Call centre workers and IT employees experience it. Long distance jet-setters –of late, Prime Minister Sri Modi, US Secretary of State John Kerry – experience it. And geographers such as my USA-based colleagues with whom I work have to deal with it.

Differences in longitudes. Hence the differences in time. If you are traveling across longitudes you face jet lag. In other cases, it is just time difference that has you up at all sorts of odd hours interacting with people located far away.

Longitudes can be a pain. And I am not saying that just because you have to deal with it in your geography textbooks. (I suffered from textbooks, too! Thank goodness my teacher, Sri Narasanna, understood the need for real learning and held us spell-bound in his classes.)

You know the routine! “Latitudes and longitudes are imaginary lines on the surface of Earth … blah blah blah.” But what does it all mean? How are we affected? Sorry, the textbook can’t go into all that. You have to prepare for the exam! Fill in the blanks, match the following, …


Longitudes (from Latin longitudo, ‘length’) are those imaginary lines that connect the two poles. They are all equal in length and form semi-circles. They are also called meridians, derived from the Latin meridianus, ‘of noon’ – where the sun is directly overhead, i.e., it is mid-day. Before that, the sun was rising and after that, the sun is setting.

If you take any one meridian and travel east or west, you eventually end up at its anti-meridian – the meridian directly opposite to it, 180˚ away. You travel through various degrees east and various degrees west.

But there is a problem. Wouldn’t you know it? It’s always something! With latitudes, it is easy to designate a reference latitude, 0˚, the Equator, the largest circle, it divides Earth into two equal parts.

But this is not so with meridians. They are all of equal length.

So, which meridian is to be taken as 0˚, the reference meridian? Any meridian could be selected. It needed two things: identify the meridian’s location, and get the world to accept that meridian as the reference.

Getting lost

Without a proper understanding of longitudes, seafarers had difficulty in knowing where they were and where they ought to be heading. Lives were lost at sea. Also a lot of loot that ‘adventurers’ were helping themselves to in distant lands.

People were lost, at sea. There’s an English expression, “to be at sea” meaning “to be totally lost”, “clueless”!

In 1714, the British government passed an Act of Parliament, called the Longitude Act. It established the Board of Longitude. The aim was to find a way to determine a meridian accurately.

One degree of meridian spans about 60 nautical (68 geographical) miles. The sun takes 15 minutes to shift its overhead position from one meridian to the next degree.

Prizes were announced to solve ‘the greatest scientific problem of the time.’ The highest prize was £ 20,000 for the method that gives the most accurate measurement. Today, that amount would be worth millions of pounds sterling.

For this, expert opinions were collected from the great minds of the time, such as Edmond Halley (after whom Halley’s comet is named), and Isaac Newton (who caused me much personal grief when I had study calculus in PUC!).


John Harrison to the rescue. This man had no formal schooling or even apprenticeship (training) under any clock-maker. He was a genius at mechanical things.

To fix a longitude, the problem was to fix the time at the starting point (call it A). Travel 60 nautical miles or 15 minutes to another point (call it B). Then compare the time at B with what time it would be at A. You are out at sea. How do you keep the time at A and know what it is while you are bobbing up and down on salt water? You need a clock that can keep the time at A, a clock that you can take with you. This was a problem. The bobbing up and down, left and right, and front and back all played havoc with the clocks. You needed a clock that would keep the time, no matter how rough the seas.

Harrison built precisely such a clock. More than once! Each attempt took years. All hand-crafted.

To cut a long – and very very fascinating – story short, thanks to Harrison, the problem was solved. But some of the great men of the time tried to refuse him his prize money! So, he had to fight for his prize.

Fixed! Now what?

The meridian passing through the Royal Observatory at Greenwich (pronounced “GREN-ich”) was chosen as the reference meridian – Prime Meridian, Greenwich Meridian, 0˚ longitude.

The British Empire extended through much of the world at the time (“the sun never sets on the British Empire” and all that, remember?). So, they adopted this meridian as standard and the rest of the world went with it.

But, but, but …

Sea-faring is not new. It is thousands of years old. How did those ancient people navigate vast oceans without knowing latitude and longitude? Perhaps they used only their observations of the heavens? Things happening in their own environments?

BPO, call centre, and IT workers who deal with international clients (a great many degrees of longitude away) end up working at hours that are convenient to their clients. This means staying awake – and sleeping – at all sorts of odd hours in their native time zones.

When jet travellers go long distances across many longitudes, their internal body rhythms are thrown out of gear. Whenever I traveled between the USA and India, I used to struggle mightily with this problem. In Bengaluru, as the day was just beginning and amma would be making delicious coffee, my body would be telling me to go to sleep because it was night back in USA where I lived at the time! Tough fight between amma’s coffee and my body’s sleep demands!

Now when I have to hold online meetings with my geographer colleagues in the USA, we have to strike a delicate balance between our respective needs – is it too early for you, is it too late for me? Will you be in the midst of breakfast or I in the midst of dinner? And so on.

But we don’t calculate our respective local times the old-fashioned way. We use an internet tool!

Yes, we are very modern!

Things you can do:

  1. Read the book “Longitude” by Dava Sobel (Harper Perennial, 2008; available at local bookstores).
  2. View a fascinating documentary about the story of how the Prime Meridian was fixed, on YouTube.  “Lost at Sea: the search for longitude
  3. If some other country had fixed the longitude problem, would it have been possible for them to get the rest of the world to adopt their solution? Why or why not? You could use maps at the Perry Castañeda Online Map Library at for your research.
  4. Instantly find the time at any place in the world using the Time Zone Converter – Time Difference Calculator.  This is what my colleagues and I use to coordinate our meetings!

(A version of this article appears in Deccan Herald Student Edition on 27 November 2014.)



2 Responses

  1. I really liked this article, because of the entire “longitude business”. The book you refer to – about John Harrison, and longitudes – is a fascinating one on so many levels; deals with science, human perseverance and genius, and finally figuring out longitude makes a positive difference in “modern” human lives. Would be nice to see schools imparting the essence of this article, and the shared this “longitude” book with their students.

  2. Kiran, yes. You are right about the many *disciplines*, not just *subjects* that are involved in this story. It is also a great example of how the boundaries among disciplines are mere human contrivances that should be transcended.

    However, The System does imposes strict page and time limits for each topic. So, neither the students nor the teachers have the time and space to *develop* ideas.

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