course, a contrail and its shadow on a thin cloud layer below. Because it was a thin layer, I started looking (when I had the chance) for fragments of halos.

When I finally stopped the car, I took a picture of the contrail and its shadow (now nearly aligned with the sun), looked up and saw a faint edge of a halo. I moved a bit to the left, putting a tree in front of the sun, and there it was: a clear 22-degree circular halo centered on the sun..

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With any luck I’ll finally post about last week’s trip to Las Vegas soon, but meanwhile, here’s something interesting that we spotted a couple of times on the drive back: The shadow of a contrail against the sky.

Here’s what it looked like, as the camera saw it. Actually, it was much more visible at the start. It faded considerably in the time it took to get the camera out and snap the photo.

Contrail and shadow, unprocessed

And here it is with the contrast enhanced. You can see a dark line extending across the sky from the end of the trail down to the lower left. The sun was at the upper right, almost but not quite in line with the trail at that point.

Contrail and shadow, with contrast enhanced

Atmospheric Optics has a huge collection of cloud shadows, rays, rainbows, ice halos, and more, including a diagram of how contrail shadows work.