Loose Wheel Nut Indicators

Today's trivia is all about loose wheel nut indicators.

These seemingly simple devices are placed over the nuts used to secure a wheel to its wheel plate. Clearly they are designed to give a visual indicator to the driver when the nut slips. However the question I wanted to answer was: why do wheel nuts slip?

Wheel Failures

The problem of a loose wheel is clearly significant. Both in terms of control of the vehicle involved and anything else in the path of the wheel.

It was estimated in 1992 by the National Transportation Safety Board (US) that there were between 750 and 1050 incidents per year relating to heavy trucks. The actual figure is expected to be higher, as these are the reported incidents.

Typically when a heavy truck loses a wheel it will continue to travel at the speed of the truck, and might fly high into the air because it is suddenly no longer under load.

Certainly we can from video examples that the wheels have a lot of energy.

Driver was ok in this video

Causes of failure

There are numerous reasons why wheels fail to remain attached to the vehicle. Of these the most common are failures of the wheel fastening. Simply put the wheel nuts that hold the wheel to the wheel plate shake loose.

Another possibility is shearing of the wheel plate lug

Nuts and Bolts

In normal use, a nut-and-bolt joint holds together because the bolt is under a constant tensile stress called the preload. The preload pulls the nut threads against the bolt threads and holds it in place. The nut cannot rotate without overcoming the friction between these surfaces.

If the joint is subjected to vibration, however, the preload increases and decreases with each cycle of movement. If the minimum preload during the vibration cycle is not enough to hold the nut firmly in contact with the bolt and the bearing surface, then the nut is likely to become loose.

The amount of tension we can apply to a nut is based on the hardness of the steel. Harder steels are able to withstand greater tension before they fail. There are various standards which govern the hardness of steel fastenings like nuts and bolts.

Graph showing the behaviour of a bolt under tension including the elastic and plastic regions

Steel

Commercial grade steel for use in joint assembly fastenings are hardened by two different methods depending on the type of steel used:

• Low (less than 0.25%) carbon mild steel which is 'case hardened'
• Medium (0.25%-0.5%) carbon and alloy steel is 'through hardened'

The carbon content of the steel is significant in how its hardness can be improved. Mild steel with a low carbon content when heated and quenched will not increase in hardness. Only medium and higher carbon steels can improve in this way. This is known as 'through hardened'.

Instead low carbon steels are heated and sprayed with a chemically reactive carbon compound. When the steel is quenched this reactive coating forms a hardened case around the softer steel.

Oil, water and high pressure gas can all be used to rapidly quench hot steel

Conclusion

The problem of a loose nut on a wheel is surprisingly complex.

In order to secure a wheel assembly correctly you need appropriate fastners. Nuts secured against the bolts hold the wheel in place, because they can generate enough friction to prevent the nut from loosening.

They can only generate that preload friction because the steel the nuts are made of is sufficiently hardened to ensure the thread does not deform under load. Too little tension and the nut will easily come loose from vibration. Too much tension and the bolt threads might strip or the entire bolt shear off.

Maintenance schedules are there to check that wheels are fastened correctly on regular intervals. However, loose wheel nut indicators are there to provide a visual inspection method by drivers prior to driving the vehicle.

References

Metallurgical engineer from MEA Forensic

Compilation of wheel failure video

Research by the Ministry of Transport Ontario

Bolt Science FAQ

Drones

Today's trivia is all about drones, and some of the interesting developments in the field of drones.

One of the key characteristics of a drone or UAV (Unmanned Aerial Vehicle) is that it unpiloted. Control for the aircraft might be remote control or it might have a varying degree of autonomous control built into it.

A drone configured for racing, as we'll see more of later.

We will only be focusing on the civilian usage of drones for this article. Military usage is ever expanding in a variety of roles. The US military is now training more UAV pilots than conventional aircraft pilots.

Technology

There have been a number of key contributing technologies which have all recently been developed to bring drones to the wider consumer market. Remote controlled aircraft have always been present in the market for hobbyists. Drones however are marketed at a much wider audience and a price which makes that feasible. It is now even easier to build your own drone.

The following are the key components which make up a quad-copter.

Battery - The battery of choice is LiPo - Lithium Polymer or more accurately a hybrid which uses a liquid electrolye instead of a completely dry cell LiPo. Functionally we are dealing a light, compact and high energy density battery technology which gives out more power than conventional rechargeable battery technologies. Because it is made of folded layers of coated material it also does not need to be packaged in a metal container thus saving weight. A trade off in these batteries is that they have less potential charges than earlier batteries.

Motors - The motors of drones are another key area of development. Small and compact with high power outputs. Either brushed or brushless motors are used, with brushless motors becoming increasingly popular. Brushless motors flip the existing motor design on it head by having the rotating part of the motor hold the permanent magnet, and the electro magnets are fixed inside the casing. This allows brushless motors increased efficiency over brushed motors.

Example of the sensor board which could be combined with Arduino to build your own drone

Flight Controller - The flight controller of a drone is made up of three main parts. Electronic Speed Control drives the motors, Inertial Measurement Unit provides position inputs and the Flight Controller which is typically an 8-bit processor. These three elements combined together allow the drone to not only hover but perform a whole range of operations.

13 people indicate they have made this mini quadcopter design

Frame - There are numerous frames to choose from, each with a different intended purpose. It is also possible to 3D print the frame for a drone. This allows even more customisation around the design and functionality of the drone. The sharing and refinement of designs might further simplify the ability of individuals to build their own drones.

Uses

The usage of drones has grown rather dramatically. The following are a subset of the uses for Unmanned Aerial Vehicles:

Delivery: Both Google, Amazon and others are actively exploring the idea of drone based delivery systems. I would hazard a guess that if they succeed in participating with the regulatory authorities in each country, drone deliveries will be actual reality.

The latest version of the proposed Amazon Prime Air drone, video

Photography: From amateur photography to journalism to wildlife research and more. The fact that a camera can be mounted on a drone and the image recorded or transmitted back makes for very compelling options. Footage often appears in the media which was recorded by a drone.

Getting unique views of something which might not be possible otherwise video

Another example of gaining a unique perspective

Racing: Perhaps the most exciting possibility of drones is the ability to race them. Typically done using FPV (First Person View) allowing the pilot to see the view from the camera on the drone. Because drones fly in a three dimensional space it also makes sense to lay out courses in locations which lend themselves well to this. Drone racing is only just beginning, but it is clear that there is interest in this novel and exciting sport.

Racing drones in an empty stadium with Drone Racing League

Another example of drones and their maneuverability Drone Racing

Safety

The aviation authorities of the US and UK and many others are rapidly issuing guidelines explaining how people should fly their drones. This is a pivotal time for drones and legislation and the next few years will see developments particularly in the commercial area of drone usage.

Flying safely should be an obvious requirement, I would imagine because people are physically disconnected from their drone they make different decisions. There doesn't seem to be much people cannot crash their drone into:

• Planes
• Trains
• Buildings
• Lakes
• Power lines
• Athletes
• The White House

etc.

Wildlife may not be impressed with your drone

Tiffin

Todays trivia is all about Tiffin, or more specifically the word Tiffin.

The word is defined in the dictionary as being synonymous with lunch, or the eating of lunch. Specifically we note that it appears to be first introduced around 1775-85 as a variant of tiffing, equivalent to tiff to sip, drink.

Tiffin (Indian English)

Food served in the popular tiffin tins

In India, we learn that tiffin refers to a midday meal, though we imagine that you could infact eat tiffin at any time of day. Tiffin does not have to be specifically a savory dish, it could be sweet as well. However it is all tiffin. Including the term for the tins it is served in, also tiffin.

In India food cooked at home with care and love is considered to deliver not only healthy (and relatively cheap) food but also divine contentment. So much so that there is a growing trend of eating home cooked food at work. Workers can pay to have food cooked at home delivered to their workplace rather than eating out at lunch time.

Dabba-Wallah

This trend is gaining popularity, particularly in the city of Mumbai (formerly Bombay). Workers often have to leave home early in the morning before there is time to prepare food, and squeeze into packed trains. Instead they can pay (200Rs = £2) to have their food collected from their home at 10am by a Dabba Walla, literally a lunch box delivery man.

The tiffin is then delivered using a combination of bicycle, train and on foot to the recipient in their place of work by lunch time, still hot and ready to eat. They then return the tiffin tins to the household in the evening.

Once arrived at the station, tiffins are sorted and loaded onto the comparatively quiet 10AM train

This impressive hot food service is provided throughout the sprawling city by the the Mumbai Tiffin Box Suppliers Association. A charity which has been operating for the last 120 years and employs 4,500 dabba-wallahs, many of whom are semi-literate.

A key characteristic of the service provided is its high reliability. Out of 200,000 tiffins delivered daily maybe once or twice a month one of the dabba-wallahs might make a mistake. This staggeringly high level of reliability is a sign of pride among the dabba-wallahs, many of whom have a limited level of education. One customer is quoted as preferring to return his daily wage home in the empty tiffin, rather than in his pocket on the train home because he trusts the dabba-wallah delivery network so much.

Code

tiffin routing code

To achieve such a sophisticated delivery network in a complex city is commendable. The workers do all of this without maps, GPS or navigation aids, relying solely on a code system written on the top of each tiffin which informs them:

• Source: A dabba-wallah will know each customer in their group area. The dabba-wallah will be part of a group number.
• Transit: Once tiffins arrive at the source station, they are sorted and loaded onto the train. At the destination station they are unloaded and handed off to the delivery team.
• Destination: The delivery team will sort and hand out tiffins to groups who know the delivery location.

With the use of color coding and alphanumerics the tiffen can reliably make round trips across the city to its intended recipient.

Tiffin (Scottish)

Tiffen as per the Scottish is a Christmas time dessert. Resembling a chocolate cake-like confectionary commonly comprising of crushed digestive or rich tea biscuits (cookies), cocoa powder, golden syrup and dried fruit with a top layer of melted chocolate.

Said to originate in the 1900s in Troon, Scotland, I was sadly unable to verify this fact. However the interesting part is that we know the same word tiff was in use in the Scotish dictionary from around the same period.

Recipe

There are lots of variations on this recipe, here is an easy one which uses Maltesers:

• 200g milk chocolate (I use Lindt milk chocolate)
• 100g unsalted butter
• 2 tbsp golden syrup
• 125g digestive biscuits
• 135g bag of Maltesers

For the topping:

• 200g milk chocolate
• 25g unsalted butter
• 1 tsp golden syrup

Method (condensed):

• Melt chocolate, butter and syrup together
• Crush Maltesers and mix into melted chocolate
• Pour into greased baking tin
• Melt topping chocolate, butter and syrup
• Spread over the mixture in the tin
• Cover and refrigerate for 1-2 hours

Eat.

References:

• Dabba-Wallah TED talk
• Journey of a tiffen
• Tiffin Company detail
• Research Paper

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Soyuz TMA Re-Entry

Today's trivia dives into the detail of how Astronauts return from space.

On March 1st 2016 Scott Kelly (NASA) and Mikhail Korniyenko (RSC) returned to Earth in the Soyuz-TMA spacecraft. How does an astronaut return from orbit in this spacecraft?

Soyuz TMA spacecraft

The Soyuz TMA-M (transport, modified, anthropometric) is the latest in a very slow evolution of Russian human-rated spacecraft.

Soyuz TMA-17 before docking

Primary Functions

• Carry up to 3 crew into a variety of orbits
• Orbital transit
• Docking
• De-orbit and re-entry
• Soft landing

Its design philosophy is based around automation. Most of the main tasks required for re-entry are automatic. It can also be fully controlled from ground control stations. Crew can override as required, for example if they encounter an emergency. A lot of its design is focused around many levels of redundancy. Automated systems have usually two backup systems and include some kind of reasonable contingency if all were to fail.

Artistic image of the 17 July 1975 Apollo Soyuz Test Program (ASTP) the first docking of a Russian and American spacecraft showing comparable scale of the Apollo and Soyuz spacecraft

The first Soyuz was developed at the same time as the American Apollo program as part of a secretive Soviet lunar mission which was eventually halted due to a number of reasons. This same craft has undergone three main design evolutions to spacecraft used today.

Its use as a crew transportation and return spacecraft for space stations was first proposed by the Russians as the Automatic Crew Return Vehicle for both the joint NASA/RSC project on the Mir space station and the International Stance Station. If the station was damaged by space debris or a medical evacuation was required, the Soyuz would be used for these tasks. With its 110+ manned launches it has an extensive track record.

Undock

Soyuz TMA-03M spacecraft (left) eases toward its docking with the Russian-built Mini-Research Module 1

Once the crew are onboard and suited up in their pressure suits, they will go through various checklists to prepare for the flight. This takes in excess of three hours, which may include time verifying there are no drops in pressure within Soyuz.

View from the on board computer system pilots view with information overlay

Once released from the station, springs inside the docking ring push the craft away from the station. The Soyuz is only able to use its reaction control thrusters once it is far enough (20m) away from the station to prevent covering the station in liquid propellant.

De-Orbit burn

The de-orbit burn is also automatic. Once the spacecraft position is accurately known, the computer calculates the angle and duration of burn to get the required landing trajectory to a pre-determined landing site.

This burn is critical as it determines the angle of descent into the atmosphere:

• Too shallow and it will bounce off the atmosphere without showing down, resulting in overheating.
• Too steep and the crew will experience too much deceleration force (in excess of 10g) which may be fatal for the crew.

Soyuz is made up of three modules, at the front is the Orbital Module, in the middle is the Descent Module and at the back is the Service Module which includes the solar panels

Once the de-orbit burn is complete, the Orbital and Service modules are jettisoned. Explosive bolts fire which push the jettisoned modules away from the descent module. They will burn up on the atmosphere on reentry. If for some reason the modules do not separate correctly, the Soyuz is designed so aerodynamic forces will break the modules apart in any case.

30 minutes later the spacecraft will cross the Kármán line at 100km and come into contact with enough atmosphere to start re-entry.

Re-Entry

Seen from the International Space Station, the Soyuz TMA-05M descent module begins to re-enter the Earth's atmosphere, leaving a plasma trail as the Expedition 33 crew streaks toward a pre-dawn landing on the steppe of Kazakhstan.

During re-entry the capsule will decelerate from orbital velocity (17,000mph) down to speeds where the parachutes can be deployed. This deceleration is the result of the capsule crashing into the atmosphere. The heat shield of Soyuz is rated to withstand the incredible temperatures of re-entry, however the shape is also crucial as well:

"If the reentry vehicle is made blunt, air cannot "get out of the way" quickly enough, and acts as an air cushion to push the shock wave and heated shock layer forward away from the vehicle. Since most of the hot gases are no longer in direct contact with the vehicle, the heat energy would stay in the shocked gas and simply move around the vehicle to later dissipate into the atmosphere." - Wikipedia

The re-entry is also completely automatic. The computer will use reaction control thrusters to create a steering effect, enough to keep it aligned with its target landing site. Should the computer fail, or an emergency arise such as depressurisation, the backup re-entry process will start a ballistic re-entry. This re-entry is faster because it is steeper but induces up to 8g of force on the crew.

Re-Entry as seen from the inside window of Soyuz Buzz Feed

Landing

Once the descent has slowed enough, the parachutes can be deployed. First two drogue chutes, followed by a main chute. This slows the capsule down to the required landing speed.

Around the same time the heat shield, and external window covers are jettisoned.

Just before landing 6 soft landing solid rockets fire to improve the landing which an astronaut still describe as "feeling like you are being hit by a truck".

During the early Soviet missions the landing site was less predictable. The cosmonaut would expect to be greeted by team parachuted in to assist. Now days helicopters and ground support vehicles arrive at the predetermined landing site and are in constant communication with the capsule as it lands.

Soyuz TMA-01M spacecraft shortly after the capsule landed

References:

• NASA Overview
• Detail on Soyuz
• PDF on Re-entry Detail
• YouTube - ESA Landing Sequence for crew training
• YouTube - Roscosmos State Corporation
• YouTube - Re-Entry Footage from Apollo 11 1969
• YouTube - Re-Entry Footage from Orion 2015

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Super Weapons of Star Wars

This trivia is entirely based on the facts as presented by the Star Wars universe and in places a bit of extra analysis. It is purely fiction and as such might sound a bit made up.

Note: To help make sense of the amounts of energy used I've helpfully added in equivalent Twinkie sizes. That is, the energy in Joules can be converted to the an equivalent energy in calories which can be scaled to an equivalent size of Twinkie. We don't have Twinkies in the UK, this probably doesn't help that much.

DS-1 Orbital Battlestation (Death Star I) and Death Star II

The second Death Star around Endor Full Size

Both the first Death Star I and the second Death Star II where improbably large structures, intended with the sole purpose of destroying all that opposed the Empire. Able to destroy fleets of ships and indeed entire planets. Both battlestations had the capability to move both within system, and via hyperspace to other star systems.

• Radius: 60km, 80km
• Crew: ~ 1.5 million, ~ 2.4 million
• Propulsion: In system Ion drives, Hyperdrives to travel between systems

Power source

In both Death Stars a Hyper Matter Annihilator reactor is used, though much larger in the second.

Hypermatter is matter that exists in hyperspace, and when constrained in real space, and accelerated to the speed of light it gives off immense amounts of energy. Combined with massive amounts of reactant fuel to generate the power required to power the Death Star. The energy generated by the power source is comparable to the output of a main sequence star.

A main sequence star like our own outputs 3 x 10t26 J per second = Twinkie ~800km in length, from Land's End in Cornwall to Newcastle in the midlands.

Schematic of the internal components of the Death Star Full Size

Super Laser

In both Death Stars, the super laser is the main feature of the station. Large amounts of the internal space are dedicated to the support machinery required to power and operate the weapon.

The laser focusing crystals are known as Kyber Crystals. These are the very same crystals used as the focusing crystals in light sabres, however those are tiny compared to the ones used in the Death Star. Finding and transporting them without some pesky Jedi blowing them up proved to be an arduous task for the Empire.

The firing of the super laser appeared to be dependent on its energy output. For example destroying a planet required a 24 hour charge period. Destroying a starship only required a 3 minute charge.

The second Death Star was designed by the same designer as the first Death Star, albeit a clone.

"A second, more powerful battle station designed by the same engineer who was killed by Darth Sidious for the first station's weak spot, and then cloned to make the second station better and without the fatal flaw of the first."

Energy Required to Destroy Alderaan

Research Paper

Needless to say, there are those in the scientific community which wondered the same question. One paper takes us through the equations and energy outputs required to destroy an Earth sized planet.

The basis of the paper covers the Gravitational Binding equation. That is, the energy required to take apart a planet, piece by piece sending each piece away from the planet until there is nothing left.

For a planet the size of Earth (and Aldaraan) this is 2.25 ⨉ 10t32 Joules = A Twinkie ~ 80,000km in length, twice the circumference of Earth.

The key finding of the paper states that because the power source of the Death Star outputs so much power, destroying a planet the size of Aldaraan is entirely possible. However a planet the size of Jupiter would require multiple firings.

StarKiller Base

Super weapons are definitely getting bigger as the series goes on source

This brings us to the First Orders StarKiller Base. The First Order where obviously impressed with the earlier Empires efforts at building large super weapons, but they clearly thought that the Empire had not set their sights high enough. So instead the converted an entire planet to the task of being a super weapon.

• Dimensions: Ice Planet
• Crew: Lots
• Propulsion: Can move between systems, within system is assumed for targetting

This thing is ridiculous.

It is unclear when construction on it started, but we can be reasonably certain that the First Order did not exist until after the fall of the Empire. It is therefore unlikely that construction started before the need for the super weapon existed. Either way the effort required to hollow out the core of a planet and replace that with the machinery required to support the super laser is incredible.

Clearly the mantle of the planet has been replaced Full Size

Super Laser:

The film demonstrates its ability to destroy planets. Five of them ... simultaneously... from a distant star system.

The offered explanation for the system is based on a number of functions:

• Solar extraction: The ability to draw the hydrogen from the star and use that to drive a fusion reactor, or capture the thermal energy from the surface of the star
• Storage: Converting and compressing the energy of the star into Dark Matter which can be stored within the planet (size of star versus size of planet)
• Targeting: The weapon is fixed within the planet and would need to be at least vaguely aligned with the target star system many light years. The weapon is able to target multiple planets at the same time.
• Subspace: Prepartion of Subspace tunnels that will allow the energy beam to travel almost instantaneously from source to target star system. This uses an alternate dimension known as Subspace which is only possible to access with the energy levels produced by this super weapon.
• Firing Weapon: The firing sequence is described as "breaching the Dark Matter storage containment" which releases the stored energy. We know it makes a mess of the nearby trees.

Power Source

A main sequence star like our own gives off 3 ⨉ 10t26 Joules per second = Twinkie ~800km in length weighing twenty-two quadrillion, six hundred trillion tons. This is a huge amount of energy to work with.

"If all the hydrogen in the Sun were to be fused into helium, the energy equivalent of this would be 8.7 x 10t44 Joules." = Twinkie ~1,000,000,000km long which is approximately 25,000 times round the Earth. Enough to destroy four trillion Alderaan planets, not counting for energy costs of operating the planet. Reference.

That is indeed a big Twinkie.

Appendix: Hyperspace

Hyperspace in Star Wars is an alternate dimension where conventional space appears quite different. In hyperspace, real space and relative distances appear "wrinkled" such that with the correct course through hyperspace a vessel can travel the vast interstellar distances in considerably short times.

This relationship between hyperspace and real space is the reason for the development of known routes through hyperspace. Large mass objects (stars, planets, super weapons etc) cast "shadows" in hyperspace such that the navigation computer must avoid these objects. Failure to do so will result in the vessel being pulled out of hyperspace early. Near a star, this would be disastrous. In "IV:A New Hope" the Falcon is pulled out of hyperspace by the Death Star for this reason, the Death Star did not appear on their navigation computers maps.

The hyperdrive functioned by sending hypermatter particles to hurl a ship into hyperspace while preserving the vessels mass/energy profile, and required a functional hyperdrive motivator to do so. The vessel would then travel along a programmed course until it dropped back into realspace and arrive at its destination.

References:

• Scott Manly with Twinkies
• Scott Manly without Twinkies
• Twinkie Converter
• How to say really big numbers
• Size comparison

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February

In today's trivia we try and work out what that deal with February is:

• Why is this month shorter than the rest?
• Why is it used for the leap year offset?

Recreation of a Roman fasti, an official list of public days when official business could be conducted and celebrations would take place, based on the Roman calendar

Origins of the Months

Before we can answer those questions we need to dig a little into the history of calendars and where the Months of the Gregorian calendar come from.

Calendar of Romulus

To start, we need to go back as far as the formation of the Roman Empire. The first documented calendar we know they used was the Calendar of Romulus. A solar calendar in that it related to the progress of the Earth around the Sun, as opposed to a Lunar calendar which tracks progress of the Moon around the Earth.

This calendar is interesting for a number of reasons:

Martius (31 days)

Aprilis (30 days)

Maius (31 days)

Iunius (30 days)

Quintilis (31 days)

Sextilis (30 days)

September (30 days)

October (31 days)

November (30 days)

December (30 days)

This calendar consists of ten months and a total of 304 days. The remainder of the year, the winter months were not tracked by the calendar. Instead the calendar was started each year at the spring equinox occurring in the first month of the calendar.

This strikes me as particularly convenient as it resolves a common problem with early calendars. That of drift of the calendar against the seasons. Lunar calendars for example track the progress of the Moon each month. But a Lunar month is 29.5 days long (354 days) and so does not coincide with the solar year (365.2 days) so for a Lunar calendar to track the seasons, they need an offset month known as an intercalary month to be added each year to correct for the drift.

Finally we see that there are some months we recognise. The origins of all the months is not entirely clear but we can certainly see a few we recognise. The last six months indicate their positions in the calendar based on the Latin words quinque, sex, septem, octo, novem and decem.

Calendar of Numa

At some point during the reign of Numa Pompilius (715–673 BC) a refined version of this calendar was introduced. The Romans of the time considered even numbers to be unlucky, so they removed a day from each of the even numbered months (Aprilis, Iunis, Sextilis, September, November and December). Combined with the winter months there was enough days to define two extra months of January (29) and February (28). February being 28 days long was considered a suitable candidate for Februa the Roman festival of purification which we imagine is where its name comes from.

Ianuarius (29)

Februarius (28)

Martius (31)

Aprilis (29)

Maius (31)

Iunius (29)

Quintilis (31)

Sextilis (29)

September (29)

October (31)

November (29)

December (29)

This brings the total days to 355. This calendar would of course drift each year.

As mentioned above, the Romans added an intercalary month when it was thought necessary (every two years) to bring the calendar inline with the solar year. On a year when they added an intercalary month, February would end on the 23rd (Terminalia) and the month would month would be added. This extra month would be either 27 or 28 days (377 or 378 for the year).

The average of every two years would bring the calendar to 366 days a calendar year. This made for a more workable system.

That was until the Romans started using the intercalary month for political purposes. The position of Pontifex Maximus was responsible for setting the length of the intercalary month. The office of Pontifex Maximus was generally held by a member of a politically prominent family. It was a coveted position mainly for the great prestige it conferred on the holder. Since the term of office for a political official was determined by the calendar year, there are indications that the length of the year was open to debate.

For example, Julius Caesar made the year of his third consulship in 46 BC 445 days long.

Julian Calendar

In the same year, Julius Caesar, as Pontifex Maximus reformed the calendar in 46 BC. The new calendar became known as the Julian calendar. This calendar proved very successful as it was in use up until 1582 when the Pope Gregory mandated the use of the Gregorian calendar system.

Ianuarius (31)

Februarius (28)

Martius (31)

Aprilis (30)

Maius (31)

Iunius (30)

Quintilis (31)

Sextilis (30)

September (30)

October (31)

November (30)

December (30)

This gives a total of 365 days with a leap day added to February every four years which gives the Julian calendar an average of 365.25 days a year. This was only later improved upon by the Gregorian calendar in the West.

This system was primarily introduced because maintaining the intercalary month of the Numa calendar was proving both an administrative burden, and a political complexity which tended towards the average Roman some distance from the city not knowing the date. The last three years before the switch to the Julian calendar where remarked as "years of confusion".

After its introduction, it proved useful. Varro used it in 37 BC to fix calendar dates for the start of the four seasons, which would have been impossible only 8 years earlier. A century later, when Pliny dated the winter solstice to 25 December because the sun entered the 8th degree of Capricorn on that date, this stability had become an ordinary fact of life.

Gregorian Calendar

The final stop on this chronological tour is the Gregorian Calendar we are all familiar with which was established in 1582 by Pope Gregory XIII. It can be summarised as follows:

"Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the year 2000 is."

The calendar was a refinement to the Julian calendar amounting to a 0.002% correction in the length of the year. The motivation for the reform was to bring the date for the celebration of Easter to the time of the year in which it was celebrated when it was introduced by the early Church. Because the celebration of Easter was tied to the spring equinox, the Roman Catholic Church considered the steady drift in the date of Easter caused by the year being slightly too long to be undesirable. The reform was adopted initially by the Catholic countries of Europe. The last European country to adopt the reform was Greece, in 1923.

Conclusion

So to conclude, we can tell that calendars became hugely important in civilisations. The moment there was demand for agriculture, civic planning, trade and commerce etc there will be a demand for coordinating activities via a calendar. Every major civilisation has developed its own calendar system to help track the days and months of the solar year.

To answer the specific questions of February, we can now say it is the short month because of a combination of factors:

• Early calendars were lunar and so each month was roughly the same length
• Most calendars could not precisely follow the solar year
• The Roman calendars used the month of February to adjust the length of the year
• The Julian calendar also uses February for the leap year adjustment
• Which is why we still use February to track leap years in the Gregorian calendar.

References

• Roman Calendars
• Julian Calendar
• Gregorian Calendar

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Giant Crystal Caves

Today's trivia is all about the a mine in North Mexico known as the Naica Mina.

This mine was first opened in 1794, though only officially exploited in 1900. The mine is of interest commercially for its deposits of lead, zinc and silver, among other minerals which are still actively being extracted.

Before mining could start the mine has to be drained of water. The water level normally resides at a depth of 110m below sea level. This needed to be drained to a depth of 850m below sea level. A complex pumping system had to be developed to be able to do this and can extract 22,000 gallons of water per minute when turned on.

full size

In the year 2000 another system of three caves were discovered which contain some rather impressive crystals. We'll be talking specifically about the "Giant Crystal Cave", located at 290m below sea level. Some of these selenite crystals are immense. The cave's largest crystal found to date is 12m (39 ft) in length, 4m (13 ft) in diameter and weights 55 tons.

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Formation of the Crystals

The Naica mine lies on an ancient fault above an underground magma chamber below the cave.

The magma heats the ground water which was saturated with sulfide ions. Meanwhile cool oxygenated surface water comes into contact with the mineral saturated heated water, but the two did not mix due to the difference in their densities. The oxygen slowly diffused into the heated water and oxidized the sulfides into sulfates.

This creates an environment where hydrated sulfate gypsum can crystallize at an extremely slow rate of over the course of at least 500,000 years forming the enormous crystals found today.

The key to this process is the slow diffusion of oxygen from the cool, low density surface water into the hot, high density ground water.

Conditions in the Cave

Exploring the cave is particularly hazardous for humans. The ambient temperature is 58C (136F), and the humidity is close to 100%.

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This represents two significant risks to humans:

• Heat Exhaustion Unprotected from the heat, the human body cannot regulate its temperature quick enough in those sorts of temperatures. You would be sweating profusely if you found yourself stuck down there would ultimately pass out from the lack of water and sodium in your body.

• Breathing The air in this sort of temperature would be incredibly difficult. It would be likely that the in insides of your lungs would be cooler than the outside temperature. The humidity would start to condense inside your lungs leaving only a short time window for exploration.

A lot of infrastructure has been put in place to support exploration of the caves.

Before you can enter the caves you reach a staging area which is at a comfortable 41C. This staging area hosts all the support equipment required to venture into the actual crystal caves. This includes freezers to store the cooling suits, video monitoring equipment and paramedics on standby in the event of a medical emergency.

Camera equipment has to be allowed to come up to temperature before it can be used in the caves, otherwise it would risk fogging up.

Refrigeration Suits

To explore the caves, researchers had to develop specific suits to help protect the wearers from the conditions in the caves.

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Ptolomea Suit

The initial suit design created by Giovanni Badinno consisted of multiple layers:

• Insulated layer: protects the wearer from direct skin contact with the icy cooling layer
• Cooling layer: Ice tube covered layer to protect the entire body from the` excessive temperature.
• Outer layer: Rugged overalls to reduce heat transfer by radiation and protect from jagged environment

This suit allows the wearer an hour of effective research time in the caves however it comes at the drawback of being heavy and restricts mobility for the wearer.

View of the inner cooling layer of the suit, total weight 22kg

Lightweight Suit

The researchers were able to optimise the design trading off some exploration time for a more mobile suit design. Instead of complete body coverage in cooling ice tubes, they opted for a cooling layer which just covered the torso in frozen gel packs. This allows more mobility for the arms and legs with an exploration time of around 30 minutes.

The lighter suit system weighs 8kg in total

Breathing System

Breathing in the cave is difficult without breathing apparatus. For this they developed a backpack based system. Replaceable frozen metal bottles are stored in the backpack with a fan which blows warm air over the bottles. This is then fed into a face mask which allows the wearer access to cool air to breath.

Fitted facemask

Inside the backpack of the air cooling system, frozen metal bottles act as the cool source

Future of the cave

Once the mining operations in the cave end, it is expected that they will turn off the water pumping system, allowing the thermal water level to rise and once again fill the the entire cave system. The facilities to support exploration of the crystal caves and the caves themselves would become inaccessible and will resume their slow growing process.

References:

• Official Website
• Suit Detail
• Video about suit design
• Account from researcher
• Overview
• Informative Video

Quiz of 2015

Today’s trivia is in the form of a quiz. It is entirely based on Friday Trivia presented in 2015. There is no score for this quiz, merely an opportunity for some afternoon entertainment.

Does the Japanese high speed train service "shinkansen" mean "bullet train"?

No, shinkansen (新幹線) means "New Branch Line". The phrase "bullet train" was an English nickname used around the 1960's to describe high speed train services like the shinkansen.

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The trilobite is named because of three parts of its body, which three parts are we talking about?

The trilobite gets its name from structure of its head. Not the head (cephalon), segmented thorax and tail (pygidium), but rather the right pleural lobe, axial lobe and left pleural lobe of the head.

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Where in an ants nest might be a good place to sleep if you were a worker ant?

Workers tend to sleep in one of three locations, the chamber floor, ceiling or side of chamber. Those that sleep on the chamber floor were most likely to be woken by other workers passing by. Seemingly the best place to sleep was the side of the chamber.

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We estimate it weighs about a pound

Which falls faster in a vacuum? A Sandwich Sandwich scotch egg, or a feather?

The mighty Sandwich Sandwich scotch egg is not a meal to be treated lightly. When modelled as a bowling ball we can estimate its behaviour in near vacuum conditions with the following animation as provided by the BBC.

One observation we concluded in this thought experiment was that given the mass of the Sandwich Sandwich scotch egg, its own gravitational pull might draw the feather closer to it over a long enough distance.

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What purpose was WD-40 originally developed for?

WD-40 (Water Displacement formula 40) was originally developed as an easily applied oil coating to the paper thin balloon fuel tank of the Atlas SM-65 ballistic missile.

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Who catches who whilst buzzing around in the territorial airspace of a lampshade?

The common house fly has a territorial behaviour of flying around a known landmark in a room. The airspace patrolled by musa domestica is 50cm by 50cm by 25cm and the males of the species will chase any other fly that enters that air space.

This proves an effective selection mechanism for this species as males of the same species will evade capture, whereas females of the same species will generally be caught. Because eggs are not laid near landmarks in the room (lampshade) we can conclude that this is a specific mating behaviour.

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When making tea is it milk first or milk last?

There were a number of conclusions in this particular trivia. In summary, if you are making tea in a teapot, then adding the milk first was preferable. If you are making tea in a mug, then milk after appeared to be the answer. It should be noted that this was a highly contentious subject which we only just managed to discuss without a full scale war breaking out.

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Of the many techniques for opening bananas, which is the technique favored by monkeys?

Amusingly of the many ways to open a banana, the one preferred by monkeys is to use their teeth to rip open the skin before eating the fruit inside.

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How does the Venus Flytrap (dionaea muscipula) tell the difference between a fly and a rain drop?

Each lobe (leaf that captures an insect) has a number of small hairs. The trap triggers when the hairs are triggered with enough time between them. The plant is successfully able to differentiate between rain fall and a fly which is feeding on the leaf. The leaves are coated in a sweet liquid designed to attract insects and spiders.

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Did Thomas Crapper invent the flush toilet?

No, he was a successful businessman in the 20th century selling toilets. Toilets and sanitation have been known about since antiquity. However the flush toilet specifically is believed to have been invented in 1596 by Sir John Harington in his publication "A New Discourse of a Stale Subject, Called the Metamorphosis of Ajax".

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