You wouldn’t think that books about astronomy and archaeology would have a lot in common, but Four Lost Cities (Annalee Newitz) and Under Alien Skies (Phil Plait) pack some odd similarities.

Both are about places we (mostly) can’t visit in person: Faraway planets in one case, the distant past in the other.

We have to piece together parts of the experience from what has come to us through time or through space: Telescopic observations, space probes, spectral analysis, and our understanding of physics — ruins, artifacts, aerial surveys and
what we know about people (both contemporary and in general).

For some sites we have very detailed and solid information: Angkor’s stone temples are still standing. Pompeii was well-preserved under volcanic ash and we still have first-hand writings about the city and its destruction. Mars and the moon have been extensively surveyed, including multiple landers and photographs from the surface. (And, in the case of the moon, a handful of people!)

Others require a lot of speculation: There’s a solid core of what we’ve figured out about Cahokia, but a lot of unknowns that we can sorta-kinda extrapolate from the histories and tales of surviving tribes in the area — but only to a point. Similarly, we know the rough structure of the TRAPPIST-1 solar system and some of its planets, but we have to speculate: if one of the planets in the habitable zone actually is habitable, what conditions would that require?

Both include major discoveries made within the last decade: Pluto and Charon were just a pair of dots until the New Horizons mission flew past it in 2015, bringing us pictures and measurements and so much data it took months just to download it from the probe back to Earth. Lidar surveys at Angkor in 2012 revealed the foundations of a vast metropolitan area around the temple complexes, upending our sense of how big the city was and identifying new sites to investigate.

It’s kind of funny how I read them so close together. Synchronicity and all that. They’re also both good (see also my review of Four Lost Cities and review of Under Alien Skies), and I’d definitely recommend them!

One of many cool facts brought up in Phil Plait’s new book, Under Alien Skies is that Martian sunsets are blue!

On Earth, nitrogen scatters light randomly, with bluer colors scattering more than redder colors, so the ambient sky is blue, but when you’re looking toward the sun at a shallow angle (like sunrise or sunset), most of the blue light is scattered into the next timezone and you see red and orange.

On Mars, tiny dust particles of iron oxides (rusty dust?) reflect yellow-orange light, making the daytime sky mostly a butterscotch color…but the particles that can stay aloft in the thin atmosphere are about the size of the wavelength of blue light, so they scatter blue light forward instead of randomly. So at the shallow angles of sunset and sunrise, the sky in the direction of the sun has more blue light than the yellows that are scattered in other directions.

Essentially the same process, but reversed because of the different content of the atmosphere!

Update: I’ve finished the book, and it’s well worth reading! Here’s a link to my review!

Twitter Blue is what happens when you start treating a tool as a status symbol, so you throw the tools away and start selling gold-plated hammers made out of thin plastic.

As anticipated, they’re getting rid of “legacy” verification in favor of charging people $8/month for the privilege of having a blue checkmark next to their name.

Not that verification was perfect before, but most of the complaints I heard prior to the enmuskification were “wait, that person got verified but this person didn’t?”…essentially treating it as a status symbol, indicating who’s worthy of being verified, rather than one tool in the toolbox to indicate that the account really does belong to who it says it does.

Dark blue sky, blurry bushes off to the right. In the middle of the sky are two bright spots right next to each other, the right one noticeably brighter.

With rainstorms for the first half of the week, I figured the sky would be clouded over, and I completely forgot about the conjunction of Venus and Jupiter tonight.

Despite wind, rain and even hail today, it cleared up this afternoon. I happened to run out for groceries and looked up from the parking lot to see a blue sky with Venus and Jupiter right next to each other!

I snapped a quick shot with my phone. And then got out the good camera and tripod when I got home.

And…I think I may have caught some of Jupiter’s moons?!?

Closeup: two white circles against a dark blue background. The one on the right is bigger and has diffraction rays radiating from it. The one on the left doesn't, but there are two faint, blurry dots above it aligned with the disc.

The brighter planet to the right is Venus. The almost-as-bright one to the left is Jupiter. Venus shows diffraction rays, but Jupiter doesn’t…but those dots lined up on one side of it? They’re in the right location to be Callisto, Ganymede and (possibly) Io!

I’ve got to remember to use the telephoto after getting the wide shot the next time I’m taking night sky photos with planets. Just in case.

Not that I’ve been particularly active on Twitter for quite a while now, but the way things have gotten, especially under its new owner, I decided it was finally time to go. I haven’t deleted my main account (yet), but I’ve deleted most of my tweet history, and the accounts I used for side projects, and I don’t plan on returning.

Mastodon has filled Twitter’s niche for me over the last few years (obviously different people have different use cases, so it may not fit yours), and you can still find me there at

As for the archive, I’m slowly going through and looking for threads (and occasional single posts) that I think are worth keeping, importing them where they seem to fit best on this website, whether on the blog or another section.

It may be time to do the same with Facebook and Instagram* too. I haven’t been active on either of them in ages, and I’d rather own my data IndieWeb style than wait for Meta to go the way of LiveJournal.

*I’ve already trimmed a lot of my Instagram history.