Is the Great Wall of China visible from space?

During the sermon last Sunday, Pastor Dan mentioned that the Great Wall of China is the only man-made structure visible from space. I had the vague impression that this wasn’t the case, but I couldn’t think of a good counterexample. (I’d heard that the Salton Sea also fits this claim, but it’s debatable whether it’s truly man-made or truly a structure.) It was time for research.

The first stop was Wikipedia, where I learned that the original version of the claim was that the Great Wall was visible from the moon, not just space. I would go on to find that this is still the most common claim about the Wall’s visibility, as various WikiAnswers-type pages frequently features this or something similar (e.g., “What are the only two man-made strucutures visible from space? Great Wall is one.”) Snopes’s article was written about it, too. It wasn’t until I checked Space.com that I found a detailed examination of the lesser claim of visiblity from “space,” (low earth orbit, for our purposes). The Straight Dope also takes on both versions extensively and declares them both factually bankrupt. I’m not sure I trust About.com, but they deny the moon claim but say that the wall is “barely visible” from orbit. Disappointingly, the Encylopedia Brittanica Online doesn’t say one way or the other, though it did answer my question about the Wall’s width–about 30 feet, which would seem to make it much less visible than a lot of other things.

But while these sources are a good start, we can do better than that. Let’s see what NASA has to say.

You can tell NASA has had to deal with this question many times in the past, for the NASA website’s page on the claim describes it somewhat tendentiously as a “space-based myth.” NASA identifies the origin of the claim as a 1938 book, and now that I know that I wonder why anyone ever took the claim seriously, much less after the age of spaceflight began. The page does allow that the Wall is visible from orbit with the aid of binoculars or a digital camera with a telephoto lenses, but then, so are a lot of things, including bridges, dams, airports, and the Egyptian pyramids. Even then it’s difficult without the right weather conditions: the Wall was built from bricks made from the surrounding dirt, so it’s awfully hard to spot a wall of dirt against the dirt if there hasn’t been a recent snowfall or the like. So NASA’s answer is basically “No,” albeit with the caveat that under the right conditions you might get extremely lucky and find something that may or may not be the actual wall.

Finally, I came across a BBC article written after one of China’s early space launches. China’s taikonaut looked for the Wall and couldn’t find it, and in response the Chinese government pressed publishers to redact the claim from their textbooks. That about settles it for me; if even China calls shenanigans on a point of Chinese pride, I feel safe declaring the claim false.

Powers of 10

Dan’s sermon tonight reminded me of the Powers of 10 video. Released in 1977, it’s a little outdated, but it’s still worth a look:

As a bonus, a certain xkcd strip should now make more sense to you.

If that’s a bit too 70s-tastic for you, check out the updated (and controllable!) version on this page. (Requires Java, which you should already have.)

Saturday, March 21

Until I checked my computer’s clock, I did not know that today was the twenty-first. I did not care. I knew today is Saturday, just as I knew each day of the week before it. It’s a tendency of mine to navigate time by days and not dates, and vacations exacerbate this habit. I don’t know how I picked it up, but I’ve done this for as long as I can remember.

Yesterday I ordered the flowers I’ll be trying this spring. Since Spring Hill Nursery is offering $20 of free plants right now, I picked out more exotic stuff than I did last year: a gladiolus mix and few toad lilies. For those who don’t know, I live on the third floor of a house converted into apartments. Since dirt is understandably rare thirty feet off the ground, my “garden” consistst of half a dozen pots in various shapes and sizes. The larger ones sit on the landing in front of my door, but most of the pots are small enough that I can keep one on each step leading up to my floor. This is the second year I’ve kept a flower garden, and I love the color they add to my world as well as the idea of a little extra life around. I’m also getting better at keeping plants alive, albeit slowly: last year I tried growing flowers from seeds, a plan that worked swimmingly until an unexpected late frost zapped them all. I managed to get a few ageratum and coleus growing later in the spring, but this year I decided to split the difference and try bulbs. We’ll see how that goes.

An interesting thing I learned today:

The Nazis drew up plans for a manned orbiting solar death ray with a life support ecosystem based on pumpkins. Really.

Reflections on seeing Raiders of the Lost Ark for the first time

Pretty good. But a few questions remain:

• Why did Belloq bring a pretty white dress to the desert dig site? Who would have worn it if they hadn’t happened to capture Marion? Maybe Belloq never wanted to be an archaeologist, he wanted to be a lumberjack!
• After Indiana Jones burned a path through the snakes to the Ark, it must have smelled terrible in there.
• When Indy finds Marion at the Nazi camp, he almost frees her but decides against it in order not to attract attention. So what does he do next? Start digging in the middle of the Nazi camp with thirty men after putting on his trademark hat. Real nice, Indy.
• Speaking of attracting attention, did nobody notice Indy and his men setting up a separate dig site about twenty feet away from the Nazis? So much for the master race.
• Why did Indy pull up the Ark in the middle of the day? Is there any reason he couldn’t do it at 3AM when everyone is asleep?
• Did Indy hold his breath the entire time while riding the U-boat? It’s not clear how he could have gotten inside, much less done it without being noticed; it’s not like submarines have copious free space.
• The Nazis took the Ark seriously enough to dress Belloq up like a high priest and have him conduct a mini-consecration. So what do they do next? Repeatedly touch the Ark. Didn’t anyone think that was dangerous? Did their copy of the Bible have only the even verses or something?
• Indy is implied to have had a relationship with Marion when they were both younger. How much younger? We aren’t told, but it looks like George Lucas had some unsettling figures in mind.

Zombie outbreak code of ethics

In nearly every zombie outbreak scenario, the biggest threat isn’t the zombies, it’s surviving humans. We’ve all seen how it goes: a few people manage to escape the slavering zombie hordes only to be attacked, exploited, and generally menaced by another, more ruthless group of survivors. With this in mind, I propose the following guidelines for behavior in the event of a catastrophic reanimation scenario:

1. Maintain a constructive attitude. Yes, corpses are reanimating and everyone is under a lot of pressure, but being a jerk to your uninfected co-survivors isn’t going to help. If you go through life being a colossal jackass, consider giving it a rest until things settle down.
2. Cooperate. Intelligence is your main advantage over a zombie horde, so you should cooperate with other survivors in order to maximize this advantage.  You have to share supplies, but having other people watching your back and helping you make traps will keep you safer in the long run–it’s been shown that most fortifications experience zombie breaches as a byproduct of survivor infighting.
3. Retain what social infrastructure you can. Zombies change a lot of things, but they don’t have to ruin everything. Just because there aren’t cops around doesn’t make it okay to exploit your fellow survivors. Besides, you need all the help you can get.
4. Loot responsibly. Yes, the zombie down the street doesn’t need his stuff anymore, but that doesn’t mean you should take everything that isn’t nailed down. Take whatever you need and leave the rest for other survivors. If circumstances permit, leave a message behind for others telling them where they can join you.
5. Get to know your fellow survivors. A zombie outbreak is a good opportunity to meet people you might not normally interact with. Learning about each other makes cooperation easier and might bring useful skills to light.
6. Practice effective quarantines. While every zombie outbreak is unique, there are best practices you can follow. You might be reluctant to write off a fellow survivor who may have been infected, and that’s fine: just isolate them for 24 hours (or however long it takes for unambiguous zombification to occur). Provide them with sufficient food and water and appoint someone to keep them company (outside the quarantine area, of course). This ensures that no one is abandoned unnecessarily and minimizes the risk to other survivors.

“In the desert” — Stephen Crane

I saw a creature, naked, bestial,

who, squatting upon the ground,

Held his heart in his hands,

And ate of it.

I said, “Is it good, friend?”

“It is bitter — bitter,” he answered;

“But I like it

Because it is bitter,

And because it is my heart.”

Speaking of which… — 1

I’m behind on posting and we talked about a lot of interesting things today. Some housekeeping:

Earlier this evening I had confused Linus Pauling’s discovery of alpha helicies with August Kekulé’s earlier discovery of the ring structure of benzene, a discovery he claimed came to him in a daydream about the ouroboros.

Pyrophoric materials burn constantly at room temperature in the presence of an oxidizer (i.e., most of the time you’d encounter them).

“Alea iacta est“–”the die is cast”–is what Julius Caesar is reported to have said as he crossed the Rubicon river in defiance of the Roman Senate, his first overt step to becoming emperor.

Maxwell’s demon is hard to explain concisely, but it has nothing to do with fire.

The Vader Sessions. James Earl Jones did the voice for Darth Vader, but he also did the voice for every movie with James Earl Jones in it. After watching this clip, you will never forget this.

Political terminology

“The usual terminology of political language is stupid…Who is ‘reactionary’ and who is ‘progressive’? Reaction against an unwise policy is not to be condemned. And progress towards chaos is not to be commended. Nothing should find acceptance just because it is new, radical, and fashionable. ‘Orthodoxy’ is not an evil if the doctrine on which the ‘orthodox’ stand is sound.”
—Ludwig von Mises, in Interventionism: An Economic Analysis (1998).