“Why do we have to change the clocks twice a year?”

Interesting question. (This was Lyddie’s question last week, when we changed ours.) “The world takes its time from Greenwich,” says the line in Mary Poppins:

– and yet England only runs on Greenwich Mean Time for half of the year.

So, why?

The inveterate conspiracy theorist in me looks first for a political motive – and indeed, it seems from Wikipedia that I might be right to do so:

Reading the English translation of that directive, I see a ruling to harmonise the change to daylight saving time across the member states so that it happens on the same day, but nothing to explain why it happens in the first place.

My suspicion is that forcing populations to adapt their body clocks twice a year is a political tool which reinforces the power of a ruling body over its people, but Lyddie and I did go through the various given reasons together.

She also asked: “Why does the world take its time from Greenwich?” which led us to the International Meridian Conference, held in Washington in 1884 and attended by 25 nations, in which the following resolutions were adopted:

1. That it is the opinion of this Congress that it is desirable to adopt a single prime meridian for all nations, in place of the multiplicity of initial meridians which now exist.
2. That the Conference proposes to the Governments here represented the adoption of the meridian passing through the centre of the transit instrument at the Observatory of Greenwich as the initial meridian for longitude.
3. That from this meridian longitude shall be counted in two directions up to 180 degrees, east longitude being plus and west longitude minus.
4. That the Conference proposes the adoption of a universal day for all purposes for which it may be found convenient, and which shall not interfere with the use of local or standard time where desirable.
5. That this universal day is to be a mean solar day; is to begin for all the world at the moment of mean midnight of the initial meridian, coinciding with the beginning of the civil day and date of that meridian; and is to be counted from zero up to twenty-four hours.
6. That the Conference expresses the hope that as soon as may be practicable the astronomical and nautical days will be arranged everywhere to begin at midnight.
7. That the Conference expresses the hope that the technical studies designed to regulate and extend the application of the decimal system to the division of angular space and of time shall be resumed, so as to permit the extension of this application to all cases in which it presents real advantages.

We found the text of the proceedings and enjoyed spotting the evolution in the 125 year-old language used. We looked through it to try to find the answer to her second question and found this, spoken by the French delegate:

“… the meridian of Greenwich is not a scientific one, and that its adoption implies no progress for astronomy, geodesy, or navigation; that is to say, for all the branches and pursuits of human activity interested in the unification at which we aim.

“Thus, science is absolutely disinterested in the selection which we are now discussing and that fact I wish to emphasize particularly, as we are about to take a vote which we can easily anticipate by the one we had a few minutes ago, in order that the opponents of the resolution may not be accused of obstructing progress and the great aims of science for private interests.

“If, on the contrary, any conclusion is to be drawn from the instructive debate at which we have assisted, it is that the principal, I will say more, the only merit of the Greenwich meridian—and our colleague from Great Britain just now reminded us of it by enumerating with complacency the tonnage of British and American shipping—is that there are grouped around it, interests to be respected, I will acknowledge it willingly, by their magnitude, their energy, and their power of increasing, but entirely devoid of any claim on the impartial solicitude of science………. For the present we decline the honor of immolating ourselves alone for progress of a problematic, and eminently secondary order; and it is with perfect tranquillity of conscience that we declare that we do not concur in the adoption of the meridian of Greenwich, persuaded as we are that France does not incur the reproach of retarding and of obstructing the march of science by abstaining from participating in this decision.”

– from which we inferred that the decision was a purely political one, formed from the alliance and to help with the then trading links between Britain and America.

We then became interested in the political history between England and France, which of course took us to Napolean, before we ran out of time and energy for studying on that day.


1 Comment

Filed under Curiosity - a delicate flower, Geography, History, Science

One response to ““Why do we have to change the clocks twice a year?”

  1. Actually at this point I’m totally confused. We just turned our clocks back one hour, why who says we have to why? can’t we have the same time all year.

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