The mechanics of the story of Falling Sky meant that it was difficult to include much technical information about the asteroid itself and what it would do, so I decided to include it here on the website instead.

The name of the asteroid, Ragnarok, comes from a Nordic legend. The legend fortells of a final battle between the Nordic gods that will take place at the end of the world.. What attracted me to it as a name was specifically that in the legend, the gods themselves are totally aware that Ragnarok will take place. They know where, when and how it will happen, who will fight whom, and who will die. Yet they are utterly powerless to stop it from happening. The significance of this in Nordic mythology is the self-recognition that nothing is destined to live forever - that the natural forces of chaos and entropy will always overcome that of human society and culture. (source: http://en.wikipedia.org/wiki/Ragnarok)

(Originally the asteroid was called Armstrong-Wagner 27, after its discoverers, which I eventually decided was a crap name. I was then going to change it to Tautatis after the Gaulic god, but unfortunately a real asteroid called Tautatis had given scientists a bit of a scare just recently as it passed by Earth. So Ragnarok it was.)

Whilst preparing this book, I had the extraordinary good fortune to find a website from which I was able to gain (theoretical) information about the kind of impact I had in mind: http://www.lpl.arizona.edu/impacteffects/ . From this website I have generated the following information about the Ragnarok Asteroid:

The theoretical asteroid itself is 25 miles in diameter, made from dense rock (3000 kg/m3 ), travelling at 20 kilometers per second. The asteroid will hit the Earth at an angle of 45%. Destined to hit the centre of Swizerland, London would be approximately 500 miles north-west from ground zero.

The with these properties, the asteroid's inherent energy before impact would total 4,890,000,000 tons of TNT (4,890 Megatons), or 25,000 times the yield of the Hirosima bomb. The average regularity of impacts of this size is once every 3.2 billion years.

Upon atmospheric entry, the asteroid would begin to break up at an altitude of 56.6 kilometers. However it would not be sufficiently broken up to disperse the fragments, and the asteroid would impact the surface more or less in one piece. Neither its velocity or its impact energy would be lessened by its trip through the atmosphere, and would strike the ground with full force.

The impact would not significantly hurt the Earth as an astral body - it would not effect the Earth's orbital path, its axis or rotation. However as a supporter of life, the Earth would be devestated.

The impact would form a crater 253 miles wide, practically wiping swizerland off the map. A fireball 308 miles wide would be created, from which the expanding thermal energy would spontaneously ignite clothing, grass, paper and wood (including living trees) all over the UK, approximately 27 seconds after impact. Anyone exposed would suffer third degree burns over much of the body, and firestorms would most likely be created all over the country.

Approximately 161 seconds after impact, a seismic shockwave measuring 11.1 on the Richter scale would hit the UK - greater than any earthquake in recorded history. The structural damage would be extensive. This would then be followed by the ejecta 436 seconds after impact. The ejecta is earth and rock thrown up by the impact and made red hot, most likely killing anything it falls on.

2440 seconds after impact (approx. 40 mins), the airblast would hit with a windspeed of 3430 mph, and with a sound intensity of 131 decibels. This would cause multistory wall-bearing buildings will collapse, wood frame buildings to almost completely collapse, multistory steel-framed office-type buildings suffer extreme frame distortion and incipient collapse, truss and girder bridges to collapse, and up to 90 percent of all trees blown down.

Without being a reasonable distance underground, it would be very difficult to survive the initial impact. However things wouldn't necessarily get much better. I have read reports (although I have no source for this) that the ejecta would cause it to rain fire for approximately two weeks, and that the ejecta remaining in the atmosphere would take decades to clear, blocking out the sun and causing temperatures to plummet, resulting in the death of a considerable amount of both plant and animal life.

It would almost certainly cause the extinction of a great many species, however mankind would not necessarily be one of them. The human population of the planet would most likely be reduced by over 75% (a rough guess) and human society as we know it would almost certainly be completely destroyed, but humanity itself has the highest level of adaptability and resorcefulness of any species to have ever lived. It's the reason for our success as a species, and it's the reason we survived previous ecological upheavals such as the ice age. It's not implausable that humanity might well survive this one too.