For Two Centuries It Was Folklore. It Turned Out To Be Dirt.

ITHACA, N.Y. — I have been forecasting weather for this newspaper since 2006 and publishing my error rate every Friday. Sixty-four point nine per cent wrong, running total. So I know something about being told you are unreliable.

Here is a story about people who were told that for two hundred years and were right.

What they reported

A glowing sphere, roughly the size of a grapefruit, drifting rather than falling. It appears during or just after a thunderstorm. It lasts seconds. It sometimes passes through a window or down a chimney. It goes out, or it bursts.

Sailors reported it. Farmers reported it. Pilots reported it. Almost none of them could get anybody to believe them.

The standard treatment for two centuries was that these people had seen ordinary lightning and misremembered it, or had an afterimage, or had made it up.

Why nobody could settle it

Professor Idrissa Bergqvist-Achebe was firm with me about this and he is right.

The phenomenon is rare, brief, unpredictable and impossible to produce on demand. You cannot build an experiment around something that shows up for four seconds once in a decade in a field you are not standing in.

So it stayed where unrepeatable things stay, which is outside.

The accident

In July 2012, a team on a high plateau had a spectrograph and a high-speed camera pointed at ordinary lightning, which is what they study.

A strike came down about nine hundred metres from the instrument. A ball appeared, and drifted, and the instruments were running.

They recorded it: a spectrum, and video. The paper came out in January 2014.

What it is made of

Not air.

Nitrogen is seventy-eight per cent of the atmosphere the thing was floating in and it is barely in the spectrum. Oxygen likewise.

What is in the spectrum is silicon, iron and calcium — which is what is in the ground underneath.

A lightning strike vaporises a patch of soil. The vapour condenses into a cloud of extremely fine particles that stay hot, oxidising as they go, and for a few seconds that cloud is a glowing ball drifting on the wind.

It is dirt. It is a burning puff of the field it came out of.

The part nobody reports

A hypothesis published in 2000 predicted this composition.

Fourteen years before anybody measured a spectrum, somebody worked out from first principles what a lightning strike does to soil and said: if this is what ball lightning is, here is what you will find in it.

Then somebody found it.

This desk thinks that is the most impressive thing in the entire story and it is in none of the coverage, because a correct prediction that waits fourteen years for its confirmation is not an event and nothing happens on a Tuesday.

Eleven letters

I asked in this column in May whether any reader had seen one, and eleven wrote to me.

Nine of the eleven had told almost nobody. Two had told nobody at all before writing to a weather column.

One of them, Ivy Latchford, a retired district nurse — named here at her daughter's request after her death on 1 August — described watching one come along the hallway of a farmhouse in 1961 and out through the open front door, and finished her letter like this:

"I told my husband and he was kind about it. I did not tell anyone else for sixty-four years. I am writing to you because you print how often you are wrong, and I thought you would not laugh."

What this desk owes people

Professor Bergqvist-Achebe's full answer runs at the foot of this page and it makes a distinction I intend to keep.

There is an enormous difference between we cannot study this yet and you did not see it. The first is honest and free. The second is a claim about somebody's mind that we were never in a position to make.

His field said the second one far more often than it had to. So, historically, has mine.

I have never seen ball lightning. If I do, I will report it in this column, and I will put it in the same notebook as everything else, and I will expect to be asked for the spectrum.