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

[Brown]

By the way, Phil eventually got around to addressing this subject on www.badastronomy.com:

My Spidey-sense always tingles when I read stuff like this. It never ever pans out. Meteorites, from everything I have so far read, just aren’t hot when they hit the ground unless they are big. Little ones slow down way up in the atmosphere, and then just fall at terminal velocity. That may be a hundred or more kilometers an hour, which is fast, but not that fast.
...
So what was this? I doubt seriously it was a meteorite. Sounds to me that someone was playing with fireworks or something like that.

 

[Skeptic Ginger]

NO, Phil is not wrong. But the reporters get this one wrong about every 2 years.

Sigh....

The question that should be resolved once just keeps coming back.

 

[Skeptic Ginger]

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.

A 10 mm meteorite would be almost impossible to find as a witnessed fall. You might come across one especially in the desert or on a glacier. But try throwing a cm diameter rock into a field then try to go find it.

Of course to stimulate the event described you'd see a streak of light well above you. Then it would go out. Then a short time later you'd hear (maybe) but certainly wouldn't see the rock fall.

Nothing in this story is the least bit credible to anyone who knows the basics of meteorites.

There isn't even a rock to show for this. It is complete (and erroneous I might add) speculation by some people that weren't there. And for all we know distorted by the reporter who interviewed the cop who inquired about it from the "experts". Sounds like a round of telephone to me.

 

[ponderingturtle]

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.

Through wires? It would be like droping a BB on them. It would be falling at terminal velocity after all.

 

[Skeptic Ginger]

I just sent the following to Snopes since I didn't find anything on this myth in the search engine results.

Meteorites Don't Pop Corn

A fireball that dazzled Americans on July 23rd was a piece of a comet or an asteroid, scientists say. Contrary to reports, however, it probably didn't scorch any cornfields.

Flaming debris from the space rock lit up the sky in Orissa state on Saturday night, and sent villagers running after its burning fragments set fire to their houses.

Meteorite wrecks houses in India. At least 20 people are reported to have been injured after a meteorite crashed to Earth in eastern India. This was total nonsense.

Witnesses claim a fast-moving fiery object streaked down and impacted into David and Donna Ayoub's back yard, where it started two small fires. (The Concord article is no longer on the Web.)

Comments On Mystery Arkansas Crash/Fire Arkansas Sleight Of Hand Assails Common Sense

An Old Cow's Tale myth

Like any good story, the "case of the cow" has some truth to it. The great fire almost certainly started near the barn where Mrs. O'Leary kept her five milking cows. But there is no proof that O'Leary was in the barn when the fire broke out – or that a jumpy cow sparked the blaze. Mrs. O'Leary herself swore that she'd been in bed early that night, and that the cows were also tucked in for the evening.

But if a cow wasn't to blame for the huge fire, who was? Over the years, journalists and historians have offered plenty of theories. Some blamed the blaze on a couple of neighborhood boys who were near the barn sneaking cigarettes. Others believed that a neighbor of the O'Leary's may have started the fire. Some people have speculated that a fiery meteorite may have fallen to earth on October 8, starting several fires that day – in Michigan and Wisconsin, as well as in Chicago.

That leaves 1 out of 10 fires caused by lightning, which is approximately the same ratio as cigarettes. (For the curious, other natural causes of fire are very rare: volcanic activity, and the occasional meteorite). myth



Alaska Science Forum
October 10, 1977; Cold Meteorites; Article #190

My mind's eye has always viewed a meteorite impact as involving a fiery object striking the earth, so I was much surprised recently to learn that this view is not necessarily correct.

Meteors enter the atmosphere at such high speed that they create a glow of light in the upper atmosphere. The light is partly from the burning of the meteor and partly emission from the surrounding air, which is heated by the passage of the meteor. Most of the meteors we see are tiny specks which quickly burn up before the meteor reaches to within several tens of miles of the earth's surface. But what about those that do reach the surface and hence become called meteorites?

A meteor weighing from several pounds to several hundred pounds will, indeed, partially burn up before striking the ground. Entry to the atmosphere may be at speeds as great as 90,000 miles per hour (40 km/see). Roughly half of the meteor will be burned away due to heating as the meteor is slowed down by the air. Depending upon the meteor's initial speed and initial weight, it will reach a terminal speed of about 45 miles per hour. It will reach that low speed roughly 10 miles above the ground.

As the meteor falls the last 10 or so miles it cools off. Meteorites picked up immediately after they fell were usually no more than lukewarm. Never has a meteorite of intermediate size been known to start a fire, even when landing in a haystack or in other combustible material.

The slow final fall rate explains also why intermediate-size meteorites penetrate so shallowly when they hit. Most go no deeper than a few feet. A meteorite weighing 2200 pounds (1000 kg) that fell in Norton County, Kansas, in 1930 made a hole only 9 feet deep.

Huge meteorites, those weighing thousands of tons, do not reach terminal velocity before striking the earth's surface. Therefore, these can remain fiery until impact. The one creating the old but newly discovered crater near Bettles, Alaska, must have burned until it struck.

Subject: Impact temp. of a metorite. (is it hot or not) can it start a fire?

Much larger meteorites will hit the ground much faster. A 1m-radius object
hits the ground at supersonic speeds. Still not hot enough to spark a
fire, I don't think, but it's pretty fast.
Something about 10 times that or greater will not even hit its terminal
velocity before reaching the ground. Generally, these things are still
very hot as they impact the surface,
and transfer a lot of heat and energy to the air and to the ground as they
pass.
On June 30, 1908, an object roughly 60 meters across didn't even make it
all the way to the ground. It exploded about 5 miles above a remote site
in Siberia, called Tunguska.
This released enough energy to flatten thousands of acres of forest, and a
large percentage of the flattened trees were also burned. The explosion
was equivalent to
15,000,000 tons of TNT.

So, depending on the size of the meteorite, it may or may not start a fire.

 

[Skeptic Ginger]

....
I presume Phil's point is not that it's impossible for a small meteorite to do so, merely statistically unlikely. ...

I think from the math and physics, short of knocking over the burning lantern and short of the largest impactors, it is IMPOSSIBLE, not merely unlikely!

 

[pdw709]

Why don't you guys check out Phil Plaits blog on this topic....

http://www.badastronomy.com/bablog/2006/10/28/meteorite-burns-a-german-cottage/

Phil

 

[Ducky]

So...

Reporter: A meteor started a fire!

Phil: No, It was always burning since the world was turning.


Damnit now i have that song stuck in my head.

 

[Skeptic Ginger]

Goody, I had the America's Funniest Videos theme song going through my head all morning. Now I can sing, "We didn't start the fire" instead. The other one was driving me crazy.