💾 Archived View for gmi.noulin.net › mobileNews › 1530.gmi captured on 2023-06-14 at 17:34:04. Gemini links have been rewritten to link to archived content
⬅️ Previous capture (2023-01-29)
-=-=-=-=-=-=-
2009-10-21 06:26:55
By Lucy Rodgers
BBC News
Without it international travel would be in turmoil and calling friends in
faraway places at the right time impossible. Exactly 125 years after the
Greenwich Meridian line was drawn, how and why did Britain become the centre of
time?
At longitude 0 0' 00", the arbitrary stroke on our maps that passes from pole
to pole and bisects the UK, France, Spain, Algeria, Mali, Burkina Faso and
Ghana divides the Earth into east and west, just as the Equator splits it into
north and south.
This imaginary line now known as the Greenwich Prime Meridian not only allows
us to navigate the globe but also keeps the world ticking to the same symbolic
24-hour clock.
But it has not always been so.
Until the 19th Century, many countries and even individual towns kept their own
local time based on the sun's passage across the sky and there were no
international rules governing when the day would start or finish.
However, with the rapid expansion of the railways and communications networks
during the 1850s and 1860s, setting a standard global time soon became
essential.
"The world was in a very big mix-up," explains Dr Avraham Ariel, author of
Plotting the Globe. "People had lots of prime meridians. Earlier in Europe
there were 20 prime meridians. The Russians had two or three, the Spanish had
their own and so on."
And so, 125 years ago this week, 41 delegates from 25 nations gathered in
Washington in the US for the 1884 International Meridian Conference to decide
from where time and space should be measured.
By the end of the difficult summit, which, according to Dr Ariel, dragged on
until "smoke came out", Greenwich had won the prize of longitude 0 by a vote
of 22 to one, with only San Domingo against and France and Brazil abstaining.
The meeting also agreed Greenwich Mean Time (GMT) would be used as the standard
for the world, with the day beginning at midnight at Greenwich and counted on a
24-hour clock.
Political opponents
One of the main reasons for British victory over key rivals Washington, Berlin
and Paris, was that 72% of the world's shipping already depended on sea charts
that used Greenwich as the Prime Meridian, says Dr Rebekah Higgitt, curator of
the history of science and technology at the Royal Observatory in Greenwich.
Greenwich's reputation among seafaring nations and the wide range of maps and
charts using Greenwich as the Prime Meridian meant those at the conference
"could see that was the way it was going", she says.
Another factor in Britain's favour was that the US had already plumped for
Greenwich as the basis for its own national rail time system.
But, as the San Domingo, French and Brazilian votes showed, the choice was not
without its opponents.
There remained some desire, particularly among Britain's European competitors,
for "something more neutral" - a location that did not have such national ties,
Dr Higgitt says.
"France suggested using an older idea of a meridian running through the
Canaries - and even after the 1884 conference, Jerusalem was suggested as a
site, particularly by Italy."
Opting out
Yet while the conference's Greenwich decision has stood until this day, the
ultimate aim of some of those at the conference - a simple centralised system
of 24 uniform time zones for 24 hours - never came into being.
LONGITUDE
from 0 to 180 W
which any position on the earth's surface can be specified
the Earth, the Prime Meridian is arbitrary
Over the years, many countries have opted out of the system to demonstrate
national independence, keep in time with neighbours or maintain standard days
within their borders.
As recently as 2007, Venezuela's president Hugo Chavez shifted the entire
country back half-an-hour, while other countries operate similar fractional
zones - half-hour or quarter-hour deviations. Yet more, such as China and
India, use single time zones even though their territory extends across many
hours.
"These things come up. Sometimes it's popular will or sometimes it is
government choice," says Dr Higgitt.
"France and Spain should be on the same time as the UK, but it is more
convenient to be in sync with those they are attached to by land."
And while such political and practical considerations have caused time zones to
change in relation to Greenwich over the years, scientific and technological
advances have also challenged Greenwich's role as the centre of time and space.
Leap seconds
Since the 1960s, atomic clocks rather than astronomy have been keeping the
world's time and have forced GMT to adapt.
The combination of atomic clocks' super-accurate measurement and the fact that
the rotation of the Earth is irregular and slowing mean atomic time and Earth
time - and therefore GMT - slowly drift apart.
To keep them in sync "leap seconds" are added and produce a compromised version
of GMT called Coordinated Universal Time, which keeps atomic time tied to the
Earth's rotation.
On top of such changes to GMT, the advent of GPS technology and its ability to
precisely track location has also had its impact on Greenwich as the zero point
of longitude.
GPS's World Geodetic System 1984 system now places the Prime Meridian 100m to
the east of Greenwich Observatory - away from the line defined by its large
"Transit Circle" telescope and its corresponding brass strips straddled by
tourists eager to have one foot in the East and one foot in the West.
Dr Ariel argues this renders the historical Prime Meridian no longer
meaningful. But Dr Higgitt believes it simply highlights the fact it is not a
scientifically-determined line and simply the result of global agreement.
"People stand on it because people think it is a predestined place," she says.
"But it has never been official. It just exists in terms of habits and
international usage. It is just something that has happened over a period of
time."
The 125th anniversary of the Prime Meridian will be celebrated with a talk by
Graham Dolan at the Royal Observatory in Greenwich at 1900 BST on Tuesday 20
October.
The article overlooks one big advantage of Greenwich for the 0 degrees
meridian: it defines an International Date Line (180 degrees) which passes over
the fewest and least populated land masses. Having one's feet straddling East/
West is bizarre enough, but how about straddling Today/Tomorrow? Ian Clark,
Whitby, England
The location of the prime meridian does have some geographical relevance
because of what happens 180 degrees away, the international date line. Having
two different dates on one piece of land would be rather inconvenient. This
needs to avoid land and although the Pacific is a huge place, there are still
many islands that it has to detour around. A Washington meridian would mean a
dateline passing through Asia. Hugh Kennedy, Essen, Germany
Imagine if the meridian were in Palestine - parts of the US (or Brazil and
Canada) would be one day and parts the next day off by 23 hours. That would
have been nasty. On this count I have to go with our imperial overlords. Sri,
Chennai
Surely the country at 0,0 (lat, long) is the "centre of the world". England has
as much claim as anywhere on that line. But being on both the equator and the
prime meridian is doubly special. Ette Nuahs, UK
Surely Harrison with his brilliant chronometers had something to do with the
world accepting Greenwich as the prime meridian? Barry Bernstein, London
The Washington conference may be interesting, but the issue was already a
foregone conclusion by then. The real reason the meridian is at Greenwich is
that the Astronomer Royal at Greenwich was the first - indeed, really the only
- person to have done the research required to calculate navigational tables.
He naturally took his own telescope as the baseline, and once the nautical
almanacs which resulted were published no-one could be bothered to do the
research all over again merely to establish a different base. It's important to
note that the meridian is at Greenwich, not Charing Cross: so it honours a
great scientist rather than Britain. And who was that scientist? None other
than Nevil Maskelyne, the villain of Dava Sobel's popular book Longitude, but
arguably the real solver of the longitude problem. Peter Hankins, Wallington
Shame the UK won't move its zone to match France. More light in the evenings in
winter, less power consumption, less depression, fewer suicides, fewer road
deaths - lots of benefits, albeit angry Goths. And since this is all arbitrary
anyway, if the Scots think this could cause problems in deepest winter with
kids going to school in the dark (as opposed to coming home in the dark, which
happens to those staying for after-school clubs...), we could always draw a
time-zone line across the UK. Craig, United Kingdom
You mention that the 1984 World Geodetic System system now places the Prime
Meridian 100m to the east of Greenwich Observatory. As a resident of Lewes,
through which the line passes, I was for some time puzzled by the fact that my
GPS device disagreed with the local markings and monuments until I discovered
this 1984 change. However, you omit to say why our meridian had to move. The
answer is, of course, that the Americans set the new standard, and decided that
the meridian line to be preserved was - obviously - 90 degrees West. Ric
Bithell, Lewes