Many ancient civilizations believed light were a gift from the Sun god. If he wasn’t worshipped daily, they believed he would show his wrath by disappearing. Then the Earth’s temperature would drop, rivers and lakes would freeze, and plants and animals would die.

The ancients knew many things about what light is. They realized that it travelled in a straight line in all directions from its source, and that if someone or something blocked its path a shadow would be created. A lunar eclipse, for example, occurs when the Earth stops sunlight from reaching the moon. In other words, the Earth’s shadow hides the moon.

While asking the question, “what is the light” many ancients realized that light was an energy source that could be used for many things, including baking mud bricks, heating water and drying meat. Plants and animals also use light to their own advantage. Plants convert light energy into chemical energy during photosynthesis, when they produce sugar and starch. Reptiles rely on sunlight’s heating effect to warm their bodies up ready for action each day. And our eyes convert light into electrical energy that travels to the brain through optic nerves.

So what is the light?

Defining the nature of light baffled scientists for years, in the 17th century, Isaac Newton theorized that light was made of a stream of tiny energy particles. Around the same time, a Dutch scientist, Christiaan Huygens, suggested that light travelled by wave motion. Today, both theories are believed to complement each other. Experiments carried out in the development of the quantum theory show that light acts as a wave in some circumstances, such as when light reflects off a mirror. But, in other circumstances it acts like a stream of energy particles (photons).