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!

An orange ring in the blackness of space

How cool is it that we now have an actual image of the event horizon of a black hole! More precisely: it’s the glowing accretion disc of matter falling into the black hole, and the event horizon’s silhouette.

The Event Horizon Telescope, actually a worldwide array of telescopes, used interferometry to effectively create a planet-sized telescope to see the light around the supermassive black hole at the center of M87, a galaxy 55 million light years away.

I remember talking with a college classmate about giant interferometry telescopes back in the late 1990s. It’s incredible to see the technique actually making discoveries like this!

What we’re seeing in this image isn’t a top-down view of the accretion disc, but an angled one — think of Saturn’s rings — and the gravity of the black hole is bending the light from the disc. Phil Plait has a great article on the science behind the image. Katie Mack has a Twitter thread on how the image was produced, why the ring looks the way it does (it tells us which direction the disc is spinning!), plus simulations of this type of black hole seen from different viewing angles.

Here’s a paper talking about the history of black hole images, with a detailed discussion of what you should expect for the “shadow” image we’ve just seen. Check Fig 12, with renderings of shadows for disks at different angles

4x4 grid of black circles with red/yellow outlines, with bright and dark spots in the outlines.

— Katie Mack (@AstroKatie) April 10, 2019

Direct links to the articles she mentions:

And this Mastodon thread by collects some more articles worth checking out:

Forbes makes the excellent point that, while we’d seen a lot of circumstantial evidence for black holes over the last few decades, this confirms that they exist.

One of the nice things about a lunar eclipse is how accessible it is. You don’t need binoculars or a telescope (though it helps). You don’t need protective gear. You can see it from a city street with lights on. You don’t need to be in exactly the right spot to see it, since the viewing area is measured in multiple continents rather than a narrow track. And since it lasts longer than a solar eclipse, if the clouds roll in moments before totality (which they did), you can wait a few minutes and you might still be able to see something!

The last time a lunar eclipse was visible in our area, I woke up at ridiculous-o’clock in the morning and went out to watch, first across the street, then trying to find a clear view in the west before sunrise and moonset drowned everything out.

This time I just walked out into the front yard.

Lunar eclipse mosaic
Four stages of the eclipse. I’m not sure what the star next to the moon is. As Sam points out, the star is Spica. The phone line bisecting the second view looked interesting, so I went with that rather than an unobstructed shot. In retrospect, I should have tried to frame it to look like the Death Star trench.

My son is almost 3 1/2 now, just old enough to appreciate this sort of thing, so I spent the last few days talking it up. We went out to look at the full moon early in the evening. We read a kids’ book on stargazing that he likes. I showed him pictures of what to expect, and diagrams showing how an eclipse happens. He’s been wanting to play with a tent ever since I mentioned the phrase “camping stuff” a few days ago, so we found the tent in the garage and set it up in the front yard. He had as much fun playing in the tent as he did watching the earth’s shadow move across the moon.

Katie stayed inside most of the time and came out a few times to check on progress.

At one point, an airplane flew across the sky leaving a sharp, bright contrail just next to Mars.

Moon Mars Power Lines and Contrail

We were all out just before totality around midnight…when a cloud started forming right in front of the moon. Mars, not too far away in the sky, was perfectly clear, but the moon got blurrier, and blurrier, until the razor-sharp sliver of a few minutes before was a blob of white. It reminded me of the time we saw about that much of an eclipse in San Simeon on the way up to (coincidentally) WonderCon when it was in San Francisco.

Fortunately the cloud started breaking up again after a few minutes, and all we had to do was hold up our hands to block the streetlight across the street and we had a clear view of the fully eclipsed moon. (We could see it without blocking the light, but it was a lot clearer without the competition.)

I should probably mention that while the pictures here look red, it looked brown to the naked eye. Maybe it was because the streetlight kept our eyes from adapting to the dark. Maybe the camera is more sensitive to red light. Katie remarked that without the sunlight shining on it, it really does look like what it is: a big ball of rock.

Eclipse Lineup

After a few minutes we went back inside. Neither of us wanted to stay up until two to watch the same thing in reverse…or manage an increasingly tired and distracted three-year-old while doing so.

I had no luck viewing the Transit of Venus. I didn’t have time to find and meet up with any sort of viewing party that might have a telescope or other equipment, and I’m kicking myself for not having tracked down a set of eclipse glasses of my own, so I was left with a handheld pinhole “camera” made out of a cardboard gum package. The clearest image I could get with that was about 1/4″, too small to see the tiny speck moving across the sun. (Though I could see the cloud bank the sun was setting into about the point that I gave up and went inside.)

Oh, well. I can’t be too upset, since I got to see a great solar eclipse two weeks ago. And there are plenty of places to watch online and find pictures.

Photo from Astronomy Picture of the Day.

I had several plans for viewing today’s solar eclipse, depending on the weather. As the hour approached and clouds loomed in the west, I decided that my best bet would be to get above the cloud cover, and drove up into the hills to Del Cerro Park at the top of the Palos Verdes peninsula.

I’m glad I did, because a lot of other people had the same idea.

Individuals, couples, families, groups of friends, groups from schools — and everyone had a different way to see the eclipse: pinhole cameras, binoculars projecting on cardboard, welding helmets, “eclipse glasses” and more. There were also people who were just out for a day at the park, and wanted to know what was going on.

If J had been a few years older it would have been a family event for us too, but at a year and a half, I don’t think I would have been able to explain anything beyond “don’t look at the sun.” A partial eclipse is easy to miss if you’re not paying attention.

I’d cobbled together a pinhole camera the day before from two Amazon boxes, a sheet of paper, a sheet of aluminum foil, and lots and lots of packing tape. I actually started with just one box and I decided the image wasn’t big enough, so I grafted on a second. Even then it was only about 3/8″ across, but when testing it I could see the edges of clouds drifting across the sun, so I figured it would work. It did. Continue reading