Rock'em Zakim

Two weeks ago portions of the Big Dig tunnel had to be shut down as portions of fireproofing material had fallen from the support beams. It was blamed on the already discovered leaks in the tunnel project. Yesterday traffic was reduced to one lane either direction on the Zakim bridge, another wonder of the Big Dig. Just after noon, when the sun was high in the sky, large chunks of ice and snow began to fall from the cables of the bridge. The snow and ice cracked the windshield of one passing motorist, prompting the authorities to close down the lanes. The scientists with the Massachusetts Turnpike Authority chalked the incident up to a “fluke of nature.” Sure it’s easy to blame mother nature, especially when we are still getting significant snowfall in March. Bostonist much prefers the explanation National Weather Service Meteorologist Bill Simpson gave to the Herald. It has just enough mix of simple concepts and numbers to impress your friends and coworkers:

The real reason for the falling ice is a little more complicated.
A combination of heavy snow on the bridge cables and a higher sun angle merged to create the perfect environment for a road hazard, Simpson said. The maximum sun angle in January and February was 24.2 degrees. Yesterday, the sun angle was almost double at 44.3 degrees.
"The sun is hitting at a more direct angle. It has less of the atmosphere to go through," Simpson said. "It's enough to do its thing - which is melt the snow."