Dateline: Bali

The phlong is dead, a victim of technology.  But the phlong - the flexible papier-mâché mould which is taken from the flat hot-metal setting of a newspaper page and used to make the curved printing plates - is not alone in being overtaken by science.  Another venerable institution also finds itself marginalised to the point of extinction - the dateline.

Curiously, the dateline is the term for the place name that is often found at the head of a news item. Originally it would have included both place and time; it was used to indicate which day the news story referred to.  When global communications were a more involved business than now, news from distant parts of the world might take a day or two to be printed; hence the need for a clarifying dateline.

Today, though, we live in one, instant world.  It takes less than a tenth of a second to send or receive information between any two points on the earth's surface.  Typically a newspaper reports one day's events from around the entire world, so the dateline has retreated to information about place.

Happily, though, we do not quite live in a single big, simultaneous village.  The earth is round; when it is noon here, it is midnight in the antipodes. This lends its own rhythm to events; it also adds a spice of complication in the form of another dateline, the International Dateline.

This is the imaginary line which joins pole to pole following the 180 degree meridian except for a rude swerve to avoid the Fijian archipelago.  Somehow at this point, the concept of now and today becomes disrupted; it is like a huge temporal chasm.

It has taken me a third of a century to understand the International Dateline.  For years I struggled with thought experiments involving super-Concordes travelling at many times the speed of the earth's rotation, setting out from the Dateline at midnight on one day and skirting round the equator to arrive back at its starting point.  I realise now that I was mixing many disparate and confusing effects.

The reality is simpler.  As everyone knows, as you travel east, hours are added to the time on your watch.  The earth can be divided up into 24 time zones, like an orange into segments, one for each hour added.  However, this means that in circumnavigating the world, you gain 24 hours on top of your watch's time; that is, you reach tomorrow.  But your twin, who sits in a plane on the tarmac for the same elapsed length of time, and whose watch shows the same time as yours, remains in today.  To avoid this paradox, you need to lose a day somewhere; that somewhere is, arbitrarily but by universal agreement, the International Dateline.  Crossing it changes your day of the week - whatever the time shown on your watch.

I first understood this pacing up and down an empty beach on Bali under the moonlight.  For an instant I was able to cross back and forth between comprehension and incomprehension, gaining and losing the knowledge just as I would later gain and lose a Tuesday crossing the Dateline itself. 

(20.10.89)

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