Astronomers, as everyone knows, use telescopes to do their work. But not all astronomy is done using telescopes - there are in fact many astronomers who never make use of them. I’m one of them; I work mostly with computer simulations. Since people are often surprised to hear how much astronomy is done by computer, I thought I’d dedicate a post to talking about what an astronomical simulation is, how they’re used, and how important they are.
The goal of astronomy, like any science, is to produce models of the world - or certain aspects of it - which explain it as well and as simply as possible. A scientific model begins with an observation of some phenomenon and an idea for a rule or law which could explain it. For example, Tycho Brahe made a series of painstaking observations of the motion of the planets over many years, which his student Kepler explained using a set of three laws of planetary motion. These in turn allowed Newton to develop his law of gravitation.
The aim of a theory though is to be able to make predictions about other observations yet to be made. That’s partly because we’d like our science to be useful, to tell us what to expect tomorrow as well as to explain what happened yesterday. But it’s also for the theory’s own good. Every prediction which turns out to be correct is another piece of evidence in its favour (as when Herschel discovered Uranus in 1781, and its motion was found to obey the same laws Kepler had derived previously). And every prediction which is false tells us we must be missing some data (as when irregularities in Uranus’s orbit compared to theory suggested the presence of another planet, Neptune, beyond it) or that our theory needs to be refined or replaced (as with changes in Mercury’s orbit not due to any known planet, which are now explained brilliantly by General Relativity).
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