Jun 302018

On this date in 1908, at around 07:17 local time, Evenki people and Russian settlers in the hills north-west of Lake Baikal in Siberia observed a column of bluish light, nearly as bright as the Sun, moving across the sky. About ten minutes later, there was a flash and a sound similar to artillery fire. Eyewitnesses closer to the explosion reported that the source of the sound moved from the east to the north of them. The sounds were accompanied by a shock wave that knocked people off their feet and broke windows hundreds of kilometers away. The majority of witnesses reported only the sounds and tremors, and did not report seeing the explosion. Eyewitness accounts vary regarding the sequence and duration of the events.

The explosion registered at seismic stations across Eurasia. It is estimated that, in some places, the resulting shock wave was equivalent to an earthquake measuring 5.0 on the Richter magnitude scale. It also produced fluctuations in atmospheric pressure strong enough to be detected in Great Britain. Over the next few days, night skies in Asia and Europe were aglow. It has been theorized that this was due to light passing through high-altitude ice particles that had formed at extremely low temperatures—a phenomenon that would be produced by space shuttles. In the United States, the Smithsonian Astrophysical Observatory and the Mount Wilson Observatory observed a months-long decrease in atmospheric transparency due to an increase in suspended dust particles. Unfortunately, investigation of the area by scientists did not commence until 10 years after the event, which contributed to confusion in the testimony of eye witnesses because they did not have any photographs or videos to supplement their memories. Here is the testimony of S. Semenov, recorded by a Russian expedition in 1930:

At breakfast time I was sitting by the house at Vanavara Trading Post [65 kilometres/40 miles south of the explosion], facing north. […] I suddenly saw that directly to the north, over Onkoul’s Tunguska Road, the sky split in two and fire appeared high and wide over the forest [as Semenov showed, about 50 degrees up—expedition note]. The split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldn’t bear it as if my shirt was on fire; from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few meters. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the Earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn, a part of the iron lock snapped.

The first scientific expedition arrived at the scene more than a decade after the event. In 1921, the Russian mineralogist Leonid Kulik, visiting the Podkamennaya Tunguska River basin as part of a survey for the Soviet Academy of Sciences, deduced from local accounts that the explosion had been caused by a giant meteorite impact. He persuaded the Soviet government to fund an expedition to the Tunguska region, based on the prospect of meteoric iron that could be salvaged to aid Soviet industry. Kulik’s party eventually undertook an expedition in 1927.

Upon arrival, Kulik made arrangements with the local Evenki hunters to guide his party to the impact site. Reaching the explosion site was an extremely arduous task. Upon reaching an area just south of the site, Evenki hunters would go no farther, fearing what they called the Valleymen. Kulik had to return to the nearby village, and his party was delayed for several days while they sought new guides. The spectacle that confronted Kulik as he stood on a ridge overlooking the devastated area was overwhelming. To the explorers’ surprise, they found no crater. There was instead around ground zero a zone 8 kilometers (5.0 miles) across of trees scorched and devoid of branches, but standing upright. The trees farther away had been partly scorched and knocked down in a direction away from the center. Much later, in the 1960s, it was established that the zone of leveled forest occupied an area of 2,150 km2 (830 sq mi), its shape resembling a gigantic spread-eagled butterfly with a “wingspan” of 70 km (43 mi) and a “body length” of 55 km (34 mi). Upon closer examination, Kulik located holes that he erroneously concluded were meteorite holes; he did not have the means at that time to excavate the holes.

During the next ten years there were three more expeditions to the area. Kulik found several dozen little “pothole” bogs, each some 10 to 50 meters (33 to 164 feet) in diameter, that he thought might be meteoric craters. After a major effort to drain one of these bogs (the so-called “Suslov’s crater”, 32 m (105 ft) in diameter), he found an old stump on the bottom, ruling out the possibility that it was a meteoric crater. In 1938, Kulik arranged for an aerial photographic survey of the area covering the central part of the leveled forest (250 km2 (97 sq mi)). The negatives of these aerial photographs (1,500 negatives, each 18 by 18 cm (7.1 by 7.1 in)) were burned in 1975 by order of Yevgeny Krinov, then chairman of the Committee on Meteorites of the USSR Academy of Sciences, as part of an initiative to dispose of hazardous nitrate film. Positive prints were preserved for further study in the Russian city of Tomsk.

Expeditions sent to the area in the 1950s and 1960s found microscopic silicate and magnetite spheres in siftings of the soil. Similar spheres were predicted to exist in the felled trees, although they could not be detected by contemporary means. Later expeditions did identify such spheres in the resin of the trees. Chemical analysis showed that the spheres contained high proportions of nickel relative to iron, which is also found in meteorites, leading to the conclusion they were of extraterrestrial origin. The concentration of the spheres in different regions of the soil was also found to be consistent with the expected distribution of debris from a meteoroid air burst. Later studies of the spheres found unusual ratios of numerous other metals relative to the surrounding environment, which was taken as further evidence of their extraterrestrial origin.

Chemical analysis of peat bogs from the area also revealed numerous anomalies considered consistent with an impact event. The isotopic signatures of stable carbon, hydrogen, and nitrogen isotopes at the layer of the bogs corresponding to 1908 were found to be inconsistent with the isotopic ratios measured in the adjacent layers, and this abnormality was not found in bogs located outside the area. The region of the bogs showing these anomalous signatures also contains an unusually high proportion of iridium, similar to the iridium layer found in the Cretaceous–Paleogene boundary. These unusual proportions are believed to result from debris from the falling body that deposited in the bogs. The nitrogen is believed to have been deposited as acid rain, a suspected fallout from the explosion.

The leading scientific explanation for the explosion is the air burst of an asteroid 6–10 km (4–6 mi) above Earth’s surface. The explosion’s effect on the trees near the hypocentre of the explosion was replicated during atmospheric nuclear tests in the 1950s and 1960s, and was similar to the effects of the conventional of the conventional explosives test Operation Blowdown, conducted to simulate the effects of high explosives in jungles. These effects are caused by the blast wave produced by large explosions. The trees directly below the explosion are stripped as the blast wave moves vertically downward, while trees farther away are knocked over because the blast wave is traveling closer to horizontal when it reaches them. Soviet experiments performed in the mid-1960s, with model forests (made of matches on wire stakes) and small explosive charges slid downward on wires, produced butterfly-shaped blast patterns strikingly similar to the pattern found at the Tunguska site. The experiments suggested that the object had approached at an angle of roughly 30 degrees from the ground and 115 degrees from north and had exploded in mid-air.

In 1930, the British astronomer F. J. W. Whipple suggested that the Tunguska body was a small comet. A comet is composed of dust and volatiles, such as water ice and frozen gases, and could have been completely vaporized by the impact with Earth’s atmosphere, leaving no obvious traces. The comet hypothesis was further supported by the glowing skies (or “skyglows” or “bright nights”) observed across Europe for several evenings after the impact, possibly explained by dust and ice that had been dispersed from the comet’s tail across the upper atmosphere. The cometary hypothesis gained a general acceptance amongst Soviet Tunguska investigators by the 1960s. In 1978, Slovak astronomer Ľubor Kresák suggested that the body was a fragment of Comet Encke. This is a periodic comet with an extremely short period of 3 years that stays entirely within the orbit of Jupiter. It is also responsible for the Beta Taurids, an annual meteor shower with a maximum activity around 28–29 June. The Tunguska event coincided with the peak activity of that shower, and the approximate trajectory of the Tunguska object is consistent with what would be expected from a fragment of Comet Encke. It is now known that bodies of this kind explode at frequent intervals tens to hundreds of kilometers above the ground. Military satellites have been observing these explosions for decades.

The indigenous Evenki have lived in this part of Siberia since the Neolithic. When the Tunguska event occurred, there were ethnic Russians living there alongside the Evenki, and their cuisines had, of course, intertwined. The Evenki are nomadic foragers and reindeer herders, so the principal proteins in their diet are reindeer meat, bear, rabbit, and fish. I hope to meet some Evenki when I attend the World Nomad Games in September this year, and possibly take a side trip to Irkutsk before returning home. That way I can wallow in local foods for a few days. I am especially interested in the indigenous fish called omul, or Baikal omul, which is endemic to Lake Baikal. It is a whitefish in the salmon family that is used locally in all manner of dishes. It is smoked, grilled, baked, pickled, and eaten raw. The two dishes I am most interested to try are are zagutai and raskolotka. Zagutai is made out of small cuts of omul that are first marinated in a special salt solution, then canned with layers of onions. These layers are later soaked in vegetable oil. Zagutai can be eaten with flavored mayonnaise, sour cream, or mustard.

Raskolotka, also known as stroganina, originated around Lake Baikal but is now popular throughout Russia, served in special restaurants. The omul is fished through ice holes in the lake in winter, and freezes quickly because the outside temperatures where the fishing takes place hover around -25˚C (-13˚F). The fish is then cut into thin strips with a special knife, and eaten raw with a half and half mix of salt and black pepper.

Apr 262016


In the early afternoon on this date in 1803 a meteorite shower of more than 3000 fragments fell upon the town of L’Aigle in Normandy. Upon hearing of this event the French Academy of Sciences sent the young scientist Jean-Baptiste Biot to investigate. After painstaking work in the field he reported two kinds of evidence pointing to an extraterrestrial origin for the stones:

Physical evidence: the sudden appearance of many identical stones similar to other stones fallen from the sky in other places

Human evidence: a large number of witnesses who said they saw a “rain of stones thrown by a meteor.”


Biot drew a detailed map of the dispersal of the meteorites, and his subsequent impassioned paper describing how these stones must undoubtedly be of extraterrestrial origin effectively gave birth to the science of meteoritics. The L’Aigle event was a real milestone in the understanding of meteorites and their origins because at that time the mere existence of meteorites was hotly debated. The existence of stones falling from the sky had long been recognized, but their origin was controversial, with most commentators agreeing with Aristotle that they were terrestrial in origin. Eye-witness accounts were treated with great skepticism. They were generally dismissed as lies or delusions.


The meteorites that fell on L’Aigle were collected and sold or sent to numerous museums in Europe where they may still be seen.

aigle5 aigle3 aigle1

Most meteorite falls, such as at L’Aigle, are recovered on the basis of eyewitness accounts of the fireball or the impact of the objects on the ground, or both. Therefore, despite the fact that meteorites fall with virtually equal probability everywhere on Earth, verified meteorite falls tend to be concentrated in areas with high human population densities such as Europe, Japan, and northern India. As of April 2016, the Meteoritical Bulletin Database has listed 1,145 confirmed falls.

Meteorite falls may have occasionally led to cult worship historically. The cult in the Temple of Artemis at Ephesus, one of the Seven Wonders of the Ancient World, possibly originated with the observation of a meteorite that was taken by contemporaries to have fallen to the earth from the home of the gods. There are reports that a sacred stone was enshrined at the temple that may have been a meteorite.


In the 1970s, a stone meteorite was uncovered during an archaeological dig at Danebury Iron Age hillfort, Danebury England. It was found deposited part way down in an Iron Age pit (c. 1200 BCE). Since it must have been deliberately placed there, this could indicate one of the first known human finds of a meteorite in Europe.

Some Native Americans treated meteorites as ceremonial objects. In 1915, a 135-pound iron meteorite was found in a Sinagua (c. 1100–1200 AD) burial cyst near Camp Verde, Arizona, respectfully wrapped in a feather cloth. A small meteorite was found in a pottery jar in an old burial found at Pojoaque Pueblo, New Mexico. Archeologists report several other such instances, in the Southwest US and elsewhere, such as the discovery of Native American beads of meteoric iron found in Hopewell burial mounds, and the discovery of the Winona meteorite in a Native American stone-walled crypt. The oldest known iron artifacts are nine small beads hammered from meteoritic iron. They were found in northern Egypt and have been securely dated to 3200 BCE.

Indigenous peoples often prized iron-nickel meteorites as an easy, if limited, source of iron metal. For example, the Inuit used chips of the Cape York meteorite to form cutting edges for tools and spear tips.

Publishing is analogous to meteorite strikes. I know editors have seen my articles that they printed, but I have absolutely no idea how many have read them or what impact, if any, they have made. Ditto for my books. I know how many have sold, but no idea how many were read. This fact would be depressing if I cared. I am not trying to make money from my writing, or become famous.  I write because it pleases me.  If it pleases others, I am glad; if not, not.


L’Aigle is in Orne, a landlocked department in Normandy that is also the site of Camembert, the village that gives its name to the famous cheese. Coincidentally, camembert was first made around the time of the L’Aigle meteorite fall. Camembert was reputedly first made in 1791 by Marie Harel, a farmer from Normandy, following advice from a priest who came from Brie.

However, the origin of the cheese known today as camembert is more likely to rest with the beginnings of the industrialization of the cheesemaking process at the end of the 19th century. In 1890, an engineer, M. Ridel, devised the wooden box which was used to carry the cheese and helped to send it for longer distances, in particular to North America, where it became very popular. These boxes are still used today.

Before fungi were scientifically understood, the color of camembert rind was a matter of chance, most commonly blue-grey, with brown spots. From the early 20th century onwards, the rind has been more commonly pure white, but it was not until the mid-1970s that pure white became standard.

My discovery of camembert occurred in 1966 when I was an exchange student in France. Before that time my culinary tastes were extremely limited. Cheese, as far as I was concerned, was generic Cheddar. But when I lived in France it was my duty, along with Jean-Loup my exchange mate, to get the baguettes for the evening meal on our way home from school. We frequently bought some camembert as well, sliced it, and stuffed it into a baguette as a quick snack on the way home. That, and Jean-Loup’s mother’s cooking, changed my outlook on food for life.

So, why not do the same in tribute to the L’Aigle meteorite fall?  I just did.

Nov 072014


The Ensisheim meteorite is a stony meteorite observed to fall on November 7, 1492 in a wheat field outside of the walled town of Ensisheim in Alsace. The meteorite is an LL6 ordinary chondrite, weighing 127 kilograms; it was described as triangular in shape, and it created a 1 meter deep hole upon impact. The fall of the meteorite through the Earth’s atmosphere was observed as a fireball for a distance of up to 150 km from where it eventually landed.


Sebastian Brant (1458–1521), satirist and author of “Das Narrenschiff” described the meteorite and its fall in the poem, “Loose Leaves Concerning the Fall of the Meteorite.”

Residents of the walled town and nearby farms and villages gathered at the location to raise the meteorite from its impact hole and began removing pieces of the meteorite. A local magistrate stopped the destruction of the stone, in order to preserve the object for King Maximilian, the son of reigning Holy Roman Emperor, Frederick III. A piece of the meteorite was sent to Cardinal Piccolomini (later Pope Pius III) at the Vatican along with a number of related verses written by Brant.


German painter and mathematician Albrecht Dürer sketched his observations of the fall of the meteorite.

There is an excellent history and analysis of the meteorite here:



Flammekuechle or tarte flambée is an Alsatian dish, perfect for today’s anniversary. It is made of bread dough rolled out very thin in the shape of a rectangle (traditionally) or circle, which is covered with fromage blanc or crème fraîche, thinly sliced onions and lardons (or fatty bacon). It is one of the most famous specialties of the region.Contrary to what the direct translation would suggest tarte flambée is not usually flambéed, but cooked in a wood-fire oven. There are many variations of the original recipe, in terms of the garniture. The standard variations are:

Gratinée: with added gruyère cheese;

Forestière: with added mushrooms;

Münster: with added münster cheese;

Sweet: dessert version with apples, cinnamon, and flambéed with Calvados or another sweet liqueur.

Legend says that the creators of this dish were German-speaking farmers from Alsace, Baden or the Palatinate who used to bake bread once a week or every other week. In fact, the tarte flam Flammekuechle was originally a homemade dish which did not make its urban debut until the “pizza craze” of the 1960’s. A Flammekuechle would be used to test the heat of their wood-fired ovens. At the peak of its temperature, the oven would also have the ideal conditions in which to bake a Flammekuechle. The embers would be pushed aside to make room for the tarte in the middle of the oven, and the intense heat would be able to bake it in 1 or 2 minutes. The crust that forms the border of the Flammekuechle would be nearly burned by the flames. The result resembles a thin pizza.

Without a very hot wood fired oven you cannot properly recreate this dish at home, but this recipe will give you a fair simulacrum.



Starter for the Dough

¼ cup flour
¼ cup moderately hot water, about 110°F
1 tablespoon sugar
1 package yeast


2 cups all-purpose flour
1 teaspoon salt
¼ cup beer
6 tablespoons milk


2 tablespoons oil
1 medium onion (3 ounces), finely chopped
1 cup crème fraîche
½ teaspoon salt
¼ teaspoon pepper
4 pinches nutmeg
3 ounces bacon, cut into matchsticks



Mix the starter ingredients together in a small bowl, cover tightly, and set aside in a warm place for 30 minutes.

When the starter is light and bubbly, mix the beer and milk into the mixture.

Put the flour and salt into a food processor, then, with the motor running, add the yeast mixture through the feeding tube. Process the dough until it forms a ball. Add very small amounts of additional flour or milk if necessary.

Process the ball until it is smooth, elastic, and warm, about 45 seconds to 1 minute.

Butter a medium-sized bowl, roll the ball around in the butter, then cover and let rise in a warm place until doubled. Punch down and let rise a second time.

While the dough is rising, heat 1 tablespoon of the oil in a nonstick skillet. Add the onion and cook, stirring, over low heat for 5 minutes or until golden brown. Let cool.

Combine the crème fraîche, salt, pepper, and nutmeg. Add the cooled onion.

Heat the remaining oil in the skillet and fry the bacon until lightly browned, stirring constantly. Remove and drain through a strainer.

Heat the oven to 500°F.

Oil a 14 x 16 inch baking sheet. Roll the dough until slightly smaller than the baking sheet. Place it on the sheet.

Spread the onion mixture over the dough, leaving a very small raised rim all the way around, then dot with the bacon.

Bake for 20 minutes, or until the tart is lightly browned.