The Formation of the Solar System: From Kant and Laplace to Nice and Grand Tack

An eBook short read (7,500 words) Theories concerning the origin and fate of our world go back to the writings of the earliest civilisations. However, for most of that time, there was no attempt to link such theories to the existence of the Solar System, because the concept of such an entity as understood in the modern sense did not exist. For a theory of Solar System formation and evolution, it was necessary to accept that the Sun was at its centre, with Earth and other planets in orbit around it. The concept of heliocentrism was suggested as early as 250 BCE by Aristarchus of Samos, but it was not widely accepted until the end of the 17th century. For the next two hundred years, astronomers assumed that our Solar System was a model for planetary systems elsewhere in our galaxy, with small, rocky planets huddled around the Sun, and much larger, gaseous planets in the colder regions further out - but in the 1990s, a very different picture began to emerge. Our familiar Solar System was revealed to be an outlier, forcing planetary scientists to revisit their theories about its early history. Why is it so different from any planetary system we have observed? One possibility is that there was a time, early in its history, when our Solar System resembled other systems we have observed – but then something untoward happened to it. Just what that 'something' was is one of the fascinating challenges facing planetary scientists.