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Experiments with jelly in his home laboratory at Glenlair helped James Clerk Maxwell observe stress patterns. This led to his paper 'On the equilibrium of elastic solids'.
James Clerk Maxwell (1831-1879)
James Maxwell was an expert in several distinct fields of science:
He produced outstanding work in all areas.
Maxwell is best known for his research in electromagnetic radiation, which unites the sciences of electricity, magnetism and optics.
Electricity flows through many metals because of the movement of electrons amongst the atoms of the metal. Moving electrons also produce a magnetic field, the strength of which depends on the number of moving electrons.
Electromagnets combine electricity and magnetism within one device, and fluctuating electron movements create electromagnetic waves.
Maxwell saw analogies between the speeds of travel of electromagnetic waves and of light, and devised four important mathematical equations which formulated these and other relationships between electricity and magnetism.
Some of Maxwell's results prompted Albert Einstein's research in relativity. Einstein is quoted as saying: 'One scientific epoch ended and another began with James Clerk Maxwell'.
Astronomy: Rings of Saturn
In 1856, aged 25, Maxwell began work on another field of research – the composition of the rings of Saturn.
In Maxwell's time, many astronomers believed that the rings were made of fluid, while Maxwell believed they were made up of small orbiting bodies.
To show audiences that it was possible for small orbiting bodies to appear to be fluid, Maxwell devised a model. This was a 'dynamical top' with small balls representing the bodies.
When the top was spun fast, it was possible to see what looked like the motion of waves.
Motion of gases: Kinetic theory of gases
Maxwell worked with Austrian physicist Ludwig Boltzmann to develop a theory called the 'Maxwell-Boltzmann distribution'.
This made it possible to determine the speeds of molecules in a gas at different temperatures. Maxwell described a hypothetical situation where gases in a container could be separated into two sections. There was a hot side, where molecules moved fast, and a cold side with slow molecular movement.
A tiny imaginary 'demon' at a trapdoor would control the flow of molecules between them, producing a perpetual energy source. This would only work if the demon was intelligent enough to distinguish the velocities of the gas molecules without requiring energy itself.
Optics: Mixing colours of light
Maxwell wanted to know why mixing different colours of light produces a different result to mixing the same colours of paint.
- Mixing blue and yellow paint gives green
- Mixing blue and yellow light gives pink.
His explanation depended on why we see things being a certain colour.
Light from the sun, though appearing white, contains the whole rainbow spectrum of colours. When it hits an object such as grass, all the spectrum is absorbed except green, which is reflected back to the eye.
If you mix light on the other hand, you are adding light beams together – a different process, with different results.
Some of Maxwell's experimentation was carried out using a device he made himself – a 'colour box' which contained glass prisms and lenses.
Optics: The first colour photograph
Maxwell went on to discover that colour photographs could be formed using red, green, and blue filters.
In 1861, Maxwell presented the world's first colour photograph – of a tartan ribbon.
Three photos were taken, each time with a different colour filter over the lens.
Maxwell developed the images then projected them onto a screen with three different projectors. Each used the same colour filter to take its image. The three images formed a full colour image.
These three photographic plates are now kept in a small museum at 14 India Street, Edinburgh, the house where Maxwell was born.