The Meteorite Age

Royal Tomb at Alaca Höyük where a hoard of meteorite objects was discovered. – CC credited to Bernard Gagnon

Metals played a crucial role in the advancement of human civilization that ancient eras, the Bronze and Iron Ages, have been named after them. But pinpointing an actual date on which humans first worked metal into objects is hard to do. In Europe, this could have been as early as 7000 BCE. Brightly coloured copper and gold were utilised first, while extraction of tin and iron came later. A move from the Stone to the Bronze Age was made possible in about 2500 BCE due to the discovery that smelting copper with tin created the durable alloy Bronze. While the move to the Iron Age came much later, about 1200 BCE. Iron is widespread in the geological landscape but extraction and smelting of this metal into a usable form proved incredibly complex. Therefore perplexing is the existence of Iron objects which predate the Iron Age, some of these objects are at least 9000 years old and are from as early as the first worked metals. Another source of iron is non-terrestrial. It arrives on Earth from outer space in the form of meteorites and it has been suggested that the utilisation of meteorites found on the surface could explain the presence of iron objects which predate the Iron Age. This would make meteorite objects some of the earliest encounters that humans had with metal.

It is not difficult to imagine that people would have admired and craved something unique, much in the way we do today. This is an easy concept to understand in a modern context, as in today’s world ‘things’ matter; there is no denying we currently live in a material world. Objects enrich our lives; we use them as embellishments and allow them to express our identities and our hopes and fears. This is not a modern phenomenon, walking around any museum we can see how longstanding the relationship to material objects is. In a world without modern materials and predating the times when the method to smelt iron was common knowledge, the properties of iron would have been special and even without knowledge of its origin would have seemed otherworldly. Manipulation of this material most likely occurred with cold hammering as open fires would not have the heat for smelting the metal. It would have shown the object to be shiny, durable, hard but malleable and made of something which could become useful such as a tool, sharp dagger, talisman or simple beads. There is no suggestion that in all cases people saw the meteorite fall and collected the deposit but in some examples, there is a real possibility this was the case.  

The examples of worked meteorite objects below will demonstrate how rare and highly prized this material was. This is not an exhaustive list as the exact number of prehistoric worked meteorite items changes continuously, not only due to new discoveries but re-examination of existing collections with better identification techniques and more precise dating of prehistoric objects. Historically the easiest and most accurate way to Identify meteoric iron has been by an inspection of its isotopes looking for raised nickel content within the object, in comparison to terrestrial iron which has no or little trace of nickel. Early methods were invasive and involved some destruction of the object to provide a sample. Further complicating identification is that different nickel readings can occur depending on the location of the object tested, so one sample from the same object may result in a different reading than another.  

Modern testing techniques aim for greater accuracy in identification and now use a ratio of three elements cobalt, iron and nickel, while non-invasive techniques such as X-Ray Spectroscopy increasingly play a part as they do not involve damaging these often fragile objects. What the use of X-Ray Spectroscopy has revealed is that particularly corroded specimens may have little nickel content at all. These objects could have been mistaken as being terrestrial but iron objects with no nickel content may still have been delivered from space. Albert Jambon, from the National Center for Scientific Research (CNRS) in France has imaged many of these fragile items with his X-Ray Spectroscope and has identified a number of new specimens and explains that “Some archaeologists were sceptical, as they thought that the amount of nickel found in Bronze Age iron tools was too low to consider them of meteoritic origin, But I’m a trained cosmochemist, so I knew the problem was just corrosion. And I was able to show that nickel was leached away during corrosion.” Modern techniques are increasing the number of known objects which are meteoritic in origin.

Meteorite fragments from inside the remains of a hut dating back more than 9,000 years in Bolków by the lake Świdwie in Western Pomerania. Credit: Archaeologists from the Institute of Archaeology and Ethnology (IAE) PAS

Only sixteen known iron objects predate 3000 BCE and these are outlined in the table below. The earliest worked meteorite objects, three beads, were discovered recently in 2014 at Lake Świdwie  Poland. This exciting discovery was mentioned in the 2020 Yearbook in Astronomy. Dating from 7000 BCE this is not only the earliest example of meteorite-worked iron but one of the earliest worked metal objects in the world. Due to the location of its discovery, the significance cannot be overstated. All the other objects from this period come from the cradle of civilisation and northern Poland sits well outside this region. Prior to this the nine blackened beads found in a pre-dynastic cemetery near el-Gerzeh, Egypt were the oldest known worked iron meteorite objects. The beads were scanned and revealed the distinctive Widmanstätten structure found in iron meteorites. During this investigation of the beads Professor Thilo Rehren of the Petrie Museum, (University College London) discovered a little about the technique used to create the objects saying “The shape of the beads was obtained by smiting and rolling, most likely involving multiple cycles of hammering, and not by the traditional stone-working techniques such as carving or drilling which were used for the other beads found in the same tomb.” Furthermore, he felt that the Egyptians had an advanced understanding of the material they were using, suggesting that they had worked with the material before. The final object in the table below is a bit of an anomaly itself. It was identified as terrestrial smelted iron, a four-sided tool which was discovered in a tomb in Samarra in Mesopotamia. One suggestion is that the iron used in this object was obtained as a by-product from the extraction of another metal, although that does not explain how the society overcame the difficulties of achieving the high temperatures needed for the smelting process. It is a real possibility that retesting using Jambon’s Spectroscopy technique would identify it as being meteoritic in origin.

ObjectDateLocation of findOther observations
Beads x37000BCELake Świdwie, PolandWorked – found in Shamans hut
Balls x34600-4100BCETepe Sialk, IranPolished but unworked – hard and heavy – found in Palace
Beads x93200BCEEl-Gerzeh, EgyptWidmanstätten structure – Grave goods. 9% Ni
Four-sided Tool5000BCESamarra MesopotamiaFirst non-meteorite smelted object?  Grave goods

The Gerzeh bead is the earliest discovered use of iron by the ancient Egyptians. Credit: Manchester Museum

During the following millennium, the number of iron objects increased, although they are still rare compared to other metallic objects made from copper or gold. Iron was still highly prized and treated as a precious metal. All the discoveries are objects of significance and include jewellery, decorative items and ceremonial weapons and have been discovered in sealed hoards, near temples or deliberately buried in rich graves. These objects were not intended for everyday use and were luxury goods, much sought after by the populous. There are nine confirmed meteorite objects from this period, including the hoard from Alaca Höyük.

One unanalysed example from this period includes an iron sword found in a Royal Tomb in Dorak, Egypt dated to 2400BCE it is a beautiful early example of a ceremonial weapon. It has an obsidian holt carved into two leopards, inlaid with gold and amber spots. Unfortunately, this example was excavated surreptitiously and is now lost, our knowledge of this object comes from a cartouche of the Fifth Dynasty of Egyptian pharaoh Sahure. This example shows the problem in making a comprehensive list and there are at least another ten examples which have not been confirmed as being meteoritic in origin and therefore do not make the list below.

ObjectDateLocation of findother observations
Fragment3100BCEUrak, MesopotamiaFound in temple
Disc2500BCEUr, Mesopotamia10.9% Ni found in tomb
Pendant2400BCEUmm el-Marra, SyriaFound in Tomb
Pins x 22400BCEAnatolia, TurkeyFound in tomb
Plaque2400BCEAlaca Höyük TurkeyFound in tomb
Dagger2400BCEAlaca Höyük TurkeyFirst discounted as terrestrial iron but retested and identified at meteoric in origin
Mace Head2400BCEAlaca Höyük TurkeyFound in tomb
Amulet2100BCEDeir el Bihari EgyptTomb of Princess Aa Shait Dynasty XI

Dagger from Alaca Höyük Turkey Credit: Noumenon Wiki Commons

During the late Bronze Age (2000-1200BCE) there are a greater number of confirmed meteorite examples with twenty-three being identified to date, although over fifty objects remain to be analysed. What is interesting is that no smelted objects from this period have been identified, with the Iron Age about to burgeon you would almost expect some isolated examples of terrestrial smelted iron objects so the lack of them is curious in itself. Once more the meteorite examples are geographically scattered. Overwhelmingly nineteen of the objects come from Tutankhamun’s tomb in Egypt, surprisingly these objects did not come from a singular iron meteorite drop but from three different meteorites. This suggests that the meteorites were being actively looked for by the populous to be made into grave goods. Within the list are objects which are more utilitarian such as chisels found in Tutankhamen’s tomb, these were still highly prized grave goods and do not demonstrate a regular usage of the material.

ObjectDateLocation of findother observations
Fragment1600BCECrete20lb piece unworked found in Minoan Palace
Axe1400BCEUgarit SyriaDecorated with gold – ceremonial
Axes x 21400BCEChinaShang Dynasty
Dagger1350BCEEgyptTutankhamen Tomb
Headrest1350BECEgyptTutankhamen Tomb
Bracelet1350BCEEgyptTutankhamen Tomb – Eye of Horus.
Chisels x 161350BCEEgyptTutankhamen Tomb – found in box together

Two early Chinese bronze weapons with meteoritic iron blades
R. J. Gettens, R. Clarke, W. Chase (1971)

Stony meteorite falls are far more prevalent than iron ones, their similarities to terrestrial rocks and the fact that many break up into smaller pieces would make the utilisation of large iron meteorites a more regular occurrence. That does not mean that stony meteorites have not been collected by humans in the past. One example was found during an archaeological dig in 1989 in the UK. Discovered in a pit at Danebury Hill Fort and identified as a piece of H5 ordinary chondrite the meteorite was dated to 2350 ± 120 year BP.  Unusually it was found in an unworn, fresh condition and has a weathering index of W1/2. The conclusion is that it had either fallen directly into the manmade pit just before it was filled, otherwise the object was found and placed in the pit deliberately. During this period Danebury fort was heavily occupied and a deliberate placing suggests that the meteorite drop may have been witnessed and the object had been revered by the owner before offering it as a gift by placing it in the pit.

Danebury Meteorite Credit: The Open University

It is worth considering if communities understood the relationship between the object and its otherworldly origin. Evidence from the names given to the material gives a suggestion they did. The Hittite, (from Anatolian, modern-day Turkey) is called iron AN-BAR GE, nepisai or black iron of the heavens, while the Egyptian term bia’ n pet means iron of heavens and both suggest an understanding of the relationship. The Egyptian term came from around the time of the 18th Dynasty or 1300BC. It was a new description at that time and linguists believe it relates to an observed fall. An impact crater at Gebel Kamil in Egypt due to an iron meteorite which fell in the last 5000 years could be the site of this observation, but without written witness accounts it is hard to pinpoint the actual event.

Many stories of impacts have been lost to prehistory; therefore it is worth exploring a modern example of an observed fall and the resulting human perceptions of the meteorite. In Duruma, East  Africa a community collected a one-pound meteorite which fell on March 6th, 1853. Local German missionaries tried to buy this from the Wanikas tribe but they refused to sell it and started to worship it as a god. They built a temple to enclose it, annotated it with oil and pearls and even clothed it. For three years they worshipped this newfound deity, until the Masai attacked the Wanikas village, burning it to the ground and killing many, where they decided it was a poor protector and gladly gave it away. The object is now in the Academy of Sciences of Munich, Germany and shows how fickle humans can be especially when superstition rules. A second example is that of the Hopewell meteorite from Hopewell Mound, Ross County, Ohio. It was found, upon an altar, made into a headdress and beads, and was displayed with a skeleton, which was worshipped by the tribe. Due to this worshipping, there is a real possibility that the people understood its cosmic origin as they had also collected iron meteorites from Brenham Kansas and these specimens were made into more mundane objects such as axes, chisels and drills.

This is not the only instance of stories of meteorites being used as mundane objects in Kansas. Meteorite objects were utilised by the first settlers of the Kiowa area for their base properties and were put to use in the most ordinary ways; such as weights to hold down rain barrel covers and stable roofs, anvils and nutcrackers. This everyday use showed a complete lack of understanding of the origin and rarity of the material. Furthermore, the objects were often considered a nuisance which would break the settler’s valuable ploughing machines.

Overwhelmingly meteorite finds have been prized and that is demonstrated by the type of objects they were fashioned into, or by the location in which they were discovered. Although rare there is no doubt that a number of early meteorites worked objects are still lying in collections around the world waiting to be identified. Less invasive techniques are revolutionising how these objects can be identified, although in some ways is a race against time as unfortunately many of them are in a fragile state and rusting away. To understand humanity’s relationship to meteoric iron objects and early metallurgy it is critical that these objects are identified and classified in the correct manner. It would be ideal to have a special meteorite category at museums for manmade meteorite artefacts, after all, we could have been living through an Age of the Meteorite.

King Tut’s Dagger Credit: online library

(This article first appeared in the Astronomy Yearbook)

Measure to the Moon 2020 – a reflection

Back in 2020 Mayes Creative ran a bit of a bonkers project where I asked you all to take photographs of Venus and the Moon wherever you were in the world. We had lots of people take part and loved how enthusiastic everyone was about joining in. One of these was the late eminent astronomer Jay Passachoff who had written about the method that could be used to measure the distance from Earth to the Moon.

I had been fortunate to meet Jay and hear all about his travels to see solar eclipses at a Society for the History of Astronomy Conference in 2018 and have been saddened to hear of his passing this week. He was always very encouraging of grassroots astronomy.

So I feel blessed to have had his support with this fun socially interactive project. Here is how what we did to measure the distance to the moon and the results we obtained.

The idea was to re-enact the historical ‘Transit of Venus’ which astronomers travelled around the world in order to measure the distance to the Sun using parallax. We attempted the same thing but with the Moon and Venus using social media with people sending their images back to us digitally. Once all the images of the Moon and Venus were received we worked out how to get a distance to the Moon using similar historical techniques. This was done by photographing the position of the crescent of the Moon in relation to Venus, as this would change depending on where you were positioned on the Earth. Over the past 3 months, we had great responses from around the world which enabled us to measure the Moon’s distance. 

We wanted to report back on how close a result we got from our ‘Measure to the Moon’ parallax project. 

February – the first event/ trial run.

A tall building in a city

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We had a good response but mainly from the UK, the furthest image we had to use as a baseline for the Parallax was from Portugal, we saw this as a trial run. The resulting distance we calculated was 271,734km and the Moon was 360,461km away from Earth, so we were a whopping 24.6% out.

March – the second event.

A lit up city at night

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We had many images for the March attempt, including some from the Abu Dhabi Observatory and also the Philippines which really helped us get a better idea of the parallax shift. This resulted in a calculated distance of 340,014km, the Moon at that time was 357,122km away so just a 5.03% difference, which we thought was pretty amazing. 

April – the third/last event.

A picture containing black, sitting, laptop, dark

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The final attempt in April was marred by clouds here in the UK, although there were clear skies in the South-West. We did have a number of US observers taking part including members of Flagstaff and Jay Pasachoff in New York – making the project international. We got a resulting distance of 315,736km, the Moon at this date was 356,906km away, so we had a difference of 11.5% – pretty respectable.

So overall the March attempt had the closest result due to the number of photos we received from all over the world. There were lots of lessons learnt along the way, but we were pretty pleased with the results. We really enjoyed this and may run something similar in the Autumn involving Mars. 

We followed Ernie Wright’s methodology to make the measurements: 

A Mayes Creative intern wrote a short computer program which scale-plated all the images and came up with averages. Then made all the calculations with guidance from astronomer Carolyn Kennett.  

If you have enjoyed this maybe you would like to check out the following which eminent astronomer Jay Pasachoff shared with Mayes Creative.

Pasachoff, Jay. M., Gährken Bernd., and Schneider, Glenn., (2017), “Using the 2016 transit of Mercury to find the distance to the Sun,” The Physics Teacher 55, 3 (March), 137-141: cover illustration plus article:

Alan Stern et al., New Horizons team, from beyond Pluto:

Udo Backhaus, Germany, from the 2019 transit of Mercury:

The Cornish Mine experiment – Weighing the World part 2

In late 2019 I was part of a small group of enthusiastic scientists and historians who came together to discuss their love of Cornwall, the history of astronomy, old scientific instrumentation and the life and work of George Biddell Airy (1801–1892). As a group we were struck by one central aspect to our interests: his Cornish Dolcoath Mine Experiments of 1826 and 1828 to measure the density of the Earth. The discussion led us to devise a plan to get together in a Cornish mine to re-enact the experiment as close to the original as possible. It was an ambitious project and when we set off on this journey we could not foresee all the setbacks and delays that would hamper our efforts to reconstruct the experiment. There have been a number of times when it seemed an impossible task, but we kept moving forward, albeit in very slow increments at times and often with similar parallels that were faced by the original experiments. But before we reach the conclusion on our progress it is important to say a little about the experiment and the reasons why we are still determined to make this happen.

The Experiment
The use of pendulums to measure the difference in gravity around the Earth was nothing new when George Biddell Airy and William Whewell set off to Cornwall in 1826. It had been known that the Earth’s gravity was variable since 1671 when the French scientist Jean Richer made measurements with a pendulum clock and discovered that gravity was not uniform and that it was running over 2 seconds slower in French Guiana than in Paris. In 1737 the French mathematician Pierre Bouguer swung pendulums at different elevations and from the rate of swing was able to make the first estimate of the density of the Earth. There was a lot of concern over the accuracy of these early experiments due to the difficulty in measuring the period of the pendulum. These concerns continued unabated until the invention in 1817 of a reversible pendulum by British Captain Henry Kater. The invention would offer the opportunity to measure the local acceleration of gravity with much more accuracy than ever before.

The experiment required the free-swinging pendulum to be hung in front of a tall grandfather-style precision clock and the timing of the swing would be measured against the clock-driven pendulum behind. To get a measurement for the gravity of the Earth you would need to run the experiment in two locations with different altitudes. Using mountains would be one option, but the mines of Cornwall offered another.

Dolcoath 1826
Dolcoath Mine in the early 1800s was the deepest mine in England. Known locally as The Queen of Cornish Mines it was located in the far west of England near Redruth. It was a very profitable working mine mainly extracting copper, but also tin, silver, arsenic and other minerals. By 1826 it was over 2000ft in depth, with its deepest recesses accessed by long series of ladders. Any equipment, mine spoil and occasionally men would travel up and down the large shafts in buckets called kibbles. The laborious activities would not be limited to the underground, on the surface were noisy pressing stamps and arsenic works which ran beside the engine house. These were working environments before the times of health and safety where accidents were frequent and life was hard for the men, women and children who made their living through mining.

The main way to get goods and occasionally people in and out of the mine – Riding the Kibble
Credit: Mines and Miners. Louis Simonin, 1868
It was in this environment that the two scientists Airy and Whewell arrived first in the summer of 1826 and brought with them precious and expensive precision instrumentation to conduct a scientific experiment. What could possibly go wrong? Well, as it turned out, quite a lot! On arrival, two stations were set up, one underground and one on the surface (perpendicular above to the underground station). Two pendulums (named Foster and Hall after their previous owners) in the design of an invariable Kater one-second pendulum were suspended on knife edges and hung in position in front of a clock pendulum. Alongside the pendulums, they arrived with seven precious and valuable chronometers, tripods, telescope sights and tents.

The surface station was set up in a tent on top of a hill which rises to the south of Dolcoath mine while the subsurface location was 1200ft underground. The cavern in which it was located was split into two with a wooden screen. The experiment was placed behind one side of the screen and separated from the person who would watch the motion from the other side through a sighting telescope looking through a small hole in the screen.

Each pendulum swung for 6-8 hours a day while being watched by either Airy or Whewell, and then the timings were compared between the two stations. The chronometers were transported between both sites at the start and end of the experiment to compare with the clocks. There were some initial concerns. The stands were not up to the job as they were not stable enough. The fragility of the chronometers and lack of agreement between the timings of these was a major concern (two soon had broken glass, damaged from being carried up and down the ladders). It was decided to make the observation runs shorter – just 5 hours of observation a day – so they could compare the chronometers to the ‘clock’ more regularly with an ambition to lead to better accuracy.

After the first cycle of measurements was made there was an attempt to raise the Foster pendulum to the surface. At this point, there was an accident and the straw packing within the kibble caught fire and the bottom of the bucket burnt through. The pendulum plunged downwards and was lost to the abyss. Airy believed it was sabotage and certainly the miners could have been to blame. They were a suspicious lot, living in a remote part of the UK and working in a job where death was commonplace. The arrival of two scientists from London with their strange requests couldn’t have gone down well. At best they were seen as an inconvenience at worst they were regarded as the source of bad luck. Sedgewick encapsulates this in his accounts of the experiment “One morning I listened to two men who had watched our descent the day before: “I think they’re no good. There must be something wicked about them – the little one (that was Airy) especially. I saw him stand with his back to the Church, and make strange faces.” (Sedgewick, 1890)

Airy immortalised the moment of disaster in a poem
The ladders of mighty Dolcoath I descended
Through caverns that yawned like an entrance to hell:

All was silent, save when through the levels came blended
The roar of the blast and the kibbul’s deep knell.
To the right, a vile path round the South Shaft was bending:
Behind, a chain-ladder from hooks was depending:
Our station’s white door in the front was ascending:
When I marked the sad spot where the pendulum fell.
Dark and drear was the spot in Dolcoath’s deepest level
Where the pendulum’s fragments were scattered around,
As when, at the close of some drunken men’s revel,
Broken bottles and plates encumber the ground
Yet though scatter’d they lay, not entirely neglected:
For the men who had packed them, with spirits dejected,
And Mid Cattell and deads the small pieces selected,
And sent up to grass all the bits that they found.
Taken from George Biddell Airy, ‘Dolcoath’, in P. D. Hingley and T. C. Daniel (eds.), A far off vision: a Cornishman at Greenwich Observatory. ‘Auto-Biographical Notes’ by Edwin Dunkin, F.R.S., F.R.A.S., (1821-1898), with notes on the lives & work of his father, brother and son, (Royal Institution of Cornwall: Truro, 1999), p. 182.

Dolcoath 1828
After the ill-fated first attempt, Airy and Whewell would return in the summer of 1828. This time they arrived with reinforcements; the intention was to keep the experiment running twenty-four/seven. Accompanying them were the eminent astronomer Richard Sheepshanks and geologist Adam Sedgewick. They also had a number of additional helpers including Airy’s younger brother.
In another change to the original experiment instead of bunking down in the local count house (now Miss Mollies Tea Rooms) they were to stay within the houses of local mine owners and aristocrats, the experiment had become in all ways something much grander. They arrived on site on the 8 July with two pendulums named Sabine and Brisbane after their previous owners and used the same setup as before except they had calculated that a one-second difference between chronometers was less significant over a longer period. So instead of 5-6 hour shifts, they would watch the pendulums continually with no breaks. There would be 3 people at the surface and 3 people below, they would work in shifts with shift work starting at 6am, 2pm and 10pm. Sheepshanks was in charge of the upper station while Airy was in charge of the lower station and he made sure he climbed the ladders to watch over every changeover: a gruelling schedule for himself while the experiment was in progress.
But by the 10 August the observations started to show an issue, something which Sheepshanks would work upon, eventually showing that it was an issue with the knife edge and agate plate. The steel knife edges of Sabine were not accurate enough. When the two pendulums were hung back to back the error was obvious. Airy fixed and made adjustments accordingly. Once this was resolved the experiment started again in earnest and the main experiment ran between the 16–19 August, when it was abandoned due to rising water in a lower part of the mine which infringed on their area. Airy left the experiment running for as long as he could until even he had to admit defeat once more and return everything to the surface.

In total 127 hours of observations were made. From this, they were able to draw the conclusion that the lower station accelerated by 2 seconds a day. These early results must have been exciting to the team, unfortunately, the experiment was cut short again this time the mine had slippage and they had to come out of the lower levels, and the experiment closed.

The Rosevale Reconstruction
The first hurdle we had was finding a location in Cornwall where we could conduct the experiment. Dolcoath has been decommissioned and flooded with water, as have many of the deep mines within Cornwall. We were in luck when we identified Rosevale mine in Zennor; this was a working mine run by enthusiasts and ex miners and offered us the opportunity of access, albeit not to the depths that Airy would encounter at Dolcoath. A predominantly Victorian mine, access to levels is by ladders and there are wonderful features such as the original tools and candle wax running down the walls. Like all mines, it is the environment, which is prone to change, and 2020 saw our first hurdle as the mine had been shut due to covid restrictions. The pumps had stopped working and the lower levels flooded, making access an impossibility, so we turned our attention instead to the manufacture of the pendulum.

One of the mine’s core team is a clock repairer, maker, and member of the Royal Horological Society. This was key as Kater pendulums were once quite common but are now incredibly rare instruments. We could not take an original into the damp, dirty and dangerous environment of a mine and quickly identified that we would need to build one of our own, which could at worst take damage from transport in and out to its subsurface location.
The making of the pendulum would require detailed information about materials, fixings, sizes and processes. We soon discovered that pendulums had been made from a number of different materials, brass, copper, wood and in some cases steel. Our investigations into exact measurements of the pendulums were equally elusive. This led us to the conclusion that we needed to see an original for ourselves. We found that one of these pendulums was housed at the Science Museum in London and after many delays due to covid restrictions one of our team Dr Daniel Belteki had the opportunity to photograph one in the late summer of 2021. This information has allowed Wayne Ridgeway the clockmaker to make a replica pendulum. A last-minute change at the end of December due to one of our team contracting covid saw us delaying the experiment until Spring 2022.

The Experiment
On 9 April 2022 we finally got the opportunity to run the experiment. Wayne Ridgeway had completed his manufacture of a Katar Pendulum replica and he had acquired a regulator to be positioned behind. We had chosen a location in the mine which was not too wet or had too much of a draft. The temperature was cool around 11 degrees and we could see your breath in the air. Dr Edward Gillin, Dr Daniel Belteki and I waited patiently as Wayne positioned and started the regulator, before leaving it to settle. He then hung the free-swinging Katar pendulum a short distance in front.

The regulator pendulum had a white dot upon it and the Katar pendulum had a black piece of wood which extended below the bob. It would be these two key elements that we would be watching during the course of the experiment. Positioning ourselves a short distance away we placed a small antique brass sighting scope on a table. Looking through this scope we would be watching for the moment that the white dot was ‘eclipsed’ by the black rod. In effect, it would disappear. This would be the timing that the two pendulums would be swinging together and the original experiments were called coincidences. We could anticipate when these would be forthcoming, as the pendulums visually started to look as though they were swinging in harmony, rather than in opposite directions. A coincidence deep in a mine would occur faster than one at the surface and it is this difference which would allow Airy and Whewell to undertake their calculations.

The first coincidence was witnessed by me. I found myself at the sighting scope just minutes before it was due to occur. It had been a challenge to focus on the pendulum through the small sighting scope, and I had felt a moment of panic when I thought that would be visually usable to undertake the measurement. A realisation that I had to use my peripheral vision, much in the way an astronomer would when teasing out detail on a planetary disc. I allowed my eyesight to settle and soon saw the inverted small image of the white dot and black rod through the sighting scope. As the first person to witness the event, it was very hard to know what to expect what I can claim to have seen is the eclipsing of the white dot, not once but twice, the first time for less than a second and then the second time for a longer period of 16 seconds. My experience was similar but unique to those that followed. Daniel Belteki made the observation of the second coincidence and he didn’t see a complete covering of the white dot, but he did see a maximum covering not once but twice, shortly spaced apart in time, Edward Gillin saw something similar when he had a go at the third coincidence.

Each coincidence was timed between 44 and 46 minutes apart and we felt this had more to do with the expertise of the instrument maker than the observers. With more time and coincidences I am sure we would have made improvements in the accuracy of the observations. It had taken a long time that morning to set up the equipment and get the regulator running smoothly. After nearly 5 hours of observations, we had to allow the mine to pack up and dismantle the experiment. Our limitations were very apparent, we had a lack of time to repeat the experiments to a similar length as Airy and Whewell (they conducted 127 hours in total), and we also lacked depth in which to conduct the experiment. Even so, this has whetted our appetite to try again and improve on our first attempt. We felt we were very successful in exploring the challenges involved in undertaking such an experiment in a less than ideal location and we are all looking forward to a time when we can reconvene and try it all over again.
See also:
George Biddell Airy, ‘Account of experiments made at Dolcoath Mine, in Cornwall, in 1826, & 1828 for the purpose of determining the density of the earth’, in P. D. Hingley and T. C. Daniel (eds.), A far-off vision: a Cornishman at Greenwich Observatory. ‘Auto-Biographical Notes’ by Edwin Dunkin, F.R.S., F.R.A.S., (1821-1898), with notes on the lives & work of his father, brother and son, (Royal Institution of Cornwall: Truro, 1999).
Sedgwick (1890) quoted in, John Willis Clark and Thomas McKenny Hughes, The Life and Letters of the Reverend Adam Sedgwick, LL.D., D.C.L., F.R.S., Fellow of Trinity College, Cambridge, Prebendary of Norwich, Woodwardian Professor of Geology, 1818-1873, Vol. I of II, (Cambridge University Press: Cambridge, 1890), p. 332.

Craddock Moor Circle and the Summer Solstice

Sun setting over a distant Brown Willy

On summer solstice eve I was able to photograph the alignment between the circle and the setting sun over Brown Willy and the setting sun lines up well with the prominent hill. Even taking into account that in prehistory the sun wouldn’t set in exactly the same position today (it would be 2 solar discs to the right in the photo above) there is a clear correlation between the two.

Craddock Moor circle isn’t the only prehistoric site where you can watch the summer solstice sunset over Brown Willy and there is an extended line of monuments across the moor where this can be seen. These include the standing stone above the Hurlers and at Goodaver circle.

Craddock Moor circle has another alignment this time with the rising summer solstice sun and Stowe’s Hill. The winter solstice sunrise and sunset have a loose arrangement with the barrows on Caradon Hill and a rolling sunset down Tregarrick Tor. This makes it a very remarkable solstice-aligned circle.

On solstice eve I was treated to sun dogs forming either side of the sun which was a magical sight which kept me watching the skies before the sunset.

The Cornish mine experiment to Weigh the World part 1

Descending ladders into the mine to seek a suitable sub-surface location to run the experiment to measure the density of the Earth. Photograph credit: © Carolyn Kennett, 2021

How did we weigh the Earth (and why did this go beyond simple curiosity)? This may be a question people asked themselves during childhood, and have not considered since. Yet it is a question a small group of scientists, including myself, have returned to as we research experiments conducted in the 1820s in a Cornish mine to measure the acceleration due to gravity of the Earth.

In 2022 our intention to re-create the mine experiments by building a replica Kater invariable pendulum and taking it down a Victorian mine in west Cornwall to make measurements of gravity. We will set the pendulum in two locations, one overground and one underground, and time the swing of the pendulum in both locations. The difference in the rate allows us to calculate the amount of gravitational pull on the pendulum, as the underground pendulum will swing at a slower rate. The original experiment was conducted by George Biddell Airy and William Whewell in the deepest mine in England, Dolcoath. This has unfortunately closed and the lower recesses are flooded, so we are using a mine named Rosevale, which gives us a difference of 250 metres between the overground and underground stations. Although Rosevale is not as deep as Dolcoath (700 metres at the time of the original experiment), it gives the opportunity to explore how the experiment was conducted in what can only be described as less than ideal conditions. Mines are dirty places which can be excessively damp and hot. During the original experiment the scientists would have had to contend with vibrations and noise from the working environment, making their achievements all the more significant.

Why is this all important now you may ask? Yes, simple curiosity does play into this but we find ourselves in a time when the power of gravity is something we have learnt to manipulate and overcome. There are frequent launches into space and discussions of journeys to far-flung destinations such as Mars. Without the arduous and at times dangerous early experimentations into measuring the gravity of the Earth untaken by Airy, Whewell and others we could still be stuck without the knowledge to reach beyond our own planet. Therefore we think it is the perfect time to highlight the work they undertook and their achievements in what was an important building block for us to travel into space.

Blog post first appeared here –