The Day Without Yesterday

Dr Stuart Clark

The Flamsteed were delighted to welcome back Dr Stuart Clark, a regular visitor to the society. Stuart has recently been awarded the 2013 European Astronomy Journalism Prize, which was richly deserved, his prize being a trip to Chile to see the telescopes in the Atacama Desert. We hope he has a fantastic trip. His articles in the national press and in astronomy magazines always make for fascinating reading. It was on the subject of his latest book “The Day without Yesterday” that he came to the Flamsteed to give his talk.

For the last few years, Stuart has been dramatising some of the key moments in the history of astronomy. His “Sky’s Dark Labyrinth” trilogy starts first with the story of Kepler and Galileo, then moves on to the time of Newton, before finishing with the story of Albert Einstein and Georges Lemaitre. The books focus on moments in history when we had to fundamentally change our perceptions of the universe, and look at it in a completely different way. Stuart realised that to properly tell these stories, it was necessary to describe the historical context of the times in which these great scientists lived. To do this, Stuart used the method of historical fiction.

The last book in Stuart’s trilogy, “The Day without Yesterday”, is based on the story of Einstein and Lemaitre. Lemaitre was the first person to propose a theory of the expansion of the Universe, a theory he discovered buried in the maths of the theory of general relativity, meaning that there must have been a moment when the universe came into existence… a day without yesterday.

However, Stuart opened his talk by trying to put this discovery into context. He began with Kepler and Galileo. Kepler was a remarkable figure, devoutly religious, and a brilliant mathematician. He truly believed that an explanation of the universe would be written in the language of mathematics, a language that he saw as divine and a method of unlocking the architecture of the universe.

He synthesised 30 years of observations of Tycho Brahe and came up with his three laws of planetary motion. These laws apply not just to the planets that Kepler knew about, they also applied to the planets that were discovered after Kepler (Uranus and Neptune). They also hold true for the many exoplanets that have been discovered in recent years orbiting around stars other than the Sun. An extraordinary achievement. Stuart believes that this was the watershed moment in rational human thought – decades of observations could be summarised in just three lines of mathematics.

Stuart takes Questions

Galileo, at the same time in Italy, was doing essentially the same thing, but for Earthly motion; trying to describe mathematically how objects fall to the ground.

However, neither Kepler nor Galileo knew why objects moved as they did. That was where Newton comes in. Newton brought in the concept of gravity, showing how Galileo’s and Kepler’s laws could be derived using this concept – a force of attraction that is proportional to the mass of the objects and the distance between the objects. Out of this came a way of describing how forces acted upon objects and cause movement. A truly revolutionary concept. Newton described this as a system of the world (we’d now call this a theory of everything).

However, Newton was aware that there were two main problems with his theory. First of all, he didn’t know what the nature of gravity actually was. Secondly, he could not understand why the stars stayed in the sky, seemingly unchanged – why were they not collapsing towards us if the force of gravity was acting on them. This is when Newton developed the concept of the “Sensorium of God” – he believed that since th