Earlier today, I put up what I thought would be the all-purpose conclusive roundup on the crucial question of whether you can see the Great Wall of China, 长城, from space. But the company spam filter trapped an additional omnibus reader message on the topic, which I reproduce here for what it says about seeing from space -- and also, after the jump, its bonus elaboration on why we should not compare the post-Sputnik science boom to what it will take to change US energy policy. On the Great Wall:

I had to smile when I saw the post posing this question. A number of years ago I was at a meeting, chatting with the person next to me during a break. Somehow we hit on this very same question, although as I recall it was posed as "is it true that the Great Wall of China is the only man-made structure visible from space", which was a popular claim. As chance would have it, at the time I was working with Sid Gutierrez, who had flown on two shuttle missions (I believe once as pilot, once as mission commander).

I called him up and asked the question. He laughed. Seems that before one of his shuttle missions this question had arisen while the crew was in a break during a planning session. Someone eventually looked up the mission profile and figured out when the shuttle would be over the Wall. They added a task to the mission to photograph the Wall at the appropriate time during the mission. The ironic part is that Sid is pretty sure the task was performed but didn't remember anyone ever reviewing the photos to answer the question that started it all.

A couple of other comments:
    1. Others have recalled that the claim about the Wall is that it is only man-made structure visible with the "naked eye" from the moon.
    2. Sid says that you can see many man-made objects from shuttle orbit, such as ships in harbors. One can also see the effects of objects like a fence, since the vegetation may differ significantly on the two sides.
    3. As to whether the wall is the only man-made structure visible from wherever, this almost certainly has to be false. The ability to actually see the wall (as opposed to it's shadow late in the day or some other artifact created by the wall) is probably determined by the width of the wall and your ability to resolve an object of that width from some distance. Other man-made structures, such as the interstate system are wider and in many areas have greater contrast to the surrounding ground. There are also many much larger objects, starting (in terms of date of construction) with the Great Pyramid. And let's not forget the Nazca Lines which again dwarf the scale of the Wall (though I'm not sure the lines are actually wide enough and of sufficient contrast to be visible from orbit). 

From the same reader, who has worked for years at US national labs, an explanation after the jump of why people should not equate the push for a new energy policy with the post-Sputnik race to the moon, something I have done several times.

The same reader on the differences between Apollo/Manhattan projects and dealing with our energy challenges. Part of the reader's rebuttal is against a point someone other than me must have been making -- that Steve Jobs or Bill Gates would be the right leader for such an effort. But the overall argument is worth considering:

A little while back you posted a link to someone else's proposal (I can't seem to find your original post) to mimic the Manhattan Project or the Apollo program. It's still eating at me, so I since I'm already writing, I'll comment that the differences are so great that the whole suggestion is almost meaningless. (Don't get me wrong, I think we're screwed and need to do something big, but whatever it is, this is the wrong comparison.)

Unlike the Apollo program and the Manhattan Project, there are huge vested interests today who will oppose whatever is suggested. There is no national consensus that we even face a problem, and neither FDR nor JFK faced a Republican Party that would walk over their grandmothers if they thought it would hurt the Democrats. I was especially put off by the notion that either Bill Gates or Steve Jobs is remotely qualified to lead such an effort. [Yes, this is not anything I ever proposed - jf] Gates was a brilliant strategist who understood how to leverage a monopoly, all the while buying or stealing technology from others. Jobs is apparently somewhat of a charismatic leader, a product visionary, and presumably a shrewd businessman. But neither of these men are technical giants.

I am not aware of anyone in America who really qualifies as a technical giant, perhaps because our current system of rewards doesn't encourage the development of those skills. If you haven't already read it, I strong encourage you to read the Oppenheimer biography "American Prometheus". A complex man with no shortage of faults, Oppenheimer's brilliance, leadership, and dedication to mission are a combination that occurs probably less than once a generation.

Often overlooked in the popular understanding of the Manhattan Project was the role of General Leslie Groves. While it is nearly impossible to overstate the importance of Oppenheimer to the success of the program, Oppenheimer's fame among the general public today (to the the extent it still exists) is probably matched by the complete ignorance of the role of Groves, who was essential in enabling Oppenheimer to get the job done. As an aside, Groves managed the construction of the Pentagon.

Only a truly existential threat (the possibility of a Nazi atom bomb) could bring together people like Oppenheimer, Bethe, Ulam, Feynman, Von Neumann, Fermi, and thousands of others to work together on a common mission. Nothing less than a common acceptance of another existential threat will bring together a team of comparable magnitude, assuming we can still find people of this caliber.