EINSTEIN'S WAR - MATHEW STANLEY BY GORDON WEIR

Einstein’s War charts the life of Albert Einstein from the years just before the first world war to 1919, when the first proof of his theory of General Relativity was achieved. Running almost parallel to Einstein’s story is that of English astronomer Arthur Eddington. The link between the two, is that it was Eddington who persuaded the British scientific institutions, The Royal Society and The Royal Astronomical Society, to provide the funds and resources needed to mount an exhibition in 1919 to view a complete solar eclipse. This was an opportunity to see if the positions of stars close to the eclipse would remain the same or else change due to the bending of their light as it passes close to the sun. The latter, if by an amount calculated by Einstein, would be one of the first proofs of his new theory.
The first part of the book, looks at Einstein’s life before the war, including his failure to graduate from high school, due in part to his desire to avoid compulsory military service, his renouncement of his German citizenship and his eventual enrolment to The Swiss Federal Polytechnic (ETH) in Zurich: where entry did not require high school graduation. Much is written about Einstein’s struggles as a student, mainly due to a tendency to miss lectures, particularly in mathematics, which he would one day come to regret, however, the reality was that he was an accomplished mathematician and it was only with the complex mathematics needed for General Relativity that he struggled. After graduation from ETH, he tried to secure a position in the physics department there but without success, eventually having to rely on the father of a friend to secure a position at the Swiss patent Office in Bern. He was now able to support himself and his new wife Mileva Matic, also a physicist, and, because the demands of his day job were not too much, he now had the time to spend on his own work, culminating in 1905 with the publication of six ground breaking papers. One paper, ‘On the Electrodynamics of Moving Bodies’ was to become the Theory of Relativity. From this point onwards, Einstein’s name began to become more known throughout the scientific world; albeit slowly as many scientists thought the theory too abstract and stating that hitherto fixed measurements such as time, length and mass are in fact malleable, was too much for many. Time for example, Einstein declared, will pass at a different rate based on the relative speed that someone is travelling at so that a person in a space craft travelling close to the speed of light will experience a slowing of time (relative to someone back on Earth – for the astronaut all will seem normal) such that, even though their journey in space lasted a few days, when they return to Earth, they find that many years have passed. The problem with time going slower was that, at the time, it was impossible to prove. This, however, didn’t stop Einstein reputation growing and, after holding academics positions in Prague and at ETH, he was lured to Berlin by Max Planck just before the onset of the Great War. By this time, he had already started his General Theory of Relativity.
Arthur Eddington had by this time built a well-respected reputation as an astronomer, becoming the Director of The Cambridge Observatory in March 1914. Perhaps what defined Eddington’s character most before and certainly during the war, was that he was born a Quaker. Eddington’s life then revolved around his work as an astronomer and what appears to be a healthy lifestyle of long walks, abstinence from alcohol and, unlike Einstein, no indication of the need for female companionship. An important principle of Eddington’s belief was that he would not bear arms against another human. On this alone, Einstein and Eddington would always be in agreement, however, with war on the horizon, it would also cause them both great difficulties.
General Relativity had begun with a thought experiment. Einstein considered a person in a room without any windows (see above). If the person in the room simply drops a weight, they notice that, due to gravity, it falls to the floor. Einstein then posed the question, ‘What if the room is instead being propelled through space (far away from any gravitational sources) by a rocket attached to its base. Would the person still see the same thing happen when they dropped the weight?’ This is the equivalence principle in that the person cannot distinguish between gravity and acceleration. Einstein surmised that the two were the same. In other words, in both cases the weight falls to the floor of the room.  Now consider what happens when a hole is cut into the room wall at the same place but on opposite walls. When the room is stationary, a beam of light shone from outside one hole will move across the room and through the other hole on the opposite wall and out. What happens when the room is being accelerated? Einstein claimed that the light would bend so that it no longer reached the second hole and if light bent due to acceleration, and if the equivalence principle was true, then light must also bend due to gravity. Einstein was desperate to prove this and two attempts were made to view the phenomena during a solar eclipse when the light from far off stars should be seen to bend as it passes close to the Sun’s gravitational influence. Unfortunately, bad weather and the war got in the way.
The war for both Einstein and Eddington, when it came, Eddington in Cambridge and Einstein in Berlin, was unpleasant to say the least. Due to the British naval blockade of German ports, food shortages were present in Berlin within months of the start of the war. As the war progressed, Einstein found food harder to come by and had several long periods of poor health due to being mal-nourished but at least, by now a Swiss citizen, he was spared being called up to fight. His work suffered due to his poor health and that many colleagues and most students had gone off to fight at the front meant that the institute was all but deserted. Up to a point, he was still allowed to travel, to Switzerland for example, including to conclude his divorce to Mileva, and to other scientists in Belgium (occupied) and Holland (neutral). Food parcels from friends in Switzerland allowed him to survive.
Eddington’s war was more comfortable, but as the war went on, and the need to replace the thousands killed or wounded at the front became more and more urgent, Eddington’s position became less secure. Eventually he became under pressure to enlist. At first his university spoke up about his work and how it was needed to support the war effort. Eventually, however, in the final months of the war, Eddington had to go before conscription tribunals and put forward his case as to why he would not fight. It is a little unclear as to why Eddington avoided being called up but what is clear is that it was his beliefs as a Quaker that he most felt excluded him from the slaughter. In all of this, it is incredible that the British were prepared to finance an exhibition to prove the theory that belonged to a German born, Berlin based scientist. Eddington had remained a firm supporter of General Relativity, and despite war time restrictions, had managed to write his own account of the theory, thus spreading the word to the British scientific community.
Much of what is written above is in a way the build up to the most exciting part of this book – ‘The Test.’ Observing a solar eclipse was not only difficult but depended on a lot of good luck. Eddington received a grant for £1,000, equivalent to £75,000 today. This amount meant that he was able, as a bit of insurance, to mount two exhibitions, one to Brazil and the other to the island of Principe (Portuguese colony), off the West African coast – Eddington choosing to go to Principe. Another reason for two separate exhibitions was to confirm their results. The Brazil exhibition enjoyed clear skies and an excellent view of the eclipse, however, images from their main telescope turned out to be out of focus due to heat expansion of a mirror. Luckily, as a standby, they had also taken four-inch telescope which did provide clear photographs of the eclipse – showing the requisite number of stars in the Sun’s vicinity. On Principe heavy rain and cloud had preceded the eclipse, which was to begin several hours after Brazil, and although it was still cloudy at the time of the eclipse, Eddington’s team were able to capture useful images. After the eclipse came the processes of first developing the pictures and then making the minute measurements which would either confirm or refute Einstein’s calculation of 1.75 arc seconds (an arc second is 1/3,600 of a degree). The out of focus measurement from Brazil gave a deflection of 0.93 arc seconds, however the results from the four-inch telescope gave a more promising 1.98 arc seconds. The result from Principe was 1.61 arc seconds. Disregarding the unreliable out of focus measurement, the average deflection was 1.795 arc seconds. Einstein was correct!
The outcome of the expeditions results was to make Einstein famous, as newspaper headlines all over the world proclaimed the new successor to Newton. Eddington and Einstein eventually met in 1921.
Einstein discovered that everything, including you, bends space and that just as a marble set off spinning around a fruit bowl will eventually fall into the middle of the bowl, assuming it is not going quick enough to continue spinning around forever, this is what happens with gravity and this is why the light from stars curves towards the Sun. This is what keeps us planted on the surface we are on – denser stuff (more gravity) beneath us and less dense stuff (e.g., air) above us. General Relativity, it should be said, pointed us towards lots more than the bending of light, including black holes, the expansion of the universe, gravitational waves and even the big bang theory.
The book then is eminently readable by anyone with an interest in science – you really don’t need a degree in physics or maths. Instead, it is presented as more of a history of one of the most important times in science, charting the lives of the two protagonists as a means of building up the drama to the test, at which point the excitement builds as you need to know what happened next. It is also the case that, as well as the science, the reader will also get a sense of what life was like at this time both in Britain and in Germany. The book then, written in an easy to follow not too scientific way, is informative, interesting, exciting and very definitely though provoking. A great read for anyone with an interest in the history of science and who wants to know a little about Einstein’s greatest achievement.