UNDERSTANDING TIME

 

If you have ever heard of Einstein`s theory of relativity you must be aware of the fact that motion affects time. Time here means the general ticking of clocks be it your wall clock, wristwatch or any other type of thing that is used to measure time or “We define time simply as a duration of an event”, going forward with this definition today we`ll be seeing by a simple example how motion really affects time of your wristwatch regardless of its brand or mechanism

For this, we consider the simplest of all clocks a light clock; its mechanism is very simple: two-plane mirror vertically aligned and a photon between them. Now here we measure time as follows==>when a photon take a round way trip it means one tick. Photon which is travelling at a constant speed i.e. speed of light takes about a billion round way trip in a second so let`s say a billion round way trip is equals to one second. The path it would follow is shown in fig 2.1 below.

Let`s us use this as stopwatch and measure duration of a race and it shows 40 billion ticks which means 40 seconds. Now we move the whole setup at a constant velocity (speed with direction) and if you now observe the path of the photon. It is not simply vertically up-down but rather at an angle (Fig 2.2).

It is because if it was like that of in first case it would not hit the upper mirror but fly off in direction, so in order to hit the upper mirror it has to follow this path. You observer this path because clock is moving relative to you .Obviously the new path is longer than the previous one and as the speed of photon is constant the time would obviously greater than 40 seconds or if I were to put it simply: more the distance more the time it will take to cover the distance with same speed.

This may not be a satisfactory explanation and you will ask would my wristwatch follow the same and the answer is yes! Let`s put this whole setup with your watch at top of the mirror attached to it in a train compartment and there are no windows no holes for you to sneak out the compartment and the train is moving with a constant velocity. The fun thing is that there is now way you could find out that the train is moving. Your wristwatch will tick normally and the path of photon will be the same like that in Fig 2.1 but for an observer outside the compartment (if you open a window) the path will be like that in Fig 2.2 and Rolex will tick slower. The effects however will not be noticeable in daily life because speed the train has to comparable to the speed of light (299,792 Km/second).