Monday, 31 December 2012

Talk - A Diamond is Forever

The East Midlands Materials Society recently hosted a fascinating talk by Paul Butler-Smith entitled “A Diamond is Forever”

Paul, who has spent a long career in the diamond industry, began by pointing out the phenomenal success of the diamond marketing machine, as illustrated by the fact that the percentage of brides who received a diamond engagement ring had increased from 20% in the 1940’s to 80% in the 1990s

Diamonds can be natural (either mined directly from diamond containing rocks, or from their eroded alluvial deposits) or synthetic.

One of the reference documents used in the talk was a marketing analysis by Bain and Company - it can be found here and is a fascinating document that concisely presents a lot of information about the formation, processing and sales of natural and synthetic diamonds.

Some 95% of the value of natural diamond is used in jewellery, while industrial applications are served overwhelmingly by synthetic diamonds.

Whilst most people are aware of the harness of diamonds, the fact that they have a thermal conductivity five times greater than that of Copper is less well known. Indeed, the combination of Diamonds thermal and chemical stability, low thermal expansion and high optical transparency makes them ideal for a number of applications in laser optics.

Natural Diamonds are formed in geological structures known as “Kimberlitic pipes” in which magma from unusually deep in the earth’s mantle is forced up to the earths surface.

Schematic of a Kimberlitic Pipe

Synthetic Diamonds are produced by two main techniques, the High Pressure, High Temperature Process (HPHT) - in which a small seed diamond is surrounded by graphite and catalysts and then subjected to temperatures of up to 2500C and pressures up to 60,000 atmospheres.

HPHT diamonds (note large size!)

and the Chemical Vapour Depositions Process (CVD) - in which diamonds can be grown by depositing a chemical vapour onto a prepared surface. This technique can produce diamonds that are single or multicrystalline and also discs and domes as well as particulate diamonds.

Cut CVD diamond - comparable in quality to natural gemstones

In both techniques, additives can be incorporated to change the colour and conductivity of the resulting diamonds. Using the CVD process in particular, it is possible to produce diamonds that are almost indistinguishable from natural stones.

Whilst the majority of synthetic diamonds are used for abrasive or tooling applications, there are a number of other niche areas where high quality synthetic diamonds can be used. You can see some of these at the website of the synthetic diamond manufacturer Element 6

One slightly strange development in the synthetic diamond market is the emergence of companies who will take the hair or ashes of a deceased relative (or pet) and then convert them to a diamond - and example of this being the company DNA2Diamonds.

Synthetic diamonds are becoming very price competitive with other abrasive materials - with the result that volumes have dramatically increased over recent years and applications have move into the mainstream. For example, a diamond coated grinding disc may be a routine purchase for a DIY’er today - but would have been a specialist item for industry only 20 years ago.

Paul presented data that showed how the ratio of natural to synthetic diamond production had changed over time:

1950 : Natural 20million carats, Synthetic 0 carats
1970 : Natural 30million carats, Synthetic 200million carats
1990 : Natural 40million carats, Synthetic 800million carats
2010 : Natural 50million carats, Synthetic 3000million carats

Continuing with a focus on synthetic diamonds, Paul described the work he was currently involved with in. This is looking at the laser ablation of diamond coated cutting micro tools to produce micro tools that can cut surfaces 5 times smoother than conventional diamond coated tools.

By a happy co-incidence, the Royal Institution Christmas Lectures mentioned carbon and diamond a number of times - in particular, the very high thermal conductivity of diamond was explained by the analogy of a bunch of people staning in a line with their arms on the shoulders of the person in front.

If the arms were loose and relexed then pushing the person at the back of the queue did not affect the person at the front because the energy was absorbed the the loose arms along the line.

In contrast, if the people held their arms out in front rigidly and held on tightly to the person in front then a push to the back of the queue was transmitted all the way through to the front by the rigid arms (analagous to the strong carbon-carbon bonds in diamond).

Image sources
Kimerlitic Pipe, HPHT diamonds, CVD diamond

Tuesday, 18 December 2012

Fee- A Biography

Fee – A Biography of an Atom

Fee, an atom of Iron born billions of years ago, has see some incredible sights in his long life and in an echo of the film character Forrest Gump, has managed to find himself at the centre of some key moments in recent history. But to get to the beginning of Fee's story, we need to go back to a time before the formation of the Sun and the Earth when the universe was perhaps three quarters of its current age and a star, not too far away, was dying...

The star, some ten times larger than our own sun was turning into a supernova and, in one of its last convulsions, it sent out a shock wave of material, including many heavy elements, into space. Part of this material was an unstable isotope of Nickel, made in the last nuclear reactions of the star. Within a few hours this had decayed to form stable Iron - and one of those newborn Iron atoms was Fee.

Fee was born in the shock wave of a Supernova

Thus Fee's first memories are of of being part of this hot, complex shockwave of material that was speeding out into space, slowly dimming as it did so.

Within the shockwave could be found every naturally occurring element and, over time, Fee came to know them and recognise their characteristics temperaments.

Hydrogen atoms, for example, had been formed at the beginning of the Universe and were invariably very busy little atoms. Like tiny, hyperactive Scottish grannies, they were full of energy and rushing about trying to make the place look neat and tidy. They always had time to talk, in their sweet highland lilt, and didn't hesitate to despair about how stars these days didn’t know they were born and that it had been much harder in their day.

Carbon, in contrast, was a much more youthful, happy-go-lucky kind of element. This was not a surprise given that there was no carbon in the early universe and that it was all formed within later stars. Always ready to form links and complex compounds with other elements, Carbon was the atom that you wanted at your party.

In contrast to Hydrogen and Carbon, the “Noble Gases”, such as Neon and Argon were very different characters. You may remember your school science teacher explaining that these elements are so unreactive because they have a full outer orbit of electrons. This is complete rubbish. The real reason these gases are unreactive is that they are so arrogant, two faced and full of themselves that nothing else will have anything to do with them.

Fee travelled through the darkness for over a thousand years until, eventually, he saw in the distance a dim, slowly rotating, disc of gas, millions of miles across. Still moving at thousands of miles per second, the shockwave closed in on the disc and then, like some kind of slow motion cosmic tsunami, crashed into it.

Fee and the rest of the material in the shockwave joined the particles of dust and gas as they orbited around the central mass of the disc. Over time, this central mass, composed mainly of Hydrogen, accumulated more material and became a discrete, rotating sphere of gas.

The Embryonic Solar System

Over a period of 50 million years Fee watched the central sphere slowly, almost imperceptibly, become hotter, brighter, and denser until it reached the temperature required to support nuclear reactions between the Hydrogen atoms.

Those first fusion reactions changed everything. They released enormous amounts of light and energy which flooded outwards in all directions, lighting up the dust and rocks around what was fast becoming a fiery ball of gas.

More than that, in fact, it was a star. And no ordinary star - it was the star you know as the Sun.

Whilst the sun had been forming, the dust and gas around it had also been changing. Small particles were constantly colliding with each other and, over time, this was resulting in the creation of lumps of material. These in turn, would combine to form larger and larger structures.

Eventually, this was also what happened to Fee, first he became part of a grain of dust, then a small agglomeration of dust grains, then an irregular, boulder sized, lump of rock.

Similar lumps of rock were colliding everywhere across the disc. The largest agglomerations were able to collect material at an increasing rate and eventually formed the beginnings of planets. Initially under constant bombardment, these planets began to clear paths around the fledgling Sun, becoming larger and larger as they did so.

The Solar System we know today was being formed, and it was a spectacular sight to behold. Collisions between rocks would often send then hurtling into the path of one of the planets, where they would be caught in the gravitational pull and spiral down to impact on the planets surface.

As if this chaos were not enough, there were also millions of comets circling the Sun, each one leaving an icy trail behind it as though it were a celestial airliner with a contrail behind it.

For the next 400 million years, Fee watched as the planets slowly increased in size and the herds of comets slowly thinned out as, one by one, they plummeted into the orbiting planets or disappeared into the Sun.

For the Hydrogen atoms that Fee still occasionally met, 400 million years seemed to be no time at all. They continued to buzz around, reacting with any spare Oxygen to form water molecules and muttering that Jupiter was being very selfish in having so many moons.

Eventually, however, the inevitable happened. A chance collision sent Fee into a orbit that took him across the paths of the third planet from the Sun - a planet which you, of course, know as the Earth.

As the Earth loomed larger and larger, it looked, in some respects, much like it does today, with oceans and a cloudy atmosphere. But in other respects it was very different. There were no vast green forests, no savannah, no cities or roads. Instead, the land comprised uniformly dull hues of rock and sand, marked with volcanoes and lava flows. It looked strange in another way too - the continents were completely different to those today, there was no recognisable Europe or Africa for example. Strange coastlines marked out the land masses, some of which have left no trace of their existence in todays world.

The early Earth contained seas, and volcanos

Famously, "In space, no one can hear your scream", so it was a new experience for Fee to hear the rush of air as he, or rather the rock he was a part of, entered the earth’s atmosphere. Within seconds friction had heated the surface of the rock to such an extent that it was starting to melt and form a fiery trail behind it as it plunged downwards.

Then, suddenly, the rock was encased not in fire but in boiling water and steam as it hit the surface of one of the planets first oceans. As the surface of the rock cooled and the surrounding water cleared, Fee could see that there were no fish, no turtles, not even plankton or krill. The water was not barren, however, and did contain a thin mist of tiny bacteria. A very early form of life on earth, these tiny creatures were unlike most bacteria today in that they did not consume or release oxygen.

Eventually, the rock landed on the sea bed. Over time, parts of the rock, including Fee, dissolved into the water and then flowed with the ocean current as it circled the globe. Each circuit took hundreds of years and Fee completed many hundreds of thousands of circuits. During this time he heard, via the grapevine, that the land remained completely barren.

As Fee circled the world, the bacteria in the oceans slowly changed and evolved. Some of these new bacteria had a biochemistry that used sunlight to produce energy, with oxygen as a waste product. These creatures became very successful and the oxygen they produced - a very toxic chemical to many other bacteria around at that time - began to accumulate in the oceans.

The oxygen reacted with pretty much everything and had a particular affinity for iron, combining with it to form iron oxide (which you may know better as “rust”).

These oxides of iron were not soluble in water and precipitated out as tiny iron oxide particles. And that was how Fee eventually found himself on the seabed again. Looking around, Fee could see that, for hundreds of miles in every direction, there was a thin red layer of layer of rust particles that had precipitated out from the ocean just as Fee had. The slow, almost imperceptible, rain of rust continued for millions of years. Periodically the conditions in the sea would change and the rust would be replaced by a gentle snowfall of some other mineral. As time (inevitably, millions of years) went by, Fee became buried under layer upon layer of sediment. Pushed down towards the hot rock of the earth’s mantle temperatures increased to over 900 degrees centigrade and pressures became almost unbearable, compressing the soft sediments into dense, dry, hard rocks - leaving Fee locked into huge rock formation that covered a vast area.

Fee was bound into a banded Banded Iron sediments like this

Even for Fee, who had a pretty relaxed view of time, the three billion years that he spent in this rock formation was a very, very long time.

By the end of this time, about 200 million years ago, the rock formation had been contorted and fractured to such a degree that it was not possible to believe that it had once been a single, banded, horizontal layer. Much of it had been elevated to form part of a mountain range in what is now known as Europe. The range was close to a shallow sea that covered much of what would eventually become the British Isles.

Much like today, mountains are weathered by sun, rain and frost. In time, this resulted in the rock layers above Fee being work away until, suddenly, Fee was again at the surface and could gaze upon the world.

It had changed.

The land had been transformed from a barren desert to a vista teeming with life, The low lying lands were covered in ferns, mosses and pine trees. Amongst these crawled and flew a variety of insects, some of a very spectacular size. This was also the time of dinosaurs, with giants such as diplodocus lumbering across the land.

The Jurassic World

Further weathering continued to break away sections of rock and Fee found himself being carried away as sediment in a river and then deposited into the sea.

Here, as on the land, there had been tremendous changes since he had last been in the ocean. Whereas his last visit had been at a time when the only life in the water was bacteria, the sea was now teeming with fish of all sizes, as well as turtles, squid and much else.

As further layers of iron-rich sediment were laid upon Fee, he resigned himself to another long stretch entombed in rock - but it was a "mere" 200 million years before he found myself lying in a rock seam a few tens of metres below the surface of nineteenth century Cleveland, in the north east of the UK.

Life gets busy
As he lay in the rock, there was a shattering explosion that left Fee and the surrounding rock fragmented on the floor of some kind of mine tunnel, and he was swept up onto a conveyor and taken to the surface of the mine.

The landscape that met Fee was one that was unremittingly industrial. In all directions lay blast furnaces, slag heaps and railway lines. The furnaces were separated by rows of workers terrace housing. It was a grey, monochrome scene. From the smoke stacks pouring out smoke into the sky to the factory walls and the dusty train yards. It was grey- all of it.

Fee emerged to a scene of blast furnaces and slag heaps

Within a day, Fee was thrown into the heat of a blast furnace and becoming part of the molten bath of iron - soemthing which, contrary to what you might expect, is rather a pleasant experience for an Iron atom. From the furnace Fee was cast into a slab of iron which was then rolled and pounded into a thin sheet before being packed up and shipped out.

The sheet iron was used to form a smokestack for a steam locomotives. Built by Robert Stephenson in 1828, it was the very first steam train to be shipped to the United States to run on their fledgling railway.

The Lancashire Witch, sister train to the "American"

Whilst the “American” was well received in the US, engine technology moved on so fast that it was soon broken up and Fee then spend several decades as part of some farm equipment before being sent off as scrap iron to be smelted down into something new.

His destiny on this occasion was to be used to form part of the suspension cables of the Grand Avenue Suspension Bridge in St Louis, built in 1891.

A majestic structure, the cables hung from two imposing twin stone towers and supported the two hundred metre span of the bridge. The bridge traversed the central railway lines of the city and was in service for some seventy years. Fee could see that the trains the bridge carried were very much more powerful than the likes of the "American" and were able to haul hundreds of carriages of freight to the Gulf, Atlantic or Pacific coasts.

The industrial might of the city was demonstrated when, in two world wars, it dedicated itself to manufacturing military equipment and munitions. A billion rounds of ammunition flowed out of the city every year from one factory alone, much of it on the railways below Fee.

In 1959 the bridge was demolished and, for the third time, Fee soon found himself floating in a blast furnace. .

Always feels good to be in a blast furnace

This time around, Fee was formed into steel sheet that was used to make tin cans - in Fee's case a tin can that ended up containing dog food!

The well developed recycling system for steel cans resulted in Fee spending the next few years moving between smelter, canning factory, grocery store and recycling facility.

Just as Fee was starting to get a little bored of this cycle, he found himslf being smelted into a very different kind of steel called "stainless” steel, which is a form that contains a large about of Chromium.

Chromium, it has to be said, is the dandy of the elemental world. No matter what the situation, Chromium always wants to look good. If you were to raise a stainless steel knife or fork to a mirror, pretty much all the Chromium atoms within it will perform the elemental equivalent of checking their collars and adjusting their hair.

A surprising turn of events
Processed into a thin sheet, Fee was then used as a part in some kind of small scientific component.

Fee was somewhere in these foils

The component was attached to a larger structure called, apparently, "Pioneer 10". . .

At the time, Fee had not idea what he was a part of.

...then, in 1972, the structure was moved across the country to Florida and attached to an even larger, tall, cylindrical construction. Workers fussed all around for days until, suddenly, they all seemed to dissapear and it became very quiet, save for a loudspeaker counting down seconds.

As the countdown reached zero, great pillars of fire blasted out from the base of the structure and it began to move skywards, slowly at first then with increasing speed, all the while the vibrations from the fiery pillars casuing the structure to shake.

Take off !

After several minutes of this acceleration, the vibration suddenly stopped, a covering shroud blew off and Fee could finally see where he was.

Behind lay the curvature of the earth, the oceans, clouds and landmasses spread out in a vast, beautiful artwork. In front lay nothing but empty space and the planets of the solar system - something that Fee had not seen for over three billion years! The solar system had changed greatly since then and was now a much calmer, quieter, more grown-up place than the noisy, dangerous cosmic kindergarten that it had been when Fee had first crashed into the earth.

Listening in on the grapvine revealed that Fee was on a vehicle called Pioneer10 and that it was heading towards Jupiter.

For nine months Fee coasted through space, heading towards Jupiter before using the gravitational pull of Jupiter as a slingshot to send Pioneer 10 speeding towards the outer edges of the solar system.

By 2010 Fee had passed beyond the orbit of even the furthest planet and was moving into interstellar space.

By now it was clear to Fee that there was no turning back, he would never return to Earth and his future lay somewhere out there amongst the stars. Apparently, Fee would pass close to the star Aldebaran in about 2 million years time. Two million years? No problem, bring it on. That was no time at all compared to the billions of years that he had spent buried in rock formations on Earth.

Fee wondered where not where he would be in two million years, but rather where he woudl be in two hundred or two thousand million years. What stars might he see? Might there be another plantetary disc with, as it were, Fee's name on it? Or perhaps he was on a course that would leave him meeting nothing, ever.

So, somewhere, far away, there is a particular sheet of thin stainless steel. If you were to look at that sheet with a very, very powerful microscope, you might be able see that it is composed of individual atoms, mostly of iron.

One of those atoms is Fee, and this has been his story….so far.

Always feels good to be in a blast furnace

Related Posts
Interview with Apollo Astronaut Trainer and Geologist Prof Farouk El-Baz
Curiosity, Twitter and the British Connection
Interview - Chris Lintott and the Zooniverse

copyright Ash Choudry Update 21-Dec-12 : Decided the story was clumsy in the first person, so amended it to be in the second person. Hopefully that has made it a little less pants.

Update 26-Dec-12 : More typos corrected (Thanks for stpotting Mike !)

Update 28-Dec-12 : Got retweeted by @NASAVoyager2 on Twitter !

Image Sources
Supernova, Solar nebula, Volcano, Banded Ironstone, Dinosaurs, Industry, Blast Furnace, Foils, Assembly, Launch, Space

Sunday, 16 December 2012

The Science of Christmas

The latest in the University of Nottingham’s Public Science Lecture Series was entitled “The Science of Christmas” and presented by Michael Merrifield, Professor of Astronomy, Faculty of Science.

Prof Merrifield took a nurmber of iconic images from traditional Christmas scenes and looked at some of the science behind them, beginning with….

Christmas is in the middle of winter (for northern hemisphere residents, at least) and the Prof took a moment to consider why that was.

Surprisingly, there are many people who still believe that the reason it is cold in winter is because this is the time at which the Earth is furthest from the Sun.

This is wrong on a two levels. Firstly, of course, the seasons are actually caused by the tilt of the earths axis, but secondly, winter is when the earth is actually closest to the sun.

The Earth's orbit around the Sun

The Prof also explained that, aside from the reduced hours of daylight, temperatures were lower in northern latitude winters because the sun was lower in the sky, resulting in its heat being spread over a larger area, as shown below:

How sunlight at northern latitudes is spread out over a larger area

Christmas Trees
Another icon of the UK Christmas season is the appearance of Christmas trees, which were actually introduced into the country relatively recently by the Royal family due to their connections with Germany.

Prof Merrifield had wondered why it was that fir trees had their characteristic triangular shape, and a little research revealed that this was because, essentially, the branches and trunk grew at relatively constant rates - meaning that the branches that had been growing for the longest time (the ones at the bottom of the tree) were also the ones that had reached the longest lengths.

In addition, a triangular shape meant that the trees could catch a larger amount of sunlight.

But if this was so advantageous to fir trees, why don’t all trees have this shape?

Prof Merrifield admitted that he initially had no idea. A look on Google revealed that this was one the few questions to which Google does not know the answer, no matter which search terms you use.

However, one of the advantages of working in a University was that there was someone, somewhere, was an expert on pretty much every subject - and in the University of Nottingham that someone turned out to be Marcus Eichhorn, Lecturer in Ecology, Faculty of Medicine & Health Sciences

Marcus explained that there was a fundamental difference in the water transport mechanisms of fir trees and deciduous trees. Fir trees could take up water through the whole thickness of their trunks, while deciduous trees could only do so through the outer part of the trunk.

His meant that deciduous trees had to manage the location of their branches more carefully - too many branches too low down would mean that there was not enough water for branches higher up the tree.

The Christmas Star
The star on the top of Christmas trees refers, of course, to the Christian story of the Star of Bethlehem, and there have been many attempts to determine what this star might have been.

The artist Giotto was one of many who thought that it might have been a comet, as shown in his 1306 fresco “The Adoration of the Magi” nativity scene has a comet arcing across the sky. It seems likely that Giotto used this image because Halleys comet had passed just a few years before he painted this work.

The Adoration of the Magi by Giotto

And some measure of the influence of the paining can be gained from the fact that the European space probe sent to intercept Halleys comet was called “Giotto” in recognition of the artist. (although the closest pass of Halleys comet was in 12BC, which is a few years too early for it to have been the Star of Bethlehem.

The astronomical records of China and Korea, both keen stargazing nations, recorded some kind of appearance in the sky in 4BC (which is pretty much exactly the right time). They noted that the object was fuzzy in appearance, did not move, and was visible for a long period of time (perhaps 70 days).

An astronomer named Tipler recently suggested that the story of the Star of Bethlehem should be interpreted literally, which implied that the star was directly overhead. It turns out that there are not many things in that part of the sky at the latitude of Bethlehem, but one of the things that is there is the galaxy Andromeda and Tipler proposed that there was a supernova in Andromeda at that time, and further, that it must have been a Type 1a or Ic supernova as any other types would have been too dim to see, or so bright that there would have been more widespread records. Tipler also said that its remnants could still be discerned, given the right equipment and technology (which astronomers do not yet have).

Prof Merrifield put up a picture of the Andromeda Galaxy as he told Tiplers story, touchingly saying that the only reason he mentioned this rather far-fetched theory was that it gave him an excuse to show a picture of a galaxy as they were so beautiful.

NSB wonders how much more beautiful they must be for astronomer like Prof Merrifield, who understands their complexity, scale and jaw-dropping physics, than they are for ordinary Joes like NSB.

And, let there be no mistake, NSB thinks galaxies are very, very beautiful indeed.

The Beautiful Andromeda Galaxy

Continuing with a look at candidates for the Star of Bethlehem, one of the most likely possibilities is a so-called “triple conjunction” of Jupiter and Saturn.

This is where Jupiter and Saturn appear to move back and forth across each other three times. The phenomena is caused by the fact that the Earth has a faster orbit that Jupiter or Saturn so periodically “overtakes” them. When this happens they appear to move backwards in the night sky for a period of time.

An Astronomical Conjunction

A triple conjunction fits a number of criteria for being the Star of Bethlehem in that :

i) It is a known astrological event
ii) It involves significant objects (Saturn was a sign of Kingship)
iii) It is visible to the naked eye
iv) It is predictable - so the “Three Wise Men” could have set off on their journey well ahead of time
v) It is rare, the last one being in 1998 and the next in 2238.

There is also an astronomical link to Gold, one of the presents brought by the “Three Wise Men” in that all the Gold on the planet (and indeed all other heavy elements) have been formed in Supernovae that occurred billions of years ago.

NSB can feel his brain melting every time he thinks about this for more than a few seconds.

One might think that there is little or no science behind presents, but one would be wrong..

The Prof pointed out that a little digging in the literature had revealed that there was a whole branch of economics called “Scrooganomics” which dealt with the economics of present giving. This school of thought suggested that giving presents was economically very inefficient as most presents were not what the recipient wanted and ended up being thrown away or lying unloved at the back of a cupboard. It would be better, this theory suggested, for everyone to simply spend the money on themselves as this way they would at least get what they really desired.

On the other hand, Prof Merrifield suggested, there was another view which held that whilst many presents weren’t what the recipient wanted, a few were presents that the recipient really did want but didn’t know it. The Prof gave an example from his own experience when he had been a little unnerved on receiving a present of a parachute jump (not least because he was afraid of heights) but he took the plunge, as it were, and discovered that he actually liked parachuting very much, to the extent that he continued jumping out of planes for several years thereafter.

Lastly, a paper entitled “Asymmetric beliefs about gift giving and feelings of appreciation” by Flynn and Adams was mentioned as this had investigated how present givers and receivers felt about the price of a present. It turns out that present givers attach a lot of value to the price of a present, while present receivers do not really care about the monetary value, only that the giver has actually given them a present. The moral of this research, suggested Prof Merrifield, is to buy cheap!

The symbol of a snowflake is another icon of Christmas time and Prof Merrifield, in an impressive jump from astronomy to chemical physics, did rather a good job of explaining why ice has a six fold nature and why ice crystals grow in a hexagonal way. The explanations for these phenomena, which are much easier told by way of diagram than by words, can be found at the “Story of Snow”.

Incidentally, microscope images of snowflakes show that they DO NOT have exact symmetry on all six sides.

Snowflakes, not quite symmetrical

Santa Claus
Inevitably, the last section of the talk looked at the science behind Santa Claus, or Father Christmas as he is often known.

Here comes the maths part :

Assume 2 billion children in the world, and 900million homes Distance : If all the homes were spread evenly over the surface of the earth (~480million km2) the distance between each home would be about 0.7km apart, making a total distance that Santa has to travel of 600million km.

Time : Assuming that Santa takes full advantage of the international date line, travels westwards, drops each present through the chimney with pin-point accuracy, does not stop for mince pies and delivers the presents between the hours of 10pm and 6am - then he has 34hrs to play with.

Speed : 600million km in 34hrs represents a speed of 17million km/hr, or Mach14,000.


Prof Merrifield pointed out that this was much faster than the speed of the Space Shuttle during re-entry (about Mach 20) and was indeed a lot faster than the speed required to escape the earth’s gravity (about Mach 400).

Achieving this kind of speed in the lower atmosphere would also result in severe frictional heating issues.

Which left NSB wondering whether, rather than a sleigh and reindeer, Santa Claus was actually using high downforce technology adopted from Formula 1 in order to avoid being flung out into space.

Or perhaps Santa uses active cooling techniques such as those used in the Apollo Moonshot missions where cryogenic fuels were pumped around the rocket nozzles to keep them from burning up?

Does Santa Claus take aerodynamic tips from Formula 1?

As is customary, there was a short question and answer session after the talk, and it was Santa Claus that had clearly caught the imagination of the audience, to the extent that Prof Merrifield shook his head at one point, wondering aloud how it had some to pass that he was discussing the merits of gift delivery methodologies with an audience at a science lecture.

Update Feb 2014
A beautiful timelapse video of snowflakes forming in the lab can be found here

Image Sources
Earth orbit, Latitudes, Giotto, Andromeda, Conjunctions, Snowflake, Formula1