Paul Hoffman and snowball Earth
Introduction
I was very lucky to attend two seminars given by Paul Hoffman in St Andrews. He is an amazing speaker who manages to convey the excitement of basic science without flashy ways that attract attention for the sake of it. The curiosity of scientists trying to understand the world, is enough, and many times it leads to unexpected discoveries that the scientists would never had predicted. There is even a bit of drama, as some of the discoveries are made after the death of the person that started them.
Paul Hoffman is probably best known for the snowball earth hypothesis, according to which the Earth was completely covered with ice from pole to pole. It is controversial, with most geologists currently being against it. I found the models of planetary dynamics based on ice cover, continent position, sunlight input and CO2 concentration very interesting, especially because they can generate stable equilibria or rapid change.
He also gave a very nice review of the geological literature of the past 200 years. It is possible for a single person to do this because there were not so many publications in the past. I realised the people studying geology during the napoleonic wars were ahead of their time, being concerned with matters beyond their everyday life. It sounds strange for someone in the present to study snail fossils, imagine what people would think 200 years back!