Page 55 - Encyclopedia Of World History Vol V

1832 berkshire encyclopedia of world history

A Kiowa (Native
American) calendar of
pictographs on a bison
skin. The bars and
attached figures in the
center form a winter
count while the figures
near the edges provide
a history of 37 months
during the 1890s.

experience: As a car acceler-
ates away from a standstill, its
speed over the ground
increases but the speed of the
light from its headlights does
not. It also has far-reaching
consequences. Imagine that
you are standing in the center
of a stadium, and I am running past you just as the lights shorter than a heartbeat was the realm of philosophy,
are turned on.You see all the lights turn on at the same anything longer than a lifetime that of history, religion, or
time—a little after they actually did, because their light myth; both were inaccessible. Authors of medieval com-
takes time to reach you. But in this time I have moved putus texts (notably Bede, the Benedictine monk) specu-
towards one side of the stadium. I see that side turn on lated on the smallest part into which a day might be
first, because that light travels a shorter distance to me divided, but were principally concerned with calculating
at the same constant speed. A third person running past the date of Easter. At the other end of the scale, Arch-
you in a different direction experiences events in a dif- bishop James Ussher of Armagh deduced around 1650
ferent order again.The profound message of relativity is that the universe was created in 4004 BCE on Saturday
that relative motion—one observer moving relative to 23 October at 6 P.M. Other cultures incorporated much
another—unavoidably leads to relative time, with no longer epochs in their chronology, for example the
unique, correct, or absolute order of events. Mayan and Indian cycles already noted, but these figures
Relativity has still stranger consequences.Time passes were largely simple mathematical progressions of shorter-
at a slower rate for a moving observer; if one of two twins scale calendars.
takes a rocket trip, he will be younger than his brother Today the range of time intervals open to direct study
when he returns, and the faster he travels the less he will has widened dramatically. Modern technology slices time
age. Time similarly slows as gravity increases, so that ever finer: Races are timed to thousandths of a second,
clocks tick slower on the ground than they do in orbit. atomic clocks are synchronized across the globe to bil-
These bizarre predictions of Einstein’s theory have been lionths of a second, and the fastest laser pulses open a
verified to extraordinary accuracy by experiment, and window to timescales shorter than one femtosecond (a
they even impact on modern life: For the Global Posi- millionth of a billionth of a second). In the realm of “deep
tioning System to provide accurate navigation, the satel- time,” the age of the Universe is believed to be around
lite atomic clocks must be corrected for these effects. thirteen billion years, of the Earth around four and a half
billion years, and of our hominid ancestors over seven
Scales of Time million years (this is still much discussed as new fossils
Science has revolutionized our understanding of the are found). These figures draw on advances in geology,
scale of time as well as its nature. In antiquity, anything palaeontology, astronomy, and cosmology, which were