Friday, September 16, 2005

More bad science reporting

With all my talk about how the problems with science reporting are similar to the problems with other kinds of reporting, it's worth pointing out that science reporting has its own unique problems. The most important of these is reporters' complete ignorance of the subject matter, as exemplified by this Reuters story, along with their unwillingness to actually learn anything.

SYDNEY (Reuters) - An Australian man built up a 40,000-volt charge of static electricity in his clothes as he walked, leaving a trail of scorched carpet and molten plastic and forcing firefighters to evacuate a building.

Frank Clewer, who was wearing a woollen shirt and a synthetic nylon jacket, was oblivious to the growing electrical current that was building up as his clothes rubbed together.

When he walked into a building in the country town of Warrnambool in the southern state of Victoria on Thursday, the electrical charge ignited the carpet.

"It sounded almost like a firecracker", Clewer told Australian radio on Friday.

"Within about five minutes, the carpet started to erupt."

Employees, unsure of the cause of the mysterious burning smell, telephoned firefighters who evacuated the building.

"There were several scorch marks in the carpet, and we could hear a cracking noise -- a bit like a whip -- both inside and outside the building", said fire official Henry Barton.

Firefighters cut electricity to the building thinking the burns might have been caused by a power surge.

Clewer, who after leaving the building discovered he had scorched a piece of plastic on the floor of his car, returned to seek help from the firefighters.

"We tested his clothes with a static electricity field metre and measured a current of 40,000 volts, which is one step shy of spontaneous combustion, where his clothes would have self-ignited," Barton said.

"I've been firefighting for over 35 years and I've never come across anything like this," he said.

Firefighters took possession of Clewer's jacket and stored it in the courtyard of the fire station, where it continued to give off a strong electrical current.

David Gosden, a senior lecturer in electrical engineering at Sydney University, told Reuters that for a static electricity charge to ignite a carpet, conditions had to be perfect.

"Static electricity is a similar mechanism to lightning, where you have clouds rubbing together and then a spark generated by very dry air above them," said Gosden.

This is very obviously a hoax. Unfortunately, people who don't know any science trust it because, understandably, they trust Reuters not to print hoaxes.

There are so many things wrong with this story. Most important, however, should be personal experience. Do YOU think you could set yourself on fire by walking around with a nylon jacket? Of course not. After a static shock, your finger isn't even a little warm. So the logical question should be, "why is this guy different"? The reporter never bothers to ask that.

The reporter, even if he knew *nothing* about science, should have at least been suspicious about the reactions from the people involved. When you get a static shock from touching a doorknob or something, it hurts. You notice it. Yet we're supposed to believe that some guy was walking around and setting things on fire and didn't even realize what was happening?

There's the bogus use of meaningless numbers. The report says that the fire officials measured a "current of 40,000 Volts." The reporter should have asked himself, "how big is that?" and maybe compared to current drawn by other household items, like light bulbs. If he had bothered to do this, he would have found that current is measured in Amperes, not Volts, and that the phrase "current of 40,000 Volts" is meaningless. It's like saying "a car weighing 40,000 inches."

I could go on (and on, and on), but you get the point. Reporters and editors, it seems, are willing to just turn off their critical thinking skills when it comes to science stories.

UPDATE: My first thought was that I wouldn't bother with actually calculating why this is so ridiculous. If you know E&M, you shouldn't need the calculation, and if you don't, it wouldn't mean anything. However, a lot of people have taken E&M courses and have just forgotten most of the material, so here's the refresher.

Your body's "capacitance" (ability to hold charge) is about 100 pF. So C=10^-12 Farads (1 pF=1 picofarad=10^-12 Farads.)

The energy stored by static charge is given in Joules by U=CV^2/2. V is voltage, 40,000 Volts according to the story.

So U=10^-10*40,000^2=0.08 Joules.

This is really tiny. For reference, one Joule can heat a gram of water by about 0.2 Celsius or roughly half a degree Fahrenheit.

The point here is that 40 kV is not that outrageously high. But your body's capacitance is so low that it hardly takes any energy (or charge) to get you to that voltage. And no, there's no way this guy just happened to have a super-high capacitance--from electricity's point of view, we're all just big bags of salt water. A very large person could hold a *little* more charge, but not a lot.

(If you're mixed up about the differences between current, charge, and voltage, the "hydraulic analogy" is pretty good. Imagine a plumbing system. Water is charge. Voltage is pressure. And current is flow. "Capacitance" is the size of a chamber in the system. So if you have a really tiny chamber (low capacitance), you don't have to put in much water (charge) before you hit a really high pressure (voltage). Well, sort of.)