This one’s for the scientists.
Tom Lehrer’s “The Elements”
Jonathan Coulton’s “That Spells DNA”
Science Groove’s “Glucose, Glucose”
And on a more somber note, Flanders & Swann’s “20 Tons of TNT”
April 14, 2009
March 25, 2009
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.
March 22, 2009
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.)
