michael_nielsen

He was somewhat mournful about his failure to see BEC. But the lesson he drew wasn't that the original papers were wrong. It's that he still had more work to do.

I asked him what he thought was wrong. "I don't know. I think it might be a problem with the power supply." He described all the (many, many!) things he was doing to get cleaner current, as well as half a dozen other issues it might be.

Two years later I saw him again, a few months after he'd achieved BEC. I asked what had been the problem. "Turns out it was the power supply!" he said. Not quite beaming -- he's not a beamer -- but as close as he got.

Actually, when I dug down into details, he'd changed or fixed a _lot_ of things in the intervening two years. And it's hard to be sure. Maybe some of those other things were essential, too. Hard to test the counterfactual.

This type of story is very common. Often, failure to replicate means the experimentalist needs to do more work. The source of the trouble is often tacit knowledge or uncontrolled elements in the original paper.

This most emphatically doesn't mean the original paper is bad. Indeed, as with BEC, the original paper may be extremely good. Instead, it may mean more work is needed to understand exactly what's required to see the effect. The original paper is merely an important first step.

Another good example: measurements of the quality factor of sapphire (basically, how good a lasing substance is it) differed by _orders of magnitude(!)_ between Russia and the West during the cold war.