The story begins back when I was four years old. I was spending a summer vacation with my grandparents in one mountain village in eastern Serbia, and was playing a lot in the grass field on the hill. I also spent some time looking at pictures in the books that I could find in the house, as well as learning to read the text below the pictures. One of the most fascinating books was the World Atlas --- it was full of nice color pictures, and my attention was mostly caught by the most unusual ones --- those of the galaxies, Sun and the planets, that were in the introduction section of the Atlas.
One day I came to my grandfather, clumsily carrying the big heavy book, pointed my finger on a word below one of the pictures, and asked: "Grandpa, what is gravity?"
My grandfather had a degree in electrical engineering, and at the time was one of the chief engineers in a big company involved in the construction of all sorts of civil engineering stuff. Back in the day (mostly before I was born) he used to travel and work in several countries across Europe, South America and Africa, working on projects ranging from household electric installations to construction of hydroelectric power plants. He had a fair knowledge of classical physics.
"Well, you see...", he slowly started to respond to my question, thinking how to put down the concept of gravity to a level of a four-year old kid. "When you go out into the field to play, you can take a rock and throw it up in the air. The rock starts to fly, and it flies up, up, up in the air. At some point though, the rock stops, and starts to think --- should I continue to go further up, or should I return back down? Hmmm... Up. No, down. Umm, or maybe a little more up. Or rather not. And so the rock thinks and thinks, until at one point it decides to come back down. And then it flies down, down, down, until it hits the ground. Then you throw another rock, and another, and another. They all decide to come back down, after flying for a while. This choice of the rock to always come down is called gravity."
I was fascinated. Of course, I knew that rocks cannot think, but a child always enjoys the imagination from those fairy-tales that older people tell so often. So I wasn't confused --- rather, I continued with the next question: "Why doesn't the rock sometimes decide to continue going up?"
By that time, grandpa already had a moment or two to think, and was prepared to extend the story as far as necessary in order to cover most of the subsequent questions that I might come up with. "Ah, but actually it can decide to continue to fly up. If you throw it hard enough, it will get angry with you, and it will continue to fly up forever, and never return back."
This was food for thought. I decided not to bother grandpa with more questions until I sort out what he already told me. A rock that could think was just a funny way to express the idea, but its behavior when I throw one in the air was quite real. The fact that the rock returns when thrown up, and doesn't return if thrown hard enough (something I could never achieve, despite my best efforts and ever stronger throws...) was something so fascinating and puzzling, and needed digesting before I ask grandpa about the next word in the Atlas. I felt compelled to understand why does this happen. It was mysterious, something that just refuses to fit in my mind in a natural way. I needed to think about this "gravity" thing, to answer the why question that kept popping up in my head over and over and over. The grass is green. Ok. The sky is blue. Ok. The water flows and makes noise while flowing. Ok. The thrown rock flies up in the air and then comes back down. Not ok. WHY does it come back down??!! It was something I had to sort out.
Thirty years later, I am still sorting it out. I do it for a living.
After this first contact with the concept of gravity, I got curious about quite a number of interesting things during my youth, as I discovered them. In elementary school, in high-school, at the university, and later in life. But all those things were interesting "up to a point", and my curiosity would inevitably wander elsewhere once I got saturated with the previous topic. But every now and then (quite rarely actually), I would get reminded of the idea of gravity, and I would feel that it still stands out, it is still a mystery, it is still something that defies my intuitive understanding. Instead of getting saturated, my curiosity would only get reinforced. In elementary school I learned that scientific disciplines dealing with describing nature were called physics, chemistry, astronomy and biology, each having its own topic of interest. And one of the physics topics was gravity. In high-school I learned about the Newton's law of gravity, explanation of the motion of planets, etc. I found out that gravity was the main concept of Newton's theory, and that the whole classical physics was founded essentially by Newton's effort to "capture" the idea of gravity. It was the main motivator for the theory --- the Newton's famous three laws of motion were basically built around it, to explain the elliptic motion of planets around the Sun. Given that at the time there were no alternative explanations, and that the motion of planets was a longstanding historical problem in "philosophy of nature", Newton's theory became a success, and established itself as a paradigm for the next 300 years. That was when I found out that gravity was not just my personal itch. Other people have been having it, and made some serious breakthroughs in understanding the nature by trying to scratch that itch. This told me that gravity is a deep concept, and that not being at peace with it is not just my personal frustration. By the time I finished elementary school, I already knew that physics is the science that I want to engage in professionally, and throughout my high-school days, no one had any doubt that I am going to take up physics at the university. The general reason was that I wanted to understand laws of nature better and deeper. The particular reason was that I wanted to understand gravity, beyond anything else.
When I began studying physics at the university, we had a course on Newtonian mechanics in the first year, which included gravity. It was basically just a rehash of high-school knowledge, just with a bit more capable math toolbox. After the course, the teacher told us: "Now you've seen the Newton's theory of gravity. With the exception of one sentence in the course of nuclear physics that you'll take up in fourth year, gravity will be completely and utterly ignored for the rest of your undergraduate studies. Actually, for the main majority of you, this is the last encounter with gravity that you will ever have, even beyond the undergraduate courses. Only a few of you who decide to enter the postgraduate courses in high-energy physics will get to face gravity again. And that will happen only in four to five years from now. If you are not one of those, this is all of gravity you'll ever learn. So remember this moment, and rejoice!". The "rejoice" part was meant to emphasize the fact that the students have obtained a certain body of knowledge (in the topic of gravity) and that their education in this topic is finished. This was the first "point of finish" that the students got to arrive at, since the beginning of elementary school. The teacher just wanted to make a point that this is a moment to remember. Of course, by that time I had already informed myself what and how I needed to study in order to enroll in the high-energy postgraduate course. I knew that I was going to be one of those "few" that will get to see gravity again. It was just a matter of going through the rest of the university courses --- essentially, doing something else while waiting for another four years. Sure, those other things were also interesting to learn and understand, but my main motivation was "idle", waiting for the postgraduate courses in gravity.
And then they came. When I finally got to graduate courses, I was already familiar with Einstein's general relativity, which was the topic of the course "Gravitation I". This was followed by the "Gravitation II", which introduced a whole bunch of further topics related to gravity. During my graduate studies, I became aware of two main things. First, a relativistic theory of gravity was so different from the classical Newtonian one that it required a complete rewiring of my way of thinking about the world in general, not just about physics or gravity. I was studying with several other students (now my good friends and colleagues), and one day we were discussing the teleparallel theory of gravity, which involved torsion but no curvature. One of my friends, revolting about the non-intuitiveness of the teleparallel idea, shouted: "Oh, come on, I just cannot believe that the space is not curved!". Then we all looked at each other, paused for a moment, and started laughing. From the point of view of an ordinary person who is familiar only with the Newtonian physics, that sentence was a prime example of the amount of brainwashing that we went through while learning all the advanced theories of gravity. This rewiring of the way one thinks about the world was the second revolution in physics that was induced by trying to understand gravity, just like with the Newton's theory 400 years ago. Again gravity presented itself to me as a deep and fundamental thing that becomes an ever greater challenge to understand. The second thing I became aware of was that the problem of understanding gravity is only yet to present itself in its full glory, suggesting another, third revolution that should happen in the future. The more I learned about gravity, the more weird it was becoming. After the graduate courses, I finally got to the point of being able to understand the Big Problem of theoretical physics --- gravity is nonrenormalizable. I will not even attempt to explain that word in this text, since it really requires several graduate-level courses to understand. It is sufficient to say that gravity is at odds with quantum mechanics (or simply put with the rest of known physics), in a very fundamental way. The Big Question of theoretical physics (the consequence of facing the Big Problem), "What is the quantum theory of gravity?", has essentially to do with ever deeper understanding of concepts like space, time and energy. Pursuing this questions leads one to the idea behind the scene --- geometry. That is, understanding quantum gravity requires understanding the geometry in terms of some simpler, deeper concept.
So, after thirty years, the apparently childish question "why does the rock fall back down" blows up into a set of very abstract and deep questions of understanding nature "beyond geometry". Sometimes I think that life was actually quite cruel to me, making me face such a fundamental and tantalizing question at the age of four. As a consequence, I developed a passion of trying to understand the basic laws of nature, gravity and otherwise. It was only natural for me to become a theoretical physicist.
Curiosity is one of the fundamental human characteristics (and not only human). From the most rudimentary "what is behind the door" curiosity to the most sophisticated "ontological" curiosity, it is often a very powerful motivator of human behavior.
Nevertheless, some humans are obviously more curious than others. In most people, curiosity has its limits. Most notably, everyone is curious "up to a point", when the "don't waste more time on this" alarm starts to ring. People mainly differ regarding to which topic and after how much time this alarm triggers. Puzzle-solving is a particular type of activity that is driven by ones curiosity. There is a certain thrill attached to the recognition of the solution of a puzzle. The prime examples are all the detective "Sherlock Holmes" stories, movie teasers, intricate TV advertisements, puzzles, anagrams, and so on. Most people enjoy all of these as a form of amusement, something to capture ones attention with a thrilling end. But most people do not go beyond this. After the murderer has been discovered and the case explained, they return to their daily lives, go to the supermarket, remember that they need to do this or that, and so on. But there are people that do go beyond the satisfaction of elementary curiosity. The famous childish neverending chain of "Why?" questions, in the case of these people, cannot be ended with a parental authoritative "Because.". These folks have an undying hunger to always ask a yet another "Why?".
That kind of people have a tendency to end up being theoretical physicists by profession. The "Why does the rock fall back down to the ground?" question will get one to the level of fundamental physics essentially in a single step. But most often, this is a sequence of several questions, each providing an answer to the previous question "up to something". That something requires the next question, and after several steps one finds oneself in the realm of fundamental physics again. A typical example:
Bang! This is a fundamental question in particle physics. [N.B. Actually, the above question can be answered in a more elaborate way within the framework of quantum field theory, but then the subsequent "why" question will become as fundamental as it gets. But both the answer and the question would be quite technical, so I don't want to elaborate that final step.] So, in several steps, the trivial everyday observation that some materials are solid while others are liquid opens up a "can of worms" that goes all the way down to the level of fundamental physics. In addition, from each of the answers above, one can branch out several other questions, all of which will eventually lead to some fundamental question of particle physics.
So, an ordinary person is going to get fed up with the answers halfway down the list. They could ask another "why" question, but they are a bit hungry, and the meeting starts at 14:30, so they need to catch a cab and... Their "don't waste more time" alarm rings. However, an incurably curious person will go all the way down the list. Such a person will not be able to sleep during the night because of the unanswered "why" question. They will seek books, articles, even an expert physicist to talk to. In extreme cases they will even invest several years to learn quantum chromodynamics themselves, in order to get to the fundamental level. And even when they get there, the question "why" will still be there and still bug them.
Those people are "born" to be theoretical physicists. Apparently, I am one of them.
Note, though, that not every physicist is like that. Some people like to do science, but do not have this "curiosity drive" to go to the fundamental level. There is quite a lot of interesting stuff to do and explore even if one does not keep asking the "why", but takes some already formulated theory, and tries to work out its consequences. Or looks at some experimental effect, and tries to reproduce the same effect from the theory. Or constructs a new experimental setup, to see what happens when matter is put in some particular conditions. These are the theoretical, phenomenological and experimental physicists, respectively. Within each of those sectors of physics there are quite intriguing and hard problems to solve. But within each group, there is a subgroup of curiosity-driven people, who end up doing fundamental physics.
This ever-hungry curiosity is the reason why such people go all the way to the fundamental level, and also why people without such curiosity mostly give up before reaching the fundamental level of science. Getting oneself to understand science at the fundamental level essentially requires devoting at least a decade of ones life to learning all sorts of quite hard-to-understand, boring, abstract and tedious stuff, math and physics alike. I would not be too far off to say that this is quite a masochistic experience. Most of my fellow students at the university sooner or later felt that abstraction and usage of ever more complicated math is getting out of hand, and they decided to give up the pursuit for the fundamental physics in favor of doing something "easier", "more down-to-earth", "more connected with everyday life", "more useful and practical", etc. And this is perfectly ok. However, I could never be satisfied with half-explained science. Getting to the bottom of every "why" chain is something I just need to do.
Aside from curiosity, there are other, more "serious" reasons for doing fundamental science. In his famous five-book trilogy called "The Hitchhiker's Guide to the Galaxy", Douglas Adams has encapsulated all possible conceptual questions in the single ultimate "Question of Life, the Universe and Everything Else". Subsequently, he reveals that the answer to that question is "42", and it turns out that one cannot know simultaneously both the exact answer and the exact formulation of the question itself. Although fictional, this is a very beautiful example of an unusual explanation of the lack of answer to some question, that scientists face every now and then. It is a situation where nature is giving us a lesson in logic, that not every question makes sense in the way we expect it to.
In other words, studying fundamental science sometimes allows us to tackle some of these profound, ontological questions. A subset of these questions is slowly converting from the realm of classical philosophy to the realm of theoretical (and in some cases even experimental!) physics. In addition, the "answers" to those questions are sometimes quite surprising, and very different from what one would naively expect, as Douglas Adams illustrated in a comical way. The ability to provide any answer at all to these kind of questions is an incredible example of the sheer power that is contained in the study of fundamental science. With every answer to some of those questions, the boundary of human knowledge is being moved forward at the deepest possible level. As such, studying fundamental physics appears to be of the most important activities of the human race. One can even go as far as to say that this is the purpose of human existence, if such a concept can be defined at all. On a smaller scale, I am quite satisfied to consider it to be the purpose of my own life. Every human needs a reason to live, a "drive", an answer to "Why am I here?" and so on. Unfortunately, most people do not recognize (or do not choose) any objective they could strive for and call it the "purpose" of their lives. For those people, unfortunately, "life" somehow becomes equated with "survival", or with "passage of time", or with "having children". They often do not have any reason for living beyond biological/animal instincts for survival, procreation and supporting their offspring. From this perspective, their "human potential" (the potential to be more than animals) is only barely used, and in most part completely wasted, irrespective of the richness of their lives and happiness and love they experience. Of course, I am not saying that this is bad, or a waste of resources. Everyone is free to choose how and why to live, or to refuse to make such a choice. I seem to have made one for myself, and believe it is challenging enough and worthy of the time I put into pursuing it.
To a common person, a theoretical physicist may appear as a "dreamer". Someone who is passionately doing something utterly abstract, philosophical, boring or otherwise not practically useful. For example, when I started studying at the university, some of my relatives were quite surprised and disappointed that I have chosen to study physics instead of medicine or law, which are commonly held in high regard. When I was at the third year of the undergraduate studies, one day my girlfriend asked me: "What do you see in this physics? Why don't you do something material, something more concrete in your life? Get a job, earn some money, go travel across the world, see things, have some fun, enjoy yourself, or start a business or something...". Back then it was hard for me to explain the answer to that question. It still is, in a way. Explaining that studying "some abstract nonsense" is by an order of magnitude more important to me than having fun and making money is never easy. Today, I can only say that in retrospect --- I was right. Eventually I did get a job --- as a theoretical physicist; I do earn money to support myself and my family --- as a theoretical physicist; I am traveling all over the world on a regular basis, even more than most people --- visiting conferences, workshops and other people at various universities, again as a theoretical physicist. In general, having a successful academic career in theoretical physics is a quite good way to live --- my working hours are extremely flexible and I do not need to wake up early every morning (I can even give myself a day off as I see fit), I get paid to do what I love doing, I see a lot of other countries and places by traveling around the world to various conferences and meetings, and have all travel expenses covered by my hosting institution, I am being held in high regard in various communities of people due to the title "Philosophy Doctor" in a very prestigious area of science, and so on. It is mainly stress-free lifestyle, without manual labor, deadlines to meet, etc. The only thing that is important is that I deliver results, and everything else is adjusted to fit that purpose. Of course, as an undergraduate student I could not be certain that such lifestyle will be possible for me in the future, while convincing my girlfriend was next to impossible. It took a lot of patience and hard work (studying) to reach all that and become a successful scientist.
Granted, it is not all flowers and roses. My salary is enough to support myself, but only for a rather modest life. Compared to some other salaries (in various factories, businesses, investments, politics, etc.), the salary of a typical postdoc is quite small. In addition, postdoc research is mainly "contracted" --- I get hired by some sponsoring institution to do some research at some host university in a given time (typically 3 to 5 years). After that, I need to look at another contract, at the same or (more commonly) different university. It is a nomadic lifestyle, changing residence (and often a country) once every 3 years on average. This has serious drawbacks when it comes to having a spouse and children, "settling down", buying a house or a car, etc. The spouse often also has a job and a career and is not willing to move every couple of years, children need some continuity in going to the same school etc.
Second, research contracts are mainly obtained by writing research proposals for the sponsoring institution --- essentially "begging for money". A bit overstated, but nevertheless also a bit humiliating, from the point of view of a researcher. The one with superior knowledge (researcher) needs to persuade the one with a lot of money (sponsor) to provide him with a "grant", i.e. money, to do research. The results of the research are typically not directly usable in practice, i.e. the sponsor cannot get any money back out of it, and the "grant" is essentially a free gift to the researcher. Consequently, there is no healthy market for researchers, where several sponsors would bid for a given researcher and compete to offer him a bigger grant for his research activity. Instead, it is completely reversed --- researchers are competing with their research proposals for the same grant the sponsor is offering. Therefore, doing research in fundamental science --- one of the most important activities for the long-term progress of the human civilization --- comes down to "begging" for financial support, in a sequence of short-period contracts. The main sponsoring institutions are mainly dedicated government foundations which receive the "grant funds" from the state budget. The part of the state budget devoted to science is often just a small percentage of the total, quite small in comparison to military, media or some others. A very disconcerting situation for the vast majority of countries in the world.
Related to that, I recently became aware that even some of my fellow colleagues consider their own work unworthy. On one occasion I was horrified to hear a colleague of mine (doing research in mathematical logic) to characterize all fundamental research scientists as "parasites of the society" --- taking money from tax payers and not giving anything in return. Of course, when I started protesting against such a viewpoint, she claimed that it was meant to be a joke that I failed to recognize... But nevertheless, judging fundamental research by its short-term usefulness (or rather uselessness) is completely hilarious, and accounts only for the utter short-mindedness of a person making such judgments. And of course, a person who does not understand the long-term importance of fundamental research should not be allowed anywhere near any sponsoring committee --- a fact that is getting ever more neglected in recent years.
All in all, being a theoretical physicist has both its advantages and its drawbacks. A layman's point of view on the fundamental research ranges mostly from utter ignorance to reserved moderate opinion, the latter describing people who do not understand anything about this research, but are afraid to label it as unimportant. All that while taking for granted things like electricity, computers, cars and airplanes, air conditioners, refrigerators, mobile phones, GPS devices and all other wonders of modern engineering. Most people do not appreciate that someone, one or two hundred years back, has made advances in fundamental physics, which eventually paved the way to all these things. Most people do not live long enough to see the connection between the initial research and its final practical usage, but this connection exists nevertheless, and should never be ignored or underestimated. I have repeated the word "fundamental" in this article over and over throughout the text, not because I am a "fundamentalist", but to underline that the research in theoretical physics, especially those parts on the very boundary of human knowledge, is a very important thing. A layman may label one Albert Einstein as a "dreamer" and be completely ignorant of his 100-year old research papers on stimulated light amplification and theory of relativity. Yet this same layman will enjoy listening to the music from the CD player in his car, while driving happily with the aid of the GPS system. I label such laymen as total hypocrites. In case you do not understand why, feel free to read this and this.
To conclude --- all the things that I discussed above: my childhood, curiosity, purpose of life, ontological questions, advancement of human knowledge, advantages of academic lifestyle, social prestige, etc. --- contributed to my choice to become a theoretical physicist. Some more and some less, some early and some later in life. I believe that by doing research in fundamental physics I am doing something important for humanity. That said, I am completely certain that I am doing something important for myself, which is what ultimately counts the most. ;-)