The Mexican media pledge

The sheer numbers of participants reveals an apparent consensus.

Back in March, owners, editors and journalists from over 40 media groups including over 700 television channels, radio stations, newspapers and magazines, gathered to sign a voluntary agreement setting up a series of guidelines in order to cover the ongoing war against organised crime in the country.

Throughout a very formal event at Mexico City's National Anthropology Museum, press officials lined up to sign this unique pledge. The gathering was broadcast live on national television.

The pact -- the Informative Violence Coverage Agreement -- sets out to establish mechanisms to ensure a better protection for Mexican journalists, preserve the anonymity of all victims involved in issues revolving around crime and prevent media outlets becoming involuntary "propaganda instruments" for criminals, mainly by refusing to question or interview them.

The sheer numbers of participants reveals an apparent consensus. It received thumbs up from conservative Mexican President, Felipe Calderón, known to be a regular critic of the coverage of violence by the Mexican media, which he accused last autumn of solely focusing on the "bad" aspects of the country.

Some parts of the agreement should be welcome. Its principal breakthrough came from the decisions that every signing outlet would have to establish a protocol aimed at protecting the lives of journalists. Measures include not sending staff members to recent crime scenes and other dangerous areas, or not signing articles likely to jeopardise their author's integrity.

Many have also praised the initiative to regulate the publication of crude or graphic images depicting murder scenes.

However, one of the stated goals of the pledge has created a controversy which has led some of the country's major newspapers in the country to opt out: it wishes to create "common editorial criteria" which all signing parties should apply when covering violence related stories.

The six-page document then details a series of criteria -- in ten bullet points -- which include: "taking a stand against" organised crime, "explicitly attributing responsibilities", be it to government human rights abuse or to criminal actions, "not interfering in the struggle against delinquency" and "giving information in its right dimension and context".

These arguments did not convince La Jornada, a centre-left daily printed in Mexico City and one of the country's most influential national papers. It published an unsigned, critical editorial soon after the pledge was signed, calling it "an unacceptable renunciation of editorial independence", an attempt at imposing "a sectoral model of uniformity". The editorial went on to criticise the pledge's will to take a clear stance against organised criminal created a "prejudice" which would likely be done "in detriment of the information inherent to the facts".

Speaking to the New Statesman, José Luis Ruiz, editor for Mexico City's El Universal -- a major national, daily paper that agreed to sign the agreement -- praised the pledge's objectives and denies it is in any way intended to standardise the news industry:

"This engagement is aimed at keeping the news central [...], it does not force anyone to adopt one particular type of conduct [...] and we still have a total and absolute freedom when it comes to choosing what content we wish to publish".

Ruiz also argued that the current dangers encountered by his fellow journalists made such an initiative necessary. He argues that criminals "threaten" his colleagues, "sometimes giving them tacit orders as to what they should or should not talk or write about".

The Agreement constitutes the second attempt in a year by outlets of the Mexican media to act against organised crime. Last August, the Human Rights Commission of the northern state of Chihuahua issued a protocol for local journalists. The state's initiative sparked heavy criticism by suggesting the latter should "avoid incisive questions" when facing dangerous situations.

The war on drug cartels and violent gangs has made Mexico one of the most dangerous places in the world for journalists. Reporters Without Borders (RSF) ranked the country 136th out of 178 in its 2010 Press Freedom Index, describing the country's situation as "dire". At least 65 journalists have been killed since the year 2000, according to the Mexican Human Rights commission, and several more have been kidnapped. Most of these events take place in the northern states bordering the US where the main trade routes for drugs and weapons are found.

Just weeks ago, two journalists -- one of which was a 20 year old -- were found dead in the north-eastern state of Nuevo León.

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Inside Big Ben: why the world’s most famous clock will soon lose its bong

Every now and then, even the most famous of clocks need a bit of care.

London is soon going to lose one of its most familiar sounds when the world-famous Big Ben falls silent for repairs. The “bonging” chimes that have marked the passing of time for Londoners since 1859 will fall silent for months beginning in 2017 as part of a three-year £29m conservation project.

Of course, “Big Ben” is the nickname of the Great Bell and the bell itself is not in bad shape – even though it does have a huge crack in it.

The bell weighs nearly 14 tonnes and it cracked in 1859 when it was first bonged with a hammer that was way too heavy.

The crack was never repaired. Instead the bell was rotated one eighth of a turn and a lighter (200kg) hammer was installed. The cracked bell has a characteristic sound which we have all grown to love.

Big Ben strikes. UK Parliament.

Instead, it is the Elizabeth Tower (1859) and the clock mechanism (1854), designed by Denison and Airy, that need attention.

Any building or machine needs regular maintenance – we paint our doors and windows when they need it and we repair or replace our cars quite routinely. It is convenient to choose a day when we’re out of the house to paint the doors, or when we don’t need the car to repair the brakes. But a clock just doesn’t stop – especially not a clock as iconic as the Great Clock at the Palace of Westminster.

Repairs to the tower are long overdue. There is corrosion damage to the cast iron roof and to the belfry structure which keeps the bells in place. There is water damage to the masonry and condensation problems will be addressed, too. There are plumbing and electrical works to be done for a lift to be installed in one of the ventilation shafts, toilet facilities and the fitting of low-energy lighting.

Marvel of engineering

The clock mechanism itself is remarkable. In its 162-year history it has only had one major breakdown. In 1976 the speed regulator for the chimes broke and the mechanism sped up to destruction. The resulting damage took months to repair.

The weights that drive the clock are, like the bells and hammers, unimaginably huge. The “drive train” that keeps the pendulum swinging and that turns the hands is driven by a weight of about 100kg. Two other weights that ring the bells are each over a tonne. If any of these weights falls out of control (as in the 1976 incident), they could do a lot of damage.

The pendulum suspension spring is especially critical because it holds up the huge pendulum bob which weighs 321kg. The swinging pendulum releases the “escapement” every two seconds which then turns the hands on the clock’s four faces. If you look very closely, you will see that the minute hand doesn’t move smoothly but it sits still most of the time, only moving on each tick by 1.5cm.

The pendulum swings back and forth 21,600 times a day. That’s nearly 8m times a year, bending the pendulum spring. Like any metal, it has the potential to suffer from fatigue. The pendulum needs to be lifted out of the clock so that the spring can be closely inspected.

The clock derives its remarkable accuracy in part from the temperature compensation which is built into the construction of the pendulum. This was yet another of John Harrison’s genius ideas (you probably know him from longitude fame). He came up with the solution of using metals of differing temperature expansion coefficient so that the pendulum doesn’t change in length as the temperature changes with the seasons.

In the Westminster clock, the pendulum shaft is made of concentric tubes of steel and zinc. A similar construction is described for the clock in Trinity College Cambridge and near perfect temperature compensation can be achieved. But zinc is a ductile metal and the tube deforms with time under the heavy load of the 321kg pendulum bob. This “creeping” will cause the temperature compensation to jam up and become less effective.

So stopping the clock will also be a good opportunity to dismantle the pendulum completely and to check that the zinc tube is sliding freely. This in itself is a few days' work.

What makes it tick

But the truly clever bit of this clock is the escapement. All clocks have one - it’s what makes the clock tick, quite literally. Denison developed his new gravity escapement especially for the Westminster clock. It decouples the driving force of the falling weight from the periodic force that maintains the motion of the pendulum. To this day, the best tower clocks in England use the gravity escapement leading to remarkable accuracy – better even than that of your quartz crystal wrist watch.

In Denison’s gravity escapement, the “tick” is the impact of the “legs” of the escapement colliding with hardened steel seats. Each collision causes microscopic damage which, accumulated over millions of collisions per year, causes wear and tear affecting the accuracy of the clock. It is impossible to inspect the escapement without stopping the clock. Part of the maintenance proposed during this stoppage is a thorough overhaul of the escapement and the other workings of the clock.

The Westminster clock is a remarkable icon for London and for England. For more than 150 years it has reminded us of each hour, tirelessly. That’s what I love about clocks – they seem to carry on without a fuss. But every now and then even the most famous of clocks need a bit of care. After this period of pampering, “Big Ben” ought to be set for another 100 or so years of trouble-free running.

The Conversation

Hugh Hunt is a Reader in Engineering Dynamics and Vibration at the University of Cambridge.

This article was originally published on The Conversation. Read the original article.