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Is Phil Plait Wrong? Did a Meteor Start a Fire?

Brown

Penultimate Amazing
Brown
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Aug 3, 2001
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Chapter 15 of "Bad Astronomy" by Phil Plait argues that meteors don't start fires. But in this story from Yahoo and Reuters, trained police officers say otherwise:
A fire that destroyed a cottage near Bonn and injured a 77-year-old man was probably caused by a meteor and witnesses saw an arc of blazing light in the sky, German police said on Friday.
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For those who are a little slow on the uptake, I am not seriously suggesting that the German cops know more about meteors than BA does.
 
I can't see any obvious reason why something hard and hot, moving at speed could not start a fire in principle. A cat can start a fire by knocking a lamp over.

A big bolide obviously can start fires.

I presume Phil's point is not that it's impossible for a small meteorite to do so, merely statistically unlikely. Most of them land in oceans, deserts , ice sheets and other intrinsically non inflammable areas, because most places are like that.
A firework factory on the other hand...
 
Brown said:
Chapter 15 of "Bad Astronomy" by Phil Plait argues that meteors don't start fires.
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That's not what he says.

He says that the smallest meteor(ites) don't cause fires, but the bigger ones can.

Page 137-138.

Yeah, I check, you bum! :p
 
CFLarsen said:
That's not what he says.

He says that the smallest meteor(ites) don't cause fires, but the bigger ones can.

Page 137-138.

Yeah, I check, you bum!
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That's "MISTER Bum" to you.

For all of folks out there who don't own a copy of this fine book, here's what CFLarsen is talking about:
By the time it impacts, or shortly thereafter, the extremely frigid temperature of the meteoroid cools the outer parts very well. Not only do small meteorites not cause fires, but many are actually covered in frost when found!

Large meteorites are a different story. If it's big enough--like a kilometer or more across--the atmosphere doesn't slow it much. To really big ones, the atmosphere might as well not exist. They hit the ground at pretty much full speed, and their energy of motion is converted to heat. A lot of heat. (Emphasis in original.)
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The supposed culprit in Germany was not a big one, but a bolide having "a size of no more than 10 mm."

According to Phil Plait (a notorious bluffer who might be making it all up, and besides, he's never been to outer space so how would he know!?), the small guys are really frigid little buggers, super-cold from spending all their time in the deep-freeze of space. When they hit the atmosphere, they don't heat up long enough to heat up most of the body, and the hottest parts of the body ablate away.
In practically every movie or television program I have ever seen, small meteorites hit the ground and start fires. But this isn't the way it really happens.
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Personally, I haven't seen many movies or shows in which such a thing happens ("Armageddon," "Men in Black" and "Meteor" are the only ones that come to mind), but Phil says he has seen this in "practically every movie or television program I have ever seen." This seems to me to say more about Phil and his preferred selection of viewing entertainment than it says about meteorites.
 
The article doesn't say how the fire started so maybe the meteor knocked over a candle, went through some electrical wiring, or caused other damage that resulted in a fire. Maybe the old guy's cigar fell out of his mouth when the meteor hit. :p
 
Getting serious now, one might take a lesson from the so-called "spontaneous human combustion" cases. Basically, those cases (the ones that are not outright frauds, anyway) involved a fire of mysterious origin and perhaps unusual burn patterns. Pseudoscientists prefer to leap to the conclusion that the source of the fire was something extraordinary, and dismiss or discount more conventional sources.

Even worse, pseudoscientists prefer to cover up evidence of conventional explanations. They fail to mention, for example, that the victim was a heavy smoker, or that he had a fire in his fireplace at the time, or that the wiring of his house or appliances was substandard.

This may be what happened in Germany. The cops (who generally are not remotely qualified to render opinions on matters of fire ignition and propagation) may have jumped to the conclusion that something extraordinary happened, and may have dismissed or discounted more conventional explanations. The Reuters report fails to mention any other more conventional possibilities.

That said, sometimes fire does have a fairly unusual source, such as lightning. Further, burn patterns in homes hit by lightning can be very strange. Nevertheless, there is ample evidence that lightning can cause a dwelling fire--it is a rare occurrence but it actually has happened--while there is scant (possibly zero) evidence that a small meteorite can cause a dwelling fire.
 
Brown said:
That's "MISTER Bum" to you.

For all of folks out there who don't own a copy of this fine book, here's what CFLarsen is talking about:The supposed culprit in Germany was not a big one, but a bolide having "a size of no more than 10 mm."
.
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That shouldn't be hot enough or fast enough to do anything. Small meteors just fall at terminal velocity, and even if it was heated something that small will radiate its heat to fast while falling at terminal velocity.

A decent sized one like the one that crushed a car a few towns over might hit something volatile and cause a fire that way.
 
Brown said:
For all of folks out there who don't own a copy of this fine book, here's what CFLarsen is talking about:The supposed culprit in Germany was not a big one, but a bolide having "a size of no more than 10 mm."
Click to expand...

A 10 mm meteorite would've just bounced off his roof. By this point it would've reached terminal velocity (pretty low for a body of this size and mass), and probably reached ambient temperature. It wouldn't have enough kinetic energy to do any real damage.

The cops were reaching way beyond their expertise, I think. :)
 
My great aunt's and uncle's was burnt down when hail bumped something that started an electrical fire. It was bigger than 10 mm though.
 
Brown said:
That's "MISTER Bum" to you.
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Yankee snob.

Brown said:
Personally, I haven't seen many movies or shows in which such a thing happens ("Armageddon," "Men in Black" and "Meteor" are the only ones that come to mind), but Phil says he has seen this in "practically every movie or television program I have ever seen." This seems to me to say more about Phil and his preferred selection of viewing entertainment than it says about meteorites.
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Well, there's Tunguska:

Even a relatively smallish asteroid a hundred meters or so across can cause widespread damage. In 1908, a rock about that size exploded in the air over a remote, swampy region in Siberia. The Tunguska Event, as it's now called, caused unimaginable disaster, knocking down trees for hundreds of kilometers and triggering seismographs across the planet. The event was even responsible for a bright glow in the sky visible at midnight in England, thousands of kilometers from the blast. The fires it started must have been staggering.
"Bad Astronomy", p. 138
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So, yes, he does say that meteors start fires. Small ones? Hmmmm....that's not what you said. :p
 
There's also a terminological issue.

A meteor is the visible glow of a former space rock or cometary fragment burning up in the atmosphere.

A meteorite is a hunk of something that survives that journey.

In order to spark off a fire on Earth, a meteor must

  • Move fast enough to get hot from friction, i.e. it can't just flutter down like the spaceship that won the X-prize.
  • Still be radiating heat when it gets close to the terrestrial stuff it sets on fire, i.e. it cannot be fully vaporized by reentry.
  • Enter the atmosphere without bouncing back out.
These three criteria constrain the size and shape of such a cause. Most visible meteors are sand-to-pebble-sized fragments of comets, and evaporate to mainly water vapor miles above the surface, making a quick and very bright streak of light along the way. A few are bigger, and some things that fall to earth have iron and nickel in them.

Most accounts of the proportionally unusually large size of the moon compared with satelites of other planets suggest it was carved out of the surface of the earth by an enormous collision a very long time ago. These accounts would thus require that the sort of gravitational sorting which separates the mostly nickel/iron core of the earth from the less dense, mostly silicon upper layers cannot have happened on the moon, as the moon should be made entirely of the same sort of stuff as the outer layers of the earth. One way to test this hypothesis is to check samples of different layers of the moon to see if layers below the surface show such density sorting. Any decent sign of much-more-dense stuff below the lunar surface would falsify the blasted-from-earth hypothesis. So 30 years ago, when people were landing on the moon, they collected exactly these kinds of samples. The hypothesis wasn't falsified, so it currently stands as our best estimate.
 
I just remembered: "Superman: The Movie" featured a fast-moving roughly spherical spaceship perhaps two meters in diameter that burned upon entry into the atmosphere, and caused scorching in a Kansas field.

It also created a rut perhaps a hundred meters long and about three meters deep, and egested a naked child capable of lifting a truck to the amazement of Glenn Ford (now deceased). The scientific absurdities in the film increased rapidly from there.

In an unrelated bit of science news, the Orionid meteor shower is just winding up. The peak of the shower occurred on about October 21. The shower occurs every October and is caused by the Earth passing through debris from Halley's Comet. Thus, if one were to perform a news search for additional info about the German fire, one might end up getting several stories about the Orionid meteor shower.
 
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