Most of the modern world conducts its commerce under a calendar decreed in the 16th Century by the Christian Pope Gregory the Thirteenth. Many people accept that Gregory's December 31, 1999, is the last day of the second millennium. But not everyone measures the passage of time this way. And nobody can answer the question, "What is time?" As a new millennium draws near, RFE/RL correspondent Don Hill discusses the meaning of time.
Prague, 30 December 1999 (RFE/RL) -- The first sound a human fetus hears is its mother's heart, about 75 beats to the minute.
So everybody born of woman knows about time.
But nobody can tell you what time is. Not Aristotle, the philosopher; not Augustine, the saint; nor Locke nor Kant nor Newton nor Einstein. They all tried, but none of them managed to define it well enough to satisfy everyone else.
A learned scientist can explain to her child that the most advanced modern scientific theories postulate that time began when the universe came into being with a Big Bang.
And then she can be silenced by the innocent question, "But, Mama, what came before that?"
Albert Einstein could prove mathematically that time is not absolute, but relative, that every observer perceives a different time according to the observer's own speed and vantage point. But Einstein couldn't change the fact that everyday people continue for practical purposes to understand time as a universally shared reality that is both measurable and limited.
Here's an interesting puzzle. Do you conceive of time as something like, say, a swamp that you pass through from where you have been to where you are going? Or do you conceive time as something that flows by like a stream while you stand on an island called "Now"?
Most people in industrialized cultures perceive time as a flow.
But if time is a current flowing around us, why do we say the future lies ahead? If time is flowing by, then isn't the past in front of us, with each remembered event receding further into the distance, bobbing along, shrinking smaller and fainter? And isn't the future, then, coming up from behind us, unseen, unknown? There are cultures in which time is perceived just that way.
People may not know exactly what time is, but from humankind's earliest days, we have observed it and measured it. One way is by what are call the circadian rhythms of the human body. The heartbeat...
Human sleep-wake patterns of nearly 25 hours...
A woman's menstrual cycle, normally the interval of a lunar month.
Another way to measure time -- used by virtually every culture whose thoughts have been recorded -- is by the observable movements of the planets and the stars.
Three thousand years before Jesus Christ walked the earth, the Egyptians used a solar calendar. But it was inexact. By Julius Caesar's time, a few years before Christ, it was 90 days out of synchronicity with the seasons. Julius Caesar ordained the Julian calendar to correct this. His calendar started in March instead of January. That explains why the name in Latin-based languages for the ninth month is September, meaning seventh month. And why October is related to the Latin word for eight.
When Pope Gregory decreed in 1582 what still is called the Gregorian calendar, he numbered the beginning of modern time from the birth of Jesus. It's now known that he got it wrong. Historical calculations say Jesus must have been four or five years old by the beginning of the first Gregorian year.
But to Jews and Muslims, Chinese and Hindus, that would be immaterial. January 1, 2000, will be in the fourth month of the 5,760th year of the Jewish calendar.
It will be the 24th day of the holy month of Ramadan in the 1,420th year since the prophet Mohammad emigrated from Mecca to Medina on what Gregory would have called July 16, 622.
It will be the 25th day of the 11th month in the year of the rabbit of the current cycle for Chinese.
In the Hindu religious calendar, it will be the 25th day of the month of Margasira in the year 1921 of the Saka era.
It is not just the months and the years about which various cultures, and various people within cultures, disagree. When, for example, does the day begin?
In October 1884, the International Meridian Conference convened in Washington, D.C. It decreed that a day begins, in the words of its declaration, "for all the world at the moment of mean midnight" in Greenwich, England. That's how Greenwich time came to be the time from which all others are measured.
But tell that to a working man or woman, whose day begins with an alarm clock going off.
Or to a Jewish or Muslim religious whose new day begins at sundown of the previous day. A devout Muslim's day is divided by five calls to prayer.
The British National Maritime Museum in Greenwich has assembled a huge exhibit called, "The Story of Time," and simultaneously published a lavish book with 300-illustrations by the same name. That's the source of much of the information in this report.
One final thought: Where will it all end?
Birth begins the human clock. Death ends it.
The earth's sun was formed 4,500 million years ago. It has burned up less than half of its hydrogen fuel so far and has about 5,000 million years to go. Then it will end and with it any chance for life on earth.
For many of the world's religions, the end will come when God or Jehovah or Allah calls the faithful to the Day of Judgment.
Quantum physicists can speculate about a black hole in which time ceases to exist.
And the innocent child still may ask, "But, Mama, what comes after that?"