Sunday, March 23, 2008

Negative evidence

Astronomers have detected indirect evidence for a spectacular supernova explosion in the Larger Magellanic Cloud long ago. The puzzle is that they're picking up the echoes, but we have no records of anyone seeing the direct event 400 years ago, when it should have become visible. The astronomers seem pretty sure that it would have been hard to miss.

I find this interesting because it raises that little point of "negative evidence." We hear often enough that "absence of evidence is not evidence of absence," but that's just not true. It depends on how hard it is to explain the absence. If I insist there's a pink elephant in the room, and you don't see it, you're likely to find negative evidence pretty darned convincing. You might even decide it's more reasonable to speculate upon the reliability of my neural functioning rather than try to explain invisible elephants in exotic colors.

How plausible is it that, in 1600, an eye-popping supernova could appear in the Southern Hemisphere and no navigators' accounts made it into the records that we have? I should think it's surprising enough that I would want to redo some calculations, just to be sure that I really do have such a mystery on my hands.


James Hanley said...

The Dutch had colonized Indonesia by the early 1600s, and I'm sure they would have noted and recorded such an event. Certainly any of the ship captains of the Dutch East India company would have, I'd think. The question is, where would you figure out who was there at the time, and where would you find their ships logs?

Scott Hanley said...

You'd be limited to what records happen to have survived, but I should think the DEI Co. has a lot still extant. I would expect a notable astronomic event to be reported widely and references could show up in a number of sources - reports, letters, memoirs. It's also entirely possible that references do exist and have never been recognized or received attention.

James Hanley said...

"It's also entirely possible that references do exist and have never been recognized or received attention."

That's what I was thinking. According to Patrick O-Brian, author of the great naval novel series, Master and Commander, English naval captains, at least, wrote very cryptic and unexpressive logs. So the evidence might be there, but recognizable for it's significance only if you know what you're looking for. Even a very bland entry, if it's on the right date, would then become meaningful.l