6 Special Relativity
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appeared strange to him. He set out once more in the direction
of the mountains and was never seen again. Whether he found
his way back to the Land of Bliss, or became lost and died in the
rugged highlands, is not known.
6.2 What is Time?
The above tale is a traditional Vietnamese fairy story. In the manner of such
stories, there are several variants which differ in their details and endings.
It has now been adapted into “The Vietnamese Legend, Giang Huong – the
Musical ”, which has been staged in the Opera House of Ho Chi Minh City.
A feature of the story is that in Fairyland, time flows more slowly than
on earth. This is a characteristic shared with other tales. “Rip Van Winkle” by
Washington Irving is one of the best known, where Rip falls asleep and wakes
to find twenty years have passed him by. In “The king of Elfland’s Daughter ”
by Irish writer, Lord Dunsany, there is much in common with the Vietnamese
story.
However, these are only stories, where the writer can create whatever
fantasy he or she desires. In the real world, here on earth, time has no
surprises, but passes at the same rate for everybody, wherever and whenever
they are.
Or does it?
Before we can talk of time, and whether it races or crawls by, we need to be
clear exactly what we are talking about. The Oxford English Dictionary offers
the following definition for time: “the indefinite continued progress of existence
and events in the past, present and future regarded as a whole.” This may be all
right, so far as it goes, provided that one does not probe too deeply into what
is meant by past, present and future. For instance, past is defined as “gone by
in time and no longer existing” , and the circularity of the definition becomes
immediately apparent.
St Augustine (354–430 CE) once famously said: “What then is time? If no
one asks me, I know what it is. If I wish to explain it to him who asks, I do
not know.” Since then, philosophers have debated the subjectivity of time,
and particularly duration which is a measure of elapsed time. The difficulty
arises because the only time one can actually experience is the present, and
an estimate of elapsed time requires the memory of a past event, which is
subjective. Time appears to pass more quickly if we are having fun.
Physicists have long tried to put the measurement of time on a quantitative basis. Galileo, in his experiments on the mechanics of falling bodies
103
appeared strange to him. He set out once more in the direction
of the mountains and was never seen again. Whether he found
his way back to the Land of Bliss, or became lost and died in the
rugged highlands, is not known.
6.2 What is Time?
The above tale is a traditional Vietnamese fairy story. In the manner of such
stories, there are several variants which differ in their details and endings.
It has now been adapted into “The Vietnamese Legend, Giang Huong – the
Musical ”, which has been staged in the Opera House of Ho Chi Minh City.
A feature of the story is that in Fairyland, time flows more slowly than
on earth. This is a characteristic shared with other tales. “Rip Van Winkle” by
Washington Irving is one of the best known, where Rip falls asleep and wakes
to find twenty years have passed him by. In “The king of Elfland’s Daughter ”
by Irish writer, Lord Dunsany, there is much in common with the Vietnamese
story.
However, these are only stories, where the writer can create whatever
fantasy he or she desires. In the real world, here on earth, time has no
surprises, but passes at the same rate for everybody, wherever and whenever
they are.
Or does it?
Before we can talk of time, and whether it races or crawls by, we need to be
clear exactly what we are talking about. The Oxford English Dictionary offers
the following definition for time: “the indefinite continued progress of existence
and events in the past, present and future regarded as a whole.” This may be all
right, so far as it goes, provided that one does not probe too deeply into what
is meant by past, present and future. For instance, past is defined as “gone by
in time and no longer existing” , and the circularity of the definition becomes
immediately apparent.
St Augustine (354–430 CE) once famously said: “What then is time? If no
one asks me, I know what it is. If I wish to explain it to him who asks, I do
not know.” Since then, philosophers have debated the subjectivity of time,
and particularly duration which is a measure of elapsed time. The difficulty
arises because the only time one can actually experience is the present, and
an estimate of elapsed time requires the memory of a past event, which is
subjective. Time appears to pass more quickly if we are having fun.
Physicists have long tried to put the measurement of time on a quantitative basis. Galileo, in his experiments on the mechanics of falling bodies