A Theory of Everything (That Matters): A Brief Guide to Einstein, Relativity, and His Surprising Thoughts on God by Alister McGrath- Part 5, Chapter 3- A Scientific Revolutionary: Einstein’s Four Papers of 1905, continued.
We are reviewing Alister McGrath’s new book, “A Theory of Everything (That Matters): A Brief Guide to Einstein, Relativity, and His Surprising Thoughts on God”. Chapter 3 is entitled- “A Scientific Revolutionary: Einstein’s Four Papers of 1905”. We covered his first paper of March 1905 which dealt with what is now known as the “photoelectric effect”. Einstein’s brilliant theoretical account for the photoelectric effect suggested that electromagnetic radiation had to be considered as behaving as particles under certain conditions, what he called the “wave-particle duality of light”. This was revolutionary; as the understanding of the day held that something could either be a particle or a wave, but not both.
Einstein’s next paper, in May 1905, was on “Brownian Motion” – the observation that very small particles of matter, when suspended in a liquid, do not remain stationary but move around randomly. The phenomena was named after Scottish botanist Robert Brown (1773-1858), who noticed that pollen behaved in this way when suspended in water and viewed through a microscope. No one could make sense of his observation, which were easily reproduced in laboratories. Einstein propounded the view that the suspended particles movement was due to the movement of molecules of the liquid itself. This was contrary to the conventional view, propounded by physicists like Ernst Mach, that atoms and molecules could not be seen or detected empirically; they were simply mental constructions that might be helpful in trying to make sense of our experience of the world. The physics establishment of 1900 was generally of the view that atoms did not exist in reality.
Based on the assumption that atoms and molecules were real, Einstein derived equations predicting that the motion of suspended particles increases with the temperature of the liquid, that it decreases with the increasing viscosity of that liquid, and that it decreases with an increasing size of the suspended particles. Einstein knew he was taking a risk in proposing such a mathematically precise formulation, which could be verified or falsified by experimentation. If his prediction of the amount of movement was shown to be incorrect, a weighty argument would be provided against the molecular kinetic conception of heat – and the physical existence of atoms. By late 1908, a steady stream of experimental results emerged which were strongly supportive of Einstein’s theory, including experiments on radioactive decay by Ernest Rutherford and Frederick Soddy. The best explanation of radioactivity was that they involved change at the atomic level. McGrath says:
Einstein’s greatest achievement in this paper was to show that Mach was wrong. It might not be possible to see atoms or molecules, but their real existence could be inferred from precisely the properties of particles suspended in liquid so carefully analyzed by Einstein in 1905.
Einstein’s third article in June 1905 set out his preliminary reflections on what we have come to know as the theory of special relativity. McGrath says:
Put simply, this is the basic idea that the fundamental laws and constants of physics are the same whether you are stationary or moving. Some will find this statement surprising in that they assume relativity is all about relativism – the idea that there are no absolutes and each of us can determine our own ideas. This is not what Einstein meant. In fact, the core assumption of Einstein’s approach to relativity is that the laws of physics are universally true.
Einstein’s argument in the third paper of 1905 is based on two central assumptions: “the principle of relativity” and “the principle of the constancy of the velocity of light in a vacuum”, which holds that the speed of light in a vacuum has the same value, c, in all inertial frames of reference. The “inertial frame of reference” can be thought of in the following analogy: Imagine you are on a plane traveling at a constant speed of 500 mile per hour. If you drop the book your reading, it falls straight to the floor, it doesn’t zoom to the back of the plane because even though the plane is moving at 500 mph, so is the book.
Here was Einstein’s analogy:
- Imagine a long train traveling along the tracks at a constant speed of 60 miles per hour. To the people on the train the carriage is their frame of reference.
- Now imagine there is an embankment next to the track. There are people on the embankment watching the train pass – they are stationary.
- Now imagine one of the people on the train starts to walk the length of the train in the direction of travel at 4 miles per hour.
- The key point is that the different observers will give different answers to the speed of the walker. To the train passengers, he is moving at 4 miles per hour, while to the embankment observers he is moving at 64 miles per hour.
- Now suppose someone on the train now turns on a flashlight and points its beam in the direction of travel. The speed of light is c, the speed of the train is v. To someone on the train light moves with speed c. But to someone on the embankment the beam of light must be moving at c + v, right?
- But that can’t be right. The laws of physics do not change from one inertial frame to another, and the speed of light has the same value, c, in all inertial frames of reference. There’s a contradiction here. How did Einstein resolve the contradiction? McGrath says:
“For Einstein, light travels at the same speed, no matter what the speed of its source of emission. So if the speed of light does not change as it moves through space and time, what other way is there of dealing with this dilemma? Einstein realized the need to rethink the relation of space and time. What the observer might see as changes in the speed of light actually reflect variations in what Einstein came to call “space-time”. The solution had to lie in rethinking classical concepts of space and time. As a result, Einstein concluded that space and time must be seen as interwoven — a single continuum, known as space-time. This is not an easy point to grasp – which perhaps explains why nobody seems to have thought of it before Einstein. The same event can occur at different times for different observers. Time does not pass in the same way for everyone. Perhaps the best know example of this is the “twin paradox”, which concerns two identical twins, one of whom spends some time in a hypothetical spaceship traveling near the speed of light and returns to discover that his twin has aged much more than he has.”
This has now been measured since clocks on GPS satellites tick more slowly than equivalent clocks here on earth by 38 microseconds per day.
Einstein’s fourth paper in September 1905 dealt with the equivalence of mass and energy and ultimately led to his famous equation E=mc2. The original paper did not have the equation and scholars are divided over whether Einstein did prove the equation. McGrath’s conclusion is that Einstein conceived the idea of “the equivalence of mass and energy” in the summer of 1905 but never managed to derive his ideas from first principles. McGrath says that the idea seems to have been an intuition on Einstein’s part rooted in a deep understanding of the physical world. It is generally agreed that the experiment that confirmed Einstein’s formula of E=mc2 was Cockcroft and Walton’s famous “splitting of the atom” in 1932. They accelerated a hydrogen atom (proton) into a Lithium atom and observed the production of alpha particles (Helium nuclei). It is represented as the following: Li3 + H = He2 + He2 they literally split the atom with the resultant release of energy from the mass lost in the reaction equal to within 99.5% of what Einstein predicted.
McGrath notes that Einstein’s concept of relativity is the result of absolute laws, not their denial. Einstein’s theory of relativity has nothing to do with moral relativism. Einstein has simply been hijacked here by people who misread his ideas and then used them to justify their own moral and social views. Einstein’s theories resolved an accumulation of scientific riddles that otherwise seemed insoluble. Einstein uncovered the deeper rules of our universe that ultimately explained these discrepancies.
As for “overturning” Newton, Einstein simply expanded on the theory. He didn’t discredit Newton’s theory. Newton’s theory works great for classical gravitation and is used a lot in the study of orbital mechanics (as well as Kepler), so it is a valid theory. Einstein simply asked the question what would happen if we moved very fast. So fast that we approach the speed of light. Einstein always viewed his theories as the logical extension of what Newton had begun. He wrote in his memoirs, “Newton, forgive me,”… “You found the only way which, in your age, was just about possible for a man of highest thought and creative power.”
Einstein was acutely aware of the need for a broader context of discussion of scientific advances that took ethical issues seriously. He said:
By painful experience we have learnt that rational thinking does not suffice to solve the problems of our social life. Penetrating research and keen scientific work have often had tragic implication for mankind, producing, on the one hand, inventions which liberated man from exhausting physical labor… but on the other hand… creating the means for his own mass destruction. (Einstein, Essays in Humanism, 24-25)