The ninety percent

Yesterday my wife and I were talking and the subject of faster than light neutrinos came up. “Someone did something wrong,” I said, “either the experimentalists or the theorists.” Then I added, half jokingly (if that) “Probably a bad cable. Ninety percent of experimental physics is finding the bad cable.”

Today’s news: It may have been a bad cable.

Well, okay, a bad connection to a cable. Messing up the GPS timing and making the neutrinos look too fast.

Well, I’m surprised I predicted it a day ago, but I’m not surprised by the news itself. Ninety percent is an exaggeration, sure, but it’s true a large fraction of all the problems you run into turn out to be something like cables or connections.

Understand, this is not really the physics equivalent of the tech support question, “Are you sure the monitor is plugged in?” Even a (relatively) small and simple particle physics experiment can easily use hundreds of cables in its data acquisition system. Big and complex ones… you don’t want to know. Here’s a photo from Brookhaven to show you what I mean:

If any one of those cables is bad, or a connection is bad, or a cable is plugged into the wrong place, it may mess up the results in ways that can drive you nuts trying to figure it out. (Or it may not; a few percent of those cables probably are actually obsolete and don’t do anything.)

As the story linked above mentions, there’s another problem they’ve found that could be making the neutrinos look too slow. They won’t know for sure what effect either problem had until they do more tests after they’ve fixed them. But I’m guessing the neutrinos will be obeying the speed limit next time they measure them.



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