About Time!

T. S. Elliot says: “Now, that is always now”. One thing about life is certain. It moves forward and it cannot be enacted. Everything happens once and then it is history. Time does not stop or revert. Time proceeds only in one direction; forward. Every one of us has only one chance to do what we do, and then it is called "past". When we are able to define time, we have achieved a great deal of knowledge. Saint Augustine was once asked to define the meaning of time. He said, “When I do not have to explain it, I know what ‘time’ is. But when someone asks me what it is, I do not know.” The universe is 14 to 15 billion years old. This measurement of time, year, is created by us in order to put history in perspective. Time has been measured by people from early ages by tools available to them.

As in measuring length, weight, space, energy, and temperature, time has been measured by its own devices. Measuring systems also vary among cultures. We have solar and lunar calendars, measured differently depending on their cultural, and mostly religous traditions. However, it is always measured according to the movements of earth and moon in relation to the sun. The difference between measuring time and other measuring systems, say length, is that we cannot go back and measure time again. In another words, a time passed is behind us and we cannot adjust it in case we make an error! We begin each day with a new hourly measure. The same goes with begining a new week, month, year, as well as a new century or millennium. But these new times have been compounded since the birth of Christ, or migration of Mohammad, or other events that were established in different societies as the beginning of time, or time zero. Some empires enjoyed acknowledging time from the time their own dynasty was established.
When people decided to measure time, they noted reccurring appearances in the heavens, and they decided to use that global movement to measure time (heavens had already been used for navigation for centuries). So, they started observing movement of the sun (as it appeared to be moving) and moon, and their relations to the movements of earth. Lunar and then solar calendars were created. Days were divided into morning, noon (when sun is in the middle of the sky), and afternoon, then evening and night and midnight. The length of each occurrence was different depending on the culture, and also they were different from the length of time we call morning or afternoon or night. There was a time when astronomers were able to measure revolution of earth around the sun, which is 365.2422. After many trials and errors, the best system that is still theoretically in place was established in ancient cultures, that is to use this number (rounded) and call it a year, divided by 12 months, divided by 30 days, and continue dividing each day by hours and minutes and seconds, with five days added at the end of each year. During Julius Caesar in 46 BC, scientists came up with the leap year to account for the extra day (Julian calendar, which was really not an invention by Caesar, as the salad dressing is not!) Then three rules were established:


1. If the year can be divided by 4 it is a leap year, unless

2. If it is divisible by 100, unless

3. If it is divisible by 400 (year 2000 was a leap year)

But because of the fraction, we are off by one day in every 2000 years. Therefore we add a day to every 2,000 years.

 

After all computations of time was completed, a need to have an instrument to show time became a new engagement. Various time pieces were created, advanced by new technologies. Inserting a stick in the ground and in the center of a circle (knowing that a circle can be divided in 360 degrees) and marking the shadow of the stick was the earliest time piece recorded. Soon after, inventors created water clocks and candles and incense clocks and hourglasses. Then, in 13th century pendulum, and in 17th century balance string were invented. The latest invention of course is the vibration of atoms in atomic clocks. These are all to measure time assuming that revolution of earth around the sun is constant, which is not! For example, when there is more snow on the North Pole, earth is heavier on one side. Also, days are longer in the summer than in the winter.
Many other changes in universe, such as gravitational pull or mass of sun and earth that warps the space around it, changes the theoretical measurement of time. Before Einstein, we had only the knowledge of Newtonian laws of gravity that considered time as absolute and time and universe independent of each other. Einstein’s theory of relativity brings a new factor of velocity to be accounted for. Based on that, depending on the state of motion, measurement of time varies. For example, there is a certain time it takes for an object to travel in a moving plain. This time is different whether it is measured inside a plane or outside on the ground. But if time is relative, how come speed of light is always 186 thousand miles per second? This is an interesting phenomenon when we realize that time slows down as we get closer to speed of light. At the speed of light, time is zero. We age because of time. If we travel close to the speed of light, everything that moves in our body slows down. Astronauts, who travel very fast, age slower than others on earth. If we build a space ship that can travel with the speed of light, it will take that space ship 16 years to get to the edge of the Milky Way. Therefore, the astronaut traveling in that space ship will get 16 years older by the time s/he reaches the destination. However, passage of time for us on earth is not 16 years but close to one million years! Time is very well relative to gravitation in universe. Gravitation is so immense in black hole that time has no meaning. Gravity causes the universe to condense because everything is pulled towards each other. The universe will finally become one big black hole and that would be the end. Time disappears in Black Hole. Then, Big Bang may start all over again and particles explode and time begin. How many times this universe has expanded and then condensed, we do not know. But every time it happens, time starts from zero.