Defining Time: Its History, Problems and Solutions

Socrates (470-399 BC) once declared that in order to say anything about X, we must first be able to answer what is X. In order to talk about time, we must first answer; “What is time?” For different people, time means different things. A famous philosopher once said that time is nature’s way of keeping everything from happening at once. It is a subtle definition but one that is without practical implications. For a physicist, time is one of the building blocks of the universe. For a biologist, time is an internal clock that keeps plants and animals (this includes humans) in synchronisation with nature. Bankers on the other hand, would regard time as money, period. For John McTaggart Ellis, time is unreal, a mere illusion. For the rest of us which I presume possess a higher degree of common sense, time is so very real.

“Everything is in a state of flux,” commented Heraclitus (c. 500 BC). Everything changes or is in a process of changing. His idea is summed up in the phrase panta rhei which means ‘everything moves’. Indeed everything in the world seems to change in time. We may think of geographical positions as fixed. But in reality, a place like London is located on a planet that rotates on its axis which in turn rotates around the sun. Even for those things that we think do not change, they would at least age as time passes by. Some mathematical concepts like the Pythagorean Theorem, for example, have never changed; but we do put a number, probably thousands of years, that mark its founding to this very day. Even the Pythagorean Theorem in trigonometry has aged since its founding! “You cannot step into the same river twice,” said Heraclitus because “upon those who step into the same rivers, different and again different water flows.” Like a flowing river, time flows in one direction without ever looking back.

We feel the presence of time in two ways. The first is through our perception of how things change. The presence of time can be felt by noticing the interval when an object of our attention shifts its position by moving from one place to another. The second way is through our memory. Even when we close our eyes, we can still remember how an object changes its location without looking at the object at all. We can safely conclude that our awareness of time is present when we know the changes happening to an object of attention (both physical and mental) from the start to the end of a time interval and also by knowing the sequence of these changes. Hence, we first remember the initial physical position of the second-hand of our clock, look as it changes its position, register its new physical position, and infer mentally that one second in time has passed. In this manner, we feel time passes by when we observe the cycles of day and night, the phases of the moon, and the changing of seasons. But time is not merely linked to the sense of sight. For a person who cannot see, he can similarly feel time by measuring his pulse or heartbeat. In this case, the act is a more of a mental state.

The way we measure time differs from the way that we feel time. In a world of constant physical change, measuring time is essentially an empirical procedure of ascertaining a magnitude, a numerical value, or a quantitative property given an interval between two separate and distinct events. This can be done more easily when the changes that are being measured reoccur at a consistent interval. For example, the change from the presence of sunlight to darkness and then to sunlight again, constitutes a full cycle which we call one day. When we measure an event with our watch, we are basically comparing the state of change that the hands (or numbers in the case of digital watches) of our watch is going through with the change happening in the event we are measuring. Because the physical movement of our watch is consistent every second, we use watches as a timekeeping device to measure its rate of change relative to other events.

The Babylonians used this principle to adopt a calendar system with one year having 360 days, divided into 12 months of 30 days each. The Egyptians, perhaps being better mathematicians, adopted a calendar with 365 days and divided one day into two cycles of 12 hours each. The calendar that we so naturally use today on the other hand, can trace its roots back to the Roman Gregorian calendar named after Pope Gregory XIII in 1582. Our present day calendar is accurate to a day in every 3,323 years!

An Anchor Escapement

As human technology and knowledge in mathematics increase over time, more accurate timekeeping devices were invented to give human beings a better measure of time. The race for increased accuracy in the ancient times was won by a Chinese scholar called Su Song who invented the first mechanical water clock in the 11th century A.D. This contraption was so colossal that it reached up to 30 feet high and was powered by a giant waterwheel. The most unique feature of this water clock was its escapement; a device that stops the clock’s movements at set intervals, forcing it to run at a consistent rate. The escapement is the reason why the second-hand of our mechanical watches change its position with a regular physical movement (the same distance) every second.

After the invention of the escapement, human beings were able to increasing measure time with ever greater precision. The first mechanical clock appeared in Europe in the 13th century inside an English monastery. By 1884 many countries have started to adopt the Greenwich Meridian as the longitude of zero degrees. To the horror of the French, the line of the Greenwich Meridian ran through the site of the Royal Observatory in London instead of Paris. In 1915, daylight saving time was introduced but the winner of precision came only in 1948 when the revolutionary atomic clocks came into existence. The introduction of the atomic clock has changed our understanding of time forever.

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