This story frustrates me like being unable to find a bug in code. That is exactly the feeling, yes. Here's an interesting fact about the profession of experim

This story frustrates me like being unable to find a bug in code. That is exactly the feeling, yes. Here's an interesting fact about the profession of experimental scientist: You feel this way all the time. Actual science is not like classroom science. There's no money or glory in doing experiments which have known, explainable, predictable, well-established answers. Nobody will pay you to measure the value of G again and again, on the off chance that one day it will be different. We're all pretty well convinced that this doesn't happen. Instead your job is to do experiments which have odd, inconsistent, unpredictable, poorly-evidenced answers. Sometimes you do those experiments for years and then find that the only reason your results are intriguingly odd is that there's a bug in your technique or your theory. That's depressingly common. Other times -- the interesting times -- you have to invent a brand-new theory to explain your experiments. And sometimes that theory is even correct, and you get to publish a bunch of papers on it -- perhaps you even get to name it! But you must constantly worry that your brand-new theory is a load of crap -- maybe you're just doing the experiments wrong. If you can't learn to live with that nagging feeling of uncertainty you may need to find a different profession. Why would you keep using the same instruments? As others have pointed out: This is undergraduate physics lab. There is no money to buy anything. More importantly, there is no time to assemble another apparatus. (This is another reason why this problem is a great model of real-world scientific life. There is never enough money. There is never enough time.) Moreover, let's consider the possibilities. The instrument was working the week before. With 20-20-hindsight, we know that it was working on the following week. Odds are that the problem was not with the instrument. It was almost certainly with the experimenters! We screwed it up. I just have no idea how, and I never will. Arrrgh!