![]()
Contents
CHAPTER 1â Introduction
CHAPTER 2â Archimedes
2.1 Biography
2.2 Inventions Of Archimedes
2.3 Archimedesâ Writings
2.4 Sources
CHAPTER 3â Copernicus
3.1 Introduction
3.2 Biography
3.3 Science
CHAPTER 4â Kepler
4.1 Biography
4.2 Science: Various Works
4.3 Science: Keplerâs Laws
CHAPTER 5â Galileo
5.1 Biography
5.2 Science
CHAPTER 6â Newton
6.1 Background
6.1.1 Some history
6.1.2 Society
6.2 Biography
6.3 Mathematics and Optics
6.4 The Principia
CHAPTER 7â Oersted and Faraday
7.1 Introduction
7.2 Oersted
7.3 Faradayâs Life
7.4 Faradayâs Science
CHAPTER 8â Ampère
8.1 Biography
8.2 Science
CHAPTER 9â Maxwell
9.1 Biography
9.2 Science
CHAPTER 10â Einstein
10.1 Biography
10.2 Science
10.3 David Hilbert
Index
![]()
Preface
My father apparently told my wife-to-be that I was interested in nothing except satisfying my own boundless curiosity. I hope that was a bit of an exaggeration, but itâs true that for as long as I can remember Iâve thought about why things are the way they are. That made physics a natural choice of subject for university.
After going on to do a PhD in theoretical elementary particle physics, I spent almost half a century writing articles and books for my fellow scientists. I wrote some of them by myself, but more often I collaborated with colleagues. For the first three decades, the books and articles were about elementary particle physics. Then, after taking a break, I moved on to cosmology.
The first book that I wrote for the general reader came out in 2016. Itâs called The History of the Universe, and it explains cosmology with no mathematics in the main text. I couldnât resist, though, a mathematical appendix and the whole bookâs about nothing except science. The second book, that youâre looking at now, goes further down the road away from academia. Thereâs no mathematics at all and most of the book isnât even about science. Instead itâs about the life and times of scientists. I hope you find it interesting.
For comments on the final draft I would like to thank my wife Margaret, my brother Peter and my son John.
![]()
Chapter 1
Introduction
If I have seen further than others, it is by standing on the shoulders of giants. (Isaac Newton, 1576)
Almost everybody knows that Einstein was a famous scientist, and most people know that he put forward a theory involving something called Relativity. Few, though, know anything about Relativity and its long history. In this book, I describe the life and times of some of the scientists who paved the way to Einsteinâs theory, and say something about the theory itself.
The basic idea of Relativity is simple. Itâs the idea that movement, in and of itself, cannot be detected; that nothing is affected simply by movement.
Put differently, the idea is that it makes sense to talk about movement only if the movement is relative to something else. In everyday life the âsomething elseâ is, of course, the surface of the Earthâthe ground. To say that something is moving is to say that itâs moving across the ground. On the other hand, we do recognise that the Earth goes in an orbit around the Sun. In that case weâre defining the Earthâs motion relative to the Sun. Also in that case, we lose no sleep over the fact that we canât feel the earthâs motion. These days we take the idea of Relativity for granted!
Attitudes were very different in 1632 when Galileo introduced the idea of Relativity. Then, there was a debate about whether the Earth really moved around the Sun or whether, instead, the age-old view was correct that the Earth was stationary with the Sun was moving around it. The suggestion that the Earth moved around the Sun wasnât particularly new, having being made by Copernicus in 1543. Even so, most people still believed that the Earth was stationary with the Sun and the stars moving around it. One argument that people used, was to say that if the Earth were really hurtling though space we would feel its motion. Galileo introduced the idea of Relativity to counter that argument.
Galileo invited us to imagine that we are in the cabin of a ship sailing smoothly across the water. Let us suppose, he says, that within the cabin are flies and butterflies, and a fish tank. The flies and butterflies go equally in all directions and so do the fish in the tank. He also invites us to suppose that thereâs a container with a small hole in its bottom, from which water is dripping. Each drop will hit the floor at the point directly below the hole. These examples could be multiplied, and in fact nothing within the cabin is affected by the motion of the cabin. We can find out that the ship is moving, only by looking out of the window. Galileo argued that, in the same way, we canât feel the motion of the Earth. We can find out that itâs moving only by making astronomical observations.
The basic idea of relativity, then, is that nothing is affected by movement. Nowadays this basic idea is replaced by a more specific statement; that the laws of physics are not affected by the movement of the region within which they are applied. It was Einstein who came up with that statement. He called it the Principle of Relativity, and it was the starting point for his theory of Special Relativity.
âThe laws of physicsâ sounds harmless enough, even a bit boring. Donât be fooled though. The laws of physics, as we now have them, are truly awesome in their scope. They seem to apply to practically everything that can ever happen and would cease to apply only in the most extreme hypothetical situations.
The journey to our present laws of physics may be said to have begun in 1687, when Isaac Newton laid down his three laws of motion. To this day, Newtonâs laws of motion are presented to students as a bedrock of physics. Newton used his laws to produce the first theory of gravity, whose most dramatic application is to the solar system.
When thinking about the solar system, we usually take the sun to be stationary. But Newtonâs laws and his theory of gravity would still apply if we took the sun to be moving, and the entire solar system with it. Newtonâs laws, and his theory of gravity, are therefore consistent with the Principle of Relativity.
So far so good for the Principle of Relativity. It seems to run into trouble though when we come to some laws of physics that appeared soon after Newtonâs death. These laws involve electricity and magnetism. An immediate problem comes with Coulombâs law, which specifies the electric force between any pair of stationary charged objects. Not stationary with respect to something else but simply stationary! More laws followed, all seemingly at odds with the Principle of Relativity. It was Einsteinâs achievement to produce the theory of Special Relativity which, despite appearances to the contrary, makes the laws of electricity and magnetism consistent with the Principle of Relativity.
Special Relativity ignores gravity. After Einstein had formulated Special Relativity he thought a lot about the nature of gravity. He knew that there was something wrong with Newtonâs theory because it fails to describe correctly the orbit of Mercury. After years of effort, he at last came up in 1915 with a new theory of gravity which he called General Relativity.
General Relativity is directly relevant for our lives, because itâs used by satellite navigation systems (satnavs) such as the American Global Positioning System (GPS). A satnav uses radio signals from three or more satellites to determine its position, and General Relativity is needed to interpret those signals. If Newtonâs theory were used instead of General Relativity, satnavs would give the wrong position causing absolute chaos!
In this book, my idea is to tell the story of the journey towards Einsteinâs theories of Special and General Relativity by focussing on key figures. I deal first with Archimedes (c. 287âc. 212 BC). He was the outstanding mathematician of the ancient world, and he enunciated Archimedesâ Principle which is the first-ever law of physics. Then I move on to some of the astronomers that paved the way for Einstein. First is Copernicus (1473â1543) who (eventually) convinced people that the Earth and the other planets were moving around the Sun. Next is Kepler (1571â1630) whose three laws tell us exactly how the Earth and the other planets move around the Sun. Then thereâs Galileo (1564â1642) who weâve already met. After that is the towering figure of Isaac Newton (1643â1727). Along with much else he gave us the inverse-square law of gravity, from which he he derived Keplerâs three laws.
After all that astronomy I come to people who worked on electricity and magnetism. First up is Hans Oersted (1777â1851) who discovered that a loop of wire with a current flowing through it acts just like a magnet. Second up is Faraday (1791â1867) who found that if you push a magnet in and out of a closed coil of wire you generate a current in the coil. (Thatâs how an electricity generator works.) Faraday also found that if you switch on an electric current through a coil, it will generate a burst of electric current in a nearby closed coil. (Thatâs how an electricity transformer works.)
Next is Andrâ˛e-Marie Amp`ere (1775â1836) after whom the amp is named. He found, among other things, the force between pieces of wire that each carry an electric current. (Thatâs the theory behind an electric motor.) Then we come to James Clerk Maxwell (1831â1879) who drew together all these discoveries, finding in the process that a beam of light consists simply of electric and magnetic fields. Finally, we come to Einstein himself, who was born in 1879 and died in 1955.
Every one of these people made earth-shaking discoveries, and some of them had very eventful lives. I hope youâll enjoy reading about them.
![]()
Chapter 2
Archimedes
Modern mathematics was born with Archimedes, and died with him for all of two thousand years. It came to life again only with Descartes and Newton. (Eric Temple Bell, in The Development of Mathematics, 1940.)
2.1 Biography
âGive me a place to stand, and with a lever I will move the whole Earthâ. Not the saying of a modest man but Archimedes had no reason to be modest. His achievements in mathematics were unparalleled until the advent of Renaissance mathematics in the fifteenth century, and he remains one of the greatest mathematicians of all time. He can also lay claim to being the first-ever physicist, through his treatise On Floating Bodies. Galileo often described Archimedes as âsuperhumanâ, and Le...
