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Throughout history, numerous books on philosophy, theology and mysticism have been written in an effort to explain the ways of the universe. Growing up in the Old City of Jerusalem, playing hide and seek in ancient alleyways, I was drawn from an early age to the romantic mystique of these ancient writings. I joined study sessions and participated in lively discussions with religious scholars. But living in an academic household, I gradually developed a sense of scientific skepticism that led me to question the basic tenets of this knowledge. When I was later introduced to the world of computer programming, I was immediately impressed with its lack of ambiguity. Ideas had to be broken up into their fundamental logical components. Hand waving simply didn't compile.
At first, I played with programs that solve brainteasers, then gradually gravitated towards problems involving dynamic systems. From the three-body problem to fractals, almost all systems with feedback seemed to create chaotic results. For example, when simulating an ideal rubber ball bouncing from side to side in a parabolic bowl, I couldn't predict its location at any given moment, but I could clearly see areas where the ball never enters. Why? Conservation of energy, which I had recently learned about, clearly couldn't solve this problem. But since I was able to empirically find simple equations that seemed to describe these areas very accurately, it struck me that there must be some other constant of motion at work. Eager to learn more, I approached Prof. E of the Institute of Mathematics, ABC University, who helped me with these problems. The results of this work became the basis of my high school honor thesis.
As soon as I was released from the military, I took a year off to travel the world and learn about other cultures. When I returned to Israel, to take up undergraduate studies at the ABC University, it was only natural that I study what had, by then, become my two passions: physics and computer science. Towards the end of my freshman year, I attended a lecture by Prof. B of the Physics Department, who was showing recent results of a cosmological simulation of the big bang. I was turned on by this topic at first sight and during the following summer, I joined Prof. B's research group. I was put straight to work measuring the distribution of mass and angular momentum of a small galactic halo spiraling into a larger one. I approached this problem using both N-body simulations and toy models, which assumed a simplified scenario in which only gravity, tidal stripping and dynamical friction took part. These two approaches gave slightly different results. While trying to understand these discrepancies, I noticed that the outer layers of the smaller galactic halo seemed to swell and be stripped away earlier than expected, while its core was compressed. This phenomenon, which is caused by the tidal force of the larger halo's mass gradient, was coined "tidal puffing" and is the basis of my first publishable paper (due to be submitted late 2001). Further work on this phenomenon, currently being carried out by the Cosmology group, could provide a theoretical basis for the profiles of many galactic haloes.
In the future, I would like to develop a new kind of simulator, one that deals with ranges instead of point values. Since there are so many uncertainties in galactic formation, I believe it would be useful to have a simulator that can test a range of possibilities at once. At each time step the simulator would find the resulting extremes, perhaps by assuming that the functions are locally monotonic, and use them as the starting points for the next time step. Despite the "butterfly effect", I expect most interesting properties would remain quite stable, but some may prove to be highly dependent on the exact choice of models and numerical approach applied. This problem is further accentuated by the fact that most N-body simulators used today make similar assumptions about both cosmological physics and the numerical algorithm employed.
Astrophysics in general and specifically cosmology, strike me as one of the most exciting areas of research today. Thanks to new observations, better methods and more powerful simulations, such as those spearheaded by the Stanford Department of Astronomy, we can now hope to answer, with reasonable confidence, some of the most profound questions ever raised. Where have we come from? Where are we going? Cosmology has emerged forever from the old books of mythology to assert itself as an exact science, an unclouded crystal ball of the universe. I would like to be a part of it.