24
would have some kind of a supernatural decelerating effect on everyone
except the Hebrew soldiers. Many ancient cultures also conceived of time as
cyclical, rather than proceeding along a straight line as in 1998, 1999,
2000, 2001,... The second quote, from a relatively modern physicist, may
sound a lot more scientific, but most physicists today would consider it
useless as a definition of time. Today, the physical sciences are based on
operational definitions, which means definitions that spell out the actual
steps (operations) required to measure something numerically.
Now in an era when our toasters, pens, and coffee pots tell us the time,
it is far from obvious to most people what is the fundamental operational
definition of time. Until recently, the hour, minute, and second were
defined operationally in terms of the time required for the earth to rotate
about its axis. Unfortunately, the Earth’s rotation is slowing down slightly,
and by 1967 this was becoming an issue in scientific experiments requiring
precise time measurements. The second was therefore redefined as the time
required for a certain number of vibrations of the light waves emitted by a
cesium atoms in a lamp constructed like a familiar neon sign but with the
neon replaced by cesium. The new definition not only promises to stay
constant indefinitely, but for scientists is a more convenient way of calibrat-
ing a clock than having to carry out astronomical measurements.
Self-Check
What is a possible operational definition of how strong a person is.
The meter
The French originally defined the meter as 10
-7
times the distance from
the equator to the north pole, as measured through Paris (of course). Even if
the definition was operational, the operation of traveling to the north pole
and laying a surveying chain behind you was not one that most working
scientists wanted to carry out. Fairly soon, a standard was created in the
form of a metal bar with two scratches on it. This definition persisted until
1960, when the meter was redefined as the distance traveled by light in a
vacuum over a period of (1/299792458) seconds.
Pope Gregory created our modern
“Gregorian” calendar, with its system
of leap years, to make the length of
the calendar year match the length of
the cycle of seasons. Not until1752 did
Protestant England switched to the
new calendar. Some less educated
citizens believed that the shortening
of the month by eleven days would
shorten their lives by the same interval.
In this illustration by William Hogarth,
the leaflet lying on the ground reads,
“Give us our eleven days.”
A dictionary might define “strong” as “posessing powerful muscles,” but that’s not an operational definition, because
it doesn’t say how to measure strength numerically. One possible operational definition would be the number of
pounds a person can bench press.
10
7
m
Chapter 0Introduction and Review
The Time Without
Underwear
Unfortunately, the French
Revolutionary calendar never
caught on. Each of its twelve
months was 30 days long, with
names like Thermidor (the month
of heat) and Germinal (the month
of budding). To round out the year
to 365 days, a five-day period was
added on the end of the calendar,
and named the sans culottides. In
modern French, sans culottides
means “time without underwear,”
but in the 18th century, it was a way
to honor the workers and peasants,
who wore simple clothing instead
of the fancy pants (culottes) of the
aristocracy.
Next Page >>
<< Previous Page
Back to the Table of Contents