From early attempts to understand the motion of stars and planets to the appreciation of the importance of light in photosynthesis, efforts to understand the nature and the characteristics of light have revolutionized nearly every field of science. This page will provide an overview and timeline of the history of our understanding of light, and will provide a link to the presentation given on this topic at the Opening Ceremony.
Where to begin?
An important stage of the evolution of the Universe occurred around 300,000 years after the Big Bang, when the temperature was cool enough (around 4000 degrees) for neutral atoms to form. Before that time, there were too many charged particles to allow light to travel more than a very short distance. After atoms were formed, light could travel immense distances. In fact, we can receive today ‘light’ (in the form of microwaves) that has been traveling for over 13 billion years.
Perhaps of more importance to us was the formation of the Sun and the solar system – including our planet – about 4.5 billion years ago. Earth has been bathed with light from the Sun ever since; it is our most important source of energy. Sunlight warms us, causes weather patterns, allows plants to manufacture oxygen and our food from carbon dioxide and water, and it allows us to find our way around in the daytime!
The use of sunlight in photosynthesis, to make oxygen and carbohydrates from carbon dioxide and water, is a process first established over two billion years ago by cyanobacteria. They made the large quantities of oxygen in the atmosphere which allowed oxygen-breathing life to evolve. Today plants use chlorophyll to achieve the same result, keeping the atmosphere breathable, and providing food energy for us and all other advanced life forms.
Of course, mankind has found other sources of light over the course of history. Fire is obviously the earliest of these: from the camp fires of our cave-dwelling ancestors to the spirit lamps still used where there is no electricity. But electricity is the source of artificial light today, starting with the invention of the incandescent light by Joseph Swan and Thomas Edison and progressing via fluorescent lighting to modern light emitting diode (LED) lights.
Mankind has also learned to control light. The use of mirrors and lenses to divert light, or to magnify images, dates from pre-history. Microscopes and telescopes, using multiple mirrors and/or lenses are two closely related inventions from just a few hundred years ago. They allow us to study objects smaller than our naked eyes can see, and objects at large distances, whether ships at sea, or astronomical bodies at enormous distances.
We can also send light from one place to another using optical fibres or ‘light guides’ . These allow us to use light to transmit large amounts of information, and to explore regions where we cannot go, such as in medical probes or endoscopes.
Text source: 2015 International Year of Light