Observing the Comet over Rome

Observing the comet over Rome

The Great Comet of 1878 (also referred to as Secchi's Comet, Comet Pius, and occasionally Wormwood) was a large comet that impacted Earth on the morning of March 20, 1878 in the shallow ocean north of island of Ishigaki, 135 kilometres off the east coast of Taiwan (Formosa).

Originally 'discovered' over a month before it's collision in the skies of the Northern Hemisphere, it's nucleus prior to impact being estimated at being 6.56 kilometres in diameter before it ultimately struck the planet at a speed of around 18 kilometres per second (64,800 kilometres per hour, or almost 60 times the speed of sound). Descending over the northern hemisphere, it impacted in the shallow ocean north of Ishigaki island (only 290 kilometres from the Chinese mainland), creating a fireball 100 kilometres in diameter, killing millions of men, women and children in a matter of minutes and leaving a complex crater 67.2 kilometres in diameter and over 1 kilometre deep.

The devastation caused in the immediate aftermath of the impact, as well as the effects that lingered on following the collision left it the most devastating natural disaster in recorded history. With the Great Firestorm and Century Without Summer a direct result of impact, the human population faced an acute fifty year decline due to freezing temperatures, famine and acidic rain brought on by the comet, over a billion men, women and children ultimately losing their lives during this period. Furthermore, tens-of-thousand (sometimes placed in the hundreds-of-thousands) of species of plant and animal died out following the 'mass extinction', with millions more facing population bottlenecks as rapid population decline affected the entire planet for decades and centuries after the event.


In line with many other 'Great Comets' of the 19th century, the Great Comet of 1878 has received a number of alternative names that allow it to stand out. The most popular of these alternative names is most noticeably 'Secchi's Comet', named after the first astronomer to properly make observations of the celestial body four days following its appearance, Angelo Secchi. Other names however, have also made appearances at both public and educational levels, with terms such as 'Comet Pius' (named after the late Pope Pius IX) being used to differentiate this 'Great Comet'. 

Furthermore, many regional names for the comet have both appeared and waned in the years since impact, with terms based on national astronomers ('Donkin's Comet' being an example, often used in Britain), as well as religious terms such as 'Wormwood' (a reference to the poison star Wormwood in the Bible), which has often been the name utilized by academia in the Americas.


Although there remains contention in who 'discovered' the comet (some having claimed to have seen it weeks prior to its appearance), it is clear that by February 18, 1878 it had achieved an apparent magnitude of -1, as well as being reported by miners in both Britain and France. The first astronomical observations of the body however came on February 22 when the then sick and dying Italian astronomer Angelo Secchi (from which the comet derives one of its names) studied its growing luminosity whilst in Rome, ultimately observing and recording information on the comet every night prior to his death on February 27, his ominous final words being "I have seen its flight, and I fear it".

As it drew closer to the planet, its apparent magnitude increasing every night, many papers began to run stories detailing its ever increasing lustre, the comet itself slowly moving south across the skies of the northern hemisphere. By March 10, the apparent magnitude of the comet was so immense that it was beginning to be seen clearly, with the naked eye, in broad daylight, some describing the spectacle as the Earth's 'second Sun'.


Lead up

As the weeks (in which the comet could be visible with the naked eye) progressed, astronomers and mathematicians began to make rough calculations on the orbit, trajectory and speed of the celestial body, many across the world reaching early conclusions that it would pass by Earth or would skim the atmosphere. However, as the comet began to grow more apparent in magnitude, these calculations were revised daily, especially in the week prior to its collision, some influential astronomers and physicists (such as Oxford Professor William Donkin) began to make claims that the comet was headed towards the planet itself, and would ultimately collide, some speculating in Europe or over Asia, or in the ocean were it would create a massive tidal wave that would wash across the world's nations. These concerns were ignored however, the leading establishment of the time claiming that even if it was to collide with the planet, it would hit with not enough force to see the planet harmed in any fashion, especially if it landed in the ocean, and concerns regarding any damage to the planet were largely ignored.

During the period of time in which the comet was visible with the naked eye, thousands of people began to grow superstitious of the celestial bolide, some regarding it as an omen of ill fate, others considering its appearance a sign of the second coming of Christ, whilst some believed that it would bring doomsday itself. Hoaxes were also common, some local newspapers across the western world claiming that 'cults' and 'new religious movements' had risen up swiftly in response to the comet's appearance. Some 'papers went as far to asset that these new movements were sacrificial in nature, and that they were murdering young women as offerings to their 'deity'.

By the night prior to the impact (February 19), the comet was beginning to get so close to the planet that it's nucleus could be seen through telescopes; this, some astronomers in Britain were claiming, being evidence that the body was indeed on a collision course with Earth, many within the establishment again rejecting their concerns as fallacious. By now the comet had clearly descended across the sky to the south-east (of Europe), and that attempts to properly observe it's final movements in places such as north Africa and America were squandered.


Comet Falling Over Australia

The comet falling over the Bornean horizon

Finally, on the morning of February 20 at around 5:30 am, after a month of observation and speculation, the comet had brought itself over the Pacific Ocean, descending towards the Earth at 18 kilometres per second on an inclination of 57 degrees. Millions of men, women and children living on islands off the coast of China, as well as those native to the Indonesian and Philippine archipelagos, awoke to an overwhelming light penetrating the planet's skies, descending (as a number of witnesses had observed) slowly down, disappearing over the horizon.

It would only be six seconds from the time the comet entered the atmosphere to when it finally collided with the shallow ocean (~530 meters deep) just north of the uninhabited island of Ishigaki, a light hundreds of times stronger than the Sun emanating from the place it struck, lifting up millions of tons of water and sedimentary rock into the atmosphere in only a few moments. In a single second, the energy of 11 million megatons of TNT was released by the colliding body, and it would be less than ten seconds before hundreds-of-thousands of civilians living on the Chinese controlled island of Formosa (Taiwan) first experienced the effects of the collision. Thermal radiation spred out from ground zero at hundreds of kilometres a second, igniting and burning organic material (such as wood, plants, trees, and clothes) whilst millions of living organisms died in a matter of seconds following the impact, an equally Earth shattering seismic shake measuring over 10 on the Richter scale emanated from the area of impact.

Immediate disaster

Thirty minutes following the initial impact, an area covering almost 1200 kilometres in diameter had received such a significant degree of thermal radiation that firestorms had begun to engulf the lands which it had touched, the lush forests of south-east China, Tiawan and even the extreme-northern Philippines were engulfed with flames, spreading at incredible speed. However, despite the extreme thermal damage done in the land just following the disaster, three more aspects of the collision would soon prove to be incredibly destructive on the first day of the impact; ejecta, tsunamis and the air blast.

Firstly, impact ejecta shot into the Earth's atmosphere by the impact fell back to the planet in only a matter of a few minutes, blanketing towns and cities in centimetres of fine ash, dust, large rocks and molten glass, strangling those unlucky enough to be present outside during the storm. Even as far away as the Beijing was from the impact sight (around 1500 kilometres), it still received considerable levels of this ejecta in a relatively short amount of time; at least 2 centimetres covering the Chinese capital city in under ten minutes. As thousands chocked, however, it would soon be apparent that even this was not to be the end of the initial disaster, the soot and ejecta that have layered itself in the ocean and across the coast lines soon to be washed away with the arrival of the tidal waves.

Tsunamis were the second major significant threat to the millions living along the coast lines of the Pacific ocean as witnessed in the wave hundreds of meters tall slamming into Taiwan, immersing the land in sea water as those that had managed to miraculously survive the thermal radiation would soon suffer at the hands of drowning. Meanwhile, tidal waves of more than fifty meters tall continued to move in all directions from the ground zero and across the Pacific ocean, taking less than an hour to first hit the south-east and east coasts of China (effectively wiping away cities such as Quanzhou and Shanghai and their citizens), before hitting the Philippines, Japan, Korea, Indochina and Indonesia in quick succession.

Cities like Tokyo, Kagoshima, Busan and Hai Phong were inundated with dozens-of-meters of flood water as hundreds of thousands of men, women and children who couldn't escape to higher land drowned, the sheer destruction evidenced with the disappearance of hundreds of islands in the vicinity of the comet strike. Even the 'western' cities of Hong Kong and Macau, despite not receiving the relatively dangerous levels of thermal radiation or choking ejecta as well as lying south-west of Taiwan (which had endured the majority of flood water heading in that direction), were still overwhelmed with tidal waves that reached over 20 meters tall.

Finally, the third major 'disaster' that was felt on the first day was the so-called 'air blast'. Emanating out at (or faster than) the speed of sound from the point of impact, it was perhaps the only one of these 'initial disasters' to be truly felt worldwide; the collision being heard across the entire world, even as far away as Washington, London and Buenos Aires, where it was as loud as heavy traffic. As the loudest recorded sound in the world, this blast was accompanied by a jet of air that adversely affected an area 2650 kilometres in diameter; knocking over concrete and wood buildings, shattering glass windows, and uprooting entire forests. In Beijing, 1150 kilometres distant from the place of impact, the speed and sound of the air blast was enough to blow down 30 to 50 percent of trees, knock over wooden structures, and sheer roofs off of houses. Areas closer to the ground zero, however, were effected much more immensely; rainforests completely cleared away, entire towns and villages removed from the maps, and industrial structures (such as railways) distorted. The areas of Asia most severely affected by this disaster were east-China, Korea, Japan, the Philippines, and Indochina.

The projected human toll that was a direct result of the first day of impact and the initial three disasters that followed it is a matter of great historical debate, with some historians placing the number of dead as low as two hundred million to as large as five hundred million (the majority of being those that died in China due to the air blast, tidal wave, or thermal radiation). If this statistics are accurate, they make up roughly 18 to 45 percent of the overall population that has been projected to have died as a result of the comet collision and its later environmental impacts on the planet. 

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