I entered now month three of leaving my mathematics blog where it can't hurt anyone or do much and nobody's complained so I guess that's all okay. My photos, meanwhile, have reached the holiday season and our visit to the Wonderland of Lights at the Potter Park Zoo so I hope you're ready for a week of that: Walking up to the zoo entrance for the Wonderland of Lights. There wasn't quite enough snow to cover the grass but a bit of snow is better than none for this kind of photograph sequence. The trees right up front, just past the entrance. The gift shop and bathrooms are on the right. Toy soldiers standing beside the plaque commemorating donors. One of the sponsored Christmas trees is off to the right there. Yes, the sponsored Christmas trees are still decorated by a suspiciously great number of dentists. Note all the tooth ornaments on this one. The Fox News that you want to watch, outside the arctic fox enclosure. We didn't see the arctic fox. The lights tunnel this year was set up over the walkway from the otters (left of this picture) to the grey wolves (not visible when we visited). Trivia: At the end of 1868 the directors of the Crédit Mobilier --- construction contractors for the deeply struggling Union Pacific Railroad --- voted shareholders a 200 percent dividend. The dividend was payable in Union Pacific stock, as opposed to the cash payouts of the five previous dividends. Source: Empire Express: Building the First Transcontinental Railroad, David Haward Bain. Currently Reading: The Rise And Fall of the DC-10 , John Godson. This is a lot of book and, like I said the other day, feels weirdly like a circa 2015 blog where the author is always hectoring you to agree that some proposition or other is absurd, but without giving quite enough context for this reader at least to be confident that it is. Like, there's several spots where he talks about the DC-10 floor design having a floor of 4.6 (or whatever) pounds per square foot, whereas the 747 has one of 7.5 (or something) and the DC-9 8.0 and, OK, from context we can understand that seems like it's low since DC-10s had this habit of the cargo doors flying open and the lower hold decompressing and the floor falling in. But we can assume the DC-10 designers supposed the floor collapsing would be a rare event so why were their calculations wrong? Henry Petroski would have made that clear. Or, for another, Godson goes on a lot about the way the FAA tried to fix the cargo-door problem by issuing Service Bulletins instead of Airworthiness Directives. There's a clear difference, in that an Airworthiness Directive is required by law to be followed (and gets publicized in much harder ways to overlook), while a Service Bulletin is enacted only by the airlines' interest in planes not crashing quite so much. And, sure, but in practice, are Airworthiness Directives obeyed that much more faithfully than Service Bulletins? From the description of the sorry mess it's not clear to me that the airlines or McDonnell-Douglass were all that good at following procedures at the time, so does it make a difference which level of requirement the design modifications were distributed on? I'm not saying Godson was wrong, just that there's a natural question not filled in there. Sometimes there seems to be a lack of imagination or empathy involved too. Like, Godson sneers at this process where McDonnell Douglass offered repair kits for the DC-10s to airlines for free, if they filled in and returned this paperwork within 90 days. They know who bought their planes; why not just send the kits and the engineers to oversee repairs? Why charge them after three months? But I can see where this should make sense: providing the kits free offers the airlines an incentive to order this stuff now, rather than 'someday when it's convenient'. And it does let them specify when they'll be able to take a plane out of service for the repairs. This may not work, but I can understand the designers of the process thinking it should; how close was my thinking to being right, and why would it not work in getting repair kits delivered and installed?