Tuesday 29 May 2007

Greenwich - The home of longitude

We have finally made it to the UK, and although jobless and homeless, have managed to have a great time so far, although today's wet and freezing London weather is testing our patience. The UK being a very old country (in the western sense in any case) means that there is an abundance of "culture" and ye olde science that appeals to me - although I must say I haven't found good coffee yet - the Anglos clearly didn't put much effort into coffee science...

I will start a series of stories on the sciencey places I have been, starting with Greenwich.


Greenwich, to the east of the city of London, is home to the Royal Observatory, whose mission is to illustrate for everyone the importance of the sea, ships, time and the stars and their relationship with people.

Greenwich is also home to Greenwich Mean Time and the prime meridian, which is the meridian at which longitude is defined to have zero degrees. Longitude is an important way of defining where on the globe you are - and was of particular importance during the 1600-1800s for seafarers, for whom knowing where they were in the ocean was paramount. Longitude defines the location of a place in a number of degrees east or west of the prime meridian that runs through Greenwich - this is a north-south line that encircles the Earth. Longitude ranges from 0 degrees at the Prime Meridian to +180 degrees eastward and −180 degrees westward on the direct opposite side of the Earth. The photo on the right is me with my bright red scarf straddling the prime meridian.

Latitude, which runs east-west around the Earth, has a natural zero-point - the equator. Longitude does not have this, which is where Greenwich's claim to fame comes in. Whilst meridians through Copenhagen, El Hierro, Jerusalem, Saint Petersburg, Paris, Philadelphia, Pisa, Rome and Washington were used in various parts of the world, Greenwich won the Meridian Idol competition in 1884, when the International Meridian Conference, which must have been the high point in the A-list social calendar of 1884, adopted the Greenwich meridian as the universal zero point of longitude.

Measuring longitude whilst at sea has historically been a very difficult business. Whereas latitude is easy to determine by looking at the positions of the stars or the sun, longitude was often measured using dead-reckoning - that is, knowing how fast you are going and knowing the time at which you started your journey gives you your final position and longitude. This is fraught with inaccuracies, especially in rough conditions.

Giovanni Domenico Cassini developed a method in 1681 that measured longitude by noting the relative positions of Jupiter's natural satellites, which have known orbits. This was difficult, however, for the average sailor. The wrecking of Sir Cloudesley Shovell's British fleet gave rise to the British Longitude Act, which created the Longitude Prize (£10,000 for any method capable of determining a ship's longitude within one degree; £15,000, within 40 minutes, and £20,000 within one half a degree) for anyone who could develop a practical method of determining longitude at sea. The winner of the prize was John Harrison with his H-4 device.

Harrison demonstrated a method of determining longitude on his voyage between Portsmouth in England's south, and Bridgetown in Barbados, by knowing the exact time of day in England using a clock (a new technology at the time), while using astronomical observations to find the exact local time on the ship as it sailed. Knowing the time in England relative to the time on the ship gives you your longitude. For instance, if its midday in Greenwich on the clock you are carrying with you, and midnight where you are, you must be on the exact opposite side of the Earth - that is, at 180 degrees longitude. Daylight saving makes this a little more difficult to work out, but the principle is the same.

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Wednesday 16 May 2007

Smoggy Pic

Just a quick extra to the last Hong Kong post. The attached picture shows the smoggy gunk I cleansed from my face at the end of just one day in the town. The pad on the left came off before my shower - the one on the right is afterwards. Clearly, there was plenty on my face!

Wednesday 9 May 2007

Travelling thru the smog....

I've just done the very Australian thing of relocating to London for 9 months, so as I sit here in a pub that's over 200 years old, yet which has a wireless hotspot, and as I try not to convert pounds into dollars, I would like to reflect on my stop-over in Hong Kong. I have been to Hong Kong before, and I love it. The food, the people, the food, did I mention the food?

But this time I was confronted by one of the more misfortunate aspects of developed cities, that of smog. The smog was so bad that visibility was down to 8 kilometres.

The words "Hong Kong" translate to "Fragrant Harbour", and this is possibly an apt description, even if the fragrance one smells is not necessarily a nice one. Most of blame falls with Hong Kong's neighbouring Guangdong Province in China, and its coal-burning factories and power plants. This region pumps out about 690,000 tons of sulphur dioxide into the air each year, compared with Hong Kong's 80,000. According to the World Health Organisation, China has 7 of the worlds 10 most polluted cities. Prevailing winds in the region carry pollution and particulate matter south to Hong Kong, and this has been exacerbated in recent years due to typhoons.

In 1993, Hong Kong had 50 days when visibility was below 8 kilometers. In 2004, it was 160. A recent survey found nearly 40 percent of Hong Kong's children suffered from a respiratory disease which linked to smog.

Hong Kong officials have recently started to take action, and this is timely as, although most of the pollution floats south from China, much of the street level pollution is locally made by Hong Kong's fleet of aging diesel powered cars. The city's 17,000 diesel taxis and minibuses are being upgraded with catalytic converters or replaced by LPG powered cars.

Sulphur Dioxide, Nitrogen Oxides, Volatile Organic Compounds, Ozone and particulate matter are all to blame. SO2 is colourless but creates acid rain. Nitrogen Oxides make breathing difficult and turn the air brown. Volatile Organic Compounds are nasty, carcinogenic things and ozone, whilst rather beneficial very high up in the atmosphere, is deadly at ground level. Particulate matter is very fine and so can penetrate the lungs and then blood making breathing very difficult.

There are a couple of excellent websites on the problem, developed locally by the Hong Kong government or concerned residents. They are:


China has ratified the Kyoto protocol, which could help alleviate this problem, however the loop-hole is that, as a developing nation, it is not bound by any targets for restraining carbon dioxide emissions. There are also few environmental laws in Guangdong. Problems have also arisen because reserves in the South China Sea gas field were overestimated, which meant that more coal was burnt to meet Hong Kong's, and China's rapidly increasing energy demand. Hong Kong and the Guangdong provincial government have set a target to reduce emissions of sulphur dioxide in the Pearl River Delta by 40 percent by 2010.

OK, I think I had better leave this pub. It might just be a little classy for me. I'm off to see Fame the Musical!

Listen to this show here