The Nature of Time

The Nature of Time

We are always fascinated by what time things begin or end. Rarely do we ask what time itself is. No one has been able to convincingly say what time is apart from using repetitive motion like earth’s rotation along its axis to define a day and earth’s orbit around the sun, which takes about 365 days, to define a year.

The nature of time on the other hand has been greatly studied. The simplistic (and sadly erroneous) understanding of time usually is that if your clock reads 9am at the department, the person in the library should see 9am as well on his/her clock.

This Newtonian view of time was dominant for over 200 years. In 1905, Albert Einstein shattered that understanding of time by hypothesizing that motion through space affects the passage of time.

In A Brief History of Time, Stephen Hawking notes that the above revelation created the unity of space and time into a four-dimensional structure called space-time.

For example, when the timetable comes out with space (venue) only, irritated students and lectures run back to complain about time (when).

Humans have the ability to look back in time. Whenever you look at the Sun, you are looking at the sun as it was eight minutes ago.

This is because the Sun is 93 million miles away from Earth. Since light travels at 186,000 miles per second, it takes the sun’s light approximately eight minutes to travel and reach our eyes.

Similarly, whenever you look at Proxima Centauri, the nearest star in the night sky, you are seeing it as it was four year ago. As a matter of fact, some of the stars that you see in the night sky no longer exist. They exploded into space.

For example, the star explosion (supernova/SN 1987A) that was observed in 1987 here on earth, had actually exploded from 168,000 light-years in another galaxy (one light-year is about 6 trillion miles).

This means the star exploded before Jesus was born but we did not see the explosion until 1987. In daily life, Einstein’s insight of time can be explained as follows.

When someone is in my office in room 29, our clocks tick the same.

However, the moment that person starts walking out, according to Einstein, our time starts to differ.

My watch ticks faster because, although I’m not moving in space (walking or running), I’m moving in time. For my visitor who started moving in space, his/her clock ticks slowly.

Between space and time, the more you have one the less you have the other. If the visitor runs (or walks at whatever speed) to  Hadijah’s photocopying machine and comes back, when we measure our clocks, my clock will be forward by a few microseconds. My visitor’s clock will have slowed down due to motion through space.

However, such differences are not visible with naked eyes because human beings never train their brains to understand time below a second.

Assuming that humans have the technical know-how to travel nearly at the speed of light, it would take the visitor about five hours to travel to the centre of another galaxy.

When he/she returns to my office, about 50 years will have passed here on earth. Another factor that will have intervened in the passage of time is gravity, which is the curvature of space and time.

There is more gravity on the ground than there is in space. For example, a person on the top floor of Mapeera House has his/her clock ticking slowly (because the gravity is weaker) than the person on the ground floor.

In 1971, the space-time idea was tested in the Hafele–Keating experiment, in which a clock was left on the ground in the US while another (after synchronising it with the ground clock) was flown east and then westwards. By the time the two clocks were put together again, they were not reading the same time. The results were published in the American Journal Science in 1972.

In conclusion, therefore, from a technical stand point, if you are active in space (moving around and doing something), then you are saving a lot of time.

If we could do things or travel around at the speed of light, time actually would stop. The real time wasters are the people who stand (or sit) in one position, as their clocks tick faster.

However, since some productivity can only be made behind a desk, then I’m left to conclude that complete time wasting can be achieved fully in sleep.

The original version of this article was published in The Standard in 2015

By Brian Semujju

Internet photos