The good times at IUCAA, Pune will soon be over and I will be back at my old rooms at ISMU. Most people have the opinion that if you stay at a place for too long, you imbibe the general qualities of the place. Having stayed here for six weeks now, I can now invariably argue that they are wrong. Astrophysics flows in every block of concrete that IUCAA is made up of. However, nothing sticks unless you want it to and you take up only the part that you really enjoyed and that becomes a memory. Now I must really thank the reader for having made this far in this article and before you quit, I would like to state that I haven’t forgotten the sole objective of this blog: “to amuse and cheer up the reader.” Having said that, I would like to ask you, did you ever imagine that your entire life can be represented by a single curve in three dimensions? That’s where the concept of World Lines comes into the picture. It is the one topic that I found the most fascinating during my stay at IUCAA.
The following perquisites are necessary to understand the fundamentals of World Lines:
• You need to know the four dimensional coordinate axes in space-time. (Bet, they didn’t teach that to you in geometry!)
• You should be fascinated by curves. Only then you can strongly appreciate the concept.
Having mastered the above, let us move on to what we set out to understand. Imagine a space-time coordinate system which represents the position of the particle in space as well as the instance of time. Thus a curve in this space-time coordinate system will represent the sequence of space-time events corresponding to the history of the object.
Now let us take this concept one level further by considering humans as points in space-time. In that case, the world line will represent the history of the human being! Thus two world lines will intersect only if space-time coordinates of two people coincide or in other words, they meet at a certain time. Not only this, since a curve can take any particular shape in space-time we can invariably argue that future has infinite possibilities and thus predicting the future or worrying about it is similar to tracing an arbitrary curve’s future path in four dimensions, or in other words: futile. We meet so many people each day and often make the best of friends. It is fantastic to imagine that when and where two unknown people will have their world lines intersected which may result in the development of a beautiful friendship or a relationship.
I found the concept of world-lines fantastic as it provides a way to think about ordinary things differently. Meeting of two people, your future, and your past can all be explained scientifically through world-lines. I hope my meagre knowledge was able to fascinate you with this charming concept. Do read Stephen Hawking’s masterpiece A Brief History of Time to know more about these curves of time.